**3. Rhizotomies**

## **3.1 Selective dorsal rhizotomy**

Normal cerebral inhibitions of the monosynaptic reflex arc at the spinal cord level are lost in children with spasticity from CP. This results with spasticity or hyperreflexia. Spasticity can be diminished via disrupting this hyperactive monosynaptic reflex arc [8]. At the dorsal root level, selectively transecting the afferent sensory fibers can significantly decrease spasticity. After lumbar laminectomy, the dorsal rootlets are localized in the cauda equina. Lumbosacral spinal sensory nerve rootlets with abnormal thresholds to electromyographic stimulation are sectioned to solve the sensory dysfunction in spasticity [6]. These are the afferent dorsal rootlets that terminate on relatively uninhibited alpha motor neurons [3]. When sectioned, spasticity can be relieved without losing other functions of dorsal roots. An abnormal response is considered when a muscle, not typically innervated at that root level, responds or when several muscle groups respond simultaneously [8]. Usually, 50% of the rootlets are cut [12]. The percentage of rootlets cut does not necessarily correspond to the level of spasticity or severity of neurologic involvement. Following the rhizotomy, there is a temporary weakness which returns to normal in few months. The other risks for this procedure are loss of bladder and bowel control, sensory loss, wound infection and meningitis, and finally leakage of the spinal fluid

through the wound. Best candidates for SDR are children with spastic diplegia, ambulatory, pure spastic, cognitively intact, and with good social structure [8]. SDR only resolves spasticity with no effect on dystonia. Children with quadriplegic CP may not benefit from SDR because of their significant dystonia. Contraindications are spasticity of spinal cord origin, athetosis, rigidity, history of previous tendon release/ lengthening, poor trunk control, severe weakness.

Selective dorsal (posterior) rhizotomy is a costly, irreversible complex neurosurgical procedure to reduce muscle tone in patients with CP. There is concern for muscle weakness, spinal deformity, and need for additional orthopedic procedures. Evaluation of multidisciplinary team when deciding to perform SDR is a must. Birth history, neuroimaging, strength, selective motor control, gait analysis, and presence of fixed deformities should be considered beforehand [13]. This procedure should be reserved for the patient population who does not respond or tolerate the pharmacological treatments and meet specific selection criteria. Also this procedure should be performed by a specialist multidisciplinary team with expertise in the management of spasticity. Intensive physiotherapy is mostly required for several months after procedure because the sensory input is reduced to sensory-motor reflex arcs in the spinal cord. Walking ability may be disrupted and different walking skills may be needed after the procedure.

Long-term follow-up studies report that SDR is well-tolerated over the years and improves functional outcomes and quality of life [13–15]. Daunter et al. reported less decline in gross motor function and required less hours of assistance in daily activities, however there was no difference for pain and fatigue [16]. Munger et al. reported improved gait quality in ten-year follow-up study [17]. In that study, non-SDR group required more orthopedic interventions and injections. Quality of life or functional and mobility measures did not differ among SDR and non-SDR groups.

### **3.2 Ventral rhizotomy**

In the presence of mixed tone, ventral rhizotomy (VR) may be performed in conjunction with SDR when there is limited access to ITB and DBS [6]. SDR inhibits the sensory dysfunction leading to spasticity, while VR aims to solve the motor abnormalities associated with dystonia. Using this procedure in diplegic/quadriplegic children with CP with mixed spasticity and dystonia, [18] reported improved joint range of motion, spasticity, and dystonia at one-year follow-up. Functional intraoperative monitoring is crucial for identifying the roots to preserve sphincter innervation. This combined intervention may have promise in children with severe mixed hypertonia.
