What is the initial management for a sacral dimple in a neonate?

Management of Sacral Dimples in Neonates

For a sacral dimple in a neonate, you should order a spinal ultrasound if the dimple is located above an imaginary line connecting the tops of the gluteal cleft or if it has associated cutaneous findings; otherwise, no imaging is necessary for simple coccygeal dimples.

Differentiating Types of Sacral Dimples

The key to management is distinguishing between two types of dimples:

Innocent Coccygeal Dimples

• Located at or below an imaginary line connecting the tops of the gluteal cleft
• Usually within 1 cm of the coccyx within the gluteal cleft
• Often only visible when buttock cheeks are separated
• No associated skin abnormalities
• Represent a normal variant found in ~4% of the population

Pathologic Lumbosacral Dermal Sinus Tracts (DSTs)

• Located above the gluteal cleft on the flat part of the sacrum
• May have associated cutaneous findings:
  • Vascular anomalies
  • Tufts of hair
  • Skin tags
  • Subcutaneous masses

Evaluation Algorithm

1. Determine the location of the dimple:

   • Use the "gluteal cleft line rule": Draw an imaginary line between the tops of the two forks of the gluteal cleft
   • Note if dimple is above or below this line

2. Examine for associated cutaneous findings:

   • Check for hair tufts, skin tags, vascular markings, or masses
   • Assess if base of dimple can be visualized (though this is less important than location)

3. Order appropriate imaging based on findings:

   • No imaging needed if:

     • Dimple is at or below the gluteal cleft line
     • No associated cutaneous findings
     • Finger can be rolled over underlying coccyx 1

   • Order spinal ultrasound if:

     • Dimple is above the gluteal cleft line
     • Associated cutaneous findings present
     • Multiple cutaneous markers present
     • Neurological abnormalities present

4. Follow-up based on ultrasound results:

   • Normal ultrasound: No further workup needed
   • Abnormal ultrasound: Proceed to MRI for further evaluation

Clinical Significance and Rationale

The concern with pathologic lumbosacral DSTs is their potential connection to the spinal cord, which can lead to serious complications including:

• CNS infections (meningitis, intraspinal abscess)
• Aseptic meningitis from associated dermoid/epidermoid cysts
• Spinal cord compression
• Neurologic deterioration from tethering 1

However, research shows the risk of significant spinal malformations in asymptomatic infants with isolated simple sacral dimples is extremely low (0.13%) 2. This justifies a selective approach to imaging.

Important Caveats

• Traditional teaching that a dimple is innocent if its base can be visualized is incorrect; location is the most important determining factor 1
• In patients with 22q11.2 deletion syndrome with sacral dimples, lumbar spine MRI should be considered to rule out tethered cord, especially with bowel/bladder dysfunction 1
• When multiple cutaneous markers are present, the risk of spinal dysraphism increases significantly 3
• Avoid unnecessary imaging for simple coccygeal dimples, as studies show benign findings in the vast majority of cases 4

By following this approach, you can appropriately identify which neonates with sacral dimples require further evaluation while avoiding unnecessary imaging for those with benign variants.