[Hypothalamic involvement in multiple sclerosis].

Hypothalamic involvement is a rare condition in patients with multiple sclerosis (MS). We report two patients with a long history of MS who presented with severe acute hypothermia with associated thrombocytopenia and elevated transaminase levels. Several cases of hypothermia or hyperthermia in patients with MS have been reported in the literature. They could be linked with hypothalamic lesions, in particular in the pre-optic area. However, other anatomical locations seem to be involved in thermoregulation and can be affected by MS. Besides, some cases of syndrome of inappropriate antidiuretic hormone secretion have been reported in patients with MS. Finally, some sleep disorders, particularly hypersomnia or narcolepsy, could be related to hypothalamic lesions, through the fall in hypocretin-1 in the cerebrospinal fluid. Hypocretin-1 is a neuropeptide that is secreted by some hypothalamic cells. It plays a role in the sleep-awake rhythm. We report one patient with narcolepsy and cataplexy before the first symptoms of MS appeared. Hypothalamic signs are rare in MS. However, several series of autopsies have shown a high frequency of demyelinating lesions in the hypothalamic area. Among these lesions, the proportion of active lesions seems elevated. Yet only few of them have a clinical or biological translation such as thermoregulation dysfunction, sleep disorders or natremia abnormalities. Thus, it seems unlikely that inflammatory hypothalamic lesions alone, even when bilateral, could be the explanation of these signs. A sufficient number of inflammatory demyelinating lesions, which we can observe in patients with a long history of MS and an already severe disability, is probably necessary to develop such a rare symptomatology. Hypothalamic signs might be a factor of poor prognosis for the disease course and progression of the disability.