Basilar Artery Migraine (BAM):
- Definition: A subtype of migraine with aura, characterized by symptoms referable to the brainstem and cerebellum, often due to vasospasm of the basilar artery.
- Key Symptoms:
- Vertigo, ataxia, dysarthria, tinnitus, diplopia, or bilateral visual disturbances (e.g., scotomas, hemianopia).
- Headache may be absent initially, but typically develops later.
- Diagnostic Criteria (IHS):
- At least two attacks fulfilling criteria A–D.
- Aura symptoms develop over ≥5 minutes, last 5–60 minutes, and are not better explained by another disorder.
- At least three of the following: dysarthria, vertigo, tinnitus, decreased hearing, diplopia, ataxia, decreased level of consciousness, or bilateral paresthesias.
- Not attributed to another disorder.
- Differential Diagnosis:
- Basilar Artery Occlusion (BAO): Sudden onset of brainstem symptoms (e.g., crossed hemiparesis, cranial nerve palsies) with prolonged deficits (>24 hours), often with imaging evidence of infarction.
- Vertebrobasilar TIA: Symptoms similar to BAM but shorter duration (5–30 minutes), often repetitive.
- Posterior Circulation Stroke: Persistent deficits, often with imaging confirmation.
- Management:
- Acute: Triptans (e.g., sumatriptan 6 mg SC) or dihydroergotamine 1 mg IV (if no contraindications).
- Prophylaxis: Beta-blockers (e.g., metoprolol), calcium channel blockers (e.g., verapamil), or topiramate (if vascular risk factors are absent).
- Avoid vasoconstrictors (e.g., ergotamines) in suspected BAO.
- Rationale: BAM is a functional disorder with reversible vasospasm, while BAO/TIA/stroke require urgent vascular workup (e.g., MRI/MRA, echo, Holter) and secondary prevention (e.g., antiplatelets, statins).
Key Distinction:
- BAM: Symptoms resolve without infarction; no vascular risk factors typically present.
- BAO/TIA/Stroke: Persistent deficits, vascular risk factors, and imaging abnormalities.