Colloid cysts are benign smooth, round lesions of endodermal origin, typically located near the foramen of Monro in the anterior aspect of the third ventricle. They are usually filled with gelatinous material and cholesterol crystals. These cysts generally occur in adults and account for approximately 1% of all intracranial tumors. Symptoms include headaches, vertigo, memory deficits, diplopia, blurred vision, and behavioral disturbances. Although these lesions do not have a malignant potential, they are managed surgically when symptomatic, because they tend to cause hydrocephalus by obstructing cerebrospinal fluid flow between the lateral ventrivules and the third ventricle. Acute hydrocephalus may cause abrupt elevation of intracranial pressure and lead to sudden death. Such a scenario is life threatening and is considered to be a neurosurgical emergency.
Highly refined endoscopes with a wide array of compatible instruments allow drainage and/or complete removal of some colloid cysts through a less invasive technique.
The procedure is performed through a small incision (approximately 2-3 cm). Entry point is defined with the help of Neuronavigation, in order to have the best angle to access the cyst, with little distorsion of brain structures. From this site, the endoscope is inserted into the ventricular compartment of the brain and then navigated toward the tumor surface. The wall of the tumor is then coagulated with an electrical current and the cyst is opened with sharp dissection. A variety of suction catheters are used to empty the contents of the cyst. The cyst wall is removed when feasible, and any remnants are destroyed using an electrical current. The endoscope is then removed, and the wound is closed. The procedure time averages 1 hour and patients can return home within 4-5 days.
In some cases (mainly failure to remove the cyst in a satisfying manner), shifting from an endoscopic technique to a mini-open transfrontal transventricular craniotomy is needed.
Treatment of hydrocephalus may require a ventricular shunt, despite successful colloid cyst resection.