Cervical sympathetic deficit in unilateral migraine headache

Area of Science:

• Neurology
• Ophthalmology
• Pain Medicine

Background:

• Migraine is a common neurological disorder characterized by recurrent headaches.
• The role of the autonomic nervous system, particularly the sympathetic nervous system, in migraine pathophysiology is not fully understood.
• Previous studies have suggested potential involvement of the cervical sympathetic system in migraine.

Purpose of the Study:

• To investigate cervical sympathetic function in migraine sufferers during headache-free intervals.
• To explore the relationship between sympathetic activity and migraine side recurrence.
• To assess for adrenergic supersensitivity in the pupils of migraine patients.

Main Methods:

• Pupil diameter was measured in 38 migraine sufferers and 40 controls during headache-free periods.
• Pharmacological testing with cocaine, tyramine, and phenylephrine eyedrops was used to assess sympathetic function.
• Anisocoria (unequal pupil size) and pupillary responses were analyzed.

Main Results:

• Migraine sufferers showed greater anisocoria than controls, but miosis (pupil constriction) was not consistently greater on the usual headache side.
• A subgroup of migraineurs exhibited pupillary dilation lag and persistent miosis after cocaine, suggesting reduced sympathetic outflow.
• Reduced pupillary dilation to tyramine in migraineurs indicated decreased post-ganglionic sympathetic fiber function, but phenylephrine response was normal, ruling out adrenergic supersensitivity.

Conclusions:

• A subgroup of migraine sufferers may have reduced cervical sympathetic outflow on the side of their usual headache.
• This sympathetic deficit could be due to dysfunction of post-ganglionic sympathetic fibers, possibly related to carotid artery changes.
• Impaired sympathetic vascular tone may exacerbate vasodilatation and pain during migraine attacks.