Myoclonus: An Electrophysiological Diagnosis.

BACKGROUND: Many different movement disorders have similar "jerk-like" phenomenology and can be misconstrued as myoclonus. Different types of myoclonus also share similar phenomenological characteristics that can be difficult to distinguish solely based on clinical exam. However, they have distinctive physiologic characteristics that can help refine categorization of jerk-like movements. OBJECTIVES: In this review, we briefly summarize the clinical, physiologic, and pathophysiologic characteristics of different types of myoclonus. The methodology and technical considerations for the electrophysiologic assessment of jerk-like movements are reviewed. A simplistic pragmatic approach for the classification of myoclonus and other jerk-like movements based on objective electrophysiologic characteristics is proposed. CONCLUSIONS: Clinical neurophysiology is an underutilized tool in the diagnosis and treatment of movement disorders. Various jerk-like movements have distinguishing physiologic characteristics, differentiated in the milliseconds range, which is beyond human capacity. We argue that the categorization of movement disorders as myoclonus can be refined based on objective physiology that can have important prognostic and therapeutic implications.

The role of the inferior parietal lobule in writer's cramp.

Humans have a distinguishing ability for fine motor control that is subserved by a highly evolved cortico-motor neuronal network. The acquisition of a particular motor skill involves a long series of practice movements, trial and error, adjustment and refinement. At the cortical level, this acquisition begins in the parieto-temporal sensory regions and is subsequently consolidated and stratified in the premotor-motor cortex. Task-specific dystonia can be viewed as a corruption or loss of motor control confined to a single motor skill. Using a multimodal experimental approach combining neuroimaging and non-invasive brain stimulation, we explored interactions between the principal nodes of the fine motor control network in patients with writer's cramp and healthy matched controls. Patients and healthy volunteers underwent clinical assessment, diffusion-weighted MRI for tractography, and functional MRI during a finger tapping task. Activation maps from the task-functional MRI scans were used for target selection and neuro-navigation of the transcranial magnetic stimulation. Single- and double-pulse TMS evaluation included measurement of the input-output recruitment curve, cortical silent period, and amplitude of the motor evoked potentials conditioned by cortico-cortical interactions between premotor ventral (PMv)-motor cortex (M1), anterior inferior parietal lobule (aIPL)-M1, and dorsal inferior parietal lobule (dIPL)-M1 before and after inducing a long term depression-like plastic change to dIPL node with continuous theta-burst transcranial magnetic stimulation in a randomized, sham-controlled design. Baseline dIPL-M1 and aIPL-M1 cortico-cortical interactions were facilitatory and inhibitory, respectively, in healthy volunteers, whereas the interactions were converse and significantly different in writer's cramp. Baseline PMv-M1 interactions were inhibitory and similar between the groups. The dIPL-PMv resting state functional connectivity was increased in patients compared to controls, but no differences in structural connectivity between the nodes were observed. Cortical silent period was significantly prolonged in writer's cramp. Making a long term depression-like plastic change to dIPL node transformed the aIPL-M1 interaction to inhibitory (similar to healthy volunteers) and cancelled the PMv-M1 inhibition only in the writer's cramp group. These findings suggest that the parietal multimodal sensory association region could have an aberrant downstream influence on the fine motor control network in writer's cramp, which could be artificially restored to its normal function.

[Clinical features of 63 patients with ataxia]. / Características clínicas de 63 pacientes con ataxia.

BACKGROUND: Ataxia can be classified as genetic, sporadic or acquired. AIM: To report the clinical features of a group of patients with ataxia. MATERIAL AND METHODS: Review of medical records of patients consulting in a specialized center in movement disorders. Those records in which the diagnosis of "ataxia" or "ataxic syndrome" appeared, were selected for the review. RESULTS: Of 4,282 records surveyed, the diagnosis of ataxia appeared in 95. After eliminating repeated or incomplete records, 63 were reviewed. RESULTS: Ataxia was sporadic, genetic and acquired in 27, 22 and 14 patients, respectively. The mean age at presentation for genetic, acquired and sporadic ataxia was 24, 46 and 53 years respectively. All autosomal dominant ataxias were type 3 spinocerebellar ataxia (SCA). Friedrich's ataxia was the most common recessive form. Most sporadic forms of ataxia were multiple system atrophy with predominant cerebellar ataxia (MSA-C) subtype. CONCLUSIONS: Considering the heterogeneity of patients with ataxia, we propose a method to approach them.

Características clínicas de 63 pacientes con ataxia / Clinical features of 63 patients with ataxia

Background: Ataxia can be classified as genetic, sporadic or acquired. Aim: To report the clinical features of a group of patients with ataxia. Material and Methods: Review of medical records of patients consulting in a specialized center in movement disorders. Those records in which the diagnosis of "ataxia" or "ataxic syndrome" appeared, were selected for the review. Results: Of 4,282 records surveyed, the diagnosis of ataxia appeared in 95. After eliminating repeated or incomplete records, 63 were reviewed. Results: Ataxia was sporadic, genetic and acquired in 27, 22 and 14 patients, respectively. The mean age at presentation for genetic, acquired and sporadic ataxia was 24, 46 and 53 years respectively. All autosomal dominant ataxias were type 3 spinocerebellar ataxia (SCA). Friedrich's ataxia was the most common recessive form. Most sporadic forms of ataxia were multiple system atrophy with predominant cerebellar ataxia (MSA-C) subtype. Conclusions: Considering the heterogeneity of patients with ataxia, we propose a method to approach them.