What is the recommended management for a patient with a sacral dimple, normal conus medullaris position, mildly dilated central canal, and a filum terminale within normal limits?

Management of Sacral Dimple with Normal Spinal Anatomy

Based on the imaging findings showing a small, shallow sacral dimple with normal conus position (L1-L2), normal filum terminale thickness (1.3 mm), and no dermal tract, this patient requires no further intervention or imaging—reassurance and routine follow-up are appropriate. 1

Key Imaging Findings Analysis

The MRI demonstrates reassuring anatomical features:

• Conus medullaris at L1-L2: This is within normal limits, as the conus should terminate at or above the L2-L3 disc space 2, 3
• Filum terminale 1.3 mm: Well below the 2 mm threshold for normal, indicating no thickening or fatty infiltration 4, 5
• Mildly dilated central canal (1 mm): This minor finding is not clinically significant in isolation without other abnormalities 2
• Thecal sac at S2: Normal anatomical position 1
• No dermal tract visualized: Critical finding that excludes the most concerning pathology 4

Clinical Significance of Dimple Location

The location and characteristics of the sacral dimple are the most important determinants of pathological significance:

• Small and shallow dimples located at or below the gluteal crease (coccygeal dimples) are considered benign variants occurring in approximately 4% of the population 4
• The absence of a visualizable dermal tract is the key protective feature, as dermal sinus tracts represent the primary risk for serious complications including CNS infection, meningitis, intraspinal abscess, and cord tethering 4
• The outdated teaching that "visibility of the dimple base" determines pathology is incorrect—location relative to the gluteal crease is what matters 4, 1

Risk Stratification Based on Evidence

This patient falls into the lowest risk category:

• Studies demonstrate that healthy infants with simple sacral dimples have an exceedingly low risk (0.13%) of significant spinal malformations requiring surgical intervention 6
• Among 3,884 healthy infants screened, only 0.13% required surgery for true tethered cord 6
• The presence of a simple sacral dimple alone denotes very low risk of occult spinal dysraphism 2
• In contrast, dermal sinus tracts correlate with higher risk of spinal cord lesions and require aggressive evaluation 2

When Additional Imaging or Intervention Would Be Indicated

MRI with or without contrast would be necessary if any of the following were present:

• Dermal sinus tract identified on examination—the most concerning finding requiring evaluation for intraspinal extension 4
• Associated cutaneous markers including hairy patches, capillary malformations, subcutaneous masses, or skin tags 4, 1
• Low-lying conus below L2-L3 disc space 3
• Thickened filum terminale >2 mm, particularly if echogenic suggesting fatty infiltration 5
• Neurological symptoms including lower extremity weakness, bowel/bladder dysfunction, or upper motor neuron signs 1, 3

Common Pitfalls to Avoid

Do not over-interpret minor anatomical variants:

• Filar cysts and borderline low-lying conus (at L2-L3 disc space) without other abnormalities are common benign findings that do not require surgery 7, 5
• Echogenic filum terminale <2 mm thick, even when containing small amounts of fat, is typically benign and low-risk 5
• The mildly dilated central canal in this case (1 mm) is not clinically significant without associated syringomyelia or other structural abnormalities 8

Do not pursue unnecessary surgical intervention:

• Among infants with simple sacral dimples and minor imaging findings, none required surgery in multiple large series 7, 6
• Surgical untethering is reserved for patients with anatomical tethered cord syndrome (conus below L2-L3) plus neurogenic bladder or other neurological deficits 3

Recommended Management Plan

For this specific patient:

• No further imaging is required given the comprehensive MRI already performed shows normal anatomy 1
• Reassurance to family that findings are within normal limits 6
• Routine pediatric follow-up with attention to developmental milestones, particularly motor development and bladder/bowel function 1
• Re-evaluation only if new symptoms develop, including changes in gait, bowel/bladder dysfunction, or back pain 3

The American Academy of Pediatrics guidelines emphasize that dimples at or below the gluteal crease without dermal tracts are normal variants requiring no workup 1, and this patient's imaging confirms the absence of any pathological findings that would change management.