Intraventricular neurocytoma presenting as Kleine-Levin syndrome: resolution after resection and review of neurosurgical conditions associated with hypersexuality. Illustrative case

Background: Kleine-Levin syndrome (KLS) is a rare disorder characterized by recurrent episodes of hypersomnia associated with one or more of the following: cognitive impairment, hyperphagia, hypersexuality, apathy, and derealization/altered perception. Headache and/or vomiting may precede the onset of hypersomnia. KLS secondary to lesions of neurosurgical interest is extremely rare and has been described once after hemorrhage complicating the endoscopic removal of a colloid cyst. Observations: A 25-year-old man, with no personal or family history of neuropsychiatric disorders, developed hypersomnia, apathy, and hypersexual behavior. Six months after the onset of the symptoms he became unable to stand without help and was admitted to the authors' hospital. Contrast-enhanced CT performed at admission and later contrast-enhanced MRI revealed an intraventricular mass extending from the right lateral ventricle to the third ventricle. The tumor was removed through a right frontal transcortical approach, and the pathological diagnosis was atypical neurocytoma. After surgery, all symptoms suggestive of KLS disappeared. Lessons: Compression by an intraventricular mass on the septal area, diencephalon, and hypothalamus may induce secondary KLS (sKLS). Tumor removal can relieve the syndrome. Hypersexualty and sKLS were reported more frequently with neurosurgical diseases of the right hemisphere, but the number of cases reported is insufficient to reach a conclusion and further observations are needed. https://thejns.org/doi/10.3171/CASE25800.