Intracortical circuits, sensorimotor integration and plasticity in human motor cortical projections to muscles of the lower face

Previous studies of the cortical control of human facial muscles documented the distribution of corticobulbar projections and the presence of intracortical inhibitory and facilitatory mechanisms. Yet surprisingly, given the importance and precision in control of facial expression, there have been no studies of the afferent modulation of corticobulbar excitability or of the plasticity of synaptic connections in the facial primary motor cortex (face M1). In 25 healthy volunteers, we used standard single- and paired-pulse transcranial magnetic stimulation (TMS) methods to probe motor-evoked potentials (MEPs), short-intracortical inhibition, intracortical facilitation, short-afferent and long-afferent inhibition and paired associative stimulation in relaxed and active depressor anguli oris muscles. Single-pulse TMS evoked bilateral MEPs at rest and during activity that were larger in contralateral muscles, confirming that corticobulbar projection to lower facial muscles is bilateral and asymmetric, with contralateral predominance. Both short-intracortical inhibition and intracortical facilitation were present bilaterally in resting and active conditions. Electrical stimulation of the facial nerve paired with a TMS pulse 5–200 ms later showed no short-afferent inhibition, but long-afferent inhibition was present. Paired associative stimulation tested with an electrical stimulation–TMS interval of 20 ms significantly facilitated MEPs for up to 30 min. The long-term potentiation, evoked for the first time in face M1, demonstrates that excitability of the facial motor cortex is prone to plastic changes after paired associative stimulation. Evaluation of intracortical circuits in both relaxed and active lower facial muscles as well as of plasticity in the facial motor cortex may provide further physiological insight into pathologies affecting the facial motor system

Facial tremor in dystonia

Tremor of the upper/middle part of the face, including the perinasal region and the forehead has been very rarely described in some patients with Parkinson's disease or Essential Tremor. It has not yet been reported in patients with idiopathic dystonia. Methods: We describe here a series of 8 patients with common forms of idiopathic focal/segmental dystonia with tremor involving the upper/middle part of the face, along with demonstrative videos and electrophysiological recordings. Results: The distribution of the tremor was confined to the face in two patients, whereas in six patients tremor was also evident either in the head/lower part of the face or in their upper limbs. Electrophysiological recordings disclosed a slightly irregular tremor with a frequency at about 3-5Hz. Conclusions: A number of patients with classical forms of dystonia can show a tremor involving the upper/middle part of the face. © 2014 Elsevier Ltd

Rest and other types of tremor in adult-onset primary dystonia.

Introduction: Knowledge regarding tremor prevalence and phenomenology in patients with adult-onset primary dystonia is limited. Dystonic tremor is presumably under-reported, and we aimed to assess the prevalence and the clinical correlates of tremor in patients with adult-onset primary dystonia. Methods: We enrolled 473 consecutive patients with different types of adult-onset primary dystonia. They were assessed for presence of head tremor and arm tremor (rest, postural and kinetic). Results: A total of 262 patients (55.4%) were tremulous: 196 patients presented head tremor, 140 patients presented arm tremor and 98 of them had a combination of head and arm tremor. Of the 140 patients with arm tremor, all presented postural tremor, 103 patients (73.6%) presented also a kinetic component, whereas 57 patients (40.7%) had rest tremor. Rest tremor was unilateral/asymmetric in up to 92.9% of them. Patients with segmental and multifocal dystonia were more likely tremulous than patients with focal dystonia. Dystonic symptoms involving the neck were more frequently observed in patients with head tremor, whereas dystonic symptoms involving the arms were more frequently observed in patients with arm tremor. Discussion: Here we show that tremor is a common feature of patients with adult-onset primary dystonia. It may involve different body segments, with the head being the most commonly affected site. Arm tremor is also frequent (postural>kinetic>rest), occurring in up to one-third of cases. There is a suggestion of a stronger tendency for spread of dystonic features in patients with associated tremor. Dystonic tremor is under-reported and this underscores the importance of careful clinical examination when assessing tremulous patients without overt dystonia

Cerebellar brain inhibition is decreased in active and surround muscles at the onset of voluntary movement

Contains fulltext : 97708.pdf (publisher's version ) (Closed access)Highly selective activation of the desired muscles for each movement and inhibition of adjacent muscles is attributed to surround inhibition (SI) which differentially modulates corticospinal excitability in active and surrounding muscles. Cerebellar brain inhibition (CBI) is another inhibitory neuronal network which is known to be active at rest and during tonic muscle contraction. The way in which CBI may be modulated at movement onset and its relationship with SI has not previously been investigated. We assessed motor evoked potential (MEP) size and CBI in first dorsal interosseus (FDI) and abductor digiti minimi (ADM) muscles at rest and during a simple motor task where FDI was an active muscle and ADM was not involved in the movement (surround muscle). At onset of movement, MEP size in ADM was significantly suppressed, confirming the existence of SI. In contrast, CBI in both muscles was found to be significantly decreased at the onset of the movement. This was confirmed even after adjustments for changes in MEP size occurring due to onset of muscle activity in FDI and the effects of SI in ADM. Our findings fail to functionally link SI with CBI, but they do indicate a non-topographically specific modulation of CBI in association with initiation of voluntary movement

Developing a tool for remote digital assessment of Parkinson's Disease

BACKGROUND: The natural fluctuation of motor symptoms of Parkinson's disease (PD) makes judgement of any change challenging and the use of clinical scales such as the International Parkinson and Movement Disorder Society (MDS)-UPDRS imperative. Recently developed commodity mobile communication devices, such as smartphones, could possibly be used to assess motor symptoms in PD patients in a convenient way with low cost. We provide the first report on the development and testing of stand-alone software for mobile devices that could be used to assess both tremor and bradykinesia of PD patients. METHODS: We assessed motor symptoms with a custom-made smartphone application in 14 patients and compared the results with their MDS-UPDRS scores. RESULTS: We found significant correlation between five subscores of MDS-UPDRS (rest tremor, postural tremor, pronation-supination, leg agility, and finger tapping) and eight parameters of the data collected with the smartphone. CONCLUSIONS: These results provide evidence as a proof of principle that smartphones could be a useful tool to objectively assess motor symptoms in PD in clinical and experimental settings

Facial tremor in dystonia.

Background: Tremor of the upper/middle part of the face, including the perinasal region and the forehead has been very rarely described in some patients with Parkinson's disease or Essential Tremor. It has not yet been reported in patients with idiopathic dystonia. Methods: We describe here a series of 8 patients with common forms of idiopathic focal/segmental dystonia with tremor involving the upper/middle part of the face, along with demonstrative videos and electrophysiological recordings. Results: The distribution of the tremor was confined to the face in two patients, whereas in six patients tremor was also evident either in the head/lower part of the face or in their upper limbs. Electrophysiological recordings disclosed a slightly irregular tremor with a frequency at about 3-5 Hz. Conclusions: A number of patients with classical forms of dystonia can show a tremor involving the upper/middle part of the face