Spinal Dysraphism

Definition

 

Spina Bifida is a congenital disorder in which the 2 halves of posterior vertebral arch fail to fuse

 

Dysraphism is maldevelopment of neural tube and skin

 

Cutaneous signs

 

Tuft of hair

Pigmented naevus

Scarred area

Post midline dimple / sinus

Lipoma

Tail

 

Associations

        

Cord tethering

Diastematomyelia

Cysts or lipoma of cord

Hydrocephalus

Arnold Chiari Malformation

- distal tethering may cause herniation of brain stem / cerebellum obstructing CSF flow

 

Epidemiology

 

10-30% of population

- 25% no cutaneous stigmata

- clinically significant dysraphism is rare

 

Embryology

 

Germ cell problem

- can get deformity in all three germ cell lines

 

1.  Somatic Ectoderm 

- cutaneous dysplasia

- hairy patch, naevus, dermal sinus

 

2.  Mesoderm

- vertebral dysplasia

- split in spinous process and laminal defects

 

3.  Neuroectodermal

- neural tube

- myelodysplasia, intramedullary and extramedullary growths associated with dysraphia

 

Commonest forms

 

Diastematomyelia

- spinal cord / filum terminale / both

- split sagittally by bony or fibrocartilaginous septum

 

Lumbosacral lipoma

 

Meningocele manque 

- loop of nerve root or trunk becomes adherent to dura

- then returns to cord or cauda close to origin

 

Arachnoid / Dermoid cyst

 

Tethered Cord

- tight filum terminale leading to tethered cord

- conus at level of coccyx in fetus

- upper border of L3 at birth

- upper border L2 by 5 years

 

Hydromyelia

 

Clinical Presentation

 

Vast majority asymptomatic

 

Any age from birth to maturity with

- short, wasted leg

- small foot

- cavovarus deformity

- paralytic valgus foot deformity

- trophic ulceration

 

DDx

 

Hemihypertrophy or hemiatrophy if small limb

CMT

CP 

 

Ultrasound 

 

Investigation of choice < 6 /12 presenting with midline lumbar dermal anomalies

 

X-ray

 

>6/12  

- varying degrees of spina bifida

- vertebral anomalies

 

MRI 

 

Management

 

Principles

 

Recognise the condition and arrest any further neurological deterioration

- MRI spine

- If find tethered cord etc needs neurosurgical opinion on whether release of cord worthwhile

 

Address foot deformity along typical lines once neurological deformity stabilised