What is the initial management for a 1-month-old infant with a sacral dimple where the base is visualized?

Management of Sacral Dimple with Visualized Base in a 1-Month-Old

The ability to visualize the base of a sacral dimple is irrelevant to determining whether it requires further workup—location relative to the gluteal cleft is what matters. 1, 2

Critical Assessment: Location Determines Management

The most important clinical decision is determining whether the dimple is located above or below an imaginary line drawn between the tops of the gluteal cleft forks. 1, 2

If the Dimple is At or Below the Gluteal Cleft Line (Coccygeal Dimple):

• No imaging or further workup is required—this is a benign anatomical variant present in approximately 4% of the population 1, 2
• The dimple should be located within 1 centimeter of the coccyx and within the gluteal cleft itself 1
• When palpated, your finger should be able to roll over the tip of the underlying coccyx 1
• These dimples have no associated cutaneous abnormalities and carry no risk of spinal dysraphism 1, 2
• The tract extends only to the coccygeal tip, well below the thecal sac, with no spinal cord connection 1

If the Dimple is Above the Gluteal Cleft Line (Lumbosacral Dermal Sinus Tract):

This is always abnormal and requires immediate imaging evaluation. 1, 2

• Obtain spinal ultrasonography as the initial imaging study since the infant is only 1 month old (under 6 months) 2, 3, 4, 5
• The dimple will be located on the flat portion of the sacrum, cranial to the gluteal cleft 1
• These represent dermal sinus tracts that occur in approximately 1 in 2,500 live births 1

Additional High-Risk Features Requiring Imaging

Examine carefully for associated cutaneous markers that significantly increase risk of occult spinal dysraphism: 1, 2, 5, 6

• Vascular anomalies (capillary malformations, hemangiomas) overlying or adjacent to the dimple 1, 2
• Tufts of hair in the lumbosacral region 1, 2
• Skin tags or appendages 1, 2
• Subcutaneous masses suggesting lipoma 1, 2
• Dermal sinus tract opening (even if minute) 7, 5

If any of these markers are present, even with a low-lying dimple, proceed with spinal ultrasonography. 2, 5, 6

Imaging Algorithm

Initial Imaging (Age <6 Months):

• Spinal ultrasonography is the appropriate first-line imaging modality 2, 3, 4, 5
• Ultrasonography should assess: conus medullaris level (normal: at or above L2-L3), conus and nerve root motion, filum terminale thickness, presence of intraspinal masses, and any dermal sinus tract extending to the thecal sac 3, 4, 5

When to Proceed to MRI:

Obtain MRI of the spine if: 2, 5, 6

• Ultrasonography reveals abnormal findings (low conus below L2-L3, decreased motion, thick filum, intraspinal mass, or dermal sinus tract to thecal sac) 2, 3, 5
• High clinical suspicion exists despite normal ultrasonography 2
• Multiple cutaneous markers are present 5, 6
• Any neurological signs are present (lower extremity weakness, bowel/bladder dysfunction, orthopedic abnormalities) 2, 6

Serious Complications of Untreated Lumbosacral Dermal Sinus Tracts

These tracts always require surgical correction to prevent devastating complications: 1, 2

• CNS infection (meningitis or intraspinal abscess)—the most feared complication that creates intradural scarring and makes subsequent surgery more difficult 1, 7
• Aseptic meningitis from desquamation of epithelial cells from associated dermoid/epidermoid cysts 1
• Spinal cord compression from growth of intra- or extradural dermoid/epidermoid cysts 1
• Progressive neurological deterioration from cord tethering 1, 6
• Irreversible neurological, orthopedic, and urological deficits if diagnosis is delayed 6

Common Pitfall to Avoid

The outdated teaching that "a dimple is innocent if its base can be visualized" is explicitly incorrect and should be abandoned. 1, 2 The presence or absence of a visible bottom has no bearing on whether the dimple is pathologic—only the craniocaudal location matters. This misconception has persisted for generations but contradicts current evidence-based guidelines from the American Academy of Pediatrics. 1, 2

Reassuring Data for Simple Sacral Dimples

• In a large study of 3,884 healthy infants with simple sacral dimples (meeting benign criteria), only 0.13% required surgical intervention for confirmed tethered cord 3
• The risk of significant spinal malformations in asymptomatic infants with isolated simple sacral dimples is exceedingly low 3, 4
• Simple dimples alone (without other markers) carry negligible risk of occult neural pathology 5, 6