Thalamic Local Field Potentials and Closed-Loop Deep Brain Stimulation in Orthostatic Tremor.

BACKGROUND: Orthostatic tremor (OT) is a rare movement disorder characterized by a feeling of unsteadiness and a high-frequency tremor in the legs (13-18 Hz) relieved by sitting or walking. OBJECTIVES: The aims were to study the brain electrophysiology captured chronically in a person with medication-refractory OT while standing and walking and in the semi-recumbent position using bilateral ventral intermedius nucleus deep brain stimulation (DBS) (Medtronic Percept PC) and to describe the clinical use of closed-loop DBS. METHODS: A sensing survey was used to capture baseline local field potentials (LFPs) while standing. Livestreamed LFPs were synchronized with data collected from two accelerometers (legs) and gait analysis during OFF stimulation and continuous and closed-loop DBS. RESULTS: Strong oscillatory coupling between thalamic LFP and leg tremor with significant coherence at 14.65 Hz was found during weight-bearing. Single-threshold adaptive DBS (sensing at this frequency) was superior to continuous stimulation in reducing tremor and stimulation-related gait ataxia. CONCLUSIONS: This study provides new insights into both the pathophysiology and management of OT. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Functional disorders as a common motor manifestation of COVID-19 infection or vaccination.

BACKGROUND AND PURPOSE: There have been over 500 million confirmed cases of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), also known as coronavirus disease 2019 (COVID-19), across the globe. To date, a broad spectrum of neurological manifestations following acute infections as well as COVID-19 vaccines have been reported. The aim of this study was to describe the spectrum of neurological manifestations seen in the 'COVID-19 clinic' established in a tertiary Movement Disorders clinic. METHODS: In this consecutive case-series study over the period March 2020-January 2022, clinical information regarding demographic data, clinical history and examination findings, investigation results and video recordings of outpatients with motor manifestations associated with COVID-19 infection or vaccination were reviewed. RESULTS: Twenty-one adult patients were reviewed in this ad hoc clinic at Toronto Western Hospital. The majority of the patients were female (76%) and the mean (range) age was 50.7 ± 17.2 (21-80) years. Nine patients (43%) presented with motor manifestations following COVID-19 infection. Twelve patients (57%) developed neurological symptoms following at least one dose of the mRNA or viral vector-based COVID-19 vaccine. The most common manifestation observed was a functional movement disorder (43%). The vaccine group demonstrated a higher number of functional disorders compared to the infection group (58% vs. 22%; p = 0.08). CONCLUSION: Functional motor manifestations can be associated with COVID-19 and are likely to be under-reported. In view of the co-existence of functional symptoms, movement disorders and mental health conditions observed in this study, we would advocate the use of dedicated COVID-19 Neurology clinics with full access to an experienced multidisciplinary team.

Dystonic crises in dopa-responsive dystonia induced by energy drinks.

We present an interesting case of recurrent dystonic crises in dopa-responsive dystonia (DRD) likely induced by excessive consumption of aspartame-containing products, in particular sugar-free energy drinks. This has a strong practical value as acute presentations to the emergency department can be avoided in these susceptible individuals. Usual medical and dietary advice in the treatment of DRD would include the avoidance of high-dose phenylalanine-containing products, and to this we would advocate the avoidance of high-dose aspartame-containing products.

"Stretched Slinky" Sign: Another Clue to Functional Tremor.

Objective: Functional tremor (FT) is the most common functional movement disorder, although its diagnosis can be challenging. Archimedes spiral drawings can be helpful in eliciting additional signs associated with tremor. Here, we present examples of an unusual looping of Archimedes spirals only seen in FT. Methods: Clinical information regarding demographic data, clinical history, and examination findings (including Archimedes spiral drawings) and investigation results of patients with FT in the movement disorders clinic were reviewed. Results: Three paradigmatic patients with FT demonstrated a unique looping appearance of Archimedes spiral drawings, akin to the appearance of a stretched slinky. The degree of randomness of the spirals varied from patient to patient and often mirrored tremor severity, regardless of the diagnosis. Discussion: The clinical hallmarks of a FT include a variable combination of positive signs, such as inconsistency (variability and distractibility), incongruence with known tremor syndromes, entrainment, and coactivation, although these findings might not always be present. We describe a unique appearance of spiral drawings, which could add as another clinical sign for FT. Consider looping of spirals as another diagnostic clue to FT.