Brainstem dermoid cyst rupture with hydrocephalus in a child.

Intracranial dermoid cysts are ectodermal lesions of embryological origin. They are of slow progression and symptoms associated with unruptured cysts are most commonly due to mass effect. However, a potential rupture in the ventricular system is rare and can cause meningitis, seizures and hydrocephalus. Hereby, we report a case of a 12-year-old boy presenting with obstructive hydrocephalus due to brainstem dermoid cyst rupture.

Intracranial dermoid cysts are uncommon dysontogenetic lesions. They present <1% of all intracranial tumors [1]. Lateral displacement of ectodermal primitive remnants in the track of developing otic vesicles or neurovasculature formations could explain their unusual intraparenchymal location [2]. A potential intraventricular rupture may lead to chemical meningitis, seizures and hydrocephalus [3].

A 12-year-old boy with signs of intracranial hypertension and complex partial seizures was brought to our emergency department. His parents reported precedent yet not plaguing symptoms of impaired dexterity and intermittent strabismus over the past year.

Upon admission the patient was alert and fully oriented. Clinical examination revealed left sided oculomotor palsy and slight left hemiparesis. Computed tomography (CT) scan revealed a space occupying lesion of the midbrain with spatial dimensions of X–Y–Z = 7 × 5 × 4 cm3. The tumor was compressing the aqueduct resulting in obstructive hydrocephalus. Emergency magnetic resonance imaging (MRI) scan revealed a well demarcated tumor with heterogeneous consistency and hyperintense intraventricular foci compatible with fat droplets (Fig. 1).

Figure 1:

(a) CT scan depicting the obstructive lesion and the hypodense fat droplets. (b) Ruptured dermoid cyst of brainstem with hyperintense intraventricular foci corresponding to fat droplets.

The patient underwent a subtotal excision with subsequent evacuation of the fat droplets and placement of an external ventricular drainage (EVD) in the right lateral ventricle. Postoperatively he was admitted to intensive care unit for 4 days. During the post operative period he could not wean from the EVD, thus, a ventriculoperitoneal shunt placement was warranted. Histopathologic examination revealed a dermoid cyst. He was discharged after 77 days with unaltered mental status, yet with residual limb paresis necessitating physiotherapy.

Dermoids usually present as well-defined hypointense lobulated midline masses on CT. CT scan, also provides useful diagnostic and preoperative information regarding osseal anatomy. On MRI scans fat is depicted, dispersed and hyperintense on T1-weighted imaging, therefore dermoid cysts present as high signal intensity on T1-weighted images. Usually these lesions do not enhance after intravenous paramagnetic substance administration. On T2 weighted imaging, fat elements turn slightly, hypointense.

Complete surgical resection constitutes the proper treatment. However, due to capsule adhesion, to vital structures and its linear rate of growth, subtotal excision remains a judicious alternative in selected cases [4].

CONFLICT OF INTEREST STATEMENT

None declared.

FUNDING

No financial support was received for this study.

ETHICAL APPROVAL

Not required.

CONSENT

Patient consent was obtained.

GUARANTOR

E.A. is a guarantor of this study.