A lumbosacral hair tuft is an abnormal patch of hair over the lower spine, which may be accompanied by skin depression, discoloration, or dimple. It often serves as a cutaneous marker of underlying spinal dysraphism, including spina bifida occulta or spina bifida cystica.

Pathophysiology

Normal physiology:

• The lower spine and sacral region usually have minimal terminal hair in infants and children.

Abnormal physiology (spinal dysraphism):

• Failure of neural tube closure during embryogenesis leads to defective vertebral arch formation.

• Cutaneous markers, such as hair tufts, dimples, lipomas, or hemangiomas, reflect the site of underlying vertebral or spinal cord anomalies.

• Hair tuft arises due to localized hypertrichosis over the malformation site.

Associated findings: May include skin dimpling, pigmentation changes, or subcutaneous masses. Neurologic deficits are usually absent in spina bifida occulta but may be present in cystica.

Examination Technique

• Patient positioning: Place the infant or child in a prone position with spine exposed.

• Inspection: Examine the lumbosacral region for abnormal hair growth, dimples, discoloration, or subcutaneous masses.

• Palpation: Gently feel for underlying bony defects or tethered cord.

• Documentation: Record location, size, shape of hair tuft, skin changes, and any neurologic signs.

Clinical Features

Differential Diagnosis

Special populations

Neonates and infants:

• Early inspection is crucial as cutaneous markers are often subtle.

• Prompt identification allows early imaging and intervention if spinal anomalies exist.

Older children:

• Hair tuft may persist unnoticed; imaging is indicated if neurologic symptoms appear.

Limitations

• Hair tuft alone does not always indicate spinal pathology.

• May be subtle or obscured by other hair growth.

• Imaging (ultrasound in neonates, MRI in older children) is necessary for confirmation.

Patient counseling

• Explain that the hair tuft may mark an underlying spinal defect, even if there are no symptoms.

• Recommend neuroimaging to assess for spinal dysraphism.

• Advise monitoring for neurological symptoms such as leg weakness, bladder/bowel issues, or gait abnormalities.

• Reassure that in many cases (occulta), no intervention may be required if imaging is normal.

Conclusion

A lumbosacral hair tuft is a cutaneous marker of underlying spinal dysraphism, including spina bifida occulta or cystica. Recognition during clinical examination prompts appropriate imaging, early diagnosis, and monitoring, potentially preventing neurological complications.

References

1. Tortori-Donati P, Rossi A, Biancheri R. Neuroradiology of the Spine and Spinal Cord: Pediatric and Adult. Berlin: Springer; 2016.

2. Pang D. Spinal dysraphism: Surgical aspects and outcomes. Neurosurg Focus. 2001;10(4):e1.

3. Kothbauer KF. Cutaneous markers of occult spinal dysraphism in children. Childs Nerv Syst. 2000;16:605–615.

4. Smith JL, Brockmeyer DL. Occult spinal dysraphism. Pediatr Clin North Am. 2009;56:1159–1175.