Acute decompensation of chronic hydrocephalus following elective abdominal surgery presenting as paroxysmal sympathetic hyperactivity: illustrative case.

Background: The management of asymptomatic untreated chronic hydrocephalus in adults remains controversial. Acute deterioration is uncommon. However, decompensation of stable patients has been described following trauma, physical activity, medical procedures, or Valsalva maneuvers. The authors report a case of acute decompensation after elective abdominal surgery in an adult with chronic hydrocephalus with an unusual clinical presentation of paroxysmal sympathetic hyperactivity.

Observations: The decompensation manifested as episodes of paroxysmal sympathetic hyperactivity associated with features of dorsal midbrain impairment. The patient presented with transient episodes of decreased level of consciousness, tachycardia, hypertension, flushing, and sweating. He had upgaze restriction, lack of convergence, and pupillary dilatation, and his pupils were unresponsive to light. There was no structural change on brain imaging. The sympathetic hyperactivity and oculomotor abnormalities resolved with CSF diversion, and the patient made a complete neurological recovery.

Lessons: Patients with chronic untreated hydrocephalus can decompensate due to increased physiological stress. Adult patients with untreated chronic hydrocephalus should be counseled about this possibility and evaluated carefully by a multidisciplinary team before consenting to major elective surgery. The presentation of acute decompensation can include paroxysmal sympathetic hyperactivity, which should be diagnosed and treated urgently, even if there is no radiological evidence of ventricular change. https://thejns.org/doi/10.3171/CASE2547.