Epidermoid tumour of lateral ventricle

A 44-year-old male presented with complaints of headache, intermittent episodes of vomiting and altered sensorium. Clinical examination revealed mild papilledema suggesting raised intracranial pressure. Routine blood investigations were within normal limits. The condition of the patient deteriorated with an increase in intracranial pressure and the patient succumbed before surgery.

There is a well-defined lobulated hyperintense lesion measuring 3.8x3cm seen in the body of the lateral ventricle with CSF intensity on T2W images and incomplete suppression of the lesion on FLAIR sequence. The lesion shows intense restricted diffusion on diffusion-weighted images with minimal peripheral enhancement.

Intracranial epidermoid tumours are congenital inclusion cysts corresponding to 0.2-1.8% of primary intracranial neoplasms [1]. They result from inclusion of ectodermal elements during neural tube closure and are composed of desquamated epithelial cells. They grow or insinuate within CSF spaces, surrounding and encasing adjacent vessels and nerves. They are classically extra-axial, most commonly found at the cerebellopontine angle followed by suprasellar cistern. In rare cases, they have been reported in other locations such as the lateral ventricles[2].

The clinical manifestations of epidermoid tumours are usually related to the mass effect of the tumour on adjacent structures. Gait disturbance is a common presenting symptom for patients with posterior fossa tumours. Hydrocephalus is not commonly seen with intracranial epidermoid tumours, possibly due to fissuring of the cyst wall and the ability of CSF to decompress into the surrounding periventricular structures and outlet foramina[3]. However, our case showed features of obstructive hydrocephalus with periventricular ooze suggestive of decompensation, which was an uncommon finding.

They appear as lobulated lesions that fill and expand CSF spaces and exert a gradual mass effect, insinuating between structures and encasing adjacent nerves and vessels. On CT the typical appearance is that of a hypodense mass without venous contrast uptake. On MR imaging, these lesions have isointense or subtle hyperintense signal as compared to CSF on T1- and T2-weighted sequences. The heterogeneity of epidermoids on FLAIR is presumed due to fibrous tissue and complex fluid within the interstices of the tumour. On DW images, epidermoids typically show restricted diffusion, unlike arachnoid cysts. Finally, although most epidermoids do not enhance, up to 25% may show minimal rim enhancement.

Surgical excision is the treatment of choice if symptomatic. The primary surgical objective is to decompress the mass by evacuating the cyst contents and removing non-adherent portions of the tumour capsule; portions of the capsule adherent to vital structures should be left undisturbed.

Although benign cystic tumours may show some degree of associated enhancement, it has been suggested that surgery should focus on resection and histologic analysis of the enhancing area when encountered due to the risk of malignant degeneration in the enhancing portion[4].

The main differential diagnostic consideration is an arachnoid cyst The distinction is usually made with FLAIR and DW imaging. Arachnoid cysts follow the signal intensity patterns of CSF with all MR pulse sequences, whereas epidermoids are not hypointense on FLAIR images and show areas of hyperintense signal relative to CSF.