Background Pathogenic variants in 5 genes (GCH1, TH, PTS, SPR, and QDPR), involved in dopamine/tetrahydrobiopterin biosynthesis or recycling, have been linked to Dopa‐responsive dystonia (DRD). Diagnosis and treatment are often delayed due to high between‐ and within‐group variability. Objectives Comprehensively analyzed individual genotype, phenotype, treatment response, and biochemistry information. Methods 734 DRD patients and 151 asymptomatic GCH1 mutation carriers were included using an MDSGene systematic literature review and an automated classification approach to distinguish between different forms of monogenic DRDs. Results Whereas dystonia, L‐Dopa responsiveness, early age at onset, and diurnal fluctuations were identified as red flags, parkinsonism without dystonia was rarely reported (11%) and combined with dystonia in only 18% of patients. While sex was equally distributed in autosomal recessive DRD, there was female predominance in autosomal dominant DYT/PARK‐GCH1 patients accompanied by a lower median age at onset and more dystonia in females compared to males. Accordingly, the majority of asymptomatic heterozygous GCH1 mutation carriers (>8 years of age) were males. Multiple other subgroup‐specific characteristics were identified, showing high accuracy in the automated classification approach: Seizures and microcephaly were mostly seen in DYT/PARK‐PTS, autonomic symptoms appeared commonly in DYT/PARK‐TH and DYT/PARK‐PTS, and sleep disorders and oculogyric crises in DYT/PARK‐SPR. Biochemically, homovanillic acid and 5‐hydroxyindoleacetic acid in CSF were reduced in most DRDs, but neopterin and biopterin were increased only in DYT/PARK‐PTS and DYT/PARK‐SPR. Hyperphenylalaninemia was seen in DYT/PARK‐PTS, DYT/PARK‐QDPR, and rarely reported in autosomal recessive DYT/PARK‐GCH1. Conclusions Our indicators will help to specify diagnosis and accelerate start of treatment. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Non-invasive brain stimulation techniques including repetitive transcranial magnetic stimulation (rTMS), continuous theta-burst stimulation (cTBS), paired associative stimulation (PAS), and transcranial direct current stimulation (tDCS) have been applied over the cerebellum to induce plasticity and gain insights into the interaction of the cerebellum with neo-cortical structures including the motor cortex. We compared the effects of 1 Hz rTMS, cTBS, PAS and tDCS given over the cerebellum on motor cortical excitability and interactions between the cerebellum and dorsal premotor cortex / primary motor cortex in two within subject designs in healthy controls. In experiment 1, rTMS, cTBS, PAS, and tDCS were applied over the cerebellum in 20 healthy subjects. In experiment 2, rTMS and PAS were compared to sham conditions in another group of 20 healthy subjects. In experiment 1, PAS reduced cortical excitability determined by motor evoked potentials (MEP) amplitudes, whereas rTMS increased motor thresholds and facilitated dorsal premotor-motor and cerebellum-motor cortex interactions. TDCS and cTBS had no significant effects. In experiment 2, MEP amplitudes increased after rTMS and motor thresholds following PAS. Analysis of all participants who received rTMS and PAS showed that MEP amplitudes were reduced after PAS and increased following rTMS. rTMS also caused facilitation of dorsal premotor-motor cortex and cerebellum-motor cortex interactions. In summary, cerebellar 1 Hz rTMS and PAS can effectively induce plasticity in cerebello-(premotor)-motor pathways provided larger samples are studied.

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Background: Deep brain stimulation of the subthalamic nucleus is effective to alleviate motor symptoms in advanced Parkinson's disease. Using a novel conditioning paradigm, it has been shown that deep brain stimulation pulses from electrodes in the subthalamic nucleus modulate corticospinal excitability as determined with transcranial magnetic stimulation applied to the motor cortex. The mechanism of action is unclear. Objective: To investigate the effects of subthalamic nucleus and dorsal premotor cortex conditioning on corticospinal excitability as a function of interstimulus intervals between target areas and deep brain stimulation frequencies. Methods: In 19 patients with Parkinson's disease with subthalamic nucleus deep brain stimulation, the premotormotor interaction was investigated in four different deep brain stimulation conditions (off, clinically used settings, 3 Hz, 20 Hz). Transcranial magnetic pulses were applied to the premotor and motor cortex and paired at certain intervals with deep brain stimulation pulses. The volume of tissue activated by deep brain stimulation was correlated with neurophysiological findings. Results: There was distinct motor cortex inhibition by premotor cortex conditioning at an interstimulus interval of 1 ms before the motor cortex stimulation. Subthalamic nucleus conditioning with deep brain stimulation frequencies of 3 and 20 Hz at an interstimulus interval of 10 ms between subthalamic nucleus and primary motor cortex reduced premotor-motor inhibition. The volume of tissue activated by deep brain stimulation correlated positively with this effect. Corticospinal excitability was not affected by subthalamic nucleus conditioning as used here. Conclusions: Premotor-motor inhibition is modulated by subthalamic nucleus conditioning, presumably through the monosynaptic hyperdirect pathway.

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