Three-dimensional magnetic resonance myelography for dorsal dermal sinus.

Abstract

Three-dimensional magnetic resonance (MR) myelography [5] is a form of MR hydrography which shows free water as high signal intensity and is useful in cases of dorsal dermal sinus to show, non-invasively, communication between the dorsal dermal sinus and the intraspinal space. A 10-month-old girl suffered meningitis with persistent fever, increased white blood cell count (20200/ll) and high C-reactive protein (28.8 mg/dl) despite appropriate antibiotic therapy. She had a small midline dimple located at the top of the intergluteal crease without any other cutaneous abnormalities such as haemangioma or hypertrichosis. The neurological examination was normal. Conventional MRI disclosed dermoid cysts and a dorsal dermal sinus [4] but did not demonstrate where the dermal sinus terminated (Fig. 1A). Three-dimensional MR myelography revealed communication between the dermal sinus and the intraspinal space (Fig. 1B) and surgical and pathological findings confirmed these observations. Congenital dermal sinuses are developmental anomalies of the spine resulting from defective separation of the epithelial ectoderm from the neural ectoderm [2]. They are superficial depressions or tracts in the skin lined by stratified squamous epithelium and extend inward for a variable distance from the skin surface. They may terminate blindly within the subcutaneous tissues or the paraspinal muscles or they may pass through the dura to terminate in the intraspinal space. Approximately 50% of all dermal sinuses are associated with dermoid or epidermoid cysts, usually at the termination of the tract [1]. MRI is the neurodiagnostic technique of choice. However, the sinus tracts may not be well shown on conventional MRI if they are small or out of the imaging plane [3]. Even in such cases, three-dimensional MR myelography [4] can demonstrate apparent communication between dorsal dermal sinuses and the intraspinal space.