Congenital Intracranial dermoid tumor: CT and MR findings

Clinical History

Patient with right eye enophtalmos with divergent strabismus due to inward gaze paralysis and minimally reactive pupil.Head CT shows an extraxial mass in the rigth temporal fossa with a low attenuation component. MR demonstrates a heterogeneous mass with some high signal intensity areas on T1W images.

Imaging Findings

A two-month-old boy was admited to the hospital because exophthalmos of the left eye first noted by his mother and right eye gaze paralysis. Physical examination demonstrated right eye enophthalmos with divergent strabismus due to inward gaze paralysis and minimally reactive pupil. Head CT revealed an heterogeneous extraxial mass in the right temporal fossa, with atrophy of the right temporal lobe, right ocular globe atrophy and right sphenoid wing hypoplasia. The mass showed different components with Hounsfield Unit (HU) values of fat,soft tissue and calcium (Fig 1). MR demonstrated the heterogenous nature of the lession with high signal intensity areas on T1W images corresponding to the fatty component, areas of intermediate signal due to the soft tissue component and low signal intensity areas due to calcifications (Fig 2). It confirmed the extraxial location of the mass and the sphenoid wing hypoplasia. It also demonstrated a right intracranial carotid and vertebral arteries hypoplasia. At surgery the tumor was attached to the dura and showed a cystic, yellowish appearance with some calcifications. Histological examination demonstrated a cyst lined by keratinised squamous epithelium, pilous follicles, sweat and sebaceous glands and calcification.

Discussion

Congenital dermoid tumors are benign lesions most commonly found in the midline, in the posterior cranial fossa or sacrococcygeal area, with no sex predilection (1). They have a well developed fibrous wall lined by stratified squamous epithelium and contain elements of mesodermal origin such as hair follicles and sweat and sebaceous glands, wich provide filling for the cavity (2) The craniocerebral dermoids have been classified as extradural or intradural (1). Intradural dermoids are more frequent than extradural ones and they tend to grow slowly, extradural tumors tend to grow in the diploe and orbit (1). The extradural location of the tumor makes our case very unusual, the temporoparietal region is also an area more typical for epidermoid tumors of the diploe rather than for true dermoids (2). Currently dermoids can be diagnosed early with CT and MR imaging. CT scans demonstrate a marked hypodense area with values ranging from 0 to 150 HU. The mass appears as well defined lesion, with regular margins. Calcification has been commonly reported (3,4). MR appearance includes high signal intensity areas on T1W images and lower signal intensity on T2W images due to the presence of fat , intermediate signal intensity areas on T1W and T2W images corresponding to the soft tissue component and signal void areas that represent calcification. Clinical history, location of the lesion, patient´s age, low absortion values on CT and high signal intensity areas on MR T1W images may be very important, helpful findings in the preoperative diagnosis (4,5).

Differential Diagnosis List

Final Diagnosis

Congenital intracranial dermoid

URL:	https://eurorad.org/case/1034
DOI:	10.1594/EURORAD/CASE.1034
ISSN:	1563-4086