Giant Intradiploic Epidermoid Cyst of the Occipital Bone

Abstract

A rare case of giant intradiploic epidermoid cyst of the occipital bone with large intracranial extension in the posterior fossa is described. The lesion was discovered when the patient presented with headache and subcutaneous swelling in the occipital region, in the absence of signs of neurological involvement.
CT scan showed extensive destruction of the occipital bone, mainly of the inner table, up to the foramen magnum. On MRI the lesion was hypointense in T₁ and hyperintense in T₂-weighted images; signal inhomogeneity was due to cellular debris and cholesterol crystals. The enhancing rim due to the thickened dura confirmed the extradural location. Complete removal of the cyst was easily accomplished despite its large size.
We found only 3 documented cases in the literature of giant intradiploic infratentorial epidermoid cysts, none of which was studied by MRI. The radiological features and differential diagnosis are discussed.

Zusammenfassung

Es wird der seltene Fall einer riesenhaften intradiploischen Epidermoidzyste des Os occipitale mit großer intrakranieller Ausdehnung in die hintere Schädelgrube beschrieben. Zur Entdeckung der Läsion führten Kopfschmerzen und eine subkutane Schwellung okzipital bei fehlenden neurologischen Ausfällen. Die Computertomographie konnte die extensive Destruktion des Okzipitalknochens gut darstellen, insbesondere der Tabula interna bis hinunter zum Foramen magnum. Im Kernspintomogramm war die Läsion hypointens in T₁- und hyperintens in T₂-gewichteten Bildern. Wegen des zellulären Debris und der Cholesterolkristalle bestanden Signalinhomogenitäten. Der Kontrastmittel aufnehmende Rand der verdickten Dura bestätigte die extradurale Lokalisation. Trotz ihrer ausgedehnten Größe war die komplette Entfernung der Epidermoidzyste leicht durchführbar. Aus der Literatur konnten nur drei Fälle von riesenhafter intradiploischer Epidermoidzyste im intratentoriellen Bereich gesammelt werden, von denen kein Bericht MRT-Befunde enthielt. Die radiologischen Charakteristika und die Differenzialdiagnosen werden diskutiert.

Key words

Epidermoid cyst - skull tumor - occipital bone

Schlüsselwörter

Epidermoidzyste - Kalottentumor - Os occipitale

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