3 months -old-child was referred to USG Local part in view of focal skin tag over the posterior aspect of neck.

Findings and discussion:

On ultrasound there was thin hypoechoic sinus tract seen extending from the skin surface to the cervical spinal cord. 

So , the diagnosis of dorsal dermal sinus is given.

Further the child underwent MRI cervical spine.

On axial and sagittal T2WI: Dorsal dermal sinus tract is seen extending from the skin surface to the cervical spinal cord opposite C3 vertebral body and the diagnosis of USG was confirmed. 

A dorsal dermal sinus (DDS) is a congenital spinal anomaly that results from incomplete closure of the neural tube during embryonic development. It presents as a midline skin opening, often with a small pit or dimple along the back, usually in the lumbosacral or thoracic region. DDS can be associated with underlying spinal cord abnormalities, including tethered cord syndrome, dermoid or epidermoid cysts, and infection risks like meningitis.

Ultrasound for Dorsal Dermal Sinus:

Ultrasound is often the first-line imaging modality for evaluating DDS in infants, especially in the neonatal period when the posterior spinal elements are not fully ossified.

Indications:

• Midline skin dimple, especially if deep, high, or associated with other cutaneous markers (e.g., hair tuft, hemangioma, deviated gluteal cleft).
• Concerns for tethered cord or intraspinal extension.
• Follow-up of known DDS.

Findings on Ultrasound:

1. Midline Tract: A hypoechoic or echogenic linear tract extending from the skin towards the deeper spinal structures.
2. Intraspinal Extension: If the sinus tract reaches the dura or spinal canal, further imaging (MRI) is required.
3. Cysts or Masses: Associated dermoid or epidermoid cysts may appear as well-defined hypoechoic or mixed echogenic lesions.
4. Cord Position: Low-lying or tethered spinal cord may be identified.

Next Steps:

• MRI Spine: If the ultrasound shows intraspinal extension, an MRI is needed for detailed evaluation of spinal cord involvement.
• Neurosurgical Consultation: Required if there is evidence of tethered cord, dermoid cysts, or other complications.