Boosting brain-computer interfaces with functional electrical stimulation: potential applications in people with locked-in syndrome.

Individuals with a locked-in state live with severe whole-body paralysis that limits their ability to communicate with family and loved ones. Recent advances in brain-computer interface (BCI) technology have presented a potential alternative for these people to communicate by detecting neural activity associated with attempted hand or speech movements and translating the decoded intended movements to a control signal for a computer. A technique that could potentially enrich the communication capacity of BCIs is functional electrical stimulation (FES) of paralyzed limbs and face to restore body and facial movements of paralyzed individuals, allowing to add body language and facial expression to communication BCI utterances. Here, we review the current state of the art of existing BCI and FES work in people with paralysis of body and face and propose that a combined BCI-FES approach, which has already proved successful in several applications in stroke and spinal cord injury, can provide a novel promising mode of communication for locked-in individuals.

Association between lesion location and sensorimotor rhythms in stroke - a systematic review with narrative synthesis.

BACKGROUND: Stroke causes alterations in the sensorimotor rhythms (SMRs) of the brain. However, little is known about the influence of lesion location on the SMRs. Understanding this relationship is relevant for the use of SMRs in assistive and rehabilitative therapies, such as Brain-Computer Interfaces (BCIs).. METHODS: We reviewed current evidence on the association between stroke lesion location and SMRs through systematically searching PubMed and Embase and generated a narrative synthesis of findings. RESULTS: We included 12 articles reporting on 161 patients. In resting-state studies, cortical and pontine damage were related to an overall decrease in alpha (∼8-12 Hz) and increase in delta (∼1-4 Hz) power. In movement paradigm studies, attenuated alpha and beta (∼15-25 Hz) event-related desynchronization (ERD) was shown in stroke patients during (attempted) paretic hand movement, compared to controls. Stronger reductions in alpha and beta ERD in the ipsilesional, compared to contralesional hemisphere, were observed for cortical lesions. Subcortical stroke was found to affect bilateral ERD and ERS, but results were highly variable. CONCLUSIONS: Findings suggest a link between stroke lesion location and SMR alterations, but heterogeneity across studies and limited lesion location descriptions precluded a meta-analysis. SIGNIFICANCE: Future research would benefit from more uniformly defined outcome measures, homogeneous methodologies, and improved lesion location reporting.

Resective Epilepsy Surgery, QUality of life and Economic evaluation (RESQUE): the change in quality of life after resective epilepsy surgery-protocol for a multicentre, prospective cohort study.

INTRODUCTION: Resective epilepsy surgery is often seen as a last resort when treating drug-resistant epilepsy. Positive results on quality of life (QoL) and economic benefits after surgery argue for a less restrictive attitude towards epilepsy surgery for drug-resistant epilepsy. QoL and economic benefits are country-dependent. The objective of the Resective Epilepsy Surgery, QUality of life and Economic evaluation (RESQUE) trial is to evaluate the change in QoL before and after epilepsy surgery in Dutch people with drug-resistant epilepsy. The results will form part of an economic evaluation of epilepsy surgery in people with epilepsy (PWE) in The Netherlands. METHODS AND ANALYSIS: A longitudinal prospective multicentre cohort study involving 100 PWE undergoing epilepsy surgery between 2019 and 2025 is being performed in three Dutch academic hospitals. Excluded are PWE who have a lower level of intelligence (TIQ<70) or who do not master the Dutch language. Before surgery and 3, 6, 12 and 24 months after surgery, PWE receive validated online questionnaires (QOLIE-31, EQ-5D, iMCQ and iPCQ) on QoL, cost of care, expectations and satisfaction. Primary outcome is the change in QoL. Secondary outcomes are change in generic QoL, seizure reduction (International League Against Epilepsy Outcome Classification), medical consumption, productivity, the correlation between QoL and seizure reduction and expectation of and satisfaction with the surgery. ETHICS AND DISSEMINATION: The study design has been approved by the Medical Ethics Review Committee (METC) of Maastricht UMC+ (2019-1134) and the Amsterdam UMC (vu). At the time of writing, UMC Utrecht is in the process of considering approval. The study will be conducted according to the Dutch Medical Research Involving Human Subjects Act and the Declaration of Helsinki. The results will be publicly disclosed and submitted for publication in international peer-reviewed scientific journals. There is no veto on publication by the involved parties. TRIAL REGISTRATION: NL8278; Pre-results.

Towards predicting ECoG-BCI performance: assessing the potential of scalp-EEG.

Objective. Implanted brain-computer interfaces (BCIs) employ neural signals to control a computer and may offer an alternative communication channel for people with locked-in syndrome (LIS). Promising results have been obtained using signals from the sensorimotor (SM) area. However, in earlier work on home-use of an electrocorticography (ECoG)-based BCI by people with LIS, we detected differences in ECoG-BCI performance, which were related to differences in the modulation of low frequency band (LFB) power in the SM area. For future clinical implementation of ECoG-BCIs, it will be crucial to determine whether reliable performance can be predicted before electrode implantation. To assess if non-invasive scalp-electroencephalography (EEG) could serve such prediction, we here investigated if EEG can detect the characteristics observed in the LFB modulation of ECoG signals.Approach. We included three participants with LIS of the earlier study, and a control group of 20 healthy participants. All participants performed a Rest task, and a Movement task involving actual (healthy) or attempted (LIS) hand movements, while their EEG signals were recorded.Main results.Data of the Rest task was used to determine signal-to-noise ratio, which showed a similar range for LIS and healthy participants. Using data of the Movement task, we selected seven EEG electrodes that showed a consistent movement-related decrease in beta power (13-30 Hz) across healthy participants. Within the EEG recordings of this subset of electrodes of two LIS participants, we recognized the phenomena reported earlier for the LFB in their ECoG recordings. Specifically, strong movement-related beta band suppression was observed in one, but not the other, LIS participant, and movement-related alpha band (8-12 Hz) suppression was practically absent in both. Results of the third LIS participant were inconclusive due to technical issues with the EEG recordings.Significance. Together, these findings support a potential role for scalp EEG in the presurgical assessment of ECoG-BCI candidates.

Distinctive tics suppression network in Gilles de la Tourette syndrome distinguished from suppression of natural urges using multimodal imaging.

BACKGROUND AND OBJECTIVES: Gilles de la Tourette syndrome (GTS) is a neuropsychiatric disorder characterized by tics. A hallmark of GTS is the ability to voluntarily suppress tics. Our aim was to distinguish the neural circuits involved in the voluntary suppression of ocular tics in GTS patients from blink suppression in healthy subjects. METHODS: Fifteen GTS patients and 22 healthy control subjects were included in a multimodal study using eye-tracker recordings during functional MRI (fMRI). The ability to suppress tics/blinks was compared both on subjective (self-rating) and objective (eye-tracker) performance. For fMRI analysis we used a novel designed performance-adapted block design analysis of tic/blink suppression and release based on eye-tracker monitoring. RESULTS: We found that the subjective self-reported ability to suppress tics or blinks showed no significant correlation with objective task performance. In GTS during successful suppression of tics, the dorsal anterior cingulate cortex and associated limbic areas showed increased activation. During successful suppression of eye blinks in healthy subjects, the right ventrolateral prefrontal cortex and supplementary and cingulate motor areas showed increased activation. CONCLUSIONS: These findings demonstrate that GTS patients use a characteristic limbic suppression strategy. In contrast, control subjects use the voluntary sensorimotor circuits and the classical 'stop' network to suppress natural urges. The employment of different neural suppression networks provides support for cognitive behavioral therapy in GTS.

Specific EEG markers in POLG1 Alpers' syndrome.

OBJECTIVE: To examine whether rhythmic high-amplitude delta with superimposed (poly)spikes (RHADS) in EEG allow a reliable early diagnosis of Alpers-Huttenlocher syndrome (AHS) and contribute to recognition of this disease. METHODS: EEGs of nine patients with DNA-proven AHS and fifty age-matched patients with status epilepticus were retrospectively examined by experts for the presence of RHADS and for accompanying clinical signs and high-frequency ripples. Reproducibility of RHADS identification was tested in a blinded panel. RESULTS: Expert defined RHADS were found in at least one EEG of all AHS patients and none of the control group. RHADS were present at first status epilepticus in six AHS patients (67%). Sometimes they appeared 5-10 weeks later and disappeared over time. RHADS were symptomatic in three AHS patients and five AHS patients showed distinct ripples on the (poly)spikes of RHADS. Independent RHADS identification by the blinded panel resulted in a sensitivity of 87.5% (95% CI 47-100) and a specificity of 87.5% (95% CI 77-94) as compared to the experts' reporting. CONCLUSION: RHADS are a highly specific EEG phenomenon for diagnosis of AHS and can be reliably recognized. Clinical expression and EEG ripples suggest that they signify an epileptic phenomenon. SIGNIFICANCE: RHADS provide a specific tool for AHS diagnosis.

Familial Cortical Myoclonic Tremor and Epilepsy, an Enigmatic Disorder: From Phenotypes to Pathophysiology and Genetics. A Systematic Review.

Background: Autosomal dominant familial cortical myoclonic tremor and epilepsy (FCMTE) is characterized by distal tremulous myoclonus, generalized seizures, and signs of cortical reflex myoclonus. FCMTE has been described in over 100 pedigrees worldwide, under several different names and acronyms. Pathological changes have been located in the cerebellum. This systematic review discusses the clinical spectrum, treatment, pathophysiology, and genetic findings. Methods: We carried out a PubMed search, using a combination of the following search terms: cortical tremor, myoclonus, epilepsy, benign course, adult onset, familial, and autosomal dominant; this resulted in a total of 77 studies (761 patients; 126 pedigrees) fulfilling the inclusion and exclusion criteria. Results: Phenotypic differences across pedigrees exist, possibly related to underlying genetic differences. A "benign" phenotype has been described in several Japanese families and pedigrees linked to 8q (FCMTE1). French patients (5p linkage; FCMTE3) exhibit more severe progression, and in Japanese/Chinese pedigrees (with unknown linkage) anticipation has been suggested. Preferred treatment is with valproate (mind teratogenicity), levetiracetam, and/or clonazepam. Several genes have been identified, which differ in potential pathogenicity. Discussion: Based on the core features (above), the syndrome can be considered a distinct clinical entity. Clinical features may also include proximal myoclonus and mild progression with aging. Valproate or levetiracetam, with or without clonazepam, reduces symptoms. FCMTE is a heterogeneous disorder, and likely to include a variety of different conditions with mutations of different genes. Distinct phenotypic traits might reflect different genetic mutations. Genes involved in Purkinje cell outgrowth or those encoding for ion channels or neurotransmitters seem good candidate genes.

Safety and efficiency of medication withdrawal at home prior to long-term EEG video-monitoring.

PURPOSE: Long-term video-EEG monitoring (LTM) is frequently used for diagnostic purposes and in the workup of epilepsy surgery to determine the seizure onset zone. Different strategies are applied to provoke seizures during LTM, of which withdrawal of anti-epileptic drugs (AED) is most effective. Remarkably, there is no standardized manner of AED withdrawal. For instance, the majority of clinics taper medication during clinical admission, whereas we prefer to taper medication at home prior to admission. Our aim was to study the advantages (efficiency and diagnostic yield) and disadvantages (safety and complication rates) of predominantly tapering of medication at home. METHOD: We report a retrospective observational cohort of 273 patients who had a LTM at our tertiary epilepsy center from 2005 until 2011. Provocation methods to induce seizures were determined on individual basis. Success rate (duration of admittance, time to first seizure, efficiency and diagnostic yield) and complications and serious adverse events were assessed. RESULTS: AED were tapered in 180 (66%) patients, in 93 (24%) of these patients with additional (partial) sleep deprivation. In all of these patients tapering started at home one to four weeks prior to admission. In the other patients, only (partial) sleep deprivation or none provocation method at all was applied. Seizure recordings were successful in 79,9% of patients. Complications occurred in 19 patients (10.9%) of which 3 had (1.7%) serious adverse events (status epilepticus (SE)) with AED withdrawal. These complications only occurred during admittance, not at home. CONCLUSIONS: AED withdrawal at home prior to LTM is an efficient and convenient method to increase the diagnostic yield of LTM and appears relatively safe.

Randomised controlled trial of escitalopram for cervical dystonia with dystonic jerks/tremor.

OBJECTIVE: Trials for additional or alternative treatments for cervical dystonia (CD) are scarce since the introduction of botulinum neurotoxin (BoNT). We performed the first trial to investigate whether dystonic jerks/tremor in patients with CD respond to the selective serotonin reuptake inhibitor (SSRI) escitalopram. METHODS: In a randomised, double-blind, crossover trial, patients with CD received escitalopram and placebo for 6 weeks. Treatment with BoNT was continued, and scores on rating scales regarding dystonia, psychiatric symptoms and quality of life (QoL) were compared. Primary endpoint was the proportion of patients that improved at least one point on the Clinical Global Impression Scale for jerks/tremor scored by independent physicians with experience in movement disorders. RESULTS: Fifty-threepatients were included. In the escitalopram period, 14/49 patients (29%) improved on severity of jerks/tremor versus 11/48 patients (23%) in the placebo period (P=0.77). There were no significant differences between baseline and after treatment with escitalopram or placebo on severity of dystonia or jerks/tremor. Psychiatric symptoms and QoL improved significantly in both periods compared with baseline. There were no significant differences between treatment with escitalopram and placebo for dystonia, psychiatric or QoL rating scales. During treatment with escitalopram, patients experienced slightly more adverse events, but no serious adverse events occurred. CONCLUSION: In this innovative trial, no add-on effect of escitalopram for treatment of CD with jerks was found on motor or psychiatric symptoms. However, we also did not find a reason to withhold patients treatment with SSRIs for depression and anxiety, which are common in dystonia. TRIAL REGISTRATION NUMBER: NTR2178.

Clinical decision-making in functional and hyperkinetic movement disorders.

OBJECTIVE: Functional or psychogenic movement disorders (FMD) present a diagnostic challenge. To diagnose FMD, clinicians must have experience with signs typical of FMD and distinguishing features from other hyperkinetic disorders. The aim of this study was to clarify the decision-making process of expert clinicians while diagnosing FMD, myoclonus, and tics. METHODS: Thirty-nine movement disorders experts rated 60 patients using a standardized web-based survey resembling clinical practice. It provided 5 steps of incremental information: (1) visual first impression of the patient, (2) medical history, (3) neurologic examination on video, (4) the Bereitschaftspotential (BP), and (5) psychiatric evaluation. After full evaluation of each case, experts were asked which diagnostic step was decisive. In addition, interim switches in diagnosis after each informational step were calculated. RESULTS: After full evaluation, the experts annotated the first impression of the patients as decisive in 18.5% of cases. Medical history was considered decisive in 33.3% of cases. Neurologic examination was considered decisive in 39.7%, the BP in 8%, and the psychiatric interview in 0.5% of cases. Most diagnostic switches occurred after addition of the medical history (34.5%). Addition of the neurologic examination led to 13.8% of diagnostic switches. The BP results led to diagnostic switches in 7.2% of cases. Psychiatric evaluation resulted in the lowest number of diagnostic switches (2.7% of cases). CONCLUSIONS: Experts predominantly rely on clinical assessment to diagnose FMD. Importantly, ancillary tests do not determine the final diagnosis of this expert panel. In general, the experts infrequently changed their differential diagnosis.

Which patients with epilepsy are at risk for psychogenic nonepileptic seizures (PNES)? A multicenter case-control study.

OBJECTIVE: We sought to examine the clinical and electrographic differences between patients with combined epileptic (ES) and psychogenic nonepileptic seizures (PNES) and age- and gender-matched patients with ES-only and PNES-only. METHODS: Data from 138 patients (105 women [77%]), including 46 with PNES/ES (39±12years), 46 with PNES-only (39±11years), and 46 with ES-only (39±11years), were compared using logistic regression analysis after adjusting for clustering effect. RESULTS: In the cohort with PNES/ES, ES antedated PNES in 28 patients (70%) and occurred simultaneously in 11 (27.5%), while PNES were the initial presentation in only 1 case (2.5%); disease duration was undetermined in 6. Compared with those with ES-only, patients with PNES/ES had higher depression and anxiety scores, shorter-duration electrographic seizures, less ES absence/staring semiology (all p≤0.01), and more ES arising in the right hemisphere, both in isolation and in combination with contralateral brain regions (61% vs. 41%; p=0.024, adjusted for anxiety and depression) and tended to have less ES arising in the left temporal lobe (13% vs. 28%; p=0.054). Compared with those with PNES-only, patients with PNES/ES tended to show fewer right-hemibody PNES events (7% vs. 23%; p=0.054) and more myoclonic semiology (10% vs. 2%; p=0.073). CONCLUSIONS: Right-hemispheric electrographic seizures may be more common among patients with ES who develop comorbid PNES, in agreement with prior neurobiological studies on functional neurological disorders.

RELN rare variants in myoclonus-dystonia.

BACKGROUND: Myoclonus-dystonia (M-D) is a hyperkinetic movement disorder with predominant myoclonic symptoms combined with dystonia of the upper part of the body. A proportion of M-D cases are caused by mutations in the epsilon-sarcoglycan gene. In remaining M-D patients, no genetic factor has been established, indicating genetic heterogeneity. METHODS: Patients were included in a prospective clinical database and recruited from referral centers and general neurology clinics in The Netherlands. To investigate new genetic causal factors in M-D syndrome, we performed homozygosity mapping combined with exome sequencing in a three-generation M-D family and genetically screened 24 additional patients with M-D. RESULTS: We found co-segregation of the rare missense variant Thr1904Met in the RELN gene. By additional screening of an M-D cohort, we identified co-segregation of RELN variants in two families (Thr1904Met, Ile1217Met) and identified two sporadic RELN mutation carriers (Pro1703Arg, Leu411Ile). Taken together, five of 25 SGCE-negative M-D patients carried RELN rare missense variants. CONCLUSION: We propose that RELN mutations contribute to the genetic heterogeneity of M-D. Reelin is a large secreted glycoprotein that plays essential roles in the cytoarchitecture of laminated brain structures and modulation of synaptic transmission and plasticity.

Propriospinal myoclonus: clinical reappraisal and review of literature.

OBJECTIVE: Propriospinal myoclonus (PSM) is a rare disorder with repetitive, usually flexor arrhythmic brief jerks of the trunk, hips, and knees in a fixed pattern. It has a presumed generation in the spinal cord and diagnosis depends on characteristic features at polymyography. Recently, a historical paradigm shift took place as PSM has been reported to be a functional (or psychogenic) movement disorder (FMD) in most patients. This review aims to characterize the clinical features, etiology, electrophysiologic features, and treatment outcomes of PSM. METHODS: Re-evaluation of all published PSM cases and systematic scoring of clinical and electrophysiologic characteristics in all published cases since 1991. RESULTS: Of the 179 identified patients with PSM (55% male), the mean age at onset was 43 years (range 6-88 years). FMD was diagnosed in 104 (58%) cases. In 12 cases (26% of reported secondary cases, 7% of total cases), a structural spinal cord lesion was found. Clonazepam and botulinum toxin may be effective in reducing jerks. CONCLUSIONS: FMD is more frequent than previously assumed. Structural lesions reported to underlie PSM are scarce. Based on our clinical experience and the reviewed literature, we recommend polymyography to assess recruitment variability combined with a Bereitschaftspotential recording in all cases.

Jerky periods: myoclonus occurring solely during menses.

BACKGROUND: In this case report, we describe an unusual case of a patient with myoclonus only occurring during menses. CASE REPORT: A 41-year-old female, known to have neurological sequelae after a car accident 1 year earlier, presented with myoclonic movements of the right arm and hand only during menses. Brain magnetic resonance imaging is compatible with head trauma. Electromyography shows brief irregular bursts with a duration of about 20 ms. DISCUSSION: This appears to be the first description of myoclonus appearing only during menses. We suggest a cortical origin for myoclonus.

Functional MRI study of response inhibition in myoclonus dystonia.

BACKGROUND: Myoclonus-dystonia (MD) is a movement disorder characterized by myoclonic jerks, dystonic postures and psychiatric co-morbidity. A mutation in the DYT11 gene underlies half of MD cases. We hypothesize that MD results from a dysfunctional basal ganglia network causing insufficient inhibitory motor control. To test this hypothesis functional MRI (fMRI) was performed using a validated "Go/No go" task, in order to localize blood-oxygen-level dependence (BOLD) effects corresponding to Response Inhibition (RI). METHODS: Twenty-four MD patients (fifteen DYT11 positive) and 24 matched controls responded with a button press to Go (Go-Response) or No go (referred to as 'Stop') cues, resulting in analyses of accurate response suppression to Stop cues (Stop-Inhibit), and incorrect responses to Go cues (Go-Inhibit), or to Stop cues (Stop-Response). RESULTS: Response accuracy in patients was impaired due to frequent Go-Inhibit errors. Image analysis of the Stop-Inhibit contrast demonstrated frontal, caudate and cingular activity in both groups. Compared to controls, MD patients showed increased primary motor cortex and insular activation. During Go-Inhibit trials, patients revealed increased activity in the contralateral thalamus (ventral lateral nucleus) and dorso-lateral-prefrontal cortex. In a post-hoc analysis comparing MD patients, DYT11 positive patients demonstrated anterior cerebellum hyperactivation on all contrasts and increased putaminal activation in the Stop-Response contrast. CONCLUSIONS: This study demonstrates a distinct association of motor symptoms in MD with the ventral lateral nucleus of the thalamus. Cerebellar dysfunction distinguishes DYT11 positive from negative patients. We suggest that MD might be best considered as a disorder of the cortico-ponto-cerebello-thalamo-cortical system.

The eye of the beholder: inter-rater agreement among experts on psychogenic jerky movement disorders.

OBJECTIVE: The current criteria for conversion disorder in the Diagnostic and Statistical Manual of Mental Disorders rely on the assumption that neurological disorders can be distinguished from conversion disorders through clinical assessment. This study aims to assess inter-rater agreement among clinicians with experience in the diagnosis of various hyperkinetic jerky movements, including psychogenic jerks. METHODS: 60 patients with psychogenic jerks, myoclonus or tics were rated by international experts using a standardised survey resembling daily clinical practice. The survey included the following diagnostic steps: a short video offering a visual impression of the patients and their jerky movements, medical history, neurological examination (on video), additional investigations and the findings of a standardised psychiatric interview. The diagnosis and diagnostic certainty were scored after each step. RESULTS: After all clinical information was given, moderate inter-rater agreement was reached (κ=0.56±0.1) with absolute agreement (100%) of experts on the diagnosis in 12 (20%) patients and reasonable agreement (>75%) in 43 (72%) patients. Psychiatric evaluation did not contribute to inter-rater agreement or diagnostic certainty. CONCLUSIONS: Our findings illustrate the fact that experienced movement disorder specialists moderately agree on the clinical diagnosis of jerky movements. Clinical assessment, especially by a team of clinicians in challenging individual cases, might improve diagnostic agreement.

Neuropsychological profile of psychogenic jerky movement disorders: importance of evaluating non-credible cognitive performance and psychopathology.

BACKGROUND: Psychogenic movement disorders are disorders of movements that cannot be explained by a known neurological disorder and are assumed to be associated with psychiatric symptoms such as depression and anxiety. OBJECTIVE: To examine the neuropsychological profile of patients with psychogenic movement disorders. METHODS: We examined cognitive functioning using neuropsychological tests in 26 patients with clinically established psychogenic jerky movement disorders (PMD). We included 16 patients with Gilles de la Tourette syndrome (GTS) who served as a patient control group, in addition to 22 healthy control subjects. Non-credible test performance was detected using a Symptom Validity Test (SVT). Psychopathology was also assessed. RESULTS: Apart from a worse performance on a verbal memory task, no evidence of neuropsychological impairments was found in our PMD sample. Interestingly however, patients with PMD reported more cognitive complaints in daily life and performed worse on the SVT than the two other groups. Patients with GTS did not report, or show, cognitive impairments. In patients with PMD, we found associations between verbal learning, SVT performance and severity of depression and anxiety complaints. CONCLUSIONS: We conclude that some patients with PMD show non-credible cognitive symptoms. In contrast, no evident cognitive impairments were present in patients with PMD or GTS. Our study underlines the importance of assessment of non-credible response in patients with PMD. Additionally, non-credible response might aid in the differentiation of PMD from other movement disorders.

The bereitschaftspotential in jerky movement disorders.

OBJECTIVE: To assess the diagnostic value of the bereitschaftspotential (BP) in jerky movement disorders. METHODS: A cross-sectional case series of 48 patients with psychogenic jerks, Gilles de la Tourette syndrome (GTS) or myoclonus was investigated. We measured the BP prior to the spontaneous jerk and voluntary wrist extension. In addition, the various jerky movements were imitated by 25 healthy subjects. RESULTS: For patients with psychogenic jerks, we observed significantly more BPs; however, the BP was not identified prior to self-paced wrist extensions in 59% of cases. In contrast, none of the patients with the clinical diagnosis of myoclonus had a BP prior to their jerks but did have a BP prior to intentional wrist extension. In GTS, we demonstrated a BP in a minority of cases preceding motor tics and with a shorter duration in comparison with patients with psychogenic jerks. In healthy control subjects, a BP was found preceding all movements in all cases. The absence of a BP prior to intended wrist extension had a sensitivity of 0.59, specificity of 0.98 and positive likelihood ratio of 25 for the diagnosis of psychogenic jerks. CONCLUSIONS: We demonstrate that the BP can aid in the differentiation of jerky movements. Patients with psychogenic jerks significantly more often have a BP prior to their jerks and with a significantly earlier onset compared with GTS patients. A novel finding of our study is the absence of a BP prior to intentional movements for patients with psychogenic jerks. Validation in a prospective cohort is needed.