Posterior fossa stroke (cerebellar / lateral medullary)
Overview
Summary
Stroke involving the cerebellum or brainstem can mimic peripheral acute vestibular syndrome but is identified by central exam features. AICA strokes can also produce hearing loss — making this the dangerous mimic of labyrinthitis.
Diagnostic criteria
See the Bárány Society / clinical practice guideline papers[21,22,1] listed on the references page for the consensus diagnostic framework used in this profile.
Epidemiology
~3% of ED dizziness presentations are stroke; up to 25% of acute vestibular syndrome.
Pathophysiology
Ischemia in the PICA, AICA, or SCA territories. PICA: lateral medulla / inferior cerebellum (Wallenberg). AICA: lateral pontomedullary / AICA-supplied labyrinth (can mimic labyrinthitis). SCA: superior cerebellum.
Prognosis
Cerebellar infarcts can swell and herniate — neurosurgical decompression life-saving.
Key examination findings
- ◆HINTS DANGEROUS pattern: NORMAL head impulse OR direction-CHANGING nystagmus OR skew deviation
- ◆Often direction-changing horizontal nystagmus, vertical or torsional nystagmus, gaze-evoked nystagmus
- ◆Skew deviation on alternate cover test
- ◆Limb dysmetria, dysarthria, Horner's, hemisensory loss (Wallenberg)
- ◆AICA stroke: ipsilateral hearing loss + central features
Investigations
- ▸HINTS+ at bedside (sensitivity for stroke in AVS approaches 100% when performed by trained clinician — exceeds early MRI-DWI).
- ▸MRI-DWI: gold standard but ~12–20% false-negative in first 48 h for posterior circulation stroke.
- ▸CTA / MRA to identify vertebrobasilar disease and dissection.
Management
- ●Standard acute stroke pathway: thrombolysis if eligible and within window.
- ●Posterior circulation thrombectomy for proximal vertebrobasilar occlusion is increasingly used.
- ●Admit to stroke unit; secondary prevention based on etiology.
Clinical pearls
- ★An AICA stroke can present indistinguishably from labyrinthitis (vertigo + sudden hearing loss + nystagmus); HINTS+ catches them.
- ★Patients with persistent severe imbalance who CAN'T walk usually have a central lesion.