Deep Brain Stimulation for Focal or Segmental Craniocervical Dystonia in Patients Who Have Failed Botulinum Neurotoxin Therapy-A Narrative Review of the Literature

(1) Background: The first-line treatment for patients with focal or segmental dystonia with a craniocervical distribution is still the intramuscular injection of botulinum neurotoxin (BoNT). However, some patients experience primary or secondary treatment failure from this potential immunogenic therapy. Deep brain stimulation (DBS) may then be used as a backup strategy in this situation. (2) Methods: Here, we reviewed the current study literature to answer a specific question regarding the efficacy and safety of the use of DBS, particularly for cervical dystonia (CD) and Meige syndrome (MS) in patients with documented treatment failure under BoNT. (3) Results: There are only two studies with the highest level of evidence in this area. Despite this clear limitation, in the context of the narrowly defined research question of this paper, it is possible to report 161 patients with CD or MS who were included in studies that were able to show a statistically significant reduction in dystonic symptoms using DBS. Safety and tolerability data appeared adequate. However, much of the information is based on retrospective observations. (4) Conclusions: The evidence base in this area is in need of further scientific investigation. Most importantly, more randomized, controlled and double-blind trials are needed, possibly including a head-to-head comparison of DBS and BoNT.

Topological differences and confounders of mental rotation in cervical dystonia and blepharospasm

Mental rotation (mR) bases on imagination of actual movements. It remains unclear whether there is a specific pattern of mR impairment in focal dystonia. We aimed to investigate mR in patients with cervical dystonia (CD) and blepharospasm (BS) and to assess potential confounders. 23 CD patients and 23 healthy controls (HC) as well as 21 BS and 19 hemifacial spasm (HS) patients were matched for sex, age, and education level. Handedness, finger dexterity, general reaction time, and cognitive status were assessed. Disease severity was evaluated by clinical scales. During mR, photographs of body parts (head, hand, or foot) and a non-corporal object (car) were displayed at different angles rotated within their plane. Subjects were asked to judge laterality of the presented image by keystroke. Both speed and correctness were evaluated. Compared to HC, CD and HS patients performed worse in mR of hands, whereas BS group showed comparable performance. There was a significant association of prolonged mR reaction time (RT) with reduced MoCA scores and with increased RT in an unspecific reaction speed task. After exclusion of cognitively impaired patients, increased RT in the mR of hands was confined to CD group, but not HS. While the question of whether specific patterns of mR impairment reliably define a dystonic endophenotype remains elusive, our findings point to mR as a useful tool, when used carefully with control measures and tasks, which may be capable of identifying specific deficits that distinguish between subtypes of dystonia.

Temporal Discrimination Thresholds and Proprioceptive Performance: Impact of Age and Nerve Conduction

Background

Increasing attention is payed to the contribution of somatosensory processing in motor control. In particular, temporal somatosensory discrimination has been found to be altered differentially in common movement disorders. To date, there have only been speculations as to how impaired temporal discrimination and clinical motor signs may relate to each other. Prior to disentangling this relationship, potential confounders of temporal discrimination, in particular age and peripheral nerve conduction, should be assessed, and a quantifiable measure of proprioceptive performance should be established.

Objective

To assess the influence of age and polyneuropathy (PNP) on somatosensory temporal discrimination threshold (STDT), temporal discrimination movement threshold (TDMT), and behavioral measures of proprioception of upper and lower limbs.

Methods

STDT and TDMT were assessed in 79 subjects (54 healthy, 25 with PNP; age 30–79 years). STDT was tested with surface electrodes over the thenar or dorsal foot region. TDMT was probed with needle electrodes in flexor carpi radialis (FCR) and tibialis anterior (TA) muscle. Goniometer-based devices were used to assess limb proprioception during (i) active pointing to LED markers, (ii) active movements in response to variable visual cues, and (iii) estimation of limb position following passive movements. Pointing (or estimation) error was taken as a measure of proprioceptive performance.

Results

In healthy subjects, higher age was associated with higher STDT and TDMT at upper and lower extremities, while age did not correlate with proprioceptive performance. Patients with PNP showed higher STDT and TDMT values and decreased proprioceptive performance in active pointing tasks compared to matched healthy subjects. As an additional finding, there was a significant correlation between performance in active pointing tasks and temporal discrimination thresholds.

Conclusion

Given their notable impact on measures of temporal discrimination, age and peripheral nerve conduction need to be accounted for if STDT and TDMT are applied in patients with movement disorders. As a side observation, the correlation between measures of proprioception and temporal discrimination may prompt further studies on the presumptive link between these two domains.

Increased Finger-Tapping Related Cerebellar Activation in Cervical Dystonia, Enhanced by Transcranial Stimulation: An Indicator of Compensation?

Background: Cervical dystonia is a movement disorder causing abnormal postures and movements of the head. While the exact pathophysiology of cervical dystonia has not yet been fully elucidated, a growing body of evidence points to the cerebellum as an important node.

Methods: Here, we examined the impact of cerebellar interference by transcranial magnetic stimulation on finger-tapping related brain activation and neurophysiological measures of cortical excitability and inhibition in cervical dystonia and controls. Bilateral continuous theta-burst stimulation was used to modulate cerebellar cortical excitability in 16 patients and matched healthy controls. In a functional magnetic resonance imaging arm, data were acquired during simple finger tapping before and after cerebellar stimulation. In a neurophysiological arm, assessment comprised motor-evoked potentials amplitude and cortical silent period duration. Theta-burst stimulation over the dorsal premotor cortex and sham stimulation (neurophysiological arm only) served as control conditions.

Results: At baseline, finger tapping was associated with increased activation in the ipsilateral cerebellum in patients compared to controls. Following cerebellar theta-burst stimulation, this pattern was even more pronounced, along with an additional movement-related activation in the contralateral somatosensory region and angular gyrus. Baseline motor-evoked potential amplitudes were higher and cortical silent period duration shorter in patients compared to controls. After cerebellar theta-burst stimulation, cortical silent period duration increased significantly in dystonia patients.

Conclusion: We conclude that in cervical dystonia, finger movements—though clinically non-dystonic—are associated with increased activation of the lateral cerebellum, possibly pointing to general motor disorganization, which remains subclinical in most body regions. Enhancement of this activation together with an increase of silent period duration by cerebellar continuous theta-burst stimulation may indicate predominant disinhibitory effects on Purkinje cells, eventually resulting in an inhibition of cerebello-thalamocortical circuits.

Pallidal neurostimulation versus botulinum toxin injections in the treatment of cervical dystonia: protocol of a randomized, sham-controlled trial (StimTox-CD)

Background

Selective peripheral denervation via botulinum neurotoxin injections into dystonic muscles is the first-line treatment for cervical dystonia. Pallidal neurostimulation is a potent alternative, but currently restricted to patients failing on neurotoxin therapy. As botulinum neurotoxin is partially effective but often unsatisfactory in a relevant proportion of patients, earlier neurostimulation might be advantageous in providing stable symptom control and preventing disability. This trial intends to demonstrate, that pallidal neurostimulation is superior to neurotoxin injections in best clinical practice for controlling the symptoms of cervical dystonia and that it is safe in patients with a partial therapy response to peripheral denervation. We hypothesize a better outcome in everyday functioning and health-related quality of life of neurostimulated patients.

Methods

We aim to recruit 66 cervical dystonia patients into a double-blind comparison of pallidal neurostimulation versus botulinum neurotoxin type A. Eligible patients need ≥25% motor symptom reduction 4 weeks after a neurotoxin test injection, but are willing to undergo DBS surgery due to unsatisfactory symptom control. All participants will be implanted with a DBS system, and randomized into 2 groups: First group will receive effective neurostimulation and saline injections into dystonic muscles. Second group is treated with regular neurotoxin injections and undergoes a sham-stimulation. Primary outcome is the change in TWSTRS total score between baseline and 6 months of therapy. Secondary outcome parameters are corresponding changes in TWSTRS motor score, Tsui score, CDQ-24 and SF-36. Safety will be assessed by frequency and severity of reported adverse events. Statistical analysis includes intention-to-treat and per protocol populations, analysis based on imputation of missing values and analysis adjusting for differences in baseline TWSTRS. After 6 months of blinded treatment all patients will receive open-label neurostimulation and neurotoxin treatment as needed, and are followed up 48 weeks after randomization.

Perspective

We will assess if pallidal neurostimulation is a safe and effective alternative to selective peripheral denervation by botulinum toxin injections in cervical dystonia, which may be offered earlier in the course of disease based on patient preference. A positive study outcome would influence future treatment guidelines of cervical dystonia.

Trial registration

EudraCT registration number: 2016-001378-13.

Fatty acid ethanolamide levels are altered in borderline personality and complex posttraumatic stress disorders

Borderline personality (BPD) and complex posttraumatic stress disorders (PTSD) are both powerfully associated with the experience of interpersonal violence during childhood and adolescence. The disorders frequently co-occur and often result in pervasive problems in, e.g., emotion regulation and altered pain perception, where the endocannabinoid system is deeply involved. We hypothesize an endocannabinoid role in both disorders. We investigated serum levels of the endocannabinoids anandamide and 2-arachidonoylglycerol and related fatty acid ethanolamides (FAEs) in BPD, PTSD, and controls. Significant alterations were found for both endocannabinoids in BPD and for the FAE oleoylethanolamide in PTSD suggesting a respective link to both disorders.