Having hair on the back is sometimes normal but the description you made typically reminds us a condition called Spina bifida occulta. If your niece has a tuft of hair in the lower part of the spinal cord (lower third bony prominence) there is a possibility of this condition. It is a harmless condition though. Spina bifida occurs in three forms, each varying in severity: 1) Occulta 2) Meningocoele and 3) Myelomeningocoele. Of which Spina bifida Occulta is the mildest form results in a small separation or gap in one or more of the vertebrae of the spine. Because the spinal nerves usually aren't involved, most children with this form of spina bifida have no signs or symptoms and experience no neurological problems. An abnormal tuft of hair, a collection of fat, a small dimple or a birthmark on the newborn's skin above the spinal defect may be the only visible indication of the condition. In fact, most people who have Spina bifida Occulta don't even know it, unless the condition is discovered during an X-ray for unrelated reasons. If your niece has any symptoms including loss of movement (paralysis), bowel and bladder problems, seizures and other medical complications, Check with the Pediatric Surgeon and take advice.