Spina Bifida Lecture

SPINA BIFIDA Defect in the vertebral arch of the spinal cord – incompletely formed or absent. Deformity occurs during development in utero Epidemiology  Incidence 1-2 per 1000, Highest rate in British isles (Ireland , Whales). Africans and African Americans have lowest rates  Familial tendency  Female predominance (60% children affected are female) Etiology Multifactorial inheritance Environmental factors – nutrition and folic acid; Teratogens–Drugs especially Carbamezapine and Valproic acid (anticonvulsants) Pathogenesis >Embryology  Trilaminar germ disk – 3rd week  Ectoderm cells overlying the notocord thicken to form the neural plate.  Lateral edges of neural plate elevate – neural folds with neural groove at the center  Neural crest cells migrate into mesenchyme and will form dorsal roots  Neural folds approach and fusei from the cervical area caudally and cranially forming neural tube  Anterior and posterior neuropores close at day 25 and 27 respectively  Spinal cord develops from neural tube  4th week, mesoderm proliferates at midline forming paraaxial mesoderm. This is arranged longitudinally forming somites. Each somite forms sclerotome around spinal cord which will differentiate to form the vertebrae Malformations Failure of fusion of dorsal vertebrae or failure of neural groove to close Classification 1. Spina bifida cystica  Menigocele – herniation of meninges  Meningomyelocele – spinal cord and nerve roots herniated. 94%  Lipomeningocele – lipomatous mass herniates and attaches to spinal cord tethering it  Myelocelemyelocele, or myeloschisis- open neural plate covered by epithelium and the neural plate has spread out onto the surface. 2. Spina bifida occulta - Lesion covered by skin, no herniation. Skin stigmata i.e. hairy patch, dimple, dermal sinus tract, lipoma, haemangioma etc seen. Lesion usually above the gluteal fold along the spinal cord Most common sites are the lumbar and sacral regions

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Associated anomalies Meningomyeloce show increased incidence of Chiari II malformation, Hydrocephalus Syringomyelia, Brainstem malformations, Cerebral ventricle abnormalities (cranial nerve) Midline abnormalities – VACTREL Pathophysiology Problem caused when spinal cord contents herniated or the neural tube is completely open and the ependymal layer is exposed (myelocele or myeloschisis) Lack of protection of nervous tissue causes damage mechanically or from lack of vascular support, desiccation, or from other insults. This results in features like neurogenic bowel and bladder, a contracted bladder leads to hydronephrosis along with infections and renal failure, Asymmetric innervation causes muscular imbalance, which leads to joint contractures and developmental deformities such as hip dislocation and spinal deformities. Seizure activity secondary to the neural tube defect may be noted. Chiari II malformations can cause deterioration of neurologic system with time and may present with signs of brainstem compression (stridor, central apnea, dysphagia, quadriparesis, nystagmus, myelopathy

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EVALUATION Aim to evaluate function and associated anomalies

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Initial examination >Local 

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Assess skin for skin stigmata If swelling, check for translucency, fluid thrill felt at the fontanelles. In meningomyelocele, sac appears velvety red or yellow with thin fragile vessels imbedded in the arachnoid may be able to se spinal cord and nerves as dark shadow when checking translucency. Meningocele usually covered partly or wholly by skin.

>General 1. Site and level of lesion 2. Motor and sensory levels Type 1 – segmental level with flacid paralysis, loss of sensation and loss of reflexes. Type 2 – Interruption of long tracts only either partially or complete 3. Associated hydrocephalus 4. Associated orthopaedic deformity (hip dislocation, CTEV, vagus and varus deformities, scoliosis etc) 5. Other associated deformities –vertebral, cardiac, anorectal, esophageal, renal. Give attention also to the anus to assess function of the sacral root

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Investigation Imaging Studies:

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Plain radiographs – orthopaedic deformities Ultrasound scan - to rule out hydrocephalus, tethering of spinal cord and urogenital tracts, kidneys

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CT scan

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To evaluate hydrocephalus and any obstructive lesions, Anatomical detail is generally good,

MRI

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Superior anatomical detail and assists the surgeon in choosing the best treatment. Necessary in endoscopic treatment, The lateral ventricles have a characteristic appearance in almost all patients with spina bifida the occipital horns are more dilated than the frontal horns, and the long axis of the lateral ventricles tend to be parallel.

Supportive investigations Full haemogram, urea and electrolytes, urine cultures and urinalysis, skin sensitivity tests, CSF studies TREATMENT Multidisciplinary orthopedics,

involving

neurology,

neurosurgery,

paediatrics,

physiotherapy,

>Immediate treatment   

Cover open NTD with saline moist sponge to avoid rupture or drying Give systemic antibiotics if leaking Constitute a management team

>Definitive Spina bifida cystica: Repair can be done immediately Step 1: Circumnavigate the neural placode without injuring any of the neural elements. Once completed, neural placode is placed into the spinal canal. Many methods available Step 2: Identification and dissection of the dura then covering the neural placode covered using the dura. If the dura is absent, the muscle fascia is used. Step 3: Skin closure in layers,

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Shunt placement during myelomeningocele closure Approximately 20% of all patients with myelomeningoceles have significant hydrocephalus at birth; another 60-70% of patients develop it after the myelomeningocele is closed. In select patients, placement of a shunt during the same operation for closure of a myelomeningocele is entirely reasonable. Outcome and prognosis

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Reduced intellect with hydrocephalus, CNS infections and degree of neurological impairment Continence – 10-15% of meningomyelocele have continence. Clean intermittent cathetirisation have better outcome Ambulation – depends on level of lesion and other muskuloskeletal affection >Hip flexors and quadriceps most important for ambulation. >Sacral lesions have better outcome. >Ability to ambulate reduces with age Classified into • Community ambulators – move indoors, outdoor with crutches with or without braces • Household ambulators – only indoors with crutches, with or without brace • Functional –On wheelchairs and learning to use crutches with or without braces • Non functional – wheelchair bound Independence – 60% will attend normal classes, 40% special classes. 10-40% of meningomyelocele patients are employable

Prevention Primary – folic acid preconception Secondary – Screening -Alpha fetoprotein in maternal blood or amniotic fluid at bwn 15 – 20 weeks; Ultrasound

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Surgery Grand round Spina bifida Presentor: Gregory Ganda