Posterior Circulation Stroke with Basilar Junction Occlusion

Anatomy and Vascular Territory

Clinical Presentation

Cardinal Features of Complete Basilar Occlusion

• Bilateral long-tract signs (motor + sensory)
• Cranial nerve deficits (multiple levels: V, VI, VII, VIII, III/IV)
• Cerebellar/vestibular signs: vertigo, nausea, vomiting, nystagmus, ataxia
• Altered consciousness (reticular activating system involvement)
• Pontine myoclonus: spontaneous repetitive, multifocal posturing movements that mimic seizure but are NOT epileptic

Locked-In Syndrome

• Quadriplegia (corticospinal tract bilateral involvement)
• Anarthria (corticobulbar tract)
• Consciousness preserved (reticular activating system spared)
• Voluntary eye movements and blinking may be the only motor output remaining
• Caused by basis pontis lesion

Level-Specific Syndromes at Basilar Junction

• Ipsilateral CN VI/VII palsy + contralateral hemiparesis
• Internuclear ophthalmoplegia (MLF involvement)
• Gaze palsy (ipsilateral pontine gaze center)
• Bilateral involvement → locked-in syndrome
• Pain/temperature loss (spinothalamic)

• CN III palsy + contralateral hemiparesis = Weber's syndrome (cerebral peduncle)
• CN III palsy + contralateral ataxia = Claude's syndrome (red nucleus involvement)
• Bilateral CN III palsy, coma, pupils fixed and dilated
• Vertical gaze palsy (rostral interstitial nucleus of MLF)

• Memory disturbance (bilateral thalamic infarction - "thalamic dementia")
• Hypersomnia, altered alertness
• Bilateral involvement of Percheron's artery territory

Superior Cerebellar Artery (SCA) Occlusion

• Ipsilateral: severe cerebellar ataxia, dysarthria, Horner's syndrome, palatal myoclonus
• Contralateral: loss of pain and temperature (spino- and trigeminothalamic tracts)
• Large SCA infarcts may cause brainstem compression and require neurosurgical decompression

Etiology

1. Atherothrombosis - most common at proximal basilar/distal vertebral junction; may be preceded by TIAs or a slowly progressive fluctuating deficit
2. Cardioembolism - more typical for "top of the basilar" (distal occlusion)
3. Vertebral artery dissection - may extend into the basilar; produces multiple penetrating artery strokes depending on true/false lumen location
4. Fibromuscular dysplasia

A series of TIAs and a slowly progressive, fluctuating stroke are extremely significant because they often herald an atherothrombotic occlusion of the distal vertebral or proximal basilar artery. - Harrison's, p. 3477

Diagnosis

• Noncontrast CT: may show basilar hyperdensity sign ("dense basilar sign") - highly specific but poorly sensitive
• CT Angiography (CTA): rapid detection of basilar thrombosis - first-line confirmation; can also assess pc-ASPECTS (posterior circulation ASPECTS score) on CTA source images
• MRI/DWI: best for brainstem infarct detection; CT underestimates posterior fossa ischemia
• CT Perfusion or MR Perfusion: identifies salvageable penumbra to extend time window
• pc-ASPECTS: scoring system on CTA/DWI - each point loss (from 10) corresponds to ischemia in thalamus, cerebellum, or posterior white matter territories

Management

Acute Reperfusion

• Standard window: within 4.5 hours of symptom onset (AHA criteria)
• For basilar artery occlusion: IV tPA may be attempted in patients with coma of brief duration and without extensive thrombosis
• The BASICS trial (2022) extended thrombolysis to 24 hours for basilar occlusion - [referenced in Goldman-Cecil Medicine]
• Dose: 0.9 mg/kg (max 90 mg), 10% as bolus, 90% over 60 min
• Tenecteplase (0.25 mg/kg bolus) is now preferred as an alternative given simpler administration for bridging to thrombectomy

• For basilar artery occlusion: EVT is the most important intervention
• Several major RCTs (BEST, BASILAR, ATTENTION, BAOCHE) have now demonstrated benefit of EVT over medical therapy alone
• The 2026 meta-analysis by Bouslama et al. (PMID 37005965) confirmed mechanical thrombectomy superiority over medical management for acute basilar artery occlusions
• Time is critical: odds of good outcome >3× if groin puncture within 2 hours; only ~1/3 achieve good outcome if 6 hours elapse
• Collateral status matters: Meta-analysis (Liu et al., 2023) confirmed good collaterals on CTA/MRA are associated with significantly better EVT outcomes
• Extended window up to 24 hours is acceptable with favorable perfusion imaging (DAWN/DEFUSE 3 criteria principles applied to posterior circulation)

Supportive and Secondary Prevention

• Blood pressure: permissive hypertension acutely (do not aggressively lower before reperfusion); target <140/90 after stabilization
• Antiplatelet therapy: aspirin +/- clopidogrel (dual antiplatelet for 21 days for minor stroke/high-risk TIA per CHANCE/POINT trials)
• Anticoagulation: if cardioembolic source (AF), initiate after hemorrhagic transformation window
• Statin: high-intensity statin regardless of baseline LDL
• Temperature management: avoid hyperthermia
• Neurosurgical consult: for large cerebellar infarcts causing brainstem compression or obstructive hydrocephalus

Key Clinical Pearls

1. Complete basilar occlusion = neurological emergency with very high mortality if untreated - rapid CTA is mandatory
2. The symptom pattern of INO + gaze palsy + bilateral motor signs is pathognomonic for posterior circulation stroke
3. Pontine myoclonus (repetitive multifocal movements) in the context of brainstem stroke must NOT be treated as seizures
4. Unilateral basilar branch occlusion reduces concern for imminent total occlusion; bilateral signs escalate urgency dramatically
5. Vertigo + headache + ataxia (the "posterior circulation triad") should prompt CTA even in young patients - do not dismiss as labyrinthitis without imaging
6. Locked-in syndrome is not brain death - these patients are conscious and require communication assessment (eye coding)