Sunday, 28 May 2017

Colloid Cyst

Colloid cysts are slow growing benign intraventricular tumor of anterior third ventricle. These constitute less than 1% of all intracranial tumors. It constitutes 14% of intraventricular tumors. It is commonest third ventricular tumor.
It is presumed that it originates from roof of third ventricle from rudimentary paraphysis ( evagination in roof of 3rd ventricle during development). It comprises of fibrous epithelial lined cyst filled with either mucoid or gelatinous or dense hyloid substance.
It is commonly seen in between age groups 20 and 40 years. Colloid cyst is usually located in the anterior third ventricle, at the level of foramen of Monro. It may block the cerebrospinal fluid ( CSF) flow causing symmetrical dilatation of both lateral ventricles and obstructive hydrocephalus. It may present insidiously or suddenly. Headache is a common presentation. Intermittent and postural nature of attacks are other common type of presentation. Drop attack due to sudden weakness of lower limbs with headache is also commonly seen in patients with colloid cyst.
Other common symptoms of colloid cyst are diplopia, gait disturbance, vomoting, disturbed mentattion, blurred vision, incontinence, and vertigo or dizziness.
Occurrence of intermittent symptoms is chracteristic of colloid cyst.
CT scan or MRI with contrast is able to detect a rounded lesion in the anterior third ventricle. Most clinicall significant cysts are more than 1.5 centimeter is size. It may show minimal enhancement or no enhancement on CT or MRI. So, the enlargement of both lateral ventricles and sparing of third and fourt ventricle along with a small globular intraventricular lesion at the level of Foramen of Monor should establish the diagnosis of colloid cyst.
Image 1: CT scan of the brain showing axial view of brain with a hyperdense lesion in the anterior third ventricle with enlargemtnt of both lateral ventricles.
                                                       Image 1 source:

Neurosurgery is the definitive treatment. Lumbar Puncture ( LP) is contraindiacted due to risk of herniation. It should be treated surgically as there is risk of acute hydrocephalus and sudden neurological detrioration. Open transcranial surgery or endoscopic neurosurgery are the treatment options. Transcranial surgery may be transcallosal  or transcortical. Endoscopic neurosurgical excisison is the mainstay of treatment.
Trancortical approach involves reaching the third ventricle through right sided middle frontal gyrus. It is feasible when ventricles are enlarged.
Transcallosal approach involves approach to the 3rd ventricle either via the foramen of Monro or by interfornicial approach. This approach can be used even if ventricles are not enlarged. There is risk of venous infarction or fornicial injury in this approach.Injury to the fornisx is associated with memory deficits or behaviour abnormalities.

1. Handbook of Neurosurgery by Mark S Greenberg 7th Deition, Thieme publication

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