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Dorsal Dermal Sinus


KEY FACTS

Terminology

  • Synonyms: Dermal sinus tract (DST)

  • Midline/paramedian stratified squamous epithelial-lined sinus tract

  • Extends inward from skin surface for variable distance

Imaging

  • Sinus tract easily identified superimposed on background of cutaneous fat

  • Terminus usually conus medullaris (lumbosacral) or central spinal canal (cervical, thoracic)

Top Differential Diagnoses

  • Low coccygeal midline dimple

  • Pilonidal sinus

  • (Epi)dermoid tumor without dermal sinus

Pathology

  • Focal incorporation of cutaneous ectoderm into neural ectoderm during disjunction at circumscribed point only → focal segmental adhesion

  • Spinal cord ascends relative to spinal canal, stretches adhesion into long, tubular tract

Clinical Issues

  • Infancy → 3rd decade

  • Presentation either asymptomatic (incidentally noted skin dimple) or infection, neurological deficits secondary to cord tethering or compression

Diagnostic Checklist

  • Must differentiate DST from simple sacral dimple or pilonidal sinus

  • Identify sinus course, termination for surgical planning

Sagittal graphic shows a dermal sinus extending from the skin surface into the spinal canal to terminate at conus with epidermoid cysts. A skin dimple with capillary angioma and hairy tuft (cutaneous marker) indicates sinus opening.

Sagittal T2WI MR shows hypointense dermal sinus
extending through L5 posterior elements and coursing intradural to tether the low-lying hydromyelic conus
at L2-L3. A vitamin E capsule has been placed to mark the skin opening of the sinus
.

Sagittal T1WI MR reveals hypointense dermal sinus
extending through L5 posterior elements and coursing intradural to tether the low-lying conus at L2-L3. A vitamin E capsule marks skin opening of the sinus
.

Sagittal T1WI C+ FS MR confirms mild dermal sinus tract enhancement
without abscess. Note that the terminal cord central canal is dilated
, probably representing syringohydromyelia rather than ventriculus terminalis because of low-lying cord and presence of dermal sinus.

TERMINOLOGY

Synonyms

  • Dermal sinus tract (DST)

Definitions

  • Midline/paramedian stratified squamous epithelial-lined sinus tract extending inward from skin surface for variable distance

IMAGING

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