Congenital defect of spine and spinal cord.
Approximately 1:1000 live births. Risk in a subsequent
sibling is 3 to 4% and up to 10% with two previously affected
Unclear. Genetic predisposition is clearly
seen in the increased incidence among siblings, but nutritional and
environmental factors also have a role in the pathogenesis.
Arises from the failure of the fetal neural tube
to close within the first 3 weeks of gestation. This leads to the incomplete
fusion of the posterior lamina and spines of the vertebral column, most
commonly in the lumbosacral segments. The underlying spinal cord tissue may
also have developmental abnormalities, including syringomyelia,
diastematomyelia, and a tethered cord.
Clinical and radiological features. Investigation of the
abnormal spine includes plain radiograph, CT scan, and MRI with or without
contrast. CT scan of head is also recommended to assess the presence of
hydrocephalus and other neural abnormalities. Prenatal diagnosis can be made
by demonstration of the defect on ultrasonography and the detection of
alpha-fetoprotein in amniotic fluid. Alpha-fetoprotein in maternal serum is
an effective test for screening in high-risk patient.
In Spina Bifida Occulta, there is a midline defect of the spinal
column without protrusion of the spinal cord or meninges. Most affected
individuals are asymptomatic and lack neurological signs. In some cases, it
may be associated with patches of hair, a lipoma, discoloration of the skin,
or a dermal sinus in the midline of the low back. In meningocele, the
meninges herniate through the defect, but the spinal cord assumes normal
position in the spinal canal. The spinal cord may or may not be normal.
In Meningomyelocele, various amounts of neural tissue and meninges herniate through
the defect to form a sac-like cystic structure covered by a thin layer of skin
tissue that may rupture and leak cerebrospinal fluid. Early repair and closure is
recommended to reduce the risk of infection and to preserve neurological
function. The extent of the neurological deficit depends greatly on the
location of the meningomyelocele; it most commonly occurs in the lumbosacral
region. The conus medullaris is usually disrupted and abnormal. Clinical
features include flaccid paralysis of the lower limbs, absence of deep
tendon reflexes, lack of response to touch and pain, and urinary and fecal
incontinence. Lesions above T4 generally result in paraplegia, whereas
lesions below S1 allow ambulation. Hydrocephalus in association with a type
II Arnold-Chiari Malformation occurs in many of these patients. Postural
abnormalities of the lower limbs including clubfeet and subluxation of the
hip are also common.
Obtain a full history, including
perinatal history, previous anesthesia and surgical procedures, and any
known allergies. Neurological examination to document the motor, sensory,
and autonomic functions and the presence of hydrocephalus. Assess presence
of coexisting disease. Assess volume status and rehydrate if required.
For infants who present for
meningomyelocele repair, protect the neural sac ...