36-year-old man with sudden severe headache

Autor: Manuel Deprez, Didier Martin, Paolo Simoni, Benoît Meunier, Tudor Racaru
Rok vydání: 2011
Předmět:
Zdroj: Skeletal Radiology. 40:1361-1362
ISSN: 1432-2161
0364-2348
Popis: DiagnosisGiant intradiploic epidermoid cyst. A large arachnoid cystof the middle fossa of the brain is visible inferior to theintradiploic epidermoid cyst.DiscussionEpidermoid cyst (EC) is a rare, benign, slow-growinglesion of the skull. The origin of ECs of the skull isdebated. According to the congenital theory, ECs arise fromectodermic inclusions during neural tube closure (weeks 3–5of embryogenesis). Epithelial cells become trapped in thebone by the laterally migrating otic or optic capsule [1–4].Acquired ECs of the skull are believed to develop frominclusions of the epithelium after trauma [1, 2, 5].Epidermoid cysts of the skull are detected incidentallyby imaging for other reasons [1].Large ECs of the skull may become symptomatic,causing compression of the brain and neurological effects,including headache, seizures, optic nerve or venous sinuscompression, and intracranial hypertension [1, 5, 6]. In ourcase, the cause of the patient's headache was nonspecific; itcould have been attributed to direct meningeal irritation bythe lesion or, less likely, to chronic changes in intracranialpressure, related to the mass.Late complications of ECs include a fistulous tract thatopens to the skin, suprainfections, and meningeal syndromesubsequent to cyst rupture [4, 7]. Rarely, intradiploic ECsundergo malignant transformation into squamous cellcarcinoma [8].On computed tomography (CT), ECs of the skullusually appear as well-defined, heterogeneous masseswith densities ranging from −20 to +20 Hounsfield units(HUs), interspersed with higher-density areas that corre-spond to protein or cholesterol deposits (Fig. 1; see TestYourself: Question) [9].Epidermoid cysts typically have low signal intensity onT1-weighted MRI and high signal intensity on T2-weightedMRI. The T1-weighted MRI signal may increase focally,corresponding to cholesterol deposits (Fig. 2; see TestYourself: Question) [1, 10].Most ECs fail to show enhancement after injection ofcontrast media (Fig. 2) [10].In our case, a large arachnoid cyst of the middle fossawas visible inferior to the EC.The EC and CSF of the arachnoid cyst could not bedifferentiated based on the density by CT (the averagedensity was approximately 12 HU for both lesions; Fig. 1),whereas EC was easily detected by MRI (Fig. 2). ECs areheterogeneous and hyperintense relative to cerebrospinalfluid (CSF) on fluid attenuation inversion recovery(FLAIR) images (Fig. 2) [11]. Further, unlike arachnoid
Databáze: OpenAIRE
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