Clinical Assessment: Posterior Circulation Stroke / Recurrent Ischemic Event

1. Differential Diagnosis (Priority Order)

Dizziness (vertigo), nausea, and vomiting involving vestibular nuclei, cerebellum, or inner ear are cardinal warning signs of vertebrobasilar ischemia. — Neuroanatomy through Clinical Cases, 3rd Ed.

2. Immediate Workup

Urgent Imaging

• Non-contrast CT head — first to exclude hemorrhage (but note: up to 25% of cerebellar infarctions are CT-negative, especially early)
• Diffusion-weighted MRI (DWI) — if initial CT unremarkable and cerebellar infarction is suspected, this is the gold standard and should be obtained emergently
• CT angiography or MR angiography — to characterize vertebrobasilar vascular lesion (stenosis, thrombosis, dissection) once diagnosis is confirmed

"Because up to 25% of non-contrasted head CTs can be normal in cerebellar infarction, if the initial noncontrasted head CT is unremarkable, obtain an emergent diffusion-weighted MRI when this diagnosis is suspected." — Tintinalli's Emergency Medicine

Clinical Evaluation

• Full neurological exam: gaze palsy, nystagmus, ataxia, dysmetria, dysarthria, altered consciousness — these are the key signs
• Glasgow Coma Scale — impaired alertness signals brainstem compromise
• NIHSS score
• Serial examinations — cerebellar edema can cause rapid unexpected deterioration

Labs

• CBC, BMP, coagulation panel, glucose (hypoglycemia mimics stroke)
• ECG (cardioembolic source — AF)
• Cardiac biomarkers
• Lipid panel, HbA1c

3. Blood Pressure Management

"BP should not be lowered acutely unless necessary for treatment of acute coronary syndrome, CHF, hypertensive crisis with end-organ involvement, or systolic BP >220 mmHg or diastolic BP >120 mmHg. BP lowering should proceed cautiously, with 15% reduction during the first 24 hours being a reasonable goal." — Washington Manual of Medical Therapeutics

"Aggressive lowering of BP has been associated with neurologic deterioration." — Washington Manual

"Permissive hypertension should be allowed after stroke because reduction of cerebral perfusion pressure (CPP) could compromise the ischemic penumbra." — Barash Clinical Anesthesia, 9e

• If no hemorrhage on CT and SBP <220: permissive hypertension — do not aggressively lower
• If hemorrhagic transformation or hypertensive emergency features present: cautious reduction
• Restart or adjust antihypertensives only after the acute phase (24–48h) unless BP is critically elevated

4. Acute Treatment

Thrombolysis

• If within 4.5 hours of symptom onset and no contraindications → IV alteplase (t-PA) is indicated
• "Generally, administration of t-PA must commence within 4.5 hours of stroke onset… do not delay to see if the patient gets better if they present early in the window." — Washington Manual
• BP must be <185/110 before administering t-PA

Thrombectomy

• If large vessel occlusion (basilar artery, vertebral artery) identified on CTA → urgent endovascular thrombectomy consideration (within 6–24h depending on imaging)

Neurosurgical Consultation — CRITICAL in cerebellar stroke

• Immediate neurosurgical consultation is mandatory given prior cerebellar stroke
• Cerebellar edema can compress the 4th ventricle → obstructive hydrocephalus or compress the brainstem → herniation
• Two syndromes to watch:
  • Tonsillar herniation (downward) → neck stiffness, opisthotonus, apnea
  • Upward transtentorial herniation → coma, upward gaze palsy, fixed pupils
• If raised ICP/herniation: mannitol or hypertonic saline + emergency posterior fossa decompression

"Cerebellar edema can lead to rapid deterioration with herniation, and consultation is required to determine the need for emergency posterior fossa decompression." — Tintinalli's Emergency Medicine

5. Secondary Prevention (Chronic Management)

"Aspirin is effective, inexpensive, and safe… Meta-analyses have shown that aspirin reduces the combined relative risk for stroke, MI, and vascular death by approximately 25%." — Bradley & Daroff's Neurology in Clinical Practice

6. Monitoring & Disposition

• ICU or high-dependency unit admission
• Serial neurological exams every 1–2 hours — watch for gaze palsy (horizontal gaze palsy = pontine involvement) and altered consciousness = deterioration
• Head of bed at 30° (reduces ICP without compromising CPP)
• Continuous telemetry, pulse oximetry, euglycemia maintenance
• NPO until dysphagia/aspiration risk assessed (posterior circulation strokes frequently cause dysphagia)
• DVT prophylaxis

Summary: Red Flags Requiring Immediate Action

• New gaze palsy, worsening consciousness → urgent neurosurgical consultation for possible decompression
• BP >220/120 → cautious pharmacologic reduction
• Within thrombolysis window → BP <185/110 and give alteplase if eligible
• Basilar thrombosis on CTA → emergent thrombectomy referral

— Tintinalli's Emergency Medicine, Neuroanatomy through Clinical Cases 3rd Ed., Localization in Clinical Neurology 8e, Washington Manual of Medical Therapeutics, Bradley & Daroff's Neurology in Clinical Practice