Diabetes insipidus as a rare cause of cognitive impairment in multiple sclerosis

Abstract

Multiple sclerosis is a complex neurodegenerative disease presenting with a diversity of clinical symptoms including palsy and cognitive impairment. We present a 59 year old woman with a history of secondary progressive multiple sclerosis since 1987 who was referred to our department because of recent onset of confusion and polydipsia. Initial lab tests showed mildly elevated serum sodium levels and low urine osmolality. Under water deprivation, diuresis and low urine osmolality persisted and serum sodium levels rose above 150 mmol/l. Oral desmopressin resulted in normalization of serum sodium as well as serum and urine osmolarity confirming a diagnosis of central diabetes insipidus. As drug induced diabetes could be excluded, pituitary MRI was performed. In comparison with a previous MR scan from two months earlier, a new demyelinating lesion was detected near the hypothalamus (Fig. 1). The patient was started on oral desmopressin treatment (0.2 mg/day) and fluid intake as well as serum sodium levels have since remained normal.