Jitter Evaluation in Distant and Adjacent Muscles after Botulinum Neurotoxin Type A Injection in 78 Cases

Abstract

To study the jitter parameters in the distant (DM) and the adjacent muscle (AM) after botulinum neurotoxin type A (BoNT/A) injection in 78 patients, jitter was measured by voluntary activation in DM (n = 43), and in AM (n = 35). Patients were receiving BoNT/A injections as a treatment for movement disorders. Mean age 65.1 years (DM) and 61.9 years (AM). The mean jitter was abnormal in 13.9% (maximum 41.4 µs) of DM, and 40% (maximum 43.7 µs) of AM. Impulse blocking was sparse. We found no correlation of the mean jitter to age, BoNT/A most recent injection (days/units), number of muscles injected, total BoNT/A units summated, number of total BoNT/A sessions, beta-blockers/calcium channel blockers use, and cases with local spread symptoms such as eyelid drop/difficulty swallowing. Maximum mean jitter (41.4/43.7 µs) for DM/AM occurred 61 and 131 days since the most recent BoNT/A, respectively. The far abnormal mean jitter (32.6/36.9 µs) occurred 229 and 313 days since the most recent BoNT/A. We suggested that jitter measurement can be done after BoNT/A in a given muscle other than the injected one, after 8 (DM) and 11 (AM) months, with reference >33 µs and >37 µs, respectively.

Concentric needle jitter: Reference values in stimulated Tibialis Anterior muscle

“…Tested facial muscles near the BoNT injections are the most affected in the percent of patients with increased jitter (up to 40%). The amount of jitter could rise to 56.6% above the reference upper limit and persist even after 11 months from the last injection (11). On the other hand, distant muscles were less affected when BoNT was injected into the facial muscles.…”

“…On the other hand, distant muscles were less affected when BoNT was injected into the facial muscles. Only 13.9% of the patients presented with increased jitter, and the rise above the reference limit was 38% and persisted even after 8 months from the last injection (11).…”

Single fiber electromyography and measuring jitter with concentric needle electrodes

“…In a recent study of 78 patients receiving BoNT for movement disorders, jitter was abnormal in a neighboring muscle in 40% and in a distant muscle in 14%. 34 The study authors suggest that jitter studies in the ED could be helpful clinically 8 mo after a previous BoNT injection in the face or neck and after 11 mo in a neighboring facial muscle if a higher upper limit of mean MCD in the tested muscle is used.…”

“…In addition to its effect on injected muscles, BoNT also spreads throughout the body and produces increased jitter in muscles distant from the injection site 33 . The effect of therapeutic BoNT is long‐lasting, often persisting to some degree for 6 mo or more, 34 and no exact time can be determined for its complete disappearance. The long‐lasting effect is usually greatest in muscles close to the injected muscles and probably is not dose‐dependent for the neighboring or distant muscles.…”

Diagnosis of Myasthenia Gravis

“…While highest in sensitivity, jitter measurements are not specific and may be abnormal in other synaptic disorders, in denervation and reinnervation processes (poly-and mononeuropathies), some myopathies, and with motor neuron disorder (MND) in particular [7,52,53,68]. Recently, it has been stated that botulinum toxin's cosmetic or therapeutic application should always be excluded by directed history [73]. In the clinical setting, the low specificity of SFEMG may be compensated, partially because not so many of the conditions with increased jitter appear as clinical MG-mimics [74].…”