The co-occurrence of multiple sclerosis and migraine headache: the serotoninergic link.

The occurrence of migraine headaches in patients with multiple sclerosis (MS) has been recognized for quite some time but the significance of this association to the pathogenesis of MS largely has been ignored. Several reports have documented that migraine headaches may occur during exacerbation of symptoms and may even herald the onset of relapse in MS. We present three MS patients in whom migraine headaches developed during a period of relapse. As migraine has been linked to changes in serotonin (5-HT) functions, the emergence of migraine headaches coincident with the onset of relapse implicates dysregulation of the 5-HT system in the pathophysiology of MS. This hypothesis is plausible considering the evidence that MS patients are serotonergically depleted and that 5-HT is involved in maintaining the integrity of the blood brain barrier, disruption of which is believed to occur in the initial stages of exacerbation of MS symptoms. Furthermore, this hypothesis may have potential therapeutic implications in the treatment of exacerbations of MS and possibly in the prevention of relapse in the disease.