A cutaneous abnormality or "blemish" overlying the spine indicates the possibility of occult spinal dysraphism. They are especially frequent in the lumbosacral area (Figure 307.1). Neonates with a subcutaneous fatty pad, angiomatous patch, a hairy tuft, or a dermal sinus in the lumbosacral region should have ultrasound or MRI of this area.

Figure 307.1.— Lumbar sinus. A spinal MRI showed an intraspinal lipoma.

Neonates with angiomatous patch may have Cobb syndrome. Cobb syndrome consists of the association of cutaneous angiomatosis and angiomatosis of the spinal cord, the adjacent meninges, or both (Figure 307.2).

A	B	C

Figure 307.2.— Cobb syndrome. [A] Angiomatous patch with prominent fat component; [B] MRI showing the patch and intramedullary pathology; [C] MRA showing the vascularity of the lesion.

Imaging studies detect the position of the conus medullaris, the presence of a tethered cord, and associated central nervous system malformations. Neonates with lumbosacral blemish should undego an ultrasound of the lumbosacral region (Figure 307.3).

Figure 307.3.— [A] Normal conus medullaris: lowest portion rests between L1 and L2 (arrow); roots are not straight (between arrow heads). [B] Abnormal conus medullaris: lowest portion rests between L4 and L5 (arrow); roots are straight (between arrow heads).