Selective Surface Electrostimulation of the Denervated Zygomaticus Muscle.

This article describes a first attempt to generate a standardized and safe selective surface electrostimulation (SES) protocol, including detailed instructions on electrode placement and stimulation parameter choice to obtain a selective stimulation of the denervated zygomaticus muscle (ZYG), without unwanted simultaneous activation of other ipsilateral or contralateral facial muscles. METHODS: Single pulse stimulation with biphasic triangular and rectangular waveforms and pulse widths (PW) of 1000, 500, 250, 100, 50, 25, 15, 10, 5, 2, 1 ms, at increasing amplitudes between 0.1 and 20 mA was performed. Stimulations delivered in trains were assessed at a PW of 50 ms only. The stimulation was considered successful exclusively if it drew the ipsilateral corner of the mouth upwards and outwards, without the simultaneous activation of other ipsilateral or contralateral facial muscles. I/t curves, accommodation quotient, rheobase, and chronaxie were regularly assessed over 1-year follow-up. RESULTS: 5 facial paralysis patients were assessed. Selective ZYG response in absence of discomfort and unselective contraction of other facial muscle was reproducibly obtained for all the assessed patients. The most effective results with single pulses were observed with PW ≥ 50 ms. The required amplitude was remarkably lower (≤5 mA vs. up to 15 mA) in freshly diagnosed (≤3 months) than in long-term facial paralysis patients (>5 years). Triangular was more effective than rectangular waveform, mostly because of the lower discomfort threshold of the latter. Delivery of trains of stimulation showed similar results to the single pulse setting, though lower amplitudes were necessary to achieve the selective ZYG response. Initial reinnervation signs could be detected effectively by needle-electromyography (n-EMG). CONCLUSION: It is possible to define stimulation parameters able to elicit an effective selective stimulation of a specific facial muscle, in our case, of the ZYG, without causing discomfort to the patient and without causing unwanted unspecific reactions of other ipsilateral and/or contralateral facial muscles. We observed that the SES success is strongly conditioned by the correct electrode placement, which ideally should exclusively interest the area of the target muscles and its immediate proximity.

Cause or effect: Altered brain and network activity in cervical dystonia is partially normalized by botulinum toxin treatment.

BACKGROUND: Idiopathic cervical dystonia (CD) is a chronic movement disorder characterized by impressive clinical symptoms and the lack of clear pathological findings in clinical diagnostics and imaging. At present, the injection of botulinum toxin (BNT) in dystonic muscles is an effective therapy to control motor symptoms and pain in CD. OBJECTIVES: We hypothesized that, although it is locally injected to dystonic muscles, BNT application leads to changes in brain and network activity towards normal brain function. METHODS: Using 3 T functional MR imaging along with advanced analysis techniques (functional connectivity, Granger causality, and regional homogeneity), we aimed to characterize brain activity in CD (17 CD patients vs. 17 controls) and to uncover the effects of BNT treatment (at 6 months). RESULTS: In CD, we observed an increased information flow within the basal ganglia, the thalamus, and the sensorimotor cortex. In parallel, some of these structures became less responsive to regulating inputs. Furthermore, our results suggested an altered somatosensory integration. Following BNT administration, we noted a shift towards normal brain function in the CD patients, especially within the motor cortex, the somatosensory cortex, and the basal ganglia. CONCLUSION: The changes in brain function and network activity in CD can be interpreted as related to the underlying cause, the effort to compensate or a mixture of both. Although BNT is applied in the last stage of the cortico-neuromuscular pathway, brain patterns are shifted towards those of healthy controls.

The Influence of Eye Closure on Somatosensory Discrimination: A Trade-off Between Simple Perception and Discrimination.

We often close our eyes to improve perception. Recent results have shown a decrease of perception thresholds accompanied by an increase in somatosensory activity after eye closure. However, does somatosensory spatial discrimination also benefit from eye closure? We previously showed that spatial discrimination is accompanied by a reduction of somatosensory activity. Using magnetoencephalography, we analyzed the magnitude of primary somatosensory (somatosensory P50m) and primary auditory activity (auditory P50m) during a one-back discrimination task in 21 healthy volunteers. In complete darkness, participants were requested to pay attention to either the somatosensory or auditory stimulation and asked to open or close their eyes every 6.5 min. Somatosensory P50m was reduced during a task requiring the distinguishing of stimulus location changes at the distal phalanges of different fingers. The somatosensory P50m was further reduced and detection performance was higher during eyes open. A similar reduction was found for the auditory P50m during a task requiring the distinguishing of changing tones. The function of eye closure is more than controlling visual input. It might be advantageous for perception because it is an effective way to reduce interference from other modalities, but disadvantageous for spatial discrimination because it requires at least one top-down processing stage.

Thalamocortical connectivity during resting state in schizophrenia.

Schizophrenia has been linked to disturbed connectivity between large-scale brain networks. Altered thalamocortical connectivity might be a major mechanism mediating regionally distributed dysfunction, yet it is only incompletely understood. We analysed functional magnetic resonance imaging data obtained during resting state from 22 DSM-IV schizophrenia patients and 22 matched healthy controls to directly assess the differences in thalamocortical functional connectivity. We identified significantly higher overall thalamocortical functional connectivity in patients, which was mostly accounted for by difference in thalamic connections to right ventrolateral prefrontal and bilateral secondary motor and sensory (superior temporal and lateral occipital) cortical areas. Voxelwise analysis showed group differences at the thalamic level to be mostly in medial and anterior thalamic nuclei and arising thalamocortical changes to be mostly due to higher positive correlations in prefrontal and superior temporal correlations, as well as absent negative correlations to sensory areas in patients. Our findings demonstrate that different types of thalamocortical dysfunction contribute to network alterations, including lack of inhibitory interaction attributed to the lack of significant negative thalamic/sensory cortical connections. These results emphasize the functional importance of the thalamus in the pathophysiology of schizophrenia.

Laryngeal electromyography: a proposal for guidelines of the European Laryngological Society.

Although recognized as a valuable diagnostic tool for more than 60 years, many laryngologists do not routinely use laryngeal electromyography (LEMG). This may be due to a persisting lack of agreement on methodology, interpretation, validity, and clinical application of LEMG. To achieve consensus in these fields, a laryngeal electromyography working group of European neurolaryngologic experts was formed in order to (1) evaluate guidelines for LEMG performance and (2) identify issues requiring further clarification. To obtain an overview of existing knowledge and research, English-language literature about LEMG was identified using Medline. Additionally, cited works not detected in the initial search were screened. Evidence-based recommendations for the performance and interpretation of LEMG and also for electrostimulation for functional evaluation were considered, as well as published reports based on expert opinion and single-institution retrospective case series. To assess the data obtained by this literature evaluation, the working group met five times and performed LEMG together on more than 20 patients. Subsequently, the results were presented and discussed at the 8th Congress of the European Laryngological Society in Vienna, Austria, September 1-4, 2010, and consensus was achieved in the following areas: (1) minimum requirements for the technical equipment required to perform and record LEMG; (2) best practical implementation of LEMG; (3) criteria for interpreting LEMG. Based on this consensus, prospective trials are planned to improve the quality of evidence guiding the proceedings of practitioners.

Habituation within the somatosensory processing hierarchy.

Habituation is a basic process of learning evident in a decrement in neuronal/behavioral responses to repeated sensory stimulation. It is generally accepted that habituation affects all sensory systems in the human brain, including the somatosensory network. However, it is not clear where habituation originates within this hierarchically organized network. In this study, we examined whether habituation effects increase relatively uniformly along the processing hierarchy or rather distinctly at a particular processing stage. We addressed these questions by performing functional magnetic resonance imaging (fMRI) on 43 healthy subjects during unilateral electrical median nerve stimulation using a block design. We found a time-dependent decrease in the positive BOLD response (indicative of habituation) in all areas of the somatosensory network with the exception of Brodmann area (BA) 3b. The increase in habituation within the presumed processing stream was most pronounced between subareas of the primary somatosensory cortex (BA3b, BA1, BA2), and no further increase in habituation effects was observed in the subsequent processing stages within either the secondary somatosensory cortex or the insula. Moreover, we found a relatively strong habituation effect within the thalamus. These findings indicate that the increase in habituation along the processing hierarchy is measurable primarily between subareas of the primary somatosensory cortex, and we hypothesize that this increase originates in thalamocortical interactions early in the processing stream.