Electrical and magnetic transcranial stimulation in patients with corticospinal damage due to stroke or motor neurone disease.

Twenty patients with hemiplegia and 13 patients with motor neurone disease were studied with electrical and magnetic transcranial stimulation. Motor evoked potentials were recorded from the biceps, thenar and tibialis anterior muscles. In both groups of patients magnetic stimulation with a Novametrix stimulator revealed fewer abnormalities than electrical stimulation with a Digitimer D180 stimulator.

Histometric study of myelinated fibers in the human trigeminal nerve.

The trigeminal ganglion, roots and the initial portion of the ophthalmic, maxillary and mandibular nerves were dissected in 3 cadavers, to study the number, area and composition of the fascicles, and the density and diameter spectra of myelinated fibers. The total number of fibers (x 1000) was 26 in the ophthalmic, 50 in the maxillary, and 78 in the mandibular division, 7.7 in the motor root and 170 in the sensory root.

Nociceptive quality of the orbicularis oculi reflexes as evaluated by distinct opiate- and benzodiazepine-induced changes in man.

The corneal reflex and the three components of the blink reflex (R1, R2, and R3) were recorded electromyographically in volunteers. The area of these responses was measured before and after administration of the narcotic-analgesic fentanyl (1.5 mg i.

Multiple firing of motoneurones is produced by cortical stimulation but not by direct activation of descending motor tracts.

In the present report we have tested whether stimulation of the motor descending tracts at the brain-stem level could set up repetitive motor unit discharges in a similar manner to that described for motor cortical stimulation. We have seen that a large descending motor volley, evoked by brain-stem stimulation, cannot produce repetitive firing of motor units. Repetitive motoneurone firing is therefore produced by multiple excitatory volleys set up by single cortical shocks.

Masseter inhibitory reflex in movement disorders. Huntington's chorea, Parkinson's disease, dystonia, and unilateral masticatory spasm.

Evoked by electrical stimulation of the mental nerve, the masseter inhibitory reflex consists of an early and a late silent period (SP1 and SP2), which interrupt the voluntary electromyographic (EMG) activity in the masseter muscle. We recorded the masseter inhibitory reflex and measured its latency, depth of suppression, duration and recovery cycle to paired stimuli, in patients with Huntington's chorea. Parkinson's disease, dystonia, or unilateral masticatory spasm.

Corticospinal potentials after electrical and magnetic stimulation in man.

The present report deals with our study of the descending volley evoked by both electrical and magnetic transcranial stimulation in man. We discuss the differences of these two techniques specifically as regards the latency and amplitude of evoked potentials. In both cases, electrodes were placed either in the epidural space or directly on the spinal cord.

Corticobulbar and corticospinal projections to neck muscle motoneurons in man. A functional study with magnetic and electric transcranial brain stimulation.

The cortical projections to neck muscle motoneurons were studied in normal subjects by electrical and magnetic transcranial brain stimulation. After magnetic stimulation with a large coil, motor evoked potentials were present in about 20% of relaxed and 100% of contracting neck muscles. The latency of these responses was short: about 7 ms in the sternomastoid and splenius and 9 ms in the trapezius muscles.

Idiopathic and symptomatic trigeminal pain.

The trigeminal reflexes (corneal reflex, blink reflex, masseter inhibitory periods, jaw-jerk) and far field scalp potentials (nerve, root, brainstem, subcortical) evoked by percutaneous infraorbital stimulation were recorded in 30 patients with "idiopathic" trigeminal neuralgia (ITN) and 20 with "symptomatic" trigeminal pain (STP): seven postherpetic neuralgia, five multiple sclerosis, four tumour, two vascular malformation, one Tolosa-Hunt syndrome, and one traumatic fracture. All the patients with STP and two of those with ITN had trigeminal reflex abnormalities; 80% of patients with STP and 30% of those with ITN had evoked potential abnormalities. The results indicate that 1) trigeminal reflexes and evoked potentials are both useful in the examination of patients with trigeminal pain, and in cases secondary to specific pathologies provide 100% sensitivity; 2) in "symptomatic" and "idiopathic" paroxysmal pain the primary lesion affects the afferent fibres in the proximal portion of the root or the intrinsic portion in the pons; 3) primary sensory neurons of the A-beta fibre group are involved in both paroxysmal and constant pain, but in the latter the damage is far more severe.

Corticobulbar projections to upper and lower facial motoneurons. A study by magnetic transcranial stimulation in man.

To investigate the human corticofacial projections, we recorded the compound motor potentials and single motor unit potentials evoked by magnetic transcranial stimulation, in the frontalis and lower facial muscles of healthy subjects. Potentials secondary to activation of the corticobulbar tract were contralateral in lower and bilateral in upper facial muscles. Even though the latency of responses was longer than would be expected for direct cortico-motoneuronal connections, these cannot be excluded either for lower or upper facial motoneurons.

Motor potentials evoked by paired cortical stimuli.

We recorded the motor evoked potentials (MEPs) from the abductor pollicis brevis muscle, after supramaximal electrical transcranial stimulation, and studied the effect of paired transcranial shocks with varying interstimulus time intervals, in 10 normal subjects, 4 patients with median nerve neuropathy and 2 patients with motoneurone disease. In relaxed muscles the amplitude of the MEP evoked by a single shock averaged 30% of the M wave. With intervals from 1 to 2.

Effects of brainstem lesions on the masseter inhibitory reflex. Functional mechanisms of reflex pathways.

The masseter inhibitory reflex (MIR) was investigated in 16 patients with localized brainstem lesions involving the trigeminal system. The MIR consists of two phases of EMG silence (S1 and S2) evoked by stimulation of the mental nerve during maximal clenching of the teeth. The extent of the lesions was assessed by neurological examination, nuclear magnetic resonance imaging (MRI), and recording of trigeminal reflexes with known paths (jaw jerk and blink reflex).

[Electric stimulation of the dental pulp in the evaluation of the central effect of analgesics].

We conducted a double-blind cross-over study in ten volunteers aged from 19 to 30 years, to compare the pain control effects of a single oral dose of two analgesic compounds (drug A: propyphenazone mg 250, ethylmorphine mg 5, caffeine mg 5; drug B: dipyrone mg 500, diphenhydramine mg 12.5, adiphenine mg 5, ethyl aminobenzoate mg 2.5) in an experimental pain model using stimulation of dental pulp.

Descending volley after electrical and magnetic transcranial stimulation in man.

The descending volley evoked by electrical and magnetic transcranial stimulation was recorded with spinal electrodes in 3 subjects undergoing spinal surgery. The descending volley evoked by electrical stimulation, as previously described, was composed by a short-latency initial wave followed by later waves. In two subjects magnetic stimulation evoked an initial wave of slightly longer latency (0.

[Changes in the RIII response of the flexion reflex with painful maneuvers].

In the search for reliable indirect indices of pain sensation, interest has recently focused on the nociceptive flexion reflex and late components of the brain evoked potentials. In ten volunteers with sciatica, the nociceptive flexion reflex (RIII) and the late component (N150-P220) of the evoked potentials were recorded, with the subjects at rest and during pain produced by the Lasegue manoeuvre. In recordings with the subjects at rest, both responses were stable.

[Modulation using racemic and levo-rotary baclofen of the trigeminal reflex in man].

Baclofen (Lioresal), a muscle relaxant, exerts a specific action on the trigeminal system by depressing excitatory synaptic transmission in the spinal trigeminal nucleus. To evaluate the effects of racemic and L-baclofen on the human trigeminal reflexes, the area of the blink reflex was measured in seven normal subjects, before and after i.v.

Functional organization of the trigeminal motor system in man. A neurophysiological study.

Transcranial stimulation (TCS) in intact human subjects was used to investigate the corticobulbar projections and the functional organization of the trigeminal motor system. Both electrical (with the anode overlying the face area of the motor cortex) and magnetic TCS (with the coil at the vertex) excite the upper motoneurons projecting to the trigeminal motor nucleus, evoking motor potentials (C-MEPs) in the jaw-closing and suprahyoid muscles, but only during voluntary contraction. At least 30% of jaw-closing motoneurons are reached by direct fast-conducting corticobulbar fibres; these projections are mainly crossed.

Corticospinal potentials after transcranial stimulation in humans.

The descending volley evoked in humans by transcranial electrical stimulation of the scalp was recorded with epidural and spinal electrodes. It consisted of an early wave, which increased in amplitude and decreased in latency when the strength of the stimulus was increased. The mean conduction velocity of the early wave was 66, SD 2.

Treatment of trigeminal neuralgia by thermocoagulation, glycerolization, and percutaneous compression of the gasserian ganglion and/or retrogasserian rootlets: long-term results and therapeutic protocol.

From 1976 to 1986, 681 patients with drug-refractory trigeminal neuralgia (TN)--typical in 641, symptomatic of multiple sclerosis in 23 and of tumor in 10, atypical in 5, and postherpetic in 2--were treated with various percutaneous procedures. Controlled differential thermocoagulation of the gasserian ganglion and/or retrogasserian rootlets was performed in 533 patients; glycerolization of the trigeminal cistern in 32; and compression of the gasserian ganglion by balloon catheter in 159. Results and complications of each procedure are assessed at a mean follow-up of 6.

The masseter inhibitory reflex is evoked by innocuous stimuli and mediated by A beta afferent fibres.

Mechanical or electrical stimulations in the area of the mouth evoke two phases of inhibition in the masseter muscle (early and late inhibitory reflex, also called masseter silent periods). The question whether the afferents of the human masseter inhibitory reflex are nociceptive or non-nociceptive has not yet been settled. We showed that an innocuous stimulus, such as a fine jet of saline directed to the lips of healthy humans, evokes an early and a late masseter inhibitory reflex, similar to those following electrical stimulation.

Stimulation of motor tracts in multiple sclerosis.

Percutaneous electrical stimulation of the motor cortex was used to evaluate corticospinal conduction to upper-limb motoneurons in 29 patients with multiple sclerosis. Central motor conduction abnormalities were correlated with clinical signs and somatosensory evoked potentials. Muscle responses to cortical stimulation were altered in 20 patients.

Impairment of masticatory function in hemiplegia.

We studied masseter muscle function in 15 hemiplegic patients. Direct motor responses to stimulation of the masseteric nerve were normal. Voluntary activity at maximum strength was reduced on the paretic side.

Correlation between facial involuntary movements and abnormalities of blink and corneal reflexes in Huntington's chorea.

Blink and corneal reflexes were studied in 11 patients with Huntington's chorea and the results compared with the severity of the disease. The latency of the R2 component of the blink reflex was delayed and the duration of R2 and of the corneal reflex (CR) prolonged. A greater habituation of the R2 component was found in the patients with involuntary movements in the face, and in some patients a long-lasting depression of R2 was present.

Intracranial stimulation of the trigeminal nerve in man. III. Sensory potentials.

Percutaneous electrical stimulation of the trigeminal root was performed in 18 subjects undergoing surgery for idiopathic trigeminal neuralgia or implantation of electrodes into Meckel's cave for recording of limbic epileptic activity. All subjects had normal trigeminal reflexes and evoked potentials. Sensory action potentials were recorded antidromically from the supraorbital (V1), infraorbital (V2) and mental (V3) nerves.