Interhemispheric transcallosal approach for hemorrhagic colloid cyst.

[BACKGROUND] Colloid cysts of the third ventricle are rare representing approximately 2% of all intracranial lesions and 15-20% of all intraventricular lesions, which typically grow in the region of the foramen of Monro. They consist of an outer layer of fibrous tissue and an inner epithelium of mucin-producing cells and many authors have supported an endodermal origin. More than half of patients with colloid cysts of the third ventricle are symptomatic at the time of diagnosis and most of them have symptoms of hydrocephalus, which include headache, nausea, vomiting, blurred vision, gait ataxia, and cognitive decline. Although a major historical concern, sudden deterioration and death is rare and almost all patients with obstructive hydrocephalus experience progressive symptoms for at least several days. However, a rare case of acute intracystic hemorrhage may prevent insidious onset and may be a potential cause of acute clinical deterioration. Surgery for symptomatic colloid cysts remains the standard of care with the primary goal of total resection, including the capsule, with low morbidity. According to a current meta-analysis, microsurgical resection, which include transcortical transventricular and interhemispheric transcallosal approaches, has been associated with a higher resection and lower recurrence rates when compared to the endoscopic approach. Furthermore, intracystic hemorrhage may lead to xanthogranulomatous inflammatory changes within the cyst resulting in focal thickening of the cyst wall and adhesion to surrounding structures, requiring a more technically demanding resection, especially for endoscopic approach.

[CASE DESCRIPTION] A 54-year-old male patient presented with subacute symptoms of gait disturbance with poor balance, cognitive impairment, urinary incontinence, and neuropsychiatric symptoms of memory disturbance, paranoid delusions, sexual disinhibition, and labile mood. Neurological examination showed normal level of consciousness, gait apraxia, impaired upper gaze with diplopia, reduced attention, and severe short-term memory impairment. Non-enhanced brain computed tomography scan showed a well-circumscribed hyperdense giant colloid cyst contributing to obstructive hydrocephalus. At this time, he underwent an emergency ventriculoperitoneal shunt. After that, brain magnetic resonance imaging showed a non-enhancing lesion with heterogeneous signal intensity on T2-weighted image and high signal intensity on T1-weighted image, and blooming artifacts on susceptibility-weighted imaging sequence suggestive of associated blood products. A left interhemispheric transcallosal approach was planned. The patient was placed in the supine position, with the head fixed in a three-pin clamp in neutral and flexed positions. A left straight transverse frontal incision crossing the midline was planned and a left parasagittal craniotomy was performed two-thirds anterior and one-third posterior to the coronal suture, exposing the sagittal sinus. The dura mater was opened with the base facing the sagittal sinus. The microscope was brought into the field. The interhemispheric cistern was dissected downwards, deeply exposing the corpus callosum. Precise and limited callosotomy was carried out with the aid of neuronavigation guidance. A firm, well-defined, grayish red capsule of the colloid cyst was reached through an interforniceal approach. The thick vascular capsule was coagulated and incised. The contents of the cyst were solid, soft and brownish yellow, resembling an organized clot, and were removed with delicate suction interspersed with sharp dissection and piecemeal resection of the adhered capsule from the surrounding fornices and thalami. The internal cerebral veins were displaced inferiorly and laterally and could be preserved with fine microdissection. Few remnants of the tela choroidea were found and served as a landmark for safe removal of the lesion, avoiding damage to the thalami in the most inferior part. A total resection was achieved without complications. Pathological examination confirmed hemorrhage within the colloid cyst. Ventriculo-peritoneal shunt was removed 3 months later due to signs of shunt independence (subdural effusion). Cognitive function and neuropsychiatric symptoms improved partially but significantly at 1, 3, and 6 months. No recurrence was reported at 1 year.

[CONCLUSION] Hemorrhagic colloid cyst is rare. Surgical removal is technically more demanding when compared to a typical colloid cyst due to distinct pathological changes such as thickened and adherent capsule and more solid contents. Microsurgery seems to be the best choice in these cases.