dorsal dermal sinus

Dorsal dermal sinus is an epithelium-lined tract from the skin to the spinal cord, cauda equina, or arachnoid as in a form of spinal dysraphism.

Clinical presentation

A dorsal dermal sinus manifests as a small dimple or pinpoint ostium, which is often associated with an area of hyperpigmented, angiomatous skin or hypertrichosis and occurs in a midline location or more rarely in a paramedian location.

Soft-tissue asymmetry and bone anomalies are common findings.

Due to spinal dysraphism, various neurological deficits may be present including weakness, paresthesias and bowel and bladder dysfunction .

In many asymptomatic individuals, however, this small abnormality is ignored and not recognized as anything but a cutaneous lesion. A complication may, therefore, be the initial presentation, including infections such as recurrent meningitisepidural or subdural abscess, and intramedullary spinal cord abscess.

Location

Dorsal dermal sinuses are predominantly located in the lumbosacral region and less often in the occipital region .

Pathology

Dorsal dermal sinuses results from incomplete separation of the superficial ectoderm from the neural ectoderm, resulting in a focal segmental adhesion. Later during embryogenesis, as the spinal cord ascends relative to the spinal canal it stretches the adhesion into a long, tubular tract.

Associations

The dorsal dermal sinus can be an isolated finding, but several associations have been described:

Radiographic features

Ultrasound
  • ultrasound can show the entire length of the tract from the skin to the spinal cord
  • the tract can be difficult to identify within the subcutaneous fat
  • the tract is clearly demonstrated in the anechoic, cerebrospinal fluid–filled subarachnoid space as an echogenic structure

Treatment and prognosis

Treatment is surgical with resection of the sinus tract and exploration of the intrathecal component. This may necessitate additional malformations (e.g. diastematomyelia) to be corrected at the same time .

The prognosis depends largely on the degree of neurological deficits, which may stabilize or improve following surgery, and the severity of any infective complications .

Differential diagnosis