Spastic Diplegia

Spastic diplegia is a form of bilateral spastic cerebral palsy in which the legs are affected more than the arms. It is the typical motor pattern of cerebral palsy after preterm birth, linked to periventricular white matter injury.

Cerebral palsy affects about 2 in 1000 live births. Spastic diplegia makes up about a quarter to a third of spastic cerebral palsy. Risk factors are preterm birth, periventricular leucomalacia, intraventricular haemorrhage, low birth weight, infection and multiple pregnancy.

Function is classified into five levels of gross motor function, from level I (walks without limitations) to level V (transported in a wheelchair). Most children with spastic diplegia are at levels I to III and walk, with or without aids.

Pathophysiology.

Injury to periventricular white matter damages the corticospinal fibres to the legs, which lie closest to the ventricles, giving more leg than arm involvement.

Spasticity, weakness and impaired selective motor control produce abnormal gait. Growth of bones outpaces muscle growth, which causes contractures and bony torsion.

• Delayed motor milestones, with stiff legs, toe walking, crossing of legs (scissoring), and difficulty with sitting or standing.
• Increased tone and brisk reflexes in the legs, clonus, contractures of the hip adductors, hamstrings and calf, with tight heel cords.
• Gait patterns: equinus, crouch, in toeing, and jump gait.
• Associated problems: strabismus and visual impairment, learning difficulties, epilepsy in a minority, and bladder problems.

Red flags.

• Regression, or progressive weakness, which suggests another diagnosis (hereditary spastic paraplegia, spinal cord lesion, dopa responsive dystonia).
• Hip migration, pain or rapid deterioration of gait.
• Bladder or bowel dysfunction or sensory level.

• Clinical diagnosis using history of risk factors, tone and reflex examination, and observation of movement, supported by MRI brain (periventricular leucomalacia).
• General movements assessment at 3 to 5 months and early developmental review for infants at risk.
• Hip surveillance with anteroposterior pelvic radiographs from age 2 years, measuring migration percentage at intervals (every 6 to 12 months for those at risk).
• Gait analysis, spine assessment, vision and hearing tests. Genetic and metabolic tests if MRI is atypical or if there is regression.

Differential diagnosis. Hereditary spastic paraplegia, dopa responsive dystonia, spinal cord lesions (tethered cord, tumour), leukodystrophy, myopathy and genetic disorders presenting as cerebral palsy.

• Physiotherapy: strengthening, stretching, gait training and task specific training. Orthoses (ankle foot orthoses) and mobility aids as needed.
• Spasticity: botulinum toxin A injections into the calf, hamstrings or adductors (total dose up to 16 units/kg and up to 400 units), combined with stretching and orthoses. Oral baclofen 0.3 mg/kg/day in 3 divided doses, increased gradually to a maximum of 2 mg/kg/day (40 mg daily under 8 years and 60 mg daily from 8 years), for generalised spasticity. Selective dorsal rhizotomy for selected children at levels II and III, aged about 3 to 8 years, with pure spasticity and good strength.
• Intrathecal baclofen is used for severe spasticity.
• Orthopaedic surgery: hip adductor release for early hip migration, and single event multilevel surgery for fixed contractures and torsional deformity, usually at age 7 to 12 years.
• Treat associated issues: epilepsy, vision, learning and pain. Provide educational and social support.

Monitoring. Hip radiographs on the surveillance schedule, gait, spasticity, contractures, spine and growth.

Referral and escalation. Refer to a paediatric neurodisability service, orthopaedics and neurosurgery for spasticity treatment, and urgently for hip displacement above 30% migration.