Aim  We aimed to investigate the induction of long‐term potentiation (LTP)‐like plasticity by paired associative stimulation (PAS) in patients with high‐functioning autism and Asperger syndrome (HFA/AS).Method  PAS with an interstimulus interval between electrical and transcranial magnetic stimulation of 25 ms (PAS₂₅) was performed in patients with HFA/AS (n=9; eight males, one female; mean age 17y 11mo, SD 4y 5mo) and in typically developing age‐matched volunteers (n=9; five males, four females; mean age 22y 4mo, SD 5y 2mo). The amplitude of motor‐evoked potentials was measured before PAS₂₅, immediately after stimulation, and 30 minutes and 60 minutes later. A PAS protocol adapted to individual N20 latency (PAS_N20+2) was performed in six additional patients with HFA/AS. Short‐interval intracortical inhibition was measured using paired‐pulse stimulation.Results  In contrast to the typically developing participants, the patients with HFA/AS did not show a significant increase in motor‐evoked potentials after PAS₂₅. This finding could also be demonstrated after adaptation for N20 latency. Short‐interval intracortical inhibition of patients with HFA/AS was normal compared with the comparison group and did not correlate with PAS effect.Interpretation  Our results show a significant impairment of LTP‐like plasticity induced by PAS in individuals with HFA/AS compared with typically developing participants. This finding is in accordance with results from animal studies as well as human studies. Impaired LTP‐like plasticity in patients with HFA/AS points towards reduced excitatory synaptic connectivity and deficits in sensory‐motor integration in these patients.

The origin of asymmetric clinical manifestation of symptoms in patients suffering from cervical dystonia (CD) is hitherto poorly understood. Dysregulated neuronal activity in the basal ganglia has been suggested to have a role in the pathophysiology of CD. Here, we re-assessed the question to what extent relative changes occur in the direct versus indirect basal ganglia pathway in CD, whether these circuit changes are lateralized, and how these alterations relate to CD symptoms. To this end, we recorded ongoing single cell and local field potential (LFP) activity from the external (GPe) and internal pallidal segment (GPi) of thirteen CD patients undergoing microelectrode-guided stereotactic surgery for deep brain stimulation in the GPi. We compared pallidal recordings from CD patients operated under local anaesthesia (LA) with those obtained in CD patients operated under general anaesthesia (GA). In awake patients, mean GPe discharge rate (52 Hz) was lower than that of GPi (72 Hz). Mean GPi discharge ipsilateral to the side of head turning was higher than contralateral and correlated with torticollis symptom severity. Lateralized differences were absent at the level of the GPe and in recordings from patients operated under GA. Furthermore, in the GPi of CD patients there was a subpopulation of theta-oscillatory cells with unique bursting characteristics. Power and coherence of GPe- and GPi-LFPs were dominated by a theta peak and also exhibited band-specific interhemispheric differences. Strong cross-frequency coupling of low-gamma amplitude to theta phase was a feature of pallidal LFPs recorded under LA, but not GA. These results indicate that CD is associated with an asymmetric pallidal outflow. Based on the finding of symmetric neuronal discharges in the GPe, we propose that an imbalanced interhemispheric direct pathway gain may be involved in CD pathophysiology.

The visualization of the human body has frequently been groundbreaking in medicine. In the last few years, the use of ultrasound (US) imaging has become a well-established procedure for botulinum toxin therapy in people with cervical dystonia (CD). It is now undisputed among experts that some of the most relevant muscles in this indication can be safely injected under visual US guidance. This review will explore the method from basic technical considerations, current evidence to conceptual developments of the phenomenology of cervical dystonia. We will review the implications of introducing US to our understanding of muscle function and anatomy of common cervical dystonic patterns. We suggest a flow chart for the use of US to achieve a personalized treatment of people with CD. Thus, we hope to contribute a resource that is useful in clinical practice and that stimulates the ongoing development of this valuable technique.

Aim: Mucopolysaccharidoses (MPS) are a group of diseases with an almost 100% lifetime incidence of carpal tunnel syndrome (CTS) in MPSsubtypes I, II, and VI. We compared nerve ultrasound with clinical signs and electrophysiology in a clinical setting to screen for CTSin MPS.Method: Twenty‐four patients (13 male, 11 female, mean age of 7y 11mo [SD8y 5mo], range 6mo–29y) were screened for CTS. Eight of these patients were re‐examined post‐operatively. Clinical signs, distal motor latency, compound muscle action potential, sensory nerve action potential amplitude and velocity, as well as echogenicity and the cross‐sectional area (CSA) of the median nerve at the wrist and forearm determined with ultrasound were assessed and the wrist to forearm ratio (WFR) calculated. Eighteen healthy participants formed a comparison group, who were also investigated with nerve ultrasound.Results: In 26% of the patients' hands, clinical signs of CTSwere present; 77% fulfilled electrophysiological and 92% nerve ultrasound criteria for CTS. Post‐operatively, electrophysiology improved significantly, whereas ultrasound results were unchanged. In the comparison group, age and height correlated with the CSA, but not with WFR.Interpretation: Nerve ultrasound is a useful and painless primary screening tool for CTSin MPS.