A newborn girl born at 37 weeks gestation after an uncomplicated vaginal delivery is evaluated due to poor tone of the lower extremities. She is not moving her legs and does not respond to heel prick. Deep tendon reflexes are 1+ in the lower extremities. Cervical spine range of motion and upper extremity examination are normal. A hemangioma is present over the midline lumbosacral area. Apgar scores were 7 and 9 at 1 and 5 minutes, respectively. Which of the following is the most likely diagnosis?
Closed spinal dysraphism | |
Pathophysiology |
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Clinical features |
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Management |
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*Age of onset & organ system involvement are variable. LMN = lower motor neuron; UTI = urinary tract infection. | |
This patient with a midline lumbosacral hemangioma has neurologic deficits in the lower extremities, findings concerning for a closed spinal dysraphism, also referred to as spina bifida occulta. The most common defect causing closed spinal dysraphism is failure of vertebral arch fusion, typically at L5-S1. Other spinal cord anomalies may also be seen, but in contrast to open spinal dysraphism, the overlying skin in closed spinal dysraphism is intact without exposure of neuronal tissue.
The severity and age of presentation of closed spinal dysraphism can vary greatly. Most newborns are asymptomatic or have only cutaneous findings, such as a lumbosacral hemangioma, pit, nevus, or hair tuft. However, a minority may have an underlying spinal cord anomaly (eg, tight filum terminale), leading to stretching of the distal spinal cord and symptoms of tethered cord syndrome. Tethered cord syndrome typically manifests as lower motor neuron signs: lower extremity weakness, loss of sensation, hypotonia, and hyporeflexia, as seen in this patient. The presence of upper motor neuron (UMN) signs (eg, hypertonia, hyperreflexia) argues against the diagnosis of tethered cord syndrome.
Older children who develop tethered cord syndrome due to closed spinal dysraphism often have abnormal gait, urinary dribbling, or back pain. In addition, orthopedic conditions are common and can include foot deformities, scoliosis, and, in nonambulatory patients, neuromuscular (ie, secondary) hip dysplasia.
(Choice A) Cerebral palsy is a nonprogressive neurologic injury that most commonly causes lower extremity weakness and UMN signs. In addition, this patient's lumbosacral hemangioma makes spinal dysraphism more likely.
(Choice B) Muscular dystrophy (eg, Duchenne) presents in early childhood with proximal muscle weakness. Hypotonia and hyporeflexia commonly develop, but sensation is not affected. Moreover, newborns with this disorder are usually asymptomatic.
(Choice C) Spinal cord infarction is extremely uncommon in newborns and results in UMN findings. This patient's age, hypotonia, and hyporeflexia make this diagnosis unlikely.
(Choice E) Vitamin B12 deficiency is chronic and does not occur in newborns because stores of this vitamin are maternally derived from placental passage.
Educational objective:
Closed spinal dysraphism (spina bifida occulta) is due to failed fusion of the vertebral arches. Symptomatic newborns can have cutaneous manifestations (eg, lumbosacral hemangioma) on the lower back and/or neurologic deficits due to tethered cord syndrome. Neurologic manifestations include lower motor neuron signs (eg, weakness, hypotonia, hyporeflexia, sensory loss).