selective dorsal rhizotomy
/ SDR, dor-sal rye-ZOT-oh-mee /
In some children with spastic cerebral palsy, the legs are gripped by stiffness that no brace or medicine fully loosens — every step is a fight against tight, overactive muscles. Selective dorsal rhizotomy is a neurosurgical operation that aims at the root of that stiffness, quite literally. The surgeon cuts a carefully chosen fraction of the sensory nerve roots entering the lower spinal cord, permanently reducing the over-strong reflex loop that drives the spasticity in the legs.
To understand it, recall that spasticity in the legs is partly a runaway spinal reflex: sensory roots (the dorsal, or back, roots) carry stretch signals into the cord, which fire the muscle back too strongly. In SDR the surgeon exposes these dorsal roots, stimulates each rootlet electrically, watches which ones produce abnormal, spreading responses, and divides those — the selective part. Sensation is largely preserved because only a portion is cut and the motor (front) roots are left alone. The result is a lasting drop in lower-limb spasticity that, unlike injections, does not wear off.
SDR matters because, for the right child, it can change the trajectory of walking — but it is not for everyone, and that selection is the whole game. It is best evidenced in younger children with spastic diplegia who already have reasonable underlying strength and few fixed contractures, typically around GMFCS levels II to III. It is not a treatment for dyskinetic or ataxic CP, and removing spasticity unmasks any underlying weakness, so intensive physiotherapy afterward is essential and recovery takes months. The honest framing: SDR reduces stiffness durably, but it cannot create strength or coordination the child never had.
A five-year-old with spastic diplegia, good leg strength, and no fixed contractures has SDR. His legs immediately feel looser, but he is briefly weaker, and only after months of intensive physiotherapy does he walk more smoothly — proof that the surgery removed the brake, while therapy still had to build the engine.
Cutting selected sensory rootlets permanently lowers leg spasticity — but unmasks underlying weakness.
SDR is irreversible and only suits carefully selected children (typically younger spastic-diplegia patients with adequate strength). It removes spasticity but cannot supply strength or coordination, and skipping the intensive post-operative therapy wastes the operation; it does nothing for dyskinetic or ataxic CP.