The clinical utility of botulinum toxin injections targeted at the motor endplate zone in cervical dystonia.

BACKGROUND AND PURPOSE: Cervical dystonia (CD) patients usually receive repeated botulinum neurotoxin (BoNT) injections. The aims of this study were to evaluate the feasibility of motor endplate zone (MEZ) detection of relevant cervical muscles in CD patients receiving chronic BoNT treatment and to compare the treatment effect of half-dosed, endplate-targeted injections to standard BoNT injections. METHODS: In study 1, high-density surface electromyography (HD-sEMG) was recorded from the sternocleidomastoid (SCM) and splenius capitis (SC) muscles in 18 CD patients with ongoing BoNT treatment, by which the location of the MEZ was determined. In study 2, nine additional patients with rotational-type CD participated in a treatment effect study where they received either half of their regular BoNT dose through endplate-targeted injections or their normal BoNT dose through standard injections (crossover design). Dystonia severity was recorded before and 4 weeks after each treatment session (Toronto Western Spasmodic Torticollis Rating Scale severity subscore). RESULTS: In the SCM muscle the MEZ was located at the lower border of the superior third part of the muscle, and in the SC muscle at half muscle length. Endplate-targeted, half-dosed BoNT injection resulted in a similar treatment effect to injecting the full dose in the standard technique. CONCLUSIONS: Half-dosed, endplate-targeted BoNT injections lead to a similar treatment effect to the standard BoNT injection protocol. MEZ detection confronts the clinician with some technical challenges, such as the ability of accurate and technically optimal placement of the electrode grid and correct interpretation of the HD-sEMG signal.

New cases of adult-onset Sandhoff disease with a cerebellar or lower motor neuron phenotype.

Sandhoff disease is a lipid-storage disorder caused by a defect in ganglioside metabolism. It is caused by a lack of functional N-acetyl-beta-d-glucosaminidase A and B due to mutations in the HEXB gene. Typical, early-onset Sandhoff disease presents before 9 months of age with progressive psychomotor retardation and early death. A late-onset form of Sandhoff disease is rare, and its symptoms are heterogeneous. As drug trials that aim to intervene in the disease mechanism are emerging, the recognition and identification of Sandhoff disease patients-particularly those with atypical phenotypes-are becoming more important. The authors describe six new late-onset Sandhoff cases demonstrating cerebellar ataxia or lower motor neuron (LMN) involvement combined with, mostly subclinical, neuropathy. Two different mutations were found: IVS 12-26 G/A and c.1514G-->A. In patients with either progressive cerebellar ataxia or LMN disease in the setting of a possibly recessive disorder, Sandhoff disease should be suspected, even when the onset age is over 45 years.