A Critical Investigation of Cerebellar Associative Learning in Isolated Dystonia.

Background: Impaired eyeblink conditioning is often cited as evidence for cerebellar dysfunction in isolated dystonia yet the results from individual studies are conflicting and underpowered.

Objective: To systematically examine the influence of dystonia, dystonia subtype, and clinical features over eyeblink conditioning within a statistical model which controlled for the covariates age and sex.

Methods: Original neurophysiological data from all published studies (until 2019) were shared and compared to an age- and sex-matched control group.

Toxic Leukoencephalopathy Presenting as Lethal Catatonia.

Introduction: Catatonia is a syndrome that can present in different forms and can occur in multiple psychiatric and somatic conditions. This case report describes lethal catatonia caused by delayed toxic leukoencephalopathy after excessive use of cocaine and methadone. The characteristic radiographic imaging and biphasic course are discussed.

Normal eyeblink classical conditioning in patients with fixed dystonia.

Fixed dystonia without evidence of basal ganglia lesions or neurodegeneration typically affects young women following minor peripheral trauma. We use eyeblink classical conditioning (EBCC) to study whether cerebellar functioning is abnormal in patients with fixed dystonia, since this is part of the pathophysiology of primary dystonia. An auditory tone (conditioning stimulus) was paired with a supraorbital nerve stimulus (unconditioned stimulus) with a delay of 400 ms in order to yield conditioned responses.

Inhibition of the dorsal premotor cortex does not repair surround inhibition in writer's cramp patients.

Writer's cramp is a task-specific form of focal dystonia, characterized by abnormal movements and postures of the hand and arm during writing. Two consistent abnormalities in its pathophysiology are a loss of surround inhibition and overactivity of the dorsal premotor cortex (PMd). This study aimed to assess a possible link between these two phenomena by investigating whether PMd inhibition leads to an improvement of surround inhibition, in parallel with previously demonstrated writing improvement.

Cerebellar theta burst stimulation impairs eyeblink classical conditioning.

Theta burst stimulation (TBS) protocols of repetitive transcranial magnetic stimulation (rTMS) have after-effects on excitability of motor areas thought to be due to LTP- and LTD-like processes at cortical synapses. The present experiments ask whether, despite the low intensities of stimulation used and the anatomy of the posterior fossa, TBS can also influence the cerebellum. Acquisition and retention of eyeblink classical conditioning (EBCC) was examined in 30 healthy volunteers after continuous theta burst stimulation (cTBS) over the right cerebellar hemisphere.

A distinctive pattern of cortical excitability in patients with the syndrome of dystonia and cerebellar ataxia.

Objective: The syndrome of dystonia and cerebellar ataxia (DYTCA) is a recently described condition where cervical dystonia and mild cerebellar ataxia are the major clinical features. Here we attempted to explore the pathophysiology of this condition by comparing measurements of cortical excitability between patients with DYTCA, typical primary dystonia and healthy controls.

Methods: Motor threshold, active MEP recruitment and CSP duration were measured and the excitability of the intracortical inhibitory and excitatory circuits was assessed at rest using a paired pulse protocol.

Cerebellar brain inhibition is decreased in active and surround muscles at the onset of voluntary movement.

Highly selective activation of the desired muscles for each movement and inhibition of adjacent muscles is attributed to surround inhibition (SI) which differentially modulates corticospinal excitability in active and surrounding muscles. Cerebellar brain inhibition (CBI) is another inhibitory neuronal network which is known to be active at rest and during tonic muscle contraction. The way in which CBI may be modulated at movement onset and its relationship with SI has not previously been investigated.

Patients with primary cervical dystonia have evidence of discrete deficits in praxis.

Background: Functional imaging and electrophysiological data from patients with primary dystonia reveal widespread abnormalities in brain areas associated with higher motor functions but to date there has been little investigation of the functional consequences of these abnormalities. The aim of this study was to use a battery of tests of praxis, based on those tests used in routine clinical examination, to uncover evidence of higher motor dysfunction in patients with primary cervical dystonia.

Methods: Praxis was assessed in 13 patients with primary cervical dystonia without hand involvement and in 29 age and sex matched controls.