Does This Sacral Dimple Need to be Evaluated?

Patient Presentation
A 15-month-old male came to clinic for his well child care after transferring from another institution. His mother reported that she was still anxious that the “hole” in his bottom hadn’t seemed to improve. She had been told that it “would go away” but that it hadn’t. He had normal development including gross and fine motor. The past medical history was negative. The family history was negative for any gastrointestinal, urological or neurological problems. The review of systems was negative for any urinary frequency, urgency or defecation problems.

The pertinent physical exam showed a happy toddler who was busy walking and climbing around the room. His vital signs were normal including his growth parameters. His examination was normal and the mother pointed out the “hole” in his gluteal cleft which was a 3 mm dimple that the bottom could be easily seen. It was oriented vertically to the skin and was 20 mm from the anus. There were no skin changes or masses noted. He had a normal neurological evaluation including normal deep tendon reflexes in the lower extremities, normal cremasteric reflex and down going Babinski reflexes bilaterally. The diagnosis of a benign coccygeal dimple was made. The mother was counseled that the dimple probably would not go away, but that it may become less noticeable as the child grew and was unlikely to cause any problem.

Discussion
Skin dimples over the spine commonly referred to as sacral dimples are common minor congenital anomalies, estimated to occur in 3-8% of children. When a clinician sees a skin dimple, the possibility of occult spinal dysraphism (OSD) usually crosses the mind. OSD is a wide-range of skin-colored spinal column and neuraxis abnormalities that are caused by abnormal neurulation. OSD lesions include dermal sinuses, tethered cord, lipomyelomeningocoele, and diastematomyelia. OSD can present with a variety of abnormalities, but is also frequently asymptomatic and can present at any age. Skin abnormalities accompany 50-80% of OSD.

Other presentations of OSD include:

• Skin
  • Dimples/pits
  • Dermal sinuses
  • Hypertrichosis
  • Lipoma or other mass
  • Pigmented lesions
  • Skin tags or tail-like appendages
  • Vascular lesions – hemangioma, telangectasis
  • Other – Aplasia cutis congenita
• Infectious
  • Signs of infection such as skin erythema or induration
  • Meningitis
• Neurological
  • Abnormal urination/defection
  • Spasticity
  • Paresthesia
  • Weakness
• Orthopaedic
  • Congenital dislocation of the hip
  • Leg length discrepancies
  • Pes cavus
  • Scoliosis
  • Talipes

Learning Point
Cutaneous markers of OSD are more likely to be associated with OSD if they are above the gluteal cleft (truly sacral in location) because they are more likely to be contiguous with the dura. Those that are within the gluteal fold are much less likely to be contiguous with the dura and are much more likely to be a normal variant. However it can be difficult to clearly distinguish all variations and therefore the clinician considering whether or not to further evaluate a patient must consider the individual circumstances.

Some indications that a skin dimple may be simple or low risk include:

• Position – within the gluteal fold or coccygeal position
• Single dimple
• < 5 mm diameter
• Base of dimple is visible
• Dimple is oriented straight down (i.e. caudal) not cephalically (i.e. toward the head)
• No other dermal abnormalities or masses
• Distance < 2.5 cm from anus
• Normal neurological examination

Evaluation for potential OSD for usually includes spinal ultrasound in infants and magnetic resonance imaging of the lumbar spine for older children. In 2005, the Royal College of Radiologists revised protocol for imaging says “[i]solated sacral dimples and pits may be safely ignored (< 5 mm [in diameter], < 25 mm from anus). Ultrasound of the neonatal lumbar spine is the initial investigation of choice if there are other stigmata of spinal dysraphism, associated congenital abnormalities or a discharging sinus".

Questions for Further Discussion
1. What are the indications for neurosurgical consultation for potential OSD?
2. What is the natural history of delayed diagnosis or unrepaired OSD?
3. How is a pilonidal cyst associated with sacral dimples?
4. What syndromes are associated with spinal dysraphism?

Related Cases

Disease: Sacral dimple | Tailbone Disorders

Symptom/Presentation: Minor Congenital Anomaly

Specialty: General Pediatrics | Neurology / Neurosurgery | Radiology / Nuclear Medicine / Radiation Oncology

Age: Toddler

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for this topic: Tailbone Disorders

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

Ackerman LL, Menezes AH. Spinal congenital dermal sinuses: a 30-year experience. Pediatrics. 2003 Sep;112:641-7.

Robinson AJ, Russell S, Rimmer S. The value of ultrasonic examination of the lumbar spine in infants with specific reference to cutaneous markers of occult spinal dysraphism.
Clin Radiol. 2005 Jan;60(1):72-7.

Schenk JP, Herweh C, Gunther P, Rohrschneider W, Zieger B, Troger J. Imaging of congenital anomalies and variations of the caudal spine and back in neonates and small infants. Eur J Radiol. 2006 Apr;58(1):3-14.

Khan AN, Trumbull I, McDonald S, Subih D, Al-Okaili rR Spinal Dysraphism/Myelomeningocele. eMedicine.
Available from the Internet at http://emedicine.medscape.com/article/413899-overview(rev. 1/14/09, cited 7/1/09).

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