Basilar Migraine

Dizzy 2
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Diagnosis and reasoning

This teenager has presented with a headache of acute onset, in a background of similar headaches recently, i.e. this is an acute recurrent headache. Migraine is by far the most common cause of acute recurrent headaches in this age group; the occipitofrontal location, throbbing nature, and presence of dizziness and blurring of vision are further supportive of this diagnosis, and additionally suggest that this is a basilar migraine. Note that the absence of an aura in no way excludes this diagnosis; Migraine without aura is common at this age. There are two other common diagnoses which might also be considered: tension headache and sinusitis. While nausea, dizziness and blurring of vision are not common in either condition, they are not unknown either. Individuals with tension headache typically complain of a band like sensation around the head; there may also be facial or neck muscle tenderness and/or nuchal rigidity. The absence of these clinical findings argue against this diagnosis. Sinusitis is less likely, given the absence of upper respiratory tract symptoms in the past, and absence of sinus tenderness. In addition, two other rare, but important diagnoses also need to be given thought: an intracranial space occupying lesion (SOL) and cerebral hemorrhage (possibly secondary to an aneurysm or arteriovenous malformation - AVM). The history lacks red flag symptoms which would suggest an SOL (such as early morning headache, vomiting in the morning, headache disturbing sleep, or worsening of the headache upon coughing); note also that the headache of SOL is typically chronic and progressive. The history here is not typical of cerebral hemorrhage (although there is a remote possibility that the episodes could be 'breakthrough' bleeds from an aneurysm or AVM). Note that current guidelines do not recommend further investigations in patients with clear-cut migraine and an unremarkable neurological examination. This is because the overwhelming majority of studies evaluating the role of neuroimaging in young patients with headache have demonstrated no abnormal findings. Thus, an MRI is unnecessary here. A lumbar puncture would have been indicated if a subarachnoid hemorrhage (SAH) or CNS infection were suspected. EEGs are of little use in the diagnosis of migraine. Prompt pain relief is essential here; an NSAIDs (such as Indomethacin) is ideal. Note that triptans are best avoid, as this may trigger cerebral vasoconstriction. An anti-emetic will provide additional symptomatic relief. Preventive therapy with Verapamil is recommended if the headaches are frequent, prolonged, or debilitating (causing functional disability). Considering his overall history, this is probably justified here.


Discussion

Basilar-type migraine (BTM) also known as Bickerstaff syndrome, basilar artery migraine, brainstem migraine or vertebrobasilar migraine is a rare variant of migraine where the primary signs and symptoms refer to the brainstem or both cerebral hemispheres, without motor weakness. Note that the term 'basilar artery migraine' is erroneous as it implies that the basilar artery is the origin of the migraine. BTM may affect any gender at any age; there is a slight female predominance. Patients with BTM may experience a headache along with or after an aura; the most common aura is vertigo. Other symptoms such as diplopia, visual symptoms, dysarthria, hyperacusis, ataxia, decreased level of consciousness, and bilateral (simultaneous) paresthesias and tinnitus may also be noted. The international headache society (IHS) released a set of guidelines for the diagnosis of BTM in 2004; these state that at least 2 attacks with the following characteristics are required: 1. at least two of the above (fully reversible) aura symptoms 2. at least one of the following i. at least one aura symptom which develops gradually over ≥5 minutes and/or different aura symptoms which occur in succession over ≥5 minutes ii. each aura symptom lasts ≥5 and ≤60 minutes 3. a headache fulfilling the criteria for migraine without aura, which begins during the aura or which follows the aura within 60 minutes. Note that if motor weakness is present, the clinician should be very careful about entertaining a diagnosis of BTM, as basilar-type symptoms occur in 60% of patients with familial or sporadic hemiplegic migraine. BTM is a clinical diagnosis; investigations are mainly of use in excluding other serious illnesses which may present in a similar fashion. Neuroimaging helps rule out intracranial SOL, brainstem AVMs, vertebrobasilar disease and stroke. This is ideally performed via a contrast-enhanced MRI of the brain; however, if recent bleeding is a concern, a CT brain should be performed first. An EEG is required in cases where there is alteration of consciousness, confusion or new onset symptoms, in which case epilepsy or encephalitis may be considered. Historically, patients with BTM were advised not to use triptans or ergotamines as it was thought that BTM was due to basilar artery spasm, which would be worsened by the vasoconstrictive effects of these drugs. As a result, there are very few trials showing efficacy of these drugs in BTM. However, a study by Klapper, Mathew and Nett has shown that triptans may be used safely in patients with BTM. However, given the absence of any other studies, most clinicians still prefer to avoid these drugs. Due to the same reason, beta-blockers have also been historically avoided; there is very limited evidence regarding their safety and efficacy. Thus, most clinicians use NSAIDs (such as aspirin, ibuprofen, naproxen, or diclofenac) with an antiemetic (metoclopramide, chlorpromazine, or prochlorperazine) to treat acute BTM; a non-oral route is preferred if the patient presents early with significant nausea or vomiting. Regardless of the medication prescribed, it is important that the patient understands the condition and their treatment as well as the fact that abortive therapy in an acute attack is more effective if taken early in the course of headache as a single large dose. Preventive therapy should be encouraged in patients suffering from frequent, prolonged or debilitating attacks; verapamil or topiramate are recommended for this group. The symptoms of BTM can be disabling at times due to their severity; however, these are usually more frightening than harmful - thus proper patient education is an important step in the long term management.


Take home messages

  1. BTM is a rare subtype of migraine.
  2. Absence of motor weakness is essential for the diagnosis.
  3. The lack of supporting evidence for triptans limits their use in these patients.
  4. Proper patient education on the benign nature of the disease is important.

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