500 - A Treatment of Painful Spasticity in a Patient with Primary Lateral Sclerosis

Primary lateral sclerosis (PLS) is a rare upper motor neuron disorder marked by progressive spasticity, most often in the lower extremities. Spasticity can impair quality of life more than weakness. Oral agents such as baclofen, tizanidine, and dantrolene are commonly used but often limited by adverse effects. Botulinum toxin type A (BoNT-A) has shown benefit in other spasticity syndromes, but evidence in PLS, particularly for pain, remains sparse.

Case Description: A 69-year-old woman with a 10-year history of PLS, confirmed by 2020 consensus criteria with EMG excluding lower motor neuron involvement, developed progressive disabling spasticity. Examination showed increased tone in the bilateral ankle plantarflexors and hamstrings. She described severe nocturnal spasms and painful cramping causing three to four nightly awakenings. Prior trials of baclofen, dantrolene, and tizanidine were ineffective or poorly tolerated. Because symptoms localized to the gastrocnemius and semitendinosus, these muscles were targeted for EMG-guided onabotulinumtoxinA injections (160 U total). Treatment produced ~90% reduction in spasms, complete resolution of nocturnal awakenings, pain relief, and improved ankle mobility. Benefits lasted ~3 months. Subsequent injection cycles with dose adjustments reproduced efficacy without adverse effects.

Discussions:

This case highlights the novel use of BoNT-A for painful spasticity in PLS. To ogur knowledge, it is the first to specifically report pain relief from BoNT-A in this population. While prior reports emphasized gait and functional outcomes, our case shows spasticity-related pain is also a critical therapeutic target. The durable benefit observed suggests BoNT-A can reduce nocturnal spasms and painful cramping, supporting its role in managing PLS-related pain.

Conclusions:

Painful spasticity in PLS is underrecognized and significantly affects QOL. EMG-guided BoNT-A provided safe, reproducible pain relief, improved sleep, and greater overall comfort. This case supports BoNT-A for refractory painful spasticity in PLS and highlights the need for studies targeting pain and sleep outcomes.