A Boy with Reset Osmostat Who Developed Chronic Hyponatremia due to Hypothalamic Injury Caused By a Giant Arachnoid Cyst.

Reset osmostat (RO) is classified as type C among the four subtypes of the syndrome of inappropriate secretion of antidiuretic hormone based on antidiuretic hormone (ADH) secretion. It is characterized by a lower plasma osmolality threshold for ADH excretion when plasma sodium concentration is reduced. We report the case of a boy with RO and a giant arachnoid cyst (AC).

Acute purulent meningitis associated with chronic subdural hematoma and subdural hygroma.

A male infant aged nine months with meningeal irritation and +3.5SD expansion of the circumference of the head was admitted. Brain computed tomography (CT) detected right chronic subdural hematoma and contralateral subdural hygroma.