What is occult spinal dysraphism and how is it managed in patients with a history of recurrent infections, neurological deficits, or orthopedic abnormalities?

Occult Spinal Dysraphism: Definition and Clinical Management

Occult spinal dysraphism is a closed congenital malformation of the spine where the neural tube fails to close properly but remains covered by skin, often presenting with cutaneous markers and progressive neurological deterioration from spinal cord tethering. 1

Definition and Pathophysiology

Occult spinal dysraphism represents a spectrum of closed spinal malformations arising from developmental variants in the distal neural tube, where a persistent anatomic connection between neuroectoderm and cutaneous ectoderm prevents proper spinal cord ascent, causing tethered cord syndrome 1, 2. The tethering involves physical stretching of the spinal cord leading to impaired blood flow, diminished oxidative metabolism, and metabolic failure at the mitochondrial level 1.

Common types include:

• Lipomyelomeningocele 1, 2
• Dermal sinus tracts 1
• Diastematomyelia (split spinal cord) 3, 4
• Thickened filum terminale 1

Clinical Presentation by Age

Infants and Young Children

• Cutaneous markers are the primary diagnostic clue in asymptomatic infants 1
• High-risk cutaneous markers include: lumbosacral midline infantile hemangiomas (associated with spinal malformations in up to 55% as part of LUMBAR syndrome), dermal sinus tracts located cranial to the gluteal cleft, and subcutaneous masses 1
• Intermediate-risk markers include: midline or juxta-midline lumbosacral port wine stains or nevus flammeus simplex 1

Critical distinction: Coccygeal dimples located at or below an imaginary line between the tops of the gluteal cleft forks are innocent and require no imaging, while lumbosacral dermal sinus tracts located cranially on the flat sacrum are always abnormal and require surgical correction 1

School-Age Children and Adolescents

• Progressive muscle weakness and gait disturbances, with children becoming "slow" athletically and unable to keep up during sports 1
• Back and/or leg pain (dull, sharp, lancinating, or dysesthetic) aggravated by spinal flexion/extension or physical activity 1
• Muscle atrophy with thinning of calf muscles or "saber shins" that may be misdiagnosed as Charcot-Marie-Tooth syndrome 1
• Orthopedic deformities: progressive scoliosis (present in 60% of cases), exaggerated lumbosacral lordosis, foot deformities, and leg length discrepancies 1, 3

Urological Manifestations (All Ages)

Recurrent urinary tract infections are the predominant presenting sign in infants 1. As children mature, urological dysfunction becomes more apparent:

• Secondary urinary incontinence (especially with concurrent fecal incontinence/constipation) is the most common presentation in toilet-trained children 1
• Urgency, urge incontinence, stress incontinence, new-onset enuresis, frequency, and nocturia 1
• Urinary retention, dribbling stream, incomplete emptying 1
• Renal ultrasonography may reveal hydronephrosis, hydroureter, or bladder wall thickening 1

Urodynamic testing demonstrates either:

• Detrusor underactivity with denervation (lower motor neuron dysfunction) 1
• Small, thick-walled bladder with detrusor overactivity and detrusor-sphincter dyssynergia (upper motor neuron dysfunction) 1

Adults

A characteristic feature is sudden appearance of new pain and/or neurologic deficits after sudden back stretching during childbirth, falls onto buttocks, vigorous sports, or automobile crashes 1. Adults often have subtle abnormalities dating to early childhood: chronic constipation, late toilet training, previous orthopedic repairs, or scoliosis 1.

Associated Conditions Requiring Evaluation

Anorectal Malformations

Between 10% and 52% of children with anorectal malformations have associated dysraphic malformations, with complex malformations showing 43% association versus 11% for simple malformations 1, 5. The intimate temporospatial relationships during early embryogenesis result in concurrent malformations of caudal spinal cord, anorectal, and urogenital systems 1, 5.

Scoliosis

As many as 75% or more of patients with spinal dysraphism present with lower extremity neurologic and orthopedic abnormalities from tethering 1. Several risk factors suggest neural axis abnormalities in scoliosis patients: left thoracic curve, short segment curve, absence of apical segment lordosis/kyphosis, rapid curve progression (>1° per month), functionally disruptive pain, focal neurologic findings, male sex, and pes cavus 1.

Important caveat: Up to 2-4% of adolescent idiopathic scoliosis patients have neural axis abnormalities (Chiari I malformation, cord syrinx, cord tethering, intrinsic spinal cord tumor) despite appearing "idiopathic" 1.

Diagnostic Approach

Initial Evaluation

Any child with cutaneous midline skin lesions, leg pain, sensorimotor loss, orthopedic deformity, gait disturbance, or urological/gastrointestinal symptoms requires evaluation for underlying spinal cord tethering 1.

Imaging strategy:

• MRI of the spine is the definitive diagnostic modality for detecting and characterizing intraspinal abnormalities 1
• Ultrasonography is highly sensitive for detecting intraspinal anomalies and tethered cord in children under 2 years due to lack of posterior element ossification 6
• Plain radiographs may reveal bony abnormalities of the spine 1
• Renal ultrasonography for urological assessment 1

Urological Assessment

Urologic function should be assessed by:

• History (incontinence, frequency, recurrent UTIs) 1
• Imaging (renal ultrasonography) 1
• Formal urodynamic testing measuring bladder response to retrograde filling 1

Management

Surgical Intervention

Surgical treatment (tethered cord release) is advised to reduce chances of delayed or progressive loss of function 2. Tethered cord release is effective in arresting or improving neurologic symptoms, sensorimotor dysfunction, or urologic deterioration 1.

Critical limitation: Long-standing or severe orthopedic deformities are unlikely to improve with cord release alone and may require subsequent orthopedic intervention 1.

Timing Considerations

Early diagnosis and treatment are necessary to prevent irreversible neurological complications 3, 7, 4. The severity and reversibility of metabolic disturbances correlates with the severity and chronicity of tethering 1.

Special Surgical Considerations

Dermal sinus tracts require surgical correction to prevent CNS infection (meningitis or intraspinal abscess), which is the most feared complication as it generates intradural scar making subsequent excision more difficult 1, 4. Three patients in one series presented with meningitis caused by unusual aetiological agents 4.

Common Pitfalls

• Misdiagnosing muscle atrophy as Charcot-Marie-Tooth syndrome rather than recognizing tethered cord 1
• Confusing innocent coccygeal dimples with pathologic lumbosacral dermal sinus tracts - location relative to gluteal cleft is key 1
• Assuming "idiopathic" scoliosis without screening for neural axis abnormalities when risk factors are present 1
• Delaying evaluation in children with subtle signs (chronic constipation, late toilet training, minor orthopedic issues) who may have occult dysraphism 1
• Performing orthopedic corrective surgery before complete neurological evaluation 3