# Antidiuretic hormone deficiency secondary to inactive hydrocephalus: a case report

## TL;DR

A 13-year-old boy with polyuria and high sodium levels was diagnosed with diabetes insipidus caused by inactive hydrocephalus and a third ventricular cyst.

## Contribution

This case report highlights central diabetes insipidus caused by inactive hydrocephalus, emphasizing the need for thorough investigation.

## Key findings

- The patient had elevated serum sodium and suppressed potassium with low urine osmolarity, indicating diabetes insipidus.
- MRI revealed inactive hydrocephalus and a third ventricular cyst compressing the pituitary gland.
- The case suggests that dormant hydrocephalus can lead to antidiuretic hormone deficiency.

## Abstract

Diabetes insipidus is a syndrome characterized by polyuria, which is almost always associated with polydipsia. The most frequent cause is central diabetes insipidus, which is the result of an inadequate secretion of the antidiuretic hormone, and diagnosis involves differentiating it from other causes of polyuria and polydipsia.

Here, we present a clinical case of a previously healthy 13-year-old Nepali boy, who, in December 2022, was found to have intense polydipsia accompanied by polyuria. He had bilateral lower limb weakness at the time of presentation. Biochemical evaluation demonstrated raised serum sodium (181 mEq/L), serum creatinine (78 μmol/L), and serum uric acid (560 μmol/L) with suppressed serum potassium (2.7 mEq/L), which was the major concern to the clinicians. Further laboratory workup revealed an increased serum osmolarity (393.6 mOsm/kg) with reduced urine osmolarity (222.7 mOsm/kg). On contrast magnetic resonance imaging of the brain, a thick-walled third ventricular cyst with bilateral foramen obstruction, thin membrane-like structure at top of aqueduct of Sylvius with gross obstructive hydrocephalus (inactive), and compressed and thinned pituitary gland with no bright spot was observed. The laboratory findings, radiological findings, and case presentation provided the provisional diagnosis of diabetes insipidus due to hydrocephalus and third ventricular cyst.

Central diabetes insipidus due to hydrocephalus, though rare, can have serious complications including the predilection to develop a deficit of other pituitary hormones. Thus, even if hydrocephalus is dormant with normal intracranial pressure, it must be addressed during investigations of central diabetes insipidus.