Projections from basal ganglia to tegmentum: a subcortical route for explaining to pathophysiology of Parkinson's disease signs ?

in Journal of Neurology (2000)

Les dissections arterielles et manipulations cervicales

Poster (1999, April)

Etude électrophysiologique des mécanismes responsables de la fatigue chronique dans la sclérose en plaques (SEP)

in Revue Neurologique (1999), 155(1S51, supp. 1),

Transcranial Magnetic Stimulation in Migraine

in Paulus, W.; Hallett, M.; Rossini, P. M. (Eds.) et al Transcranial Magnetic Stimulation (1999)

Impairment of neuromuscular transmission in a subgroup of migraine patients

in Neuroscience Letters (1999), 276(3), 201-3

Neuronal voltage-dependent P/Q Ca2+ channels are genetically abnormal in many cases of familial hemiplegic migraine and possibly associated with the more common forms of migraine with and without aura ... [more ▼]

Neuronal voltage-dependent P/Q Ca2+ channels are genetically abnormal in many cases of familial hemiplegic migraine and possibly associated with the more common forms of migraine with and without aura. Besides the brain, these channels are found in motor nerve endings where they control stimulation-induced acetylcholine release. Using single fiber EMG recordings we were able to demonstrate subclinical abnormalities of neuromuscular transmission in a subgroup of patients suffering from migraine with aura. This could be related to genetic abnormalities of P/Q Ca2+ channels in certain patients suffering from migraine with aura, which needs to be explored by proper genetic analyses. [less ▲]

Corticomotoneuronal synaptic connections in normal man. An electrophysiological study.

in Brain : A Journal of Neurology (1999), 122

In order to determine the mono- or oligosynaptic character of connections between pyramidal axons and individual spinal motor neurons, we constructed peri-stimulus time histograms (PSTHs) of the firing ... [more ▼]

In order to determine the mono- or oligosynaptic character of connections between pyramidal axons and individual spinal motor neurons, we constructed peri-stimulus time histograms (PSTHs) of the firing probability of voluntarily activated single motor units (SMUs) of various upper and lower limb muscles upon slightly suprathreshold transcranial anodal electrical stimulations of the motor cortex in normal subjects. Weak anodal cortical stimuli are known to activate preferentially fast-conducting pyramidal axons directly, bypassing cell bodies and cortical interneurons. A narrow bin width (0.1 ms) was chosen to measure precisely the duration of the PSTH excitatory peak, which corresponds to the rise time of the underlying compound excitatory post-synaptic potentials (EPSP). A short duration PSTH peak indicates sharp-rising EPSPs, most commonly encountered in the case of monosynaptic connections. In flexor carpi radialis and soleus SMUs, the PSTHs of built-in responses to anodal cortical stimuli were compared with those produced by 1A afferent stimulation able to elicit a Hoffmann reflex, which is known to be largely monosynaptic. In all upper and lower limb muscles, excitable SMUs responded to anodal cortical stimuli with a highly synchronized peak of increased firing probability. In flexor carpi radialis and soleus SMUs, the mean duration of this peak was significantly narrower than that evoked by 1A afferent stimulation, indicating that monosynaptic corticomotor neuronal transmission dominates low-threshold motor units, even in proximal arm and leg muscles. In the various muscles studied, and particularly in forearm SMUs, we did not observe broad PSTH peaks against the activation of non-monosynaptic corticomotor neuronal pathways, even with near-threshold stimuli. In some triceps and forearm flexor SMUs, subthreshold anodal pulses caused significant inhibition of their voluntary firing, with a latency consistent with activation of 1A inhibitory interneurons by the descending volleys. Measurements of the maximal number of counts in the excitatory PSTH peak upon anodal cortical stimuli provide comparisons of the strength of monosynaptic inputs to various muscles which seems to be maximal for hand and finger extensor muscles, and also for deltoid. [less ▲]

Intracortical inhibitory circuits are hyperactive in untreated patients with de novo idiopathic grand mal seizures

in Annals of Neurology (1998), 44

Interictal cortical excitability in migraine: a study using transcranial magnetic stimulation of motor and visual cortices.

in Annals of Neurology (1998), 44(2), 209-15

We performed transcranial magnetic stimulations of the motor and visual cortices in healthy controls (n = 27) and in patients suffering from migraine without (n = 33) or with (n = 25) aura between attacks ... [more ▼]

We performed transcranial magnetic stimulations of the motor and visual cortices in healthy controls (n = 27) and in patients suffering from migraine without (n = 33) or with (n = 25) aura between attacks. By using a 13-cm circular coil placed over the vertex and recordings of the first dorsal interosseus muscle, we measured thresholds (at rest and during contraction), amplitudes of motor evoked potentials and cortical silent periods. Paired stimulations with short (1-20 msec) interstimulus intervals were performed to assess intracortical inhibition. The visual cortex was stimulated with the same coil placed over the occipital scalp (7 cm above the inion) and the prevalence and threshold of phosphene production was determined. In patients with migraine with aura, motor thresholds during isometric contraction were significantly higher, whereas the prevalence of stimulation-induced phosphene production was lower compared with healthy controls. These changes were not correlated with attack frequency or disease duration. No differences were found between subject groups in thresholds at rest, motor evoked potential amplitudes, cortical silent periods, or response curves after paired stimuli. These results are in favor of cortical hypoexcitability rather than hyperexcitability in patients with migraine with aura between attacks. [less ▲]

Motor and somatosensory evoked potentials in cervical spondylotic myelopathy

in Electroencephalography and Clinical Neurophysiology (1998), 108

Intraoperative Localisation of the Primary Motor Cortex Using Single Electrical Stimuli

in Journal of Neurology, Neurosurgery & Psychiatry (1996), 60(4), 442-4

A new method of intraoperative localisation of the primary motor cortex is described, based on the application of single anodal electric pulses to the brain surface. Patients were anaesthetised with ... [more ▼]

A new method of intraoperative localisation of the primary motor cortex is described, based on the application of single anodal electric pulses to the brain surface. Patients were anaesthetised with propofol infusion, and neuromuscular blockade was temporarily alleviated to allow recording of surface EMG responses (CMAPs) to the stimuli. Primary motor areas could be localised in 18/19 patients studied. In the other patient, no responses were elicited, as the operative field was posterior to the motor cortex. When compared with MEPs elicited in awake patients by magnetic stimuli, responses to intraoperative anodal stimulation were of small amplitude (usually less than 10% of MEPs) and their latency was some 1 to 2 ms longer. One month after the operation, only 1/19 patients was left with a slight muscle weakness, although seven showed preoperative motor deficit. The procedure proved easy and fast, needing no preliminary surgery or time consuming preparation. It did not induce any detectable side effects. [less ▲]