Although relapses of multiple sclerosis occur unpredictably and at odd intervals, two factors have been identified that may trigger an exacerbation: viral infections and the puerperium.1 2Viral infections probably act through a release of inflammatory cytokines, such as interferon-γ (INF-γ), that stimulate the immune system and facilitate the entry of activated T lymphocytes into the CNS.1 Relapses during the puerperium are likely to be precipitated by changes in the hormonal milieu after delivery.2 We report on three patients with multiple sclerosis in whom successive exacerbations occurred exclusively during the premenstrual period.

Patient 1, a 21 year old women student sought evaluation for episodes of alternating right and left sided paraesthesias, which existed for about 4 months. She also complained of fatigue. There was a history of infectious mononucleosis 6 years earlier. She did not use an oral contraceptive. Neurological examination showed hyperreflexia and Babinski’s sign in the right leg. Magnetic resonance imaging of the brain showed multiple white matter lesions on T2 weighted sequences, mainly in the left occipital and right parietal lobe. Oligoclonal bands were present in the CSF. One month later she was admitted to hospital because of weakness in the left leg, urge incontinence, and diminished sensation below Th7. Symptoms had started 3 days before her menstruation. She was treated with 1 g/day intravenous methylprednisolone for 5 days with rapid improvement over the next …