Cutaneous Back Lesions

Illustration of a child with spina bifida
https://en.wikipedia.org/wiki/Spina_bifida

Introduction

Careful assessment of cutaneous back lesions should be conducted on the newborn physical examination. These lesions may be associated with neural tube defects (NTDs) or spinal dysraphism, and may be the only physical manifestation of such an abnormality. Early detection is vital, as serious deficits can be prevented with early intervention.

Physlical Exam

Visual assessment of lesions

1. Sinus tracts: can connect cysts – that look like 1-4 cm rubbery nodules – to the bone, CNS, or nasal sinuses, and when they connect to the CNS, can cause meningitis with non-classical organisms
2. Lipomas: can be in the dermis or spinal canal and pass through vertebral defect into the intraspinal space, which can be a cause of tetehered cord; small connections may be missed
3. Hairy tufts (hypertrichosis): hair can be any color or texture but is often “silky” (“faun tail nevus”), V-shaped, and not well circumscribed. If prominent, this is a strong marker of an NTD, but it can also be normal if not localized and prominent.
4. Hemangiomas, telangiectasias, and other capillary malformations: proliferative, common vascular tumors. Those that are associated often have a defect within it, pass the midline, are large, and associated with another lesion (e.g. lipoma).
5. Dimples: Some dimples are benign, such as those over the coccyx with a visible base that is intact and most of those in the gluteal crease. Others are more worrisome, such as those that are deep and greater than 5 mm, are more than 2.5 cm from the anus, or are associated with other NTD markers. The gluteal fold should be separated and examined carefully for these.
6. Aplasia cutis: absence of skin, rarely reported in lumbosacral region
7. Skin tags/acrochordons/pseudotails: nodules extending from skin
8. Skin hypertrophy/atrophy or hyperpigmentation/hypopigmentation

Additional history and physical

In addition to observation, the spine should be palpated to feel for incomplete fusion of the bony spine, and legs should be examined for length discrepancies and sensory abnormalities. A history of bladder abnormalities (e.g. failure to urinate or empty bladder completely) should be assessed in older patients.

Imaging and Further Management

All of the above can indicate an underlying NTD. Hypertrichosis, dimples, skin tags, lipomas, hemangiomas, aplasia cutis, or sinus tracts, there is a higher index of suspicion than with telangiectasias, hyperpigmentation, nevi, or teratomas.  Notably, mongolion spots, which can also be mistaken for bruises, are benign.

Infant with slate grey nevus
https://en.wikipedia.org/wiki/Mongolian_spot

If any cutaneous back lesion or abnormality is noted, an ultrasound of the lower back is the next screening tool, followed by an MRI (or CT if visualization of the bones is required) as well as a neurosurgery consult.

Neural Tube Defects

NTDs are broadly distinguished as either open or closed. Closed NTDs include spina bifida occulta, meningocele, and myelominingocele. In spina bifida, the vertebral arch is incompletely fused but no herniation of contents occurs – classically, this presents with a tuft of hair. In myelomeningocele, the meninges and neural tissue protrudes, and in meningocele, only the meninges protrudes. Open NTDs include anencephaly, which, together with spina bifida, is one of the most common NTDs.

NTDs occur due to failure of closure of the neural tube, which happens by week 4 of gestation, before most women know they are pregnant. They can be prevented by supplementation of 0.4 mg/daily of folic acid in the diet from conception to the end of the first trimester (larger doses of 4mg/day are necessary for mothers of children with previous NTDs).

In the United States, 1-2 of every 1000 newborns has a neural tube defect. It is the second most common congenital anomaly, and there are multiple factors that determine risk of an NTD, such as geographical location (Ireland and Wales high-risk), SES (poor high risk), maternal age (teenagers and older moms increased risk), and prenatal exposure to valproic acid (and other drugs) and maternal diabetes. If a first degree relative is affected that means another is more likely to have another affected.

Complications of NTDs

Meningocele/Myelomeningocele

If a neural tube defect goes undetected, serious consequences may occur that can be prevented with early diagnosis and neurosurgical intervention. Meningocele and myelomeningocele may result in bowel and bladder sphincter dysfunction and sensorimotor loss below the lesion. The infant may initially be neurologically intact, but as the caudal end of cord is tethered to distal spine, as the spine grows traction injury leads to abnormalities in gait and sphincter function. Patients with spina bifida may also develop infectious complications, cortical malformations, and Chairi II malformations.

Tethered Cord

Patients with tethered cord can be identified through detection of a cutaneous lower back lesion, which is present in more than half of those affected even if otherwise asymptomatic. As the spine grows, the cord cannot ascend normally, leading to traction injuries and damage to the lower cord. Symptoms that result are pain in legs, limp, atrophy, sensory deficits, incontinence, and bowel/bladder difficulties. They may also develop frequent UTIs and enuresis. At the time symptoms arise, many alterations are irreversible. Early surgery can prevent motor and sphincter deterioration in function and can partially reverse already-acquired defects.

References

1. Botto l.D.,  et al. Neural Tube Defects NEJM Nov 1999. 
2. Weprin and Oakes Cocygeal Pits Pediatics May 2000
3. Drolet B.A. Cutaneous signs of neural tube dysraphism. Pediatr Clin North Am 2000
4. Sneineh A.K. Gabos P.G. Keller M.S. and Bowen J.R. Ultrasonography of the spine in neonates and young infants with a sacral skin dimple. J Pediatr Orthop 2002
5. Ackerman L. Spinal congenital Dermal Sinuses: A 30 Year Experience. Pediatrics Sept 2003
6. Benton T.J. Cheema R. and Nirgiotis J.G. A newborn with a skin lesion on the back. J Fam Pract Jan 2007
7. Ben-Sira L., et al. Low-risk lumbar skin stigmata in infants: the role of ultrasound screening. J Pediatr 2009
8. Zywicke H. and Roxxelle C.  Sacral Dimples.  Pediatrics in Review March 2011