Adipsia in association with an arachnoid cyst

A hydrocephalic patient with recurrent hypernatremia due to impaired thirst in the presence of normal ADH responses, reported by Hays et al.,¹³ died at age 49 with multiple infections. Postmortem examination showed a large arachnoid cyst at the base of the brain that extended upward into the ventricular system producing partial obstruction of the foramina of Monro and perhaps of the cerebral aqueduct. The abnormalities of water and electrolyte balance most probably were due to compression of the hypothalamus, but a precise anatomical correlation was not possible.