Out-of-third ventricle colloid cysts: review of the literature on pathophysiology, diagnosis and treatment of an uncommon condition, with a focus on headache

Abstract

Colloid cysts are rare benign intracranial lesions classically described as "third ventricle colloid cysts" because of their location within the third ventricle. These lesions' clinical and diagnostic features are mainly related to intermittent or persistent obstruction of foramina of Monro causing cerebrospinal fluid (CSF) circulation impairment and symptoms of raised intracranial pressure. Few reports on colloid cysts located outside the third ventricle have been published over the years. This paper aims to review the existing literature on out-of-third ventricle colloid cysts, and introduces a new illustrative case of lateral ventricle colloid cyst surgically managed with endoscopic technique. A literature review was performed through a Medline web-search, using "colloid cysts," "lateral ventricle colloid cysts," "fourth ventricle colloid cysts," "brain colloid cyst," "spinal colloid cysts" as keywords. All retrieved abstracts were screened and full-length text of papers suitable for inclusion were examined. An illustrative case has been added to the existing literature. A 45-year-old man complaining of recurrent headache underwent conservative treatment for 4 years. The unusual headache features as well as the uncommon onset and association with episodic mental impairment led to an initial diagnosis of anxiety disorder triggering the headache. A further worsening of headache and the lack of significant clinical benefit prompted further investigation. Computed-tomography (CT) of the brain showed asymmetrical dilatation of the right lateral ventricle, due to the presence of a cystic mass obstructing the foramen of Monroe. Patient underwent endoscopic resection of the cyst. The literature review revealed 16 papers reported between 1952 and 2016. In all cases included histological diagnosis of colloid cyst had been obtained. Clinical and radiological features, as well as surgical management in each case have been analyzed. In the case here reported, histological examination documented a colloid cyst. The postoperative course was uneventful, with progressive resolution of headache. Despite third ventricle colloid cysts are related to typical clinical and diagnostic features, non-third ventricle colloid cysts may be responsible for unusual clinical presentation, so making a correct diagnostic approach challenging. We submit that in cases of recurrent headache with unusual features and lacking signs of neurological deficits, a rare neurosurgical condition as an "ectopic" colloid cyst should be included in the differential diagnosis.