Teaching Case

A 38-year-old male patient presented with complaints of headache for the last 6 months, with intermittent episodes of vomiting and a single episode of seizure 15 days back. For these complaints, the patient was referred to department of Radiodiagnosis for MRI investigation and aid in further management.

MRI findings revealed cystic space occupying lesion in pineal region displaying cerebrospinal spinal fluid (CSF) signal intensity on T2W-images (Fig 1 and 2). The lesion showed incomplete suppression of CSF signal intensity on FLAIR images (Fig 3). The lesion showed bright signals on DWI image (Fig 4) and dark signals on ADC image (Fig 5), thus confirming restricted diffusion. The lesion showed no post-contrast enhancement on post gadolinium contrast image (Fig 6).

Intracranial epidermoid cysts are one of the rare intracranial neoplastic lesions. Reported literature suggest that epidermoid cysts account for approximately 1% of all the intracranial tumours, and 3%–4% of intracranial epidermoid cysts occur in the pineal region[1]. Pineal region is very rare site for intracranial epidermoid cysts. Cerebellopontine angle is the most common site of intracranial epidermoid cysts. In 1928 cushing was the first to report the pineal localisation of the intracranial epidermoid cyst[2]. Up to now, 85 cases of pineal epidermoid cyst have been published in the literature.
A variety of theories have been published suggesting the origin of intracranial epidermoid cysts, such as a defect in cleavage process of the neural tissue from the cutaneous ectoderm and presence of embryonic ectodermal inclusions[3].
Clinically patient present with history of headache and vomiting secondary to hydrocephalus. Patient can also present with symptoms characteristic of parinaud's syndrome secondary to compression of tectal plate. Hemiparesis & cerebellar signs may also be seen in few cases[3].
The Contrast CT imaging reveals a nonenhancing cystic lesion with CSF density. Sometimes, density is higher in few of the cases due to presence of cholesterol and protein content and the presence of haemorrhage in the lesion. Calcification is usually absent. Typical MRI findings include, epidermoid cyst is hypointense on T1-weighted images and hyperintense on T2-weighted with incomplete suppression of CSF signals on FLAIR images with no post contrast enhancement[4]. The diffusion-weighted images (DWI) allow to make a difference between an epidermoid cyst and an arachnoid cyst as epidemoid cysts are bright on DWI and show restricted diffusion[5].
The main stay of treatment include radical excision of the epidermoid cyst with its capsule[6]. A therapeutic stereotactic aspiration is described as a part of management for the treatment of epidermoid cyst.
Teaching Points:
1)This case report describes the characteristic imaging findings of a rare case of pineal epidermoid cyst.
2)DWI and ADC images help us to differentiate epidermoid cyst from the more common differential like arachnoid cyst as epidermoid cyst shows restricted diffusion.
3)Absence of contrast enhancement and calcifications help us to differentiate from germinoma and pineocytoma.
4)Although rare case, every radiologist should know the characteristic MR imaging findings in pineal epidermoid cyst.