Intra-axial CNS dermoid cyst.

Intracranial dermoid cysts are rare tumors. They constitute 0.3% of intracranial tumors. These are commonly seen in the midline and sylvian area. Intraaxial lesions are extremely rare. We report the case of a 35-years-old female with a large intraaxial dermoid cyst, which was reported as oligodendroglioma on imaging studies done preoperatively, but was confirmed to be a dermoid cyst intra-operatively and on histopathological examination; thus highlighting a diagnostic dilemma. Patient did well post operatively and there is no recurrence in the one year follow-up. To conclude, dermoid cysts are rare benign tumors, and intraaxial lesions are still rarer. Complete surgical excision may become difficult due to adherence to nerves and vessels.

Introduction

Intracranial dermoid cysts are rare tumors.[12] They constitute 0.3% of intracranial tumors. These are commonly seen in the midline and sylvian area.[3] Intra-axial lesions are extremely rare.[4-6] We report the case of a 35-year-old female with a large intra-axial dermoid cyst.

Case Report

A 35-year-old, right-handed house-wife presented to the hospital with complaints of headache and generalized tonic clonic seizures of three years duration. On neurological examination, the patient was conscious, oriented, with normal higher mental functions, no cranial, motor or sensory nerve deficit.

Computed tomography (CT) scan showed an iso- to hypo-dense lesion in the right temporal region which was intraaxial, having a calcified rim Figure 1.

Figure 1

Pre operative CT scan brain

Magnetic resonance imaging (MRI) findings were suggestive of an iso- to hyper-intense lesion in the right temporal lobe with mixed intensity, having a peripheral calcified rim, without much perilesional edema [Figure 2–Figure 5].

Figure 2

MRI T1W axial image

Figure 5

Diffusion image

MRI brain T1W contrast image

T2W images

CT scan and MRI findings were diagnostic of oligodendroglioma.

Patient was operated by a right pterional craniotomy with transsylvian approach[Figure 6].

Figure 6

Post operative CT scan brain

Operative findings: Tumor was intraaxial, pearly white, soft, and suckable, and had pultaceous material with hair and calcified hard tissue inside.

The tumor capsule was excised totally, leaving behind the calcified hard bony part which was adherent to the middle cerebral artery.

Post operatively, the patient recovered well. Post operative scan showed minimal residual lesion, the calcified part which was deliberately left behind.

The patient was discharged on 10th post operative day, without any neurological deficit. Neuropathological diagnosis was suggestive of dermoid cyst [Figure 7.]

Figure 7

Histopathological slide

Discussion

Dermoid cysts are rare, slow growing, and benign tumors commonly seen in the midline.[1-3] Of these rare tumors, the intracranial intraaxial variety is exceptional, with only few case reports in literature,[56] that too in the posterior fossa region. Our case of an intracranial intraaxial supratentorial lesion is a very rare one, not reported in isolation or as part of case series in the literature. They are congenital inclusion cysts which arise from more than one germ layer and at a later stage, may contain fat, keratin, hair, bone, cartilage, sebaceous, and sweat glands.[7] These tumors present with headache, seizures, neurological deficits and aseptic meningitis, and ventriculitis, if rupture occurs.[78] Radiological diagnosis at times is difficult unless fat particles and calcification can be demonstrated.[9] Intraoperative diagnosis is the only sure means of detecting a dermoid, after careful examination of the contents, though newer imaging techniques like use of fat suppression images may help in making an accurate diagnosis, preoperatively.

Surgical excision of the tumor is the treatment of choice. However, adherence of the wall to important structures like vessels, makes the complete removal challenging. As intracranial dermoids are rare tumors, there is no data available on long term follow-up of patients in whom the cysts have been partially excised.

Our patient has been attending regular follow-up, and at the end of one year, has not shown any increase in the size of the residual lesion.