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Biomedical subjects

E S Tolosa

Publications and source records attributed to E S Tolosa.

At least 19 recordsLinked to original sources
PubMed1995

Reaction time and acoustic startle in normal human subjects.

We studied the effects of collision between a voluntary command and the startle response by interrupting a simple visual reaction time task with an acoustic startle. We observed two main effects. First, the reaction time was markedly shortened when the startle was delivered at intervals of 0-75 ms after the 'go' signal. Second, the startle response elicited when the subject's attention was focused onto reacting to the visual 'go' signal involved more muscles and induced larger EMG responses than when the startling stimulus was delivered unexpectedly. Startle response and voluntary commands may share a number of structures along the motor path. Reaction time can be shortened up to the latency of a startle response if the voluntary command is issued a short time after the startling stimulus. Facilitation of the startle responses during motor preparation may be due to the excitability enhancement that occurs in various neural structures along the motor path before the onset of EMG activity.

Acoustic Stimulation↗
PubMed1995

Striated anal sphincter denervation in patients with progressive supranuclear palsy.

Anal sphincter electromyography may contribute to the differential diagnosis between Parkinson's disease (PD) and other parkinsonisms featuring autonomic dysfunction, such as multiple system atrophy (MSA). Although patients with progressive supranuclear palsy (PSP) do not normally exhibit clinical signs of autonomic dysfunction, a few may be first seen with urinary and fecal incontinence. We performed an electromyographic study of the anal sphincter in 12 patients with clinical criteria of probable or definite PSP, two of them with clinical manifestations of vesical and anal sphincter dysfunction. The results have been compared with those obtained from six patients with PD and six patients with MSA. An abnormal anal sphincter examination was present in five of 12 PSP patients (41.6%). The abnormal motor units of these patients were indistinguishable from those observed in patients with MSA. Patients with MSA had the largest, and patients with PD had the lowest, proportion of abnormal motor units. We conclude that some patients with PSP may have electromyographic signs of denervation in the anal sphincter, which make them indistinguishable by using this test alone from patients with MSA.

Adult↗
PubMed1994

Vibration-induced presynaptic inhibition of the soleus H reflex is temporarily reduced by cortical magnetic stimulation in human subjects.

We have examined the effects of a transcranial magnetic stimulus (TMS) on the H reflex of the soleus muscle during vibration-induced presynaptic inhibition of the reflex, in seven normal volunteers. Without vibration, the H reflex was facilitated at interstimulus time intervals of > or = 5 ms after TMS. With vibration, the H reflex was markedly reduced or completely inhibited in control trials, but facilitation by TMS was noticed at intervals as short as -2.5 ms. These findings indicate an effect of TMS on the spinal interneurons mediating presynaptic vibratory inhibition of the H reflex.

Cerebral Cortex↗
PubMed1994

Responses of the soleus muscle to transcranial magnetic stimulation.

Soleus muscle responses are difficult to elicit by cortical stimulation in normal humans at rest. We have studied in normal volunteers the behavior of the soleus and tibialis anterior muscle responses to maximal intensity transcranial magnetic stimulation (TMS) in the following experimental conditions: lying in supine position, active ankle dorsal flexion, active plantar flexion, standing on the soles, standing on the toes, and standing on the heels. At rest, consistent responses were recorded in the soleus to 61% of the stimuli, only. Maximal facilitation of the response in the soleus occurred when standing on the toes. In this condition, responses were recorded to 100% of the stimuli, at a latency that was, on average, 5.2 msec shorter than the latency of the responses at rest, and similar to the latency of the responses recorded in the tibialis anterior muscle when standing on the heels. Central motor conduction time, calculated in conditions of maximal facilitation, was not different for soleus or tibialis anterior muscles. We conclude that the soleus muscle receives short latency excitatory inputs from cortico-spinal axons activated by TMS, with a conduction time similar to that for the tibialis anterior. Such short latency cortico-spinal connections to the soleus muscle may become functionally effective only during maximum enhancement of motoneuronal excitability by muscle contraction.

Adult↗
PubMed1994

New and emerging strategies for improving levodopa treatment.

Soon after the successful introduction of large oral doses of levodopa or of levodopa plus a decarboxylase inhibitor, such as carbidopa or benserazide, for the treatment of Parkinson's disease, it became evident that several disturbing side effects were limiting the therapeutic efficacy of this amino acid. This paper discusses novel practical approaches for the management of these levodopa-related complications. These approaches include therapeutic strategies for controlled delivery of levodopa to the brain (controlled-release preparations), rescue treatment with subcutaneous, intranasal, or sublingual administration of the dopamine agonist apomorphine, and the administration of an atypical neuroleptic, such as clozapine. Other approaches for prolonging the response of levodopa that are being used or investigated are also reviewed in this paper. These include the use of levodopa prodrugs and blocking the degradation in the brain with inhibitors of monoamine oxidase-B and catechol-O-methyltransferase.

Animals↗
PubMed1993

Magnetic resonance imaging in patients with concurrent Tourette's disorder and Asperger's syndrome.

OBJECTIVE: The purpose of the study was to examine behavioral/cognitive and neuroradiological features of patients with concurrent Tourette's disorder (TD) and Asperger's syndrome (AS). METHODS: The authors studied the occurrence of structural brain abnormalities using magnetic resonance imaging (MRI) in seven males with concurrent TD and AS, and in nine age-matched males, who had TD but did not have AS. Both groups were tested with an extensive battery of neurological and psychiatric rating scales and cognitive tests. RESULTS: Five of the seven patients with TD and AS had developmental brain anomalies. In contrast, normal MRI scans were found in all but one TD patient without AS. Both groups were not significantly different in the severity of motor and phonic tics, obsessionality, depression and anxiety, or in measures of general intelligence, memory, and language function; but patients with TD and AS had a history of more psychiatric hospitalizations, poor academic achievement, more neurological soft signs and appeared more impaired on complex problem-solving and spatial tests than did TD patients without AS. CONCLUSION: These findings suggest that structural cortical and subcortical abnormalities are more common among individuals with concurrent TD and AS than among sex- and age-matched TD patients without AS. Dysfunction of frontal-subcortical systems may play a role in the pathophysiology of concurrent TD and AS.

Adolescent↗
PubMed1992

Myokymic discharges and enhanced facial nerve reflex responses after recovery from idiopathic facial palsy.

A functional disorder of facial muscle activity commonly occurs in patients after recovery from Bell's palsy with axonal degeneration. The postparalytic facial dysfunction is probably related to the aberrant growing of regenerating axons, although other theories such as ephaptic transmission, spontaneous generation of impulses, and enhancement of motoneuron excitability should also be considered. In this work, we have carried out a comparative electrophysiological study of both sides of the face in 23 patients who had recovered from a unilateral Bell's palsy with axonal degeneration. At rest, spontaneous firing of motor units was observed in muscles of the previously paralyzed side. Direct motor responses to facial nerve stimulation were smaller in the muscles of the previously paralyzed side, but reflex responses obtained in the same muscles by stimulation of either the facial or trigeminal nerve were larger when compared with those of the contralateral side. These data indicate that patients with "postparalytic facial dysfunction" may have an increased background muscle activity, as well as an enhanced recruitment of facial motoneurons to reflex activation in the side of the previous paralysis. These findings are compatible with an enhanced level of motoneuron excitability in the facial nucleus.

Action Potentials↗
PubMed1992

Recurrent hypersomnia in two adolescent males with Asperger's syndrome.

Two individuals with Asperger's syndrome, a rare pervasive developmental disorder, developed recurrent episodes of hypersomnia and abnormal behavior (Kleine-Levin syndrome) during adolescence. The possible etiological role of developmental structural brain anomalies and the differential diagnosis of recurrent hypersomnia and abnormal behavior in patients with pervasive developmental disorders are discussed.

Adolescent↗
PubMed1992

Tics and myoclonus.

This article describes advances occurring over the last year in the pathophysiology, etiology and treatment of tics and myoclonus. Progress is being made in the clinical definition of Tourette syndrome (TS). The search for the TS gene has already excluded more than 50% of the autosomal genome. Progress in the understanding of myoclonus is slow but continuous. Several paper are devoted to clinical aspects but much recent attention has been focused on the pathophysiological mechanisms underlying myoclonus.

Brain↗
PubMed1991

Neurophysiological observations on the effects of botulinum toxin treatment in patients with dystonic blepharospasm.

Botulinum toxin treatment improves dystonic blepharospasm by inducing transient paresis of the orbicularis oculi muscle. It is not known if it also reduces the enhanced brainstem neuronal excitability found in this disorder. We have performed conventional electromyography (EMG) and blink reflex excitability studies on fifteen patients with blepharospasm before and after botulinum toxin treatment. Denervation signs were found with needle EMG in all treated muscles. Amplitude of the facial compound muscle action potential (CMAP) and R1 response was reduced after botulinum toxin injections. In blink reflex excitability studies, the recovery of R2 response was enhanced after treatment even when patients were tested at the time of maximal benefit from botulinum toxin injections. The results suggest that there is little influence of botulinum toxin treatment upon the enhanced excitability of brainstem interneurons in patients with blepharospasm.

Adult↗
PubMed1990

Normal proprioceptive trigeminal afferents in patients with Sjögren's syndrome and sensory neuronopathy.

A pure sensory neuropathy due to neuronal damage in the gasserian and spinal ganglia has been described in patients with Sjögren's syndrome. Conventional electromyographic (EMG) studies can demonstrate the selective involvement of the sensory pathways but they do not provide definite evidence for the site of the lesion. Noting that the trigeminal sensory neurons carrying cutaneous and muscular afferents are differentially located in the gasserian and mesencephalic nuclei, respectively, we carried out an electrophysiological study of the trigeminofacial and trigeminotrigeminal reflexes in 5 patients with Sjögren's syndrome and pure sensory neuropathy, in 10 patients with sensory-motor neuropathies of other causes, and in 10 healthy subjects. Our results show that patients with Sjögren's syndrome and pure sensory neuropathy who exhibited abnormal blink reflexes and an abnormal, cutaneous-induced masseter silent period had normal jaw jerks, whereas patients with sensory-motor neuropathies who exhibited abnormal cutaneous responses had abnormal jaw jerks. These findings suggest that the lesion in pure sensory neuropathy involves damage to the neurons of the gasserian ganglia and not to the trigeminal axons, since an axonal lesion would be expected to involve the large axons from muscle spindle receptors.

Adult↗
PubMed1989

Blink reflex excitability cycle in hemifacial spasm.

We studied electrically elicited blink reflex responses in patients with hemifacial spasm (HFS) by applying single isolated, as well as paired (conditioning and test), stimuli at both sides of the face. Responses after single stimuli were of larger size on the side of the spasm compared with the uninvolved side and controls. With paired stimuli, the inhibitory effect of the conditioning stimuli upon the test stimuli late response (R2), which was always observed in normals, was significantly less pronounced at short interstimuli intervals. This resulted in an enhanced recovery curve of R2, which was observed on the side of the spasm and the contralateral, clinically normal side. Patients with longer disease duration showed more striking abnormalities of the recovery curve. We suggest that there is enhanced excitability of facial motoneurons and of those brainstem interneurons that mediate the blink reflex pathway in patients with HFS.

Action Potentials↗
PubMed1984

Parkinsonism and basal ganglia infarcts.

A subacute parkinsonian syndrome was seen in three patients with CT evidence of basal ganglia infarcts. The clinical picture improved spontaneously, making the diagnosis of idiopathic Parkinson's disease untenable, and other causes of parkinsonism were not detected. This extrapyramidal syndrome was therefore compatible with "vascular parkinsonism," even though it lacked features often ascribed to this syndrome, such as a history of previous strokes and the presence of dementia and corticospinal tract signs.

Aged↗
PubMed1981

Clinical features of Meige's disease (idiopathic orofacial dystonia): a report of 17 cases.

Seventeen patients with prominent orofacial dystonia of unknown cause (idiopathic orofacial dystonia: Meige's disease) were examined and several clinical features seen that, to my knowledge, had previously not been recognized. These include a family history of dystonia or other extrapyramidal disorders, a high incidence of depression, and frequent extension of spasms beyond the orofacial muscles. The course of the muscle spasms varies: rapid progression (eg, two months) to maximal disability occurred in some patients, and clear improvement after years of severe disability was observed in others. In addition to the muscle spasms, neurological abnormalities that suggest dysfunction of the basal ganglia were frequently present. The "spasm facial median" of Meige may be a distinct dystonic disorder, unrelated to idiopathic torsion dystonia.

Adolescent↗
PubMed1981

Myotatic reflexes and the on-off effect in patients with Parkinson's disease.

Reflex activity in the biceps and triceps muscles evoked by applied torque perturbations was studied in patients with Parkinson's disease. The perturbations consisted of single pulses or of pseudo-random sequences of pulses of torque. The patients were treated with levodopa and some exhibited marked fluctuations in their clinical disabilities ("on-off" effect). The study was undertaken to see if reflex activity changed in parallel with the fluctuations of their clinical symptoms. It was found that the reflex activity in these patients could be classified into two types, a Type I response differing little from normal and a Type II response exhibiting marked high-frequency (8-14 Hz) oscillations in EMG activity. Both Type I and Type II responses were virtually the same in the "on" as in the "off" state.

Adult↗