Relationship between event-related beta synchronization and afferent inputs: analysis of finger movement and peripheral nerve stimulations.

OBJECTIVE: We compared beta synchronization associated with voluntary finger movement with beta synchronization produced by sensory stimulation, in order to better understand the relationship between event-related beta synchronization (ERS) and the different afferent inputs. METHODS: Twenty-four subjects performed an index finger extension. They also received three types of electrical stimulation (cutaneous stimulation of the index finger, single and repetitive stimulation of the median nerve). An EEG was recorded using 38 scalp electrodes. Beta ERS was analyzed with respect to movement offset and the stimulus (or the last stimulus in the series, for repetitive stimulation). RESULTS: Median nerve stimulation and finger extension induced more intense beta ERS than cutaneous stimulation. The magnitude of beta ERS induced by movement or by single median nerve stimulation were not different but post movement beta synchronization duration was longer than beta ERS induced by single median nerve stimulation and cutaneous stimulation. CONCLUSIONS: This study demonstrates that beta ERS depends on the type and quantity of the afferent input. SIGNIFICANCE: This work reinforces the hypothesis of a relationship between beta ERS and processing of afferent inputs.

The place of perceptual analysis of dysarthria in the differential diagnosis of corticobasal degeneration and Parkinson's disease.

OBJECTIVE: To characterize the dysarthria in patients with corticobasal degeneration (CBD) and determine if analysis of speech in isolation helps to distinguish CBD patients from patients with Parkinson's disease (PD). METHODS: 60 subjects were assessed by means of perceptual analysis of speech: 15 patients with CBD, 15 patients with PD and 30 control subjects. A detailed profile was furnished with the help of 33 perceptual items. A global perceptual approach was used to classify patients by judges blind to the medical diagnosis. Rating scales were adapted to quantify the degree of spasticity and hypokinesia in the speech of each patient. RESULTS: Dysarthria was frequent in CBD even though it remained mild for a long period of time. Group analysis revealed the importance of temporal errors of speech control in CBD patients while voice disturbances were most frequent in PD patients. However, attempts to classify patients according to global perceptual analysis remained below a reasonable level of clinical acceptability. Finally, even though the widespread neuropathological changes suggest that deviant speech dimensions of several types of dysarthria might be found in CBD, evidence for a mixed dysarthria with presence of spastic elements could not be established. CONCLUSION: The findings support the view that even though perceptual analysis is mandatory in the management of dysarthric patients, it does not help in the clinical differential diagnosis of CBD.

[MRI of hippocampal malformations in patients with intractable temporal lobe epilepsy]. / IRM des malformations de l'hippocampe dans l'épilepsie temporale réfractaire.

OBJECTIVE: In some patients with temporal lobe epilepsy, recent MRI studies have revealed several morphological features indicative of discrete hippocampal malformation (HM). Its prevalence is unknown and the relationship between the HM and the origin of seizures has never been investigated. Our purpose is to define the MRI findings of this new entity and to determine its incidence in a group of patients and in a control group in order to evaluate its clinical significance. MATERIALS AND METHODS: MR imaging findings in 97 patients suffering from medically intraceable temporal epilepsy were prospectively evaluated during the preoperative evaluation of surgical candidates. The MR-imaging protocol included oblique coronal slices perpendicular to the temporal lobes using high resolution T2 weighted (HR TSE T2), Fluid attenuated inversion recovery (FLAIR) and inversion-images. This protocol has been completed by axial FLAIR images and axial and sagittal IR images of the whole brain. Coronal HR TSE T2 images were performed in 50 healthy control subjects. Cerebral lesion and hippocampal morphology were evaluated in both groups. RESULTS: Fourteen patients (14%) showed hippocampal morphological modification. The most frequent and specific findings were lack of visualization of the internal hippocampal (lack of linear T2 hypointensity within the hippocampus) and the abnormal shape (pyramidal, vertically oriented or globular-shaped). Other signs were: abnormal position of the hippocampus (medically located hippocampus) and vertical collateral sulcus. Cases without visualization of the internal structure of the hippocampus were considered as a complete form of HM and were correlated with temporal epilepsy. A vertical collateral sulcus was observed in some control group subjects. CONCLUSION: Complete forms of HM could be considered as epileptogenic lesions. Nevertheless, interpretation of the incomplete form is delicate: the abnormal angle of the collateral sulcus can be encountered in healthy subjects and could therefore be considered a normal variant.

Changes in oscillatory cortical activity related to a visuomotor task in young and elderly healthy subjects.

OBJECTIVE: In order to better understand the spatio-temporal interaction of the activated cortical areas when the movement is visuo-guided and to assess the age effect on the spatio-temporal pattern of cortical activity, we have compared a proximo-distal movement with visual-motor control and hand-eye coordination (targeting movement) with a distal and a proximal movement. METHODS: Brain's electrical activity was studied using the analysis of event-related (de)synchronizations (ERD/S) of cortical mu and beta rhythms in 17 subjects, 8 young and 9 elderly subjects. RESULTS: In both populations, we found an earlier and broader mu and beta ERD during the preparation of the targeting movement compared to distal and proximal movements, principally involving the contralateral parietal region. During the execution, a spreading over the parietocentral region during proximal movement and over the parietal region during targeting movement was observed. After the execution of proximal and targeting movements, a wider and higher beta ERS was observed only in the young subjects. In the elderly subjects, our results showed a significant decrease of beta ERS during the targeting task. CONCLUSIONS: These results suggest there was a larger recruitment of cortical areas, involving notably the parietal cortex when the movement is visuo-guided. Moreover, cerebral aging-related changes in the spatio-temporal beta ERS pattern suggests an impaired sensory integration.

Influence of internal globus pallidus stimulation on motor cortex activation pattern in Parkinson's disease.

OBJECTIVES: Indications of the functional neurosurgical treatments become more and more numerous, however, few methods were used to study the mechanism of action and some discrepancies came to light. We assessed the influence of internal globus pallidus (GPI) stimulation and L-Dopa on cortical activation during the preparation and execution phases of the movement compared to clinical improvement of Parkinson's disease. METHODS: We recorded the movement-related cortical potential and movement-related desynchronization. RESULTS: The Unified Parkinson's Disease Rating Scale was improved by 46% under stimulation and 64% under stimulation with L-Dopa. Premovement desynchronization was significantly increased on central contralateral derivation under stimulation with L-Dopa and decreased on frontocentral ipsilateral derivation under stimulation with and without L-Dopa. Movement desynchronization was improved on the contralateral motor cortex under stimulation with and without L-Dopa (benefit correlated with bradykinesia improvement). The movement-related postmotor potential was significantly increased under stimulation with L-Dopa. CONCLUSIONS: GPI stimulation alone influenced the premotor cortex activation during the planning and induced a selective and focal effect on the organisation of motor cortical activity during the movement execution which may explain bradykinesia improvement. The motor cortex activation improvement under stimulation with L-Dopa concerned both the movement preparation and execution but remained very localised to the contralateral motor cortex.