Neuro exam localizer

PICA Wallenberg

Crossed pain-temperature loss plus dysphagia, hoarseness, Horner, vertigo, ataxia, and no limb weakness is lateral medulla. That is PICA.

Medically reviewed by Kaitlyn Cocuzzo, MD and Fatima Ali, DO
Last updated 2026-07-13T16:16:47-04:00 (ET)

Before you scroll: A 67-year-old man develops vertigo, nausea, hoarseness, dysphagia, decreased gag reflex, ipsilateral facial pain and temperature loss, and contralateral body pain and temperature loss. Motor strength is preserved. Which artery is most likely occluded?

The crossed sensory pattern places the lesion in the brainstem, and the nucleus ambiguus signs localize it to lateral medulla. PICA hits lateral medulla and spares the corticospinal tract, so strength is preserved. AICA is one floor up in the pons and adds facial paralysis or hearing loss. Crossed pain-temperature + dysphagia/hoarseness + no weakness = PICA Wallenberg.

Brainstem floor check

PICA vs Its Look-Alikes

The artery answer follows the level: medulla, pons, medial medulla, or cortex.

PICA

Lateral medulla

SignatureIpsilateral face pain/temp loss plus contralateral body pain/temp loss

Nucleus ambiguusDysphagia, hoarseness, decreased gag

Other cluesHorner, vertigo, nystagmus, ipsilateral ataxia

MotorLimb strength preserved

AICA

Lateral pons

AddsIpsilateral facial paralysis and hearing loss

SharedVertigo, ataxia, crossed sensory loss can overlap

LevelPons, not medulla

TrapHearing loss or CN VII palsy means switch from PICA to AICA

Anterior spinal artery

Medial medulla

MotorContralateral limb weakness

CN XIIIpsilateral tongue deviation

SensationContralateral vibration/proprioception loss

TrapPain and temperature are usually spared

Basilar and PCA

Pontine or cortical traps

BasilarLocked-in syndrome, quadriplegia, preserved awareness

PCAContralateral homonymous hemianopia, visual cortex

Shared trapPosterior circulation label is too broad

RuleName the level before the vessel

Board trap: Do not pick AICA just because vertigo and ataxia are present. AICA needs pontine CN VII or CN VIII clues.

Stroke switchboard

Find the Floor

Pick the clue. The readout names the level before it names the artery.

Which stroke territory owns this clue?

Pick a clue.Start with cranial nerves and long tracts. Then add the artery.

Board trap: No weakness matters. PICA is lateral medulla and usually spares corticospinal motor fibers.

Two-gate discriminator

Decision Tree

Use the stem to choose the brainstem floor before you choose the named artery.

Are there crossed pain-temperature findings with face on one side and body on the other?

Yes. This is a brainstem lateral sensory pattern.

No. Think cortex, medial tract, or non-brainstem lesion.

Are dysphagia, hoarseness, or decreased gag present without facial paralysis or hearing loss?

Yes. Lateral medulla.

No. Facial paralysis or hearing loss points one level up.

Make it stick

Hooks and Images

The memory anchor is floor plus nerve: medulla swallows, pons hears and moves the face.

Brainstem vessels · tap to expand

Crossed sensory · tap to expand

Stroke imaging · tap to expand

Board walkthrough

Prove It

One vignette at a time. Choices shuffle. The bank does not repeat until it is exhausted.

Vignette 1Never-repeat tracking ready

Exam tools: right-click or long-press to cross out a choice. Double-click or double-tap to highlight one. Tools switch off after you answer.