User:Skittleys/ICHD classification and diagnosis of migraine

Migraine with aura
The second-most common form of migraine goes by many names (including any of classic, ophthalmic, aphasic, hemiplegic, hemiparaesthetic or complicated migraine, as well as migraine accompagn&eacute;e), but is referred to in the ICHD-2 simply as migraine with aura. The hallmark characteristic of this class is the aura, a temporary neurological perceptual disturbance that can take many forms. The aura usually occurs for less than 60 minutes, with a 5-20 minute "development" period, and is not necessarily followed by a migraine headache or even any headache at all.

Migraine with aura comes in many varieties, as outlined below. The generalized ICHD-2 diagnostic criteria required for each of these diagnoses appear to the right.

Often, a person who suffers from migraine with aura with also have migraine without aura, and will be diagnosed with both.

In migraine with aura, the aura may or may not be accompanied by other premonitory signs. These symptoms include fatigue, blurred vision, photophobia, phonophobia, neck stiffness, yawning and pallor, and may begin as early as 2 days before the attack itself.

It was once believed that aura only accompanied migraine headaches or epileptic seizures. In recent years, aura in conjunction with other headache types, particularly cluster headaches, have been described.

Pathophysiologically, it appears that the aura is attributable to the cortical spreading depression phenomenon described by Brazilian scientist Aristides Leão. Blood flow in the affected cortical region decreases, often to above the ischaemic threshold; after several hours, blood flow increases, transitioning into hyperaemia, before eventually returning to normal.

The term hemiparaesthetic migraine refers to aura symptoms experienced in the limbs. This almost always occurs in conjunction with a visual aura, however. The IHS has deemed this distinction "probably artificial", and only recognizes it under migraine with visual aura. However, where motor system weakness is involved, a patient is likely to be diagnosed with familial hemiplegic migraine or sporadic hemiplegic migraine.

Typical aura with migraine headache
Typical aura with migraine headache is the most common and well-recognized form of migraine with aura.

Historically, this was a straightforward diagnosis. However, it has now been compounded by recent evidence that other types of headaches also occur in conjunction with aura (see above). Also, an aura may be secondary to a potentially life-threatening medical problem such as a carotid dissection, seizure or arteriovenous malformation.

The aura will involve at least one of a visual, sensory or speech disturbance. As mentioned above, other symptoms (e.g., symptoms in the extremities may be involved, but appear in conjunction with one of these 3 types.

Auras are most often visual in nature. Numerous kinds of visual aura have been reported over the centuries, including "zig-zags" (a scintillating scotoma or fortification spectrum), visual snow, spots of various colours, and more.

...[Other potential aura criteria:]
 * Fully reversible motor weakness...
 * Each aura symptom lasts [from] 5 minutes [to] 24 hours...
 * [In the case of a "Basilar-type" migraine], Dysarthria [difficulty speaking], vertigo [dizziness], tinnitus [ringing in the ears], [and other symptoms].

Basilar type migraine
Basilar type migraine (BTM) (previously basilar artery migraine [BAM] and basilar migraine [BM]) is an uncommon, complicated migraine with symptoms caused by brainstem dysfunction. Serious episodes of BTM can lead to stroke, coma, and death. Using triptans and other vasoconstrictors as abortive treatments for BTM is contraindicated. Abortive treatments for BTM address vasodilation and restoration of normal blood flow to the vertebrobasilar territory to restore normal brainstem function.

Familial and sporadic hemiplegic migraine
Familial hemiplegic migraine (FHM) is migraine with a possible polygenetic cause—in fact, FHM can only be diagnosed when at least one close relative has it too. The patient experiences typical migraine with aura headache either preceded or accompanied with one-sided, reversible limb weakness and/or sensory difficulties and/or speech difficulties. FHM is associated with ion channel mutations.

There also exists the "sporadic hemiplegic migraine" (SHM), which is the same as FHM but with no close family members showing the symptoms.

Effecting a differential diagnosis between basilar migraine and hemiplegic migraine is difficult. Often, the decisive symptom is either motor weakness or unilateral paralysis, which occur in FHM and SHM. Basilar migraine can present tingling and numbness, but true motor weakness and paralysis occur only in hemiplegic migraine.