Intracranial Dermoid

A 59-year-old woman with past history of seizure disorder of unknown etiology since childhood came to hospital for incision and drainage of a right thigh abscess. During her stay in hospital, she had a fall with possible head trauma. A noncontrast CT scan showed an incidental finding of a large frontal midline calcified ovoid lesion containing fat with partial agenesis of corpus callosum consistent with a dermoid (Figures 1 and 2). 

Figure 1. CT scans showing hypodense lesions with low attenuation values consistent with fat.
Figure 2. Large frontal midline calcified ovoid lesion containing fat with partial agenesis of corpus callosum consistent with a dermoid.

Laboratory tests. CT scans shows hypodense lesions with low attenuation values consistent with fat. MRI reveals a heterogeneous mass with T1 hyperintensity and minimal contrast enhancement. Peripheral calcification occurs frequently and may be seen on plain radiographs of skull (Figure 3). Differential diagnosis on imaging is chiefly lipoma. 

Discussion. Intracranial dermoids are benign, accounting for about 0.3% of all brain tumors. These are cysts formed by ectopic inclusion of ectodermal elements during neural tube closure. They are often located along midline; posterior fossa is the most common site of occurrence. Presentations are dependant upon mass-effect of these lesions and may vary from asymptomatic incidental finding to headaches and seizures.¹ Spontaneous rupture of intracranial dermoid cysts is a rare phenomenon and result in scattering of fat droplets throughout ventricles and subarachnoid space. Rupture results in headaches, seizures, and chemical meningitis.² 

Figure 3. Peripheral calcification in a frontal midline ovoid lesion.

Treatment. Observation is sufficient in most asymptomatic tumors. Symptomatic cysts need surgical resection. Ruptured dermoid cysts often cause symptoms and necessitate surgical removal²; surgery is the only way to deal with these benign lesions. If the capsule is adherent to vital areas, incomplete removal is advised to prevent neurological deficits since recurrence is uncommon.³ Malignant transformation is unlikely but if it occurs, it is associated with poor prognosis.⁴

References:

1.Orakcioglu B, Halatsch ME, Fortunati M, et al. Intracranial dermoid cysts: variations of radiological and clinical features. Acta Neurochir (Wien). 2008;150(12):1227-1234.

2.Stendel R, Pietilä TA, Lehmann K, et al. Ruptured intracranial dermoid cysts. Surg Neurol. 2002;57(6):391-398.

3.Liu JK, Gottfried ON, Salzman KL, et al. Ruptured intracranial dermoid cysts: clinical, radiographic, and surgical features. Neurosurgery. 2008;62(2):377-384.

4.Hamlat A, Hua ZF, Saikali S, et al. Malignant transformation of intra-cranial epithelial cysts: systematic article review. J Neurooncol. 2005;74(2):187-194.