Spina Bifida

Populations and Risk Factors

• Congenital defect occurring between day 14 and 28 after conception, often before the woman knows she is pregnant
• Incidence approximately 0.5–1 per 1,000 live births; varies by ethnicity (higher in Hispanic and Caucasian populations)
• Risk significantly reduced (up to 70%) by folic acid supplementation (400 mcg daily) prior to and during early pregnancy
• Maternal risk factors: diabetes mellitus, obesity, valproic acid or carbamazepine use, folate deficiency, hyperthermia in early pregnancy
• Approximately 85% of children with myelomeningocele develop hydrocephalus
• Prior pregnancy with neural tube defect increases recurrence risk to 2–5%
• Higher prevalence in lower socioeconomic groups (associated with nutritional deficiency)

Causes and Pathophysiology

Neural Tube Closure Failure

• Between gestational days 14 and 28, the neural plate folds and fuses to form the neural tube; failure of posterior closure at any spinal level produces a defect in the vertebral arch
• The level and completeness of the closure failure determines the severity: incomplete posterior arch fusion only (occulta) vs. herniation of meninges (meningocele) vs. herniation of cord and nerve roots (myelomeningocele)
• The defect most commonly occurs at the lumbosacral junction (L5/S1), where the neural tube is last to close

Three Classifications

• Spina Bifida Occulta (SBO): mildest and most common form; one or more vertebral arches fail to fuse (usually L5 or S1) but the spinal cord and meninges remain in their normal position; often discovered incidentally on X-ray; cutaneous markers (dimple, tuft of hair, or birthmark over the sacrum) may be the only visible sign; neurological function is usually normal
• Meningocele: rare cystic form (approximately 4% of cystic cases); meninges protrude through the vertebral defect forming a CSF-filled sac, but the spinal cord remains in the canal; neurological deficit is typically minimal because the neural tissue is not involved
• Myelomeningocele: most severe and most common cystic form (approximately 94% of cystic cases); the spinal cord, nerve roots, and meninges all protrude through the defect; all neural structures below the lesion level sustain permanent lower motor neuron damage — this determines the pattern of paralysis, sensory loss, and autonomic dysfunction

Level-Dependent LMN Effects

• The neurological level of the myelomeningocele determines which nerve roots are damaged and therefore which muscles are weak or paralyzed — this creates predictable muscle imbalance patterns:
• Thoracic level (T12 and above): complete lower extremity paralysis; trunk instability; wheelchair-dependent; severe scoliosis from trunk muscle imbalance
• High lumbar (L1–L2): hip flexion present (iliopsoas) but no hip extension, abduction, or knee function; hip flexion contracture develops from unopposed iliopsoas
• Mid-lumbar (L3–L4): hip flexion and knee extension present (quadriceps); hip extension, abduction, and ankle dorsiflexion weak or absent; hip adduction contracture and genu recurvatum from quadriceps dominance without hamstring opposition
• Low lumbar (L5): ankle dorsiflexion present; plantarflexion weak; foot eversion present but inversion weak; calcaneus foot deformity from dorsiflexor dominance
• Sacral (S1–S2): near-normal lower extremity function; mild calf weakness; may ambulate independently; bladder/bowel dysfunction may be the primary deficit
• Muscle imbalance from the level-dependent LMN pattern drives secondary skeletal deformities over time: scoliosis, hip dislocation/subluxation, knee contractures, and foot deformities (equinovarus, calcaneus, cavovarus)
• Tethered cord: the spinal cord may adhere to surrounding tissues at the surgical repair site and fail to ascend normally during growth; cord tethering produces progressive neurological deterioration during growth spurts — new weakness, scoliosis progression, or bowel/bladder changes require urgent neurosurgical evaluation

Associated Conditions

• Hydrocephalus (85%): obstruction of CSF circulation at the level of the fourth ventricle (Arnold-Chiari II malformation) requires ventriculoperitoneal (VP) shunt placement; shunt malfunction produces sudden headache, nausea, altered consciousness — this is a medical emergency
• Bladder and bowel dysfunction: LMN damage to S2–S4 nerve roots causes neurogenic bladder (overflow incontinence) and bowel dysfunction; many patients require intermittent catheterization
• Decubitus ulcers: insensate skin over bony prominences (sacrum, ischial tuberosities, heels, greater trochanters) is highly vulnerable to pressure injury — the patient cannot feel the warning pain
• Latex allergy: repeated early surgical exposure (multiple corrective procedures in infancy) sensitizes approximately 50–70% of myelomeningocele patients to latex proteins; reactions range from contact dermatitis to life-threatening anaphylaxis

Signs and Symptoms

Spina Bifida Occulta

• Often asymptomatic and discovered incidentally
• Cutaneous markers over the sacrum or lower spine: dimple, tuft of hair, port wine stain, or lipoma
• Rarely causes neurological symptoms unless complicated by tethered cord

Myelomeningocele

• Visible at birth: open defect or repaired surgical scar over the lumbar/lumbosacral spine
• Lower limb muscle wasting — shriveled, flaccid legs with absent or diminished reflexes below the lesion level (LMN pattern)
• Level-dependent paralysis and sensory loss (see Causes and Pathophysiology)
• Skeletal deformities: scoliosis (neuromuscular — present in up to 90% of thoracic-level lesions), hip dislocation or subluxation, knee flexion/extension contractures, foot deformities
• Bladder and bowel incontinence
• Hydrocephalus: enlarged head circumference in infants; VP shunt visible/palpable under the scalp
• Wheelchair use (thoracic and high lumbar levels) or ambulatory with orthotics (low lumbar and sacral levels)
• Compensatory upper body patterns: shoulder impingement, carpal tunnel syndrome, and thoracic spine complaints from wheelchair propulsion and transfer activities

Assessment Profile

Subjective Presentation

• Chief complaint: varies by age and level — children may present through parental report of tightness, posture changes, or skin problems; adults typically present with upper body pain from wheelchair use, hip/knee contracture discomfort, back pain from scoliosis, or skin integrity concerns; functional goals center on maintaining independence and managing secondary MSK complications
• Pain quality: musculoskeletal pain from contractures, compensatory overuse, and skeletal deformities; neuropathic pain (burning, tingling) at the transition zone between innervated and denervated tissue; absence of pain below the lesion level is itself a critical clinical finding
• Onset: congenital; current complaints typically reflect progressive secondary complications (contracture development, scoliosis progression, wheelchair overuse injuries) rather than the primary lesion
• Aggravating factors: prolonged sitting (wheelchair users — pressure on ischial tuberosities); transfer activities (upper body strain); growth spurts in children (may worsen scoliosis or tether the cord); sustained positioning without pressure relief
• Easing factors: regular position changes; pressure redistribution; stretching of contractured muscles within available range; warmth for musculoskeletal discomfort
• Red flags: sudden headache with nausea, vomiting, lethargy, or altered consciousness in a shunted patient — VP shunt malfunction — emergency referral immediately; new or progressive weakness, change in bowel/bladder function, or worsening scoliosis in a growing child — possible tethered cord — urgent neurosurgical referral; skin breakdown over bony prominences in insensate areas — pressure ulcer requiring wound care

Observation

• Local inspection: surgical scar over the lumbosacral spine (repaired myelomeningocele); VP shunt tubing visible under the scalp and running subcutaneously along the neck/chest; lower limb muscle wasting; skin integrity — inspect all insensate areas for pressure redness, breakdown, or ulceration (sacrum, ischial tuberosities, heels, greater trochanters, medial malleoli); orthotics and assistive devices
• Posture: neuromuscular scoliosis (thoracic curve common in higher-level lesions); hip flexion contracture producing anterior pelvic tilt; kyphotic thoracolumbar posture in wheelchair users; compensatory upper body patterns — forward head, rounded shoulders, thoracic kyphosis from wheelchair propulsion
• Gait: level-dependent — thoracic/high lumbar: non-ambulatory (wheelchair); mid-lumbar: reciprocating gait orthosis or forearm crutches with characteristic circumduction pattern; low lumbar: ankle-foot orthosis (AFO) with residual gait deviation; sacral: near-normal gait with mild push-off weakness

Palpation

• Tone: LMN pattern below the lesion — flaccid, hypotonic muscles with absent or diminished deep tendon reflexes; above the lesion, compensatory hypertonicity in muscles doing double duty — hip flexors (if innervated), trunk extensors (scoliosis compensation), shoulder girdle muscles (wheelchair propulsion); chronic fibrotic contractures in shortened muscles opposing paralyzed antagonists (hip flexors, knee flexors, gastrocnemius depending on level)
• Tenderness: compensatory overuse areas — shoulders (infraspinatus, posterior deltoid), wrists (carpal tunnel from wheelchair propulsion), thoracic paraspinals (scoliosis compensation); transition zone between innervated and denervated tissue may be hypersensitive; insensate areas have NO tenderness — this is the critical safety finding
• Temperature: insensate limbs may have altered temperature regulation (cool to touch) due to reduced vascular tone and autonomic dysfunction below the lesion; warm areas over bony prominences in insensate regions may indicate early pressure injury
• Tissue quality: atrophied, thin, inelastic muscle tissue in denervated limbs; fibrotic contracture bands at hip, knee, and ankle; skin over bony prominences may be thin, fragile, and adherent; subcutaneous tissue loss in paralyzed limbs; VP shunt tubing palpable subcutaneously — avoid pressure on the shunt tract

Motion Assessment

• AROM: level-dependent — assess each joint systematically against the expected neurological level to confirm or identify changes; ROM is limited by contractures (hip flexion, knee flexion/extension, ankle plantarflexion/dorsiflexion depending on level); scoliosis limits trunk rotation and lateral flexion; upper extremity ROM should be assessed for wheelchair overuse injuries (shoulder impingement pattern)
• PROM / end-feel: firm (fibrotic) end-feel at contractured joints — long-standing contractures develop dense periarticular fibrosis; PROM should NOT be performed aggressively in insensate limbs — the patient cannot report pain, and excessive force risks fracture (osteoporotic bone from disuse) or soft tissue injury; assess hip, knee, and ankle PROM to document contracture severity and track change
• Resisted testing: meaningful only above the lesion level and at the transition zone; below the lesion, muscles are denervated (LMN) and resisted testing produces no contraction; at the transition zone, document strength grades to monitor for tethered cord progression (new weakness); upper extremity strength testing for wheelchair overuse injuries

Special Test Cluster

Monitoring note: In children and adolescents, reassessment of neurological level at each visit is important. New weakness, sensation change, or scoliosis progression may indicate tethered cord requiring neurosurgical referral.

Differential Assessment