Purpose: Paroxysmal tonic spasms (PTS) are brief, stereotypic, repetitive events of painful dystonic posturing that occur in association with multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD). They are a hallmark of central nervous system demyelination and are putatively due to ion channel dysfunction on or adjacent to demyelinated axons. In MS, responsible lesions have been reported in the internal capsule, cerebral peduncles, thalamus, and medulla. We reviewed the clinical characteristics, localization, and therapy of PTS associated with NMOSD. Methods: A retrospective patient chart review was conducted on consecutive Mayo Clinic Arizona patients evaluated for NMOSD over a two-year span. Clinical, laboratory, and neuroimaging data were collected for each patient. Results: Eighteen of 41 patients (43%) experienced PTS during evolution of NMOSD. Mean age of NMOSD onset was 42 years (range 10-68 years) and was similar in patients with and without PTS. Serum NMO-IgG was positive in 14/17 (82%) of PTS-affected and 14/21 (67%) of PTS-unaffected patients for which data were available (p=0.46; Fisher exact test). PTS occurred with the first myelitis attack of NMOSD in 7/18 (39%). Occurrence of PTS was associated with moderate to severe attacks of motor and sensory impairment in PTS-affected limbs and gadolinium-enhancing cord MRI lesions were detected in 60%. Brain MRI did not reveal acute lesions in any affected patient. Most PTS events began in one limb and spread to one or more limbs, but unilateral, single limb events occurred in 6/18 patients. The trunk was involved in 4 patients. PTS event duration ranged from 5 seconds to 2 minutes with a daily frequency of 2 to greater than 100 events. Aggravating factors included limb or trunk movement and event frequency increased at night. Marked reduction or elimination of PTS frequency and severity was achieved most commonly with carbamazepine or oxcarbazepine (5/7 trials) compared with other drugs (baclofen 2/6 trials; gabapentin 0/4 trials, diazepam 1/1 trial, other drugs or combinations 1/6 trials). Conclusions: Paroxysmal tonic spasms frequently accompany acute myelitis lesions in NMOSD. The phenotype of PTS appears similar in NMOSD and MS but the lesion localization differs. PTS do not appear to be associated with NMO-IgG serological status. Anticonvulsants, especially carbamazepine or oxcarbazepine, are usually effective in reducing or eliminating PTS.
Read More: Paroxysmal tonic spasms in neuromyelitis optica spectrum disorders