[Neuromyelitis optica with syndrome of inappropriate secretion of antidiuretic hormone and hypersomnia associated with bilateral hypothalamic lesions: a case report].

A 31-year-old woman with a 5-year history of recurrent optic neuritis and encephalomyelitis underwent repeated steroid therapy. She developed general malaise and fever in October 2009. Laboratory tests revealed marked reduction in serum Na (106 mEq/L). Because the plasma osmotic pressure was lower than the urinary osmotic pressure and the serum antidiuretic hormone (ADH) level was elevated, she was diagnosed with the syndrome of inappropriate secretion of antidiuretic hormone (SIADH). Magnetic resonance imaging (MRI) revealed high signal intensities on symmetrical T2 weighted and fluid attenuated inversion recovery (FLAIR) images of both sides of the hypothalamus. The serum samples tested positive for the antibody to aquaporin-4 (AQP4). Previously conducted cervical MRI had revealed a longitudinally extending lesion in the cervical cord, and brain MRI had revealed brainstem lesions. We diagnosed the patient with neuromyelitis optica (NMO) according to the revised diagnostic criteria for NMO proposed by Wingerchuk in 2006. Furthermore, she complained of excessive daytime sleepiness. The concentration of orexin in the cerebrospinal fluid was mildly reduced and the orexin levels returned to normal when her sleepiness decreased. ADH and orexin neurons localized in the hypothalamus; hence, we considered the above-mentioned symptoms to be caused by bilateral hypothalamic lesions.