Neurology

Cranial nerves and clinical localization

Trace visual, ocular motor, facial and lower cranial nerve pathways to localize deficits, distinguish shared spaces and recognize urgent clinical patterns.

A drooping eyelid, a weak smile and a hoarse voice each narrow the examination, but none identifies the cause by itself. Cranial nerve localization works when you connect the failed function to its pathway, then ask which neighboring structures share the same space.

Localize first, then test the explanation against every finding. Pupil sparing does not guarantee a benign third nerve palsy, and weakness of the entire face does not automatically mean Bell palsy.

Start with function and the route out of the skull

For each nerve, ask what the person cannot sense or do. Then examine a second function traveling nearby. CN I conveys smell through the cribriform plate. CN II carries retinal output through the optic canal. III and IV arise in the midbrain; V enters the pons; VI, VII and VIII are associated with the pontomedullary region; IX, X and XII attach to the medulla. The spinal component of XI begins in the upper cervical cord, enters through the foramen magnum and leaves through the jugular foramen. Nuclear, fascicular and extracranial lesions therefore produce different combinations. [1] [19]

Skull exits organize neighboring deficits
Passage	Relevant travelers	Useful combination
Superior orbital fissure	III, IV, V1, VI	Ophthalmoplegia and forehead or corneal sensory loss
Foramen rotundum	V2	Cheek and upper dental sensation
Foramen ovale	V3	Lower facial sensation and mastication
Internal acoustic meatus	VII, VIII	Facial and auditory or vestibular findings
Jugular foramen	IX, X, XI	Pharyngeal, voice and shoulder findings
Hypoglossal canal	XII	Ipsilateral tongue motor deficit

The table is a map of shared passages, not a rule that every lesion must injure every traveler. A small lesion can produce an incomplete syndrome. [1]

I, II and VIII are sensory nerves; III, IV, VI, XI and XII primarily supply motor functions. V, VII, IX and X carry both sensory and motor components, including the autonomic functions specified below. Test smell with a familiar nonirritating odor in each nostril. Irritants can stimulate trigeminal sensation and are poor substitutes for an olfactory test.

Anosmia after head trauma can reflect injury near the cribriform plate. Lifelong impaired smell plus absent puberty suggests Kallmann syndrome, linking olfactory development to gonadotropin-releasing hormone neuron migration. A new combination of anosmia, ipsilateral optic atrophy and contralateral papilledema suggests a mass producing Foster-Kennedy syndrome and warrants imaging. These are different mechanisms behind the same initial smell complaint. [1] [22] [23]

Try it here · Checkpoint 1 of 3

Make your prediction before reading the choices. A first attempt is just a starting point.

Case 16

Show answer and explanations

A. Right V1 through the superior orbital fissure (Why this does not fit)
V1 supplies the forehead and corneal territory, which are preserved.
B. Right V3 through foramen ovale (Why this does not fit)
V3 supplies the lower facial territory and mastication, both preserved here.
C. Right VII through the stylomastoid foramen (Why this does not fit)
VII chiefly supplies facial expression at that exit rather than cheek and dental general sensation.
D. Right V2 through foramen rotundum (Best answer)
V2 supplies the cheek and upper teeth and is sensory, fitting the preserved mastication.

Takeaway: Map trigeminal sensory territory before naming a skull passage.

Case sources: [1]

Try a question on this topic

A 34-year-old man undergoes a long shoulder reconstruction under general anesthesia in the beach-chair position with prolonged endotracheal intubation. In the recovery unit he is hoarse and cannot keep liquids from spilling when he speaks. Flexible laryngoscopy shows a fixed, immobile left vocal cord. When he protrudes his tongue it deviates to the left, and over the following weeks the left half of the tongue looks wasted. His soft palate elevates symmetrically with the uvula in the midline, and his gag reflex is intact. He shrugs both shoulders with equal power and turns his head against resistance normally to both sides. There is no drooping eyelid, no pupil asymmetry, and no change in facial sweating.

Injury to which combination of structures best explains this patient's deficits?

Choose an answer before revealing the reasoning.

Get one of these every morning · Practice more in the QBank

Separate visual input from the pupil's motor output

The optic nerve carries information into the pupil reflex; the oculomotor parasympathetic pathway drives constriction through the ciliary ganglion. With a unilateral afferent defect, illuminating the affected eye produces less constriction in both pupils than illuminating the better eye. With an isolated parasympathetic III defect, the affected pupil cannot constrict normally regardless of which eye receives light. The swinging flashlight test compares input, not simply pupil size. [1] [3]

Visual fields cross by retinal half

Before the chiasm

Left optic nerve injury affects the left eye's vision. The right eye has a separate optic nerve.

At the chiasm

Crossing nasal retinal fibers carry the temporal visual fields. Midline compression can therefore cause loss of the outer field in both eyes.

Behind the chiasm

The right retrochiasmal pathway carries the left visual hemifield from both eyes. A lesion can cause a left homonymous field defect.

Read the patient's visual field, not the name of the retinal half, when naming the deficit. A pituitary mass compressing the chiasm classically causes bitemporal, not binasal, loss. [8]

Optic neuritis often causes subacute monocular visual decline, impaired color perception and pain with eye rotation, with a relative afferent pupillary defect when involvement is asymmetric. The disc can appear normal if inflammation is retrobulbar. This is an optic neuropathy pattern, not proof of multiple sclerosis. Clinical assessment and appropriate imaging investigate the cause. In typical demyelinating optic neuritis, corticosteroids can accelerate visual recovery without improving the final visual outcome demonstrated in the Optic Neuritis Treatment Trial.

That result should not be generalized to every inflammatory optic neuropathy; the suspected cause and specialist assessment determine treatment. Papilledema specifically means disc swelling from raised intracranial pressure; it is not interchangeable with every swollen disc. [9] [24]

A complete III palsy produces ptosis and an eye resting outward and downward because lateral rectus and superior oblique retain their innervation. Pupillary dilation increases concern for compression, including a posterior communicating artery aneurysm. Diabetes can cause a microvascular palsy, often with pupil sparing, but preserved pupil function cannot exclude compression. Acute acquired III palsy needs prompt assessment and imaging rather than a diabetes-based assumption.

Thunderclap headache or a newly dilated pupil makes emergency vascular assessment especially pressing. Horner syndrome instead reflects sympathetic pathway dysfunction: mild ptosis with a small pupil, sometimes with reduced facial sweating. The pupil remains capable of parasympathetic constriction. The associated findings and onset determine where to investigate the sympathetic pathway. [19] [3] [4]

Use eye position to distinguish muscle, nerve and connection

Most extraocular muscles receive III. Lateral rectus receives VI and abducts the eye. Superior oblique receives IV, intorts the eye and is especially useful for depressing an adducted eye. The inferior oblique extorts, rather than intorts. The superior rectus also intorts while raising the eye. Test vertical muscles with the eye in the position that separates their actions instead of treating each muscle as a single-direction arrow. [2]

A right IV palsy typically gives right hypertropia that is worse in left gaze and on right head tilt. Tilting away can reduce diplopia. On right tilt, normal compensatory intorsion recruits the right superior oblique and superior rectus; weak superior oblique leaves the superior rectus's upward action relatively unopposed. A longstanding childhood head tilt or unusually large vertical fusion range favors a decompensated congenital palsy.

Trauma is another important cause. The IV nerve exits dorsally, crosses before emerging and has the longest intracranial course. A nuclear lesion affects the contralateral superior oblique; a peripheral nerve lesion affects the ipsilateral muscle. [5]

A VI nerve palsy causes impaired abduction with horizontal binocular diplopia, usually worse at distance and toward the affected side. Its course near the clivus and petrous apex makes it vulnerable to pressure-related displacement. Raised intracranial pressure can cause unilateral or bilateral VI palsy as a false localizing sign, but bilateral palsies do not prove that cause. A VI nuclear lesion can impair conjugate gaze toward the lesion; an isolated peripheral VI lesion chiefly weakens one lateral rectus. [6]

Follow the signal for rightward gaze

Right pontine gaze system activates the right VI nucleus
Motor neurons activate the right lateral rectus so the right eye abducts.
VI interneurons cross and ascend in the left MLF
This connection reaches the left III medial rectus pathway.
Left medial rectus adducts the left eye
A left MLF lesion interrupts this part of conjugate rightward gaze.

Left internuclear ophthalmoplegia means impaired left adduction on right gaze, often with right abducting nystagmus. Convergence may remain intact, but preserved convergence is not required in every case. The diagram represents pathway direction, not physical scale. [7]

INO localizes a connection, not a disease. Demyelination and stroke are important causes, but the patient's age alone cannot diagnose either. A complete III palsy includes a different set of deficits, such as ptosis and impaired vertical actions, rather than an isolated failure of adduction during conjugate gaze.

Trace sensation and expression separately

V1 supplies the forehead and cornea, V2 the cheek and upper teeth, and V3 the lower face and general sensation from the anterior tongue. V3 also supplies muscles of mastication. With unilateral pterygoid weakness, the jaw deviates toward the weak side on opening. Anterior tongue touch and anterior tongue taste travel through different cranial nerve systems; taste fibers from VII join the lingual nerve for part of their route. [1] [2]

Corneal reflex is an input-output comparison

Left V1 afferent failure

Touching the left cornea does not trigger either blink. Touching the right cornea triggers both blinks if both VII pathways work.

Left VII efferent failure

The left eyelids do not close after either cornea is stimulated. The right eyelids can close after stimulation of either intact corneal input.

The pattern assumes an isolated lesion and otherwise intact reflex circuitry. Compare both stimulus sides and both responses. [1] [19]

Brief electric facial pain provoked by chewing, toothbrushing or light touch suggests trigeminal neuralgia. The pain commonly follows V2 or V3. Vascular compression can damage the nerve's myelin, helping explain abnormal trigeminal signaling. [30] Carbamazepine is a standard initial medicine, with oxcarbazepine an alternative. MRI evaluates neurovascular compression and secondary causes; younger onset, bilateral symptoms or sensory loss deserve particular attention.

A vascular contact alone must be interpreted with the clinical syndrome. Secondary causes include multiple sclerosis and tumors. If medication is ineffective or poorly tolerated, discuss surgical options; microvascular decompression is considered for demonstrable neurovascular compression in a patient fit and willing to undergo the procedure. [14]

VII innervates facial expression. A supranuclear lesion often causes contralateral lower facial weakness with relative forehead preservation because upper facial motor input is bilateral. A facial nucleus, fascicle or peripheral VII lesion can weaken the ipsilateral upper and lower face. Therefore, whole-face weakness describes a lower motor neuron pattern, not the cause or whether the lesion is inside the brainstem. Associated gaze or limb findings can expose a pontine lesion. [19]

VII gives off branches before reaching facial muscles

Within the temporal bone, the greater petrosal pathway carries parasympathetic fibers for lacrimation through the pterygopalatine ganglion.
The nerve to stapedius supports dampening of sound transmission. Its dysfunction can produce hyperacusis.
Chorda tympani carries anterior tongue taste and parasympathetic fibers for submandibular and sublingual glands.
The main motor trunk exits the stylomastoid foramen and branches toward facial expression muscles.

A proximal lesion can affect several functions. An isolated distal motor lesion may spare taste, stapedius and lacrimal output. Real lesions can be partial; these are branch relationships, not a guarantee of every symptom. [1]

Bell palsy is an acute idiopathic peripheral facial palsy after alternative causes are considered. For eligible patients aged 16 or older, oral corticosteroids within 72 hours and eye protection for incomplete closure are core treatment. An antiviral can be offered with steroids; it is not mandatory for every case and should not be used alone. Severe ear pain with vesicles suggests VZV-associated Ramsay Hunt syndrome. Epidemiologic exposure with facial palsy, sometimes bilateral, can suggest Lyme disease and prompt appropriate serology and antibiotics. These diagnoses cannot be supplied by facts absent from the history. [11] [13] [12]

Try it here · Checkpoint 2 of 3

Make your prediction before reading the choices. A first attempt is just a starting point.

Case 18

Show answer and explanations

A. Bilateral optic nerve disease (Why this does not fit)
The corneal reflex uses trigeminal input rather than optic input.
B. Left V1 afferent deficit (Best answer)
Left corneal input fails to trigger either side, while right input demonstrates that both facial motor outputs can work.
C. Left VII efferent deficit (Why this does not fit)
That would prevent left eyelid closure regardless of which cornea was touched; the left eye closes with right stimulation here.
D. Right VII efferent deficit (Why this does not fit)
The right eye demonstrably blinks after right corneal stimulation, contradicting this isolated output lesion.

Takeaway: Change the stimulus side to distinguish afferent failure from motor failure.

Case sources: [1] [19]

Let adjacent deficits identify a shared space

VIII contains cochlear and vestibular components. Progressive unilateral sensorineural hearing loss, tinnitus and imbalance warrant assessment for retrocochlear disease, including vestibular schwannoma. Larger cerebellopontine angle lesions can involve V or VII, but there is no fixed tumor size at which facial weakness must appear. Bilateral vestibular schwannomas suggest NF2-related schwannomatosis, the current name for the condition historically called neurofibromatosis type 2. NF2 encodes the tumor-suppressor protein merlin on chromosome 22. Associated findings can include meningiomas, ependymomas and early cataracts. Management depends on hearing, growth, size, symptoms and patient priorities. [15] [16]

Brief positional vertigo with a characteristic posterior-canal response on Dix-Hallpike testing supports BPPV and treatment with canalith repositioning. Observation with planned follow-up is also an accepted initial BPPV option. Reassess within one month after observation or treatment. [28] Continuous acute vertigo is a different presentation. Vestibular neuritis classically lacks new hearing loss; labyrinthine disease can include hearing symptoms. [25] Neither a recent viral illness nor a hearing complaint safely excludes stroke. Acute vestibular syndrome requires appropriate assessment; HINTS is for the suitable syndrome when performed by a trained clinician, not a general screening test for every dizzy patient. [17] [18]

Three nearby spaces with overlapping eye findings
Location	Structures that may be involved	Useful extension
Superior orbital fissure	III, IV, V1, VI	Optic nerve function is relatively preserved in a lesion limited to the fissure.
Orbital apex	Optic nerve plus neighboring ocular motor and V1 pathways	Optic neuropathy with ophthalmoplegia increases concern for the apex.
Cavernous sinus	III, IV, V1, V2, VI, internal carotid artery and sympathetic fibers	V2 loss supports this location, but spared V2 does not exclude a partial cavernous lesion.

Within the cavernous sinus, VI runs near the carotid artery; III, IV, V1 and V2 travel in its lateral wall. VII, IX and X are not cavernous sinus contents. Hoarseness cannot be explained by an isolated lesion there. [10] [1]

Painful ophthalmoplegia is a syndrome requiring a cause. Thrombosis, fistula, tumor and inflammatory disease can affect the cavernous region. Pituitary apoplexy can produce acute headache, visual loss and ocular palsies and requires emergency assessment. In uncontrolled diabetes, invasive fungal disease becomes particularly concerning with sinus symptoms, necrotic tissue, proptosis or rapidly progressive orbital findings. Diabetes plus diplopia alone does not establish mucormycosis. Steroid responsiveness alone does not establish Tolosa-Hunt syndrome. ICHD-3 requires a compatible clinical pattern and granulomatous inflammation demonstrated by MRI or biopsy, without a better explanation; infection, vascular disease and malignancy must be considered. [26] [10] [21]

Use palate, shoulder and tongue to distinguish medulla from skull base

IX is not purely sensory. It carries posterior tongue taste and pharyngeal sensory input, supplies stylopharyngeus and provides parasympathetic output to the parotid through the otic ganglion. Carotid sinus and body afferents also travel through IX. X supplies most palatal, pharyngeal and laryngeal muscles and carries parasympathetic output to thoracic and abdominal viscera. The usual gag framework is IX afferent and X efferent, but an absent gag in isolation is not a complete assessment of swallowing safety. Observe palate, voice and swallowing and investigate aspiration concern directly. [1] [2] [20]

With a unilateral lower motor neuron X lesion, the ipsilateral palate is weak and the uvula is typically drawn toward the stronger side. Hoarseness points to laryngeal involvement. The superficial course of XI across the posterior neck triangle makes it vulnerable during procedures there. XI weakness reduces ipsilateral shoulder shrug and the sternocleidomastoid's ability to turn the head toward the opposite side.

XII supplies intrinsic and most extrinsic tongue muscles; palatoglossus receives X through the pharyngeal plexus. A peripheral XII lesion causes ipsilateral weakness, with the protruded tongue pointing toward the weak side; atrophy and fasciculations support a lower motor neuron process. [1] [2]

Crossed findings can place the lesion in the brainstem. In lateral medullary syndrome, ipsilateral facial pain-temperature loss accompanies contralateral body pain-temperature loss, with possible ipsilateral Horner syndrome, ataxia and nucleus ambiguus-related dysphagia or hoarseness. Vertebral or posterior inferior cerebellar artery territory ischemia is an important cause. A jugular foramen lesion instead groups IX, X and XI without requiring the crossed body sensory pattern. XII travels through a separate canal, so its addition suggests a broader lesion. [19] [20] [1]

Bulbar weakness from motor nuclei or nerves may include atrophy and fasciculations. Pseudobulbar dysfunction reflects bilateral corticobulbar disease and can include spastic speech and a brisk jaw jerk. Involuntary disproportionate crying or laughing can coexist, but does not by itself establish corticobulbar localization. [31] [29] Motor neuron disease can produce both patterns and may begin asymmetrically. [27] Do not exclude it merely because early tongue findings are unilateral. Conversely, an isolated progressive XII palsy deserves imaging along its anatomical course rather than an automatic motor neuron disease diagnosis. [19] [20]

Try it here · Checkpoint 3 of 3

Make your prediction before reading the choices. A first attempt is just a starting point.

Case 36

Show answer and explanations

A. Left cavernous sinus (Why this does not fit)
It neither explains the crossed body sensory pattern nor contains the lower cranial motor structures for hoarseness.
B. Isolated right recurrent laryngeal nerve (Why this does not fit)
That could affect voice but cannot cause crossed sensation and limb ataxia.
C. Right lateral pons without medullary involvement (Why this does not fit)
Some crossed sensory findings overlap, but prominent nucleus ambiguus-related hoarseness and dysphagia favor the lateral medulla.
D. Right lateral medulla (Best answer)
Ipsilateral trigeminal and cerebellar connections, contralateral spinothalamic findings and nucleus ambiguus dysfunction align here.

Takeaway: Crossed facial and body sensory findings with bulbar symptoms strongly support a brainstem localization.

Case sources: [19] [20]

Localization cases

Case 1

Show answer and explanations

A. Obtain routine nonvascular brain imaging at an outpatient visit (Why this does not fit)
Routine delayed imaging does not address the immediate aneurysm concern raised by severe headache and a pupil-involving III palsy.
B. Begin corticosteroids for presumed inflammatory painful ophthalmoplegia (Why this does not fit)
Inflammation is one differential, but treating it before urgent vascular evaluation risks missing an aneurysm.
C. Emergency assessment with vascular imaging for a compressive aneurysm (Best answer)
The acute painful pupil-involving III palsy raises concern for an aneurysm, including at the posterior communicating artery.
D. Arrange serial pupil examinations before deciding whether to image (Why this does not fit)
The abnormal pupil and sudden headache already warrant urgent assessment; serial observation is not an adequate initial plan.

Takeaway: A pupil-involving acute III palsy is an emergency until dangerous compression is assessed.

Case sources: [3] [4]

Case 2

Show answer and explanations

A. Manage as presumed diabetic mononeuropathy with review in six weeks (Why this does not fit)
Microvascular ischemia is possible, but this defers evaluation of a new acquired III palsy before compression has been assessed.
B. Microvascular ischemia is possible, but pupil sparing does not eliminate the need for prompt imaging assessment (Best answer)
Diabetes supports one cause but does not safely exclude a compressive lesion at presentation.
C. Reserve vascular imaging for subsequent pupillary dilation (Why this does not fit)
Pupil sparing does not reliably exclude an aneurysm, so later dilation should not be the prerequisite for imaging.
D. Begin empiric steroids for inflammatory oculomotor neuropathy (Why this does not fit)
No inflammatory cause has been established. The first assessment must also address dangerous compressive and vascular causes.

Takeaway: A plausible vascular risk factor is not a substitute for evaluating an acute acquired III palsy.

Case sources: [3] [4]

Case 3

Show answer and explanations

A. Right superior oblique supplied by IV (Best answer)
The affected eye cannot depress normally when adducted, and the ipsilateral tilt increases the characteristic hypertropia.
B. Left lateral rectus supplied by VI (Why this does not fit)
That deficit produces impaired left abduction and chiefly horizontal diplopia, not this vertical pattern.
C. Right medial rectus supplied by III (Why this does not fit)
An isolated adduction deficit does not explain the head-tilt-dependent right hypertropia.
D. Right inferior rectus supplied by III (Why this does not fit)
Inferior rectus depression is most effectively assessed with the eye abducted; the supplied pattern is worse in adduction and on ipsilateral tilt.

Takeaway: The affected superior oblique is on the side of the hypertropic eye in this peripheral palsy pattern.

Case sources: [5]

Case 4

Show answer and explanations

A. A newly acquired left VI palsy (Why this does not fit)
A left abduction deficit would not explain the longstanding opposite compensatory tilt and vertical fusion findings.
B. Acute pupil-involving right III palsy (Why this does not fit)
No acute ptosis, pupillary change or broad III deficit is supplied.
C. Acquired right inferior oblique palsy (Why this does not fit)
The inferior oblique raises the adducted eye and extorts; its weakness does not fit the supplied right hypertropia and compensatory tilt pattern.
D. Decompensated congenital right IV palsy (Best answer)
The childhood compensatory tilt and large fusion range support longstanding compensation that has become insufficient.

Takeaway: Old photographs can distinguish longstanding compensation from a newly acquired palsy.

Case sources: [5] [2]

Case 5

Show answer and explanations

A. Right lateral rectus (Why this does not fit)
Lateral rectus is supplied by VI, whose nucleus is in the pons.
B. Right superior rectus (Why this does not fit)
Superior rectus receives III; a lesion confined to the trochlear nucleus instead affects the crossed superior oblique output.
C. Left superior oblique (Best answer)
Trochlear fibers decussate before dorsal emergence, so a nuclear lesion affects the opposite superior oblique.
D. Right superior oblique (Why this does not fit)
That is the usual side for a right peripheral IV lesion after crossing, not the stated nuclear lesion.

Takeaway: The side rule changes across the trochlear decussation.

Case sources: [5]

Case 6

Show answer and explanations

A. Left II (Why this does not fit)
Optic nerve dysfunction impairs visual input rather than isolated abduction.
B. Left VI (Best answer)
A left lateral rectus deficit explains impaired abduction and greater separation in left gaze at distance.
C. Left IV (Why this does not fit)
Superior oblique weakness chiefly gives vertical or torsional diplopia, especially in adduction.
D. Right III (Why this does not fit)
The supplied findings do not show right adduction, vertical action, eyelid or pupillary deficits.

Takeaway: Match the weak action to the muscle before considering the cause.

Case sources: [6]

Case 7

Show answer and explanations

A. They may be false localizing signs of raised intracranial pressure (Best answer)
The pressure-related context can affect the vulnerable VI course without a focal lesion at each abducens nucleus.
B. Bilateral microvascular VI neuropathies are the most coherent explanation (Why this does not fit)
Two ischemic neuropathies do not explain the bilateral papilledema and pressure-type symptoms as coherently as raised intracranial pressure.
C. Bilateral MLF lesions explain the abduction deficit (Why this does not fit)
MLF lesions chiefly impair adduction on conjugate gaze, rather than causing the bilateral abduction weakness described.
D. A single abducens nuclear lesion explains both weak lateral recti (Why this does not fit)
A unilateral VI nuclear lesion causes an ipsilateral conjugate gaze deficit, not isolated abduction weakness in both eyes.

Takeaway: Pressure-related VI weakness does not necessarily localize a mass to the pons.

Case sources: [6] [5] [24]

Case 8

Show answer and explanations

A. Right medial longitudinal fasciculus (Why this does not fit)
A right MLF lesion would instead impair right adduction on left gaze.
B. Left peripheral VI nerve (Why this does not fit)
A left VI lesion impairs left abduction, not left adduction on right gaze.
C. Left oculomotor nerve (Why this does not fit)
An isolated adduction deficit can raise this possibility, but preserved convergence and contralateral abducting nystagmus favor an internuclear connection; broad III signs are absent.
D. Left medial longitudinal fasciculus (Best answer)
The left MLF conveys the crossed signal from the right VI nucleus to the left medial rectus pathway during right gaze.

Takeaway: INO is named for the side of the adduction deficit.

Case sources: [7]

Case 9

Show answer and explanations

A. Isolated left MLF (Why this does not fit)
A left MLF lesion can impair left adduction on right gaze, but should not itself prevent the right eye from abducting.
B. Isolated right MLF (Why this does not fit)
A right MLF lesion affects right adduction on left gaze, not both eyes ability to look right.
C. Right abducens nucleus or immediately associated pontine gaze circuitry (Best answer)
This region coordinates ipsilateral abduction and contralateral adduction for conjugate rightward gaze.
D. Isolated right peripheral abducens nerve (Why this does not fit)
That would weaken the right lateral rectus but would not by itself prevent left adduction.

Takeaway: A conjugate gaze palsy points beyond an isolated peripheral VI nerve.

Case sources: [6] [7] [19]

Case 10

Show answer and explanations

A. An isolated left oculomotor neuropathy (Why this does not fit)
III dysfunction affects pupil output and ocular motor function, rather than causing this afferent defect and color desaturation.
B. A retrobulbar optic neuropathy compatible with optic neuritis (Best answer)
The combination of painful visual decline, dyschromatopsia and an afferent defect fits optic nerve inflammation behind the visible disc.
C. Papilledema from raised intracranial pressure (Why this does not fit)
Papilledema is disc swelling due to pressure; the normal disc and painful monocular optic neuropathy favor another mechanism.
D. Compression of the central optic chiasm (Why this does not fit)
A central chiasmal lesion more typically impairs temporal fields in both eyes; the described unilateral afferent findings favor the left optic nerve.

Takeaway: A normal-looking disc does not exclude optic nerve disease.

Case sources: [9] [24] [8]

Case 11

Show answer and explanations

A. Both pupils constrict less and appear to dilate relatively (Best answer)
Reduced left afferent input decreases the bilateral constrictor drive despite intact motor pathways.
B. The left pupil dilates relatively while the right pupil constricts more (Why this does not fit)
A unilateral reduction in afferent drive changes the drive to both intact pupil motor pathways, not just the illuminated eye.
C. Both pupils constrict more strongly (Why this does not fit)
Illuminating the affected optic nerve supplies less afferent drive, so stronger bilateral constriction is the opposite of the expected relative afferent defect.
D. Both pupils maintain the same degree of constriction (Why this does not fit)
Equal drive would not demonstrate the asymmetric afferent deficit specified in the stem.

Takeaway: An afferent pupil defect is identified by comparing the stimulus sides.

Case sources: [1] [3] [9]

Case 12

Show answer and explanations

A. Uncrossed temporal retinal fibers in both optic nerves exclusively (Why this does not fit)
Those fibers represent nasal fields and do not explain the stated classic chiasmal pattern.
B. The left optic nerve alone (Why this does not fit)
A unilateral prechiasmal lesion produces monocular rather than symmetric bitemporal involvement.
C. The right optic tract alone (Why this does not fit)
A right retrochiasmal lesion affects the left hemifield of both eyes, producing a homonymous defect.
D. Crossing nasal retinal fibers at the optic chiasm (Best answer)
Nasal retina receives the temporal visual field, so injury to these crossing fibers produces bitemporal loss.

Takeaway: Name a visual field deficit from the visual world, then map it to the retina.

Case sources: [8]

Case 13

Show answer and explanations

A. Central optic chiasm causing classic compression (Why this does not fit)
Midline chiasmal compression preferentially affects crossing fibers and produces bitemporal loss.
B. Left oculomotor nerve (Why this does not fit)
A III palsy affects ocular motor or pupillary output, not this homonymous visual field pattern.
C. Right retrochiasmal visual pathway (Best answer)
Each retrochiasmal side carries the opposite visual hemifield from both eyes.
D. Left optic nerve (Why this does not fit)
That would primarily affect the left eye rather than matching left hemifields in both eyes.

Takeaway: Homonymous loss indicates a postchiasmal pathway rather than an isolated eye nerve.

Case sources: [8]

Case 14

Show answer and explanations

A. Isolated androgen insensitivity (Why this does not fit)
Androgen insensitivity does not explain the supplied hypogonadotropic hormonal pattern together with anosmia.
B. Kallmann syndrome (Best answer)
Impaired olfaction with deficient reproductive hormonal signaling reflects the characteristic developmental association.
C. Constitutional delay of puberty with normal olfactory development (Why this does not fit)
Constitutional delay does not explain the demonstrated lifelong olfactory deficit as coherently as the combined developmental syndrome.
D. Primary testicular failure (Why this does not fit)
Primary gonadal failure usually produces increased rather than inappropriately low gonadotropins and does not account for anosmia.

Takeaway: Smell loss can be part of a developmental endocrine syndrome.

Case sources: [22]

Case 15

Show answer and explanations

A. An anterior intracranial mass compressing the right optic nerve and raising intracranial pressure (Best answer)
Direct compression explains ipsilateral atrophy, while raised pressure can swell the other disc in Foster-Kennedy syndrome.
B. Isolated acute left optic neuritis as the complete explanation (Why this does not fit)
That does not explain the right optic atrophy and olfactory deficit as one process.
C. Right peripheral VII palsy (Why this does not fit)
It cannot cause optic nerve atrophy or pressure-related disc swelling.
D. Typical uncomplicated migraine established without imaging (Why this does not fit)
The progressive optic findings and anosmia require investigation for structural disease.

Takeaway: Different optic disc appearances can result from direct compression and pressure in the same patient.

Case sources: [23]

Case 17

Show answer and explanations

A. Left facial expression muscles push the mandible right (Why this does not fit)
VII facial muscles do not provide the relevant pterygoid action.
B. A right V1 lesion weakens mastication (Why this does not fit)
V1 is sensory and does not carry the motor supply to the pterygoids.
C. Unopposed action of the right pterygoid muscles toward the weak side (Best answer)
A unilateral V3 motor deficit allows the intact side to push the mandible toward the injured side.
D. Unopposed left pterygoid action after a right V3 injury (Why this does not fit)
That would tend to direct the jaw right, contrary to the observed deviation and stated left mandibular nerve injury.

Takeaway: Jaw opening points toward the weak pterygoid side.

Case sources: [1] [2]

Case 19

Show answer and explanations

A. Carbamazepine (Best answer)
The triggerable brief V2-distribution pain fits trigeminal neuralgia, for which carbamazepine is a standard initial medicine.
B. Prednisone alone for presumed Bell palsy (Why this does not fit)
There is no facial weakness, and the pain phenotype points to trigeminal neuralgia.
C. A triptan as the initial treatment for migraine (Why this does not fit)
Migraine attacks have a different time course; these seconds-long touch-triggered V2 attacks fit neuralgia.
D. Chronic opioid therapy as the preferred first treatment (Why this does not fit)
Opioids are not the recommended initial treatment for this neuralgic pain syndrome.

Takeaway: A trigger zone and brief electric pain suggest trigeminal neuralgia, while imaging assesses its cause.

Case sources: [14]

Case 20

Show answer and explanations

A. Isolated left facial nerve after the stylomastoid foramen (Why this does not fit)
A complete distal VII lesion would affect upper and lower facial expression and would not explain arm weakness.
B. Left pontine facial nucleus and adjacent corticospinal tract (Why this does not fit)
This would favor left whole-face weakness with right limb weakness, rather than preserved left forehead function and left arm weakness.
C. Left supranuclear corticobulbar and motor pathways (Why this does not fit)
A left supranuclear lesion would chiefly affect the opposite lower face and arm; the deficits here are left-sided.
D. Right supranuclear corticobulbar and motor pathways (Best answer)
Predominantly contralateral lower facial weakness with a matching limb deficit supports a central motor lesion.

Takeaway: Forehead preservation and limb findings favor a supranuclear lesion in this pattern.

Case sources: [19]

Case 21

Show answer and explanations

A. Right peripheral facial neuropathy (Why this does not fit)
This explains whole-face weakness but not conjugate gaze paralysis and contralateral limb weakness.
B. Left cerebral motor pathway lesion (Why this does not fit)
A left cerebral lesion could weaken the right lower face but does not explain this right pontine gaze pattern with left limb weakness.
C. A right pontine lesion is concerning despite the whole-face weakness (Best answer)
Facial fascicular or nuclear involvement can give a peripheral-type facial pattern alongside gaze and long-tract deficits.
D. Right hemispheric corticobulbar lesion (Why this does not fit)
That lesion would tend to affect the left lower face, not the entire right face and ipsilateral gaze circuitry.

Takeaway: A lower motor neuron facial pattern can still arise inside the brainstem.

Case sources: [19] [6]

Case 22

Show answer and explanations

A. Eye protection alone with reassessment after two weeks (Why this does not fit)
Eye protection is necessary, but this eligible adult is within the 72-hour window in which oral corticosteroids are recommended.
B. Oral corticosteroids within the treatment window and eye protection (Best answer)
Eligible adults benefit from early steroids, and incomplete closure requires corneal protection.
C. Antiviral monotherapy as the preferred regimen (Why this does not fit)
The guideline does not recommend antivirals alone for Bell palsy.
D. Delay corticosteroids until facial nerve electrodiagnostic testing is completed (Why this does not fit)
Electrodiagnostic testing is not a prerequisite to timely corticosteroids in this established, otherwise uncomplicated presentation.

Takeaway: Protect the eye while treating an appropriately diagnosed acute Bell palsy.

Case sources: [11]

Case 23

Show answer and explanations

A. Ramsay Hunt syndrome from varicella-zoster reactivation (Best answer)
Painful otic vesicles with a peripheral facial palsy support herpes zoster oticus.
B. Trigeminal neuralgia involving V2 (Why this does not fit)
V2 belongs to V and carries maxillary sensation. Neuralgia does not explain a vesicular otic eruption plus upper and lower facial paralysis.
C. Pure vestibular neuritis (Why this does not fit)
Vestibular neuritis does not explain the characteristic vesicles and facial paralysis.
D. Idiopathic Bell palsy despite the identified zoster pattern (Why this does not fit)
The specific infectious findings supply a cause, so an idiopathic label is less appropriate.

Takeaway: Ear examination can identify a specific cause of a peripheral facial palsy.

Case sources: [13]

Case 24

Show answer and explanations

A. Treat as idiopathic facial palsy with corticosteroids alone (Why this does not fit)
Bilateral weakness after a compatible rash and tick exposure requires evaluation and treatment for Lyme disease; steroids alone do not treat that infection.
B. Treat as zoster-associated facial palsy with antiviral monotherapy (Why this does not fit)
The supplied expanding rash and tick exposure favor Lyme disease rather than the otic vesicles and ear-pain pattern of zoster.
C. Use serial facial examinations while awaiting spontaneous recovery (Why this does not fit)
Observation alone leaves a plausible treatable infection unaddressed; eye care and appropriate infection assessment are needed.
D. Evaluate neurologic Lyme disease with recommended serology and provide appropriate antibiotics (Best answer)
The exposure, rash history and facial pattern support targeted Lyme assessment and treatment.

Takeaway: An infectious diagnosis should be supported by actual exposure and clinical evidence in the history.

Case sources: [12] [13]

Case 25

Show answer and explanations

A. Isolated right V3 (Why this does not fit)
V3 carries anterior tongue general sensation but does not supply the specified taste, lacrimal and facial motor functions.
B. Isolated right VIII (Why this does not fit)
VIII could explain auditory or vestibular deficits but not this facial taste and lacrimal combination.
C. Right VII proximal to the greater petrosal branch (Best answer)
A sufficiently proximal injury can affect motor fibers and pathways later destined for lacrimation, stapedius and chorda tympani.
D. Right VII limited to a distal facial expression branch (Why this does not fit)
A distal motor branch lesion would not explain loss of the earlier intratemporal functions.

Takeaway: Multiple facial nerve modalities can place an injury proximal to their branch points.

Case sources: [1]

Case 26

Show answer and explanations

A. Right corticobulbar pathway as the only lesion (Why this does not fit)
That usually produces a contralateral lower-face-predominant pattern rather than this ipsilateral complete peripheral pattern.
B. Left VII motor trunk after its intratemporal branches (Best answer)
A distal motor lesion can weaken facial expression while sparing chorda tympani, stapedius and greater petrosal functions.
C. Left VII before the greater petrosal branch as a complete lesion (Why this does not fit)
A complete proximal lesion would be expected to affect more than facial motor output.
D. Left optic nerve (Why this does not fit)
Optic neuropathy affects visual input, while the supplied deficit is weakness of voluntary forehead and eyelid motor output.

Takeaway: Preserved nonmotor facial functions support a lesion distal to their branches when the lesion is complete and isolated.

Case sources: [1] [19]

Case 27

Show answer and explanations

A. MRI directed to the internal auditory canals and cerebellopontine angles (Best answer)
This assesses a retrocochlear mass along the vestibular nerve course.
B. Repeat pure-tone audiometry as the sole next investigation (Why this does not fit)
Audiometry establishes and follows hearing asymmetry but does not directly image the suspected retrocochlear tumor.
C. A noncontrast head CT as the only test to exclude a small canal lesion (Why this does not fit)
A routine head CT does not assess a small internal auditory canal or cerebellopontine angle lesion as directly as the dedicated MRI study.
D. Auditory brainstem response testing instead of imaging (Why this does not fit)
Auditory response testing can supply functional evidence, but directed MRI is the more direct anatomical assessment of a suspected schwannoma.

Takeaway: Progressive asymmetric sensorineural hearing loss warrants retrocochlear assessment.

Case sources: [15]

Case 28

Show answer and explanations

A. Neurofibromatosis type 1 (Why this does not fit)
Bilateral vestibular schwannomas specifically support NF2-related schwannomatosis rather than the usual NF1 tumor pattern.
B. LZTR1-related schwannomatosis (Why this does not fit)
Unilateral vestibular schwannoma can occur in this disorder, but bilateral vestibular schwannomas strongly support NF2-related schwannomatosis.
C. SMARCB1-related schwannomatosis (Why this does not fit)
This schwannomatosis subtype does not account for the characteristic bilateral vestibular tumor pattern as well as NF2-related disease.
D. NF2-related schwannomatosis (Best answer)
Bilateral vestibular schwannomas are characteristic of this condition, historically called neurofibromatosis type 2.

Takeaway: Use the actual bilateral imaging findings and current disease name.

Case sources: [16]

Case 29

Show answer and explanations

A. Oral antibiotics for presumed bacterial labyrinthitis (Why this does not fit)
The brief provoked episodes and characteristic positional response do not establish bacterial labyrinthitis.
B. Oral corticosteroids for presumed vestibular neuritis (Why this does not fit)
Vestibular neuritis presents with sustained acute vertigo rather than these brief position-triggered episodes with a characteristic posterior canal test response.
C. A canalith repositioning maneuver such as Epley (Best answer)
The brief positional episodes and characteristic test response support posterior canal BPPV.
D. A prolonged course of vestibular suppressants as definitive treatment (Why this does not fit)
Symptom suppression does not correct displaced canaliths and is not the recommended definitive approach to this posterior canal pattern.

Takeaway: A specific positional response supports a specific mechanical vestibular treatment.

Case sources: [17] [28]

Case 30

Show answer and explanations

A. Perform positional testing before deciding whether to seek stroke assessment (Why this does not fit)
Continuous symptoms with dysarthria and inability to stand demand immediate stroke assessment rather than a BPPV-first pathway.
B. Urgent stroke assessment (Best answer)
The acute persistent syndrome with speech and severe balance abnormalities requires central-cause assessment.
C. Treat as vestibular neuritis and arrange outpatient review (Why this does not fit)
A peripheral vestibular diagnosis does not adequately account for the new dysarthria and severe postural instability.
D. Give a vestibular suppressant and reassess after the medication takes effect (Why this does not fit)
Symptom relief must not defer stroke evaluation in this acute focal neurologic presentation.

Takeaway: Time course and accompanying neurologic findings outrank the general word dizziness.

Case sources: [18]

Case 31

Show answer and explanations

A. Right cavernous sinus (Best answer)
III, IV, VI, V1 and V2 share this region with the internal carotid artery, while VII is elsewhere.
B. Right orbital apex (Why this does not fit)
The apex can combine ocular motor and V1 deficits with optic neuropathy, but the V2 cheek deficit favors the cavernous sinus.
C. Right superior orbital fissure alone (Why this does not fit)
A lesion restricted to the fissure would not ordinarily affect V2, which travels through foramen rotundum.
D. Right cerebellopontine angle (Why this does not fit)
That region more commonly combines V, VII and VIII findings, rather than this ocular motor and V1/V2 pattern.

Takeaway: Cavernous sinus localization combines ocular motor deficits with trigeminal territory and imaging.

Case sources: [10] [1] [15]

Case 32

Show answer and explanations

A. Spared cheek sensation is sufficient to localize the lesion to the fissure (Why this does not fit)
A partial cavernous lesion can spare V2, so this finding cannot make the localization certain.
B. An isolated traumatic optic neuropathy is the best explanation (Why this does not fit)
The preserved vision and ocular motor plus forehead sensory deficits point beyond an isolated optic nerve lesion.
C. A traumatic III neuropathy alone explains the examination (Why this does not fit)
An isolated III lesion does not explain the accompanying V1 sensory deficit.
D. A superior orbital fissure lesion is plausible, but spared V2 does not exclude a partial cavernous lesion (Best answer)
The clinical overlap requires anatomical imaging rather than treating one spared division as absolute proof.

Takeaway: A missing deficit narrows probabilities but does not guarantee a small lesion respects a textbook boundary.

Case sources: [10]

Case 33

Show answer and explanations

A. Isolated facial nerve in the parotid (Why this does not fit)
This does not account for visual input or ocular motor deficits.
B. A lesion confined to the cavernous sinus without extension (Why this does not fit)
Cavernous disease can cause ophthalmoplegia and V1 loss, but the added optic neuropathy points to apical involvement or a more extensive process.
C. Orbital apex (Best answer)
The optic nerve at the apex lies near the ocular motor and V1 pathways, permitting combined optic neuropathy and ophthalmoplegia.
D. A lesion confined to the superior orbital fissure that leaves the optic canal uninvolved (Why this does not fit)
A strictly fissure-limited process does not directly include the optic nerve and fails to explain the added optic neuropathy.

Takeaway: Adding optic neuropathy to ophthalmoplegia raises concern for the orbital apex or a broader process.

Case sources: [10] [9]

Case 34

Show answer and explanations

A. Microvascular ischemic optic neuropathy without orbital infection (Why this does not fit)
That does not unify rapidly progressive proptosis, ophthalmoplegia, sinus pain and necrotic palatal tissue.
B. Rhino-orbital-cerebral mucormycosis (Best answer)
The combination of risk context, invasive orbital findings and necrotic tissue is concerning for an angioinvasive fungal infection.
C. Benign diabetic III palsy as the complete explanation (Why this does not fit)
An isolated microvascular palsy does not explain palatal necrosis, sinus disease and proptosis.
D. Tolosa-Hunt syndrome established before excluding infection (Why this does not fit)
Steroid-responsive inflammation is not a safe assumption in this invasive infectious pattern.

Takeaway: Diabetes becomes informative when combined with evidence of tissue-invasive disease.

Case sources: [21] [26]

Case 35

Show answer and explanations

A. Left jugular foramen affecting lower cranial nerves including X and XI (Best answer)
Palatal and laryngeal weakness combine with ipsilateral trapezius and sternocleidomastoid dysfunction, while XII has a separate exit.
B. Left cavernous sinus (Why this does not fit)
The cavernous sinus does not contain the vagus or spinal accessory pathways needed to explain voice and shoulder findings.
C. Right hypoglossal canal (Why this does not fit)
There is no right tongue weakness, and XII alone cannot explain the palate, voice and shoulder pattern.
D. Left superior orbital fissure (Why this does not fit)
That location groups ocular motor nerves and V1 rather than the described lower cranial nerves.

Takeaway: Voice plus palate plus shoulder findings identify a lower cranial nerve neighborhood.

Case sources: [1] [2] [20]

Case 37

Show answer and explanations

A. Right vagal motor injury (Why this does not fit)
Vagal injury can weaken the palate, pharynx and larynx, but does not innervate most tongue muscles or explain this pattern of tongue wasting.
B. Left supranuclear corticobulbar injury alone (Why this does not fit)
A contralateral supranuclear lesion can weaken the tongue, but isolated upper motor neuron injury does not explain focal denervation atrophy and fasciculations.
C. Right lower motor neuron XII injury (Best answer)
The imaging location and ipsilateral wasting, fasciculations and deviation match hypoglossal motor dysfunction.
D. Left lower motor neuron XII injury (Why this does not fit)
A left peripheral XII lesion would weaken and waste the left side and typically direct protrusion left, opposite the findings here.

Takeaway: Tongue atrophy and deviation should be matched to the hypoglossal pathway and the supplied imaging.

Case sources: [1] [2] [19]

Case 38

Show answer and explanations

A. Submandibular gland parasympathetic output through chorda tympani (Why this does not fit)
Chorda tympani belongs to VII; IX parasympathetic fibers instead reach the parotid through the otic ganglion.
B. Stylopharyngeus motor supply and posterior tongue taste (Best answer)
IX is mixed, carrying this motor function as well as taste and pharyngeal sensory pathways.
C. Motor supply to every intrinsic tongue muscle (Why this does not fit)
Intrinsic tongue muscles receive XII motor fibers; the stated isolated IX injury instead threatens stylopharyngeus and other glossopharyngeal functions.
D. Palatoglossus motor supply (Why this does not fit)
Palatoglossus receives X through the pharyngeal plexus, whereas IX supplies stylopharyngeus.

Takeaway: Glossopharyngeal function includes motor and parasympathetic components as well as sensation.

Case sources: [1] [2]

Case 39

Show answer and explanations

A. Bilateral corticobulbar dysfunction producing a pseudobulbar pattern (Best answer)
Spastic speech, brisk reflexes and emotional lability support bilateral upper motor pathway dysfunction.
B. An isolated unilateral distal XII lesion (Why this does not fit)
That more often gives ipsilateral tongue weakness and lower motor neuron signs, not this bilateral corticobulbar pattern.
C. An isolated lower motor neuron bulbar process (Why this does not fit)
A purely lower motor process would be more compatible with wasting and weakness than a brisk jaw jerk and spastic speech.
D. Purely sensory IX loss (Why this does not fit)
Sensory pharyngeal loss alone cannot account for spastic speech and a brisk jaw jerk.

Takeaway: Bulbar symptoms can arise from bilateral upper motor pathways as well as lower motor nerves.

Case sources: [19] [20] [29] [31]

Sources

UAMS nerves of the head and neck
Cranial nerve functions, branches, skull exits and reflex anatomy.
UAMS muscles of the head and neck
Extraocular actions, tongue and pharyngeal exceptions, sternocleidomastoid and trapezius.
AAO EyeWiki acquired oculomotor nerve palsy
Third nerve examination, parasympathetic anatomy and compressive causes.
Isolated third cranial nerve palsies, modern management principles (2020-12-15)
Primary clinical series and recommendation for imaging at presentation irrespective of pupil status; online publication date.
AAO EyeWiki fourth nerve palsy
Superior oblique action, head tilt, congenital and traumatic palsy, dorsal exit and crossing.
AAO EyeWiki abducens nerve palsy
Lateral rectus function, sixth nerve course and raised-pressure false localization.
AAO EyeWiki internuclear ophthalmoplegia
MLF side, adduction deficit, abducting nystagmus and convergence limitations.
AAO EyeWiki compressive visual field defects
Retinal field mapping and chiasmal versus retrochiasmal localization.
AAO EyeWiki demyelinating optic neuritis
Painful monocular visual loss, color dysfunction, RAPD and diagnostic limits.
AAO EyeWiki superior orbital fissure syndrome
Comparison of orbital apex, superior orbital fissure and cavernous sinus involvement, including partial cavernous lesions.
AAO-HNS Bell palsy guideline fact sheet (2013-11-04)
Steroids within 72 hours in eligible adults, eye protection and optional adjunctive antiviral therapy.
CDC clinical care of neurologic Lyme disease (2025-03-05)
Facial palsy, two-step serology and antibiotic treatment.
NINDS herpes zoster oticus
Ramsay Hunt syndrome, ear pain, vesicles, facial weakness and associated auditory symptoms.
Royal College of Surgeons of England trigeminal neuralgia guideline (2021)
Clinical pain pattern, MRI assessment and carbamazepine or oxcarbazepine treatment.
NIDCD vestibular schwannoma and neurofibromatosis (2017-03-06)
Progressive unilateral auditory symptoms, MRI and individualized management; update date.
GeneReviews NF2-related schwannomatosis (2023-04-20)
Current nomenclature and bilateral vestibular schwannomas; update date.
AAO-HNS benign paroxysmal positional vertigo guideline (2017-03-01)
Posterior canal positional testing and canalith repositioning.
NICE NG127 recognition and referral of neurological conditions
Urgent assessment of acute vestibular syndrome and appropriate expertise for HINTS.
UTHealth neuroscience laboratory guide (2013)
Brainstem tracts, corticobulbar facial input and lateral medullary localization.
UTHealth nucleus ambiguus laboratory anatomy
Palatal, pharyngeal and laryngeal motor findings and bilateral corticobulbar input.
CDC clinical overview of mucormycosis
Risk context, angioinvasion, necrosis and rhino-orbital-cerebral presentation.
MedlinePlus Genetics Kallmann syndrome
Impaired smell with hypogonadotropic hypogonadism and developmental migration.
AAO EyeWiki Foster-Kennedy and pseudo-Foster-Kennedy syndromes
Optic compression, raised pressure, anosmia and need for imaging.
AAO EyeWiki papilledema
Optic disc swelling from raised intracranial pressure and distinction from other optic neuropathies.
NHS labyrinthitis and vestibular neuritis (2026-08-06)
Hearing distinction between labyrinthine and vestibular nerve inflammation; page review date.
ICHD-3 Tolosa-Hunt syndrome diagnostic criteria
Granulomatous inflammation on MRI or biopsy and exclusion of alternative causes; URL retained as served by the official site.
Study of motor asymmetry in ALS (2014-05-09)
Primary study documenting asymmetric onset and spread of motor dysfunction; online publication date.
AAO-HNS Bulletin: BPPV guideline action statements, March 2017 (2017-03)
Posterior-canal testing, repositioning, optional observation with follow-up and one-month reassessment.
University of Utah NeuroLogic Exam: pseudobulbar palsy
Bilateral corticobulbar disease, jaw reflex and voluntary versus reflex palatal function.
NIDCR trigeminal neuralgia (2024-12)
Vascular compression can damage trigeminal myelin; last reviewed December 2024.
Impaired corticopontocerebellar tracts underlie pseudobulbar affect in motor neuron disorders (2014)
Primary motor neuron disorder study: involuntary crying or laughing can coexist with bulbar dysfunction, with broader network involvement.

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