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Biomedical subjects

N Mavroudakis

Publications and source records attributed to N Mavroudakis.

34 records · Page 2Linked to original sources
PubMed1991

Acute effects of diphenylhydantoin on peripheral and central somatosensory conduction.

We studied the acute effects of an intravenous loading dose of DPH (16 mg/kg body weight) on peripheral and central somatosensory conduction in 10 normal volunteers. Somatosensory evoked potentials were recorded before and at regular intervals after DPH infusion. There was no effect on peripheral conduction. DPH significantly delayed N13 peak latency without changing conduction in the posterior spinal columns. Although the N13-N20 interpeak interval remained stable because of the parallel shift of the 2 peaks, the central conduction time measured from onset latencies of N11 and N20 significantly increased. We conclude that acute administration of DPH at serum levels below 30 micrograms/ml induces a reversible delay of synaptic transmission in spinal and central somatosensory structures.

Adult↗
PubMed1991

Synaptic effects of halogenated anesthetics on short-latency SEP.

We evaluated the effects of different stable end-tidal concentrations of isoflurane, enflurane, or halothane on short-latency somatosensory evoked potentials recorded during general anesthesia. Isoflurane and enflurane significantly enhanced the P22 over the pre-central scalp, whereas the parietal N20 amplitude did not increase. The P22 increase did not occur with halothane, which indicates that the P22 changes are a specific effect of certain anesthetics, probably related to their influence on synaptic events. At the subcortical level, isoflurane and enflurane increased significantly the N13 peak latency and decreased the interval between the N13 peak and P14 peak, which implicates interference with synaptic transmission at the spinal level. Halothane had no effect at the spinal level. All three anesthetics significantly increased the central conduction time.

Adult↗
PubMed1991

Treatment of supraventricular tachyarrhythmias associated with hyperthyroidism by radioiodine, amiodarone and propylthiouracil.

Beta-blockers and calcium antagonists have been advocated for thyrotoxicosis induced tachyarrhythmias. Amiodarone is generally considered as contraindicated because of its high iodine content. Since amiodarone combined with propylthiouracil induced a greater fall in serum thyroid hormone concentrations than propylthiouracil alone, we treated 2 hyperthyroid patients with supraventricular arrhythmias by radioiodine (day 0) followed after 24 h by amiodarone and propylthiouracil. Serum T3 was normalized on day 2 (patient 1) and 3 (patient 2). Effective t1/2 of intrathyroidal 131I were 6.6 and 4.3 days (versus 5.9 days for 131I given alone). In patient 1, atrial fibrillation, reverted to sinus rhythm after verapamil and digoxin, and did not recur. In patient 2, conversion of atrial fibrillation to sinus rhythm occurred on day 11; from day 0 to day 11, ventricular rate decreased and was significantly correlated to T3 (r = 0.82; p < 0.05). In conclusion, amiodarone may be beneficial in thyrotoxicosis associated tachyarrhythmias, given with propylthiouracil 24 h after radioiodine, it did not decrease thyroid irradiation and rapidly decreased serum T3.

Adult↗
PubMed1991

Magnetic stimulation of the human motor cortex: ipsilateral and contralateral facilitation effects.

Voluntary contraction of a muscle greatly increases the amplitude and decreases the latency of the motor potentials evoked by electromagnetic coil brain stimulation (facilitation). Facilitation has also been observed with contraction of a nearby ipsilateral and a contralateral homologous muscle. We studied these facilitatory relationships in 5 normal subjects in small hand, forearm and upper arm muscles using surface-recorded compound motor action potentials, single motor unit recordings, and post-stimulus time histograms. There was no evidence for spread of facilitation between any pair of muscles if the muscle from which motor evoked potentials (MEPs) were recorded was completely at rest during brain stimulation, although this sometimes required training to accomplish or could not be achieved. Thus, although spread of facilitation has been observed by others under these conditions, we did not find this effect. There may be significant interindividual variations in the degree of facilitatory spread.

Action Potentials↗
PubMed1990

Neuroradiologic findings in leptomeningeal carcinomatosis: the value interest of gadolinium-enhanced MRI.

Four patients with leptomeningeal metastases documented by neuroradiological examinations are reported. All had central nervous system or systemic neoplasms and showed clinical signs of carcinomatous meningitis. Gadolinium-enhanced MRI (Gd-MRI) disclosed for each patient pathological foci, allowing delineation of the extent of meningeal disease. Although non-specific, these findings, combined with the clinical context and CSF analysis, may lead to a rapid diagnosis and treatment of carcinomatous meningitis, even when malignant cells are not detected in the cerebrospinal fluid.

Adult↗
PubMed1989

Local anti-P32 humoral response in tuberculous meningitis.

We report five cases of severe pulmonary tuberculosis admitted to hospital with a suspicion of meningeal involvement. The diagnosis of tuberculous meningitis was confirmed by standard bacteriological techniques in two of the five patients. Specific IgG class antibodies directed against the recently purified BCG antigen P32 were detected by a dot immunoblotting technique in the serum and in the cerebrospinal fluid of each patient; however, a higher anti-P32 immunoglobulins/total immunoglobulins ratio was observed in the cerebrospinal fluid of patients with tuberculous meningitis than in their serum while the reverse situation was observed in the other patients.

Adult↗
PubMed1989

Global aphasia without hemiparesis following prerolandic infarction.

Acute global aphasia without hemiparesis (GAWH) is said to result from the association of 2 separate lesions in the anterior and posterior left hemisphere language areas. We present 2 unusual cases of GAWH whose CTs revealed only a single lesion of the posterior part of F2 and F3. There was good recovery of verbal communicative abilities. Functional disconnection of posterior language areas seems responsible for this syndrome in such cases.

Aged↗
PubMed1988

The effect of acute hemiplegia on intercostal muscle activity.

We recorded the EMG of parasternal intercostal muscles in 25 patients with flaccid hemiplegia during quiet spontaneous breathing, voluntary hyperventilation, and CO2-induced hyperventilation. The respiratory drive was abnormal on the hemiplegic side and the function of the intercostal muscles was affected specifically during voluntary hyperventilation.

Acute Disease↗
PubMedDate not supplied

The effect of stimulus frequency on post- and pre-central short-latency somatosensory evoked potentials (SEPs).

We assessed the influence of the stimulus frequency on short-latency SEPs recorded over the parietal and frontal scalp of 26 subjects to median nerve stimulation and 16 subjects to digital nerve stimulation. When the stimulus frequency is increased from 1.6 Hz to 5.7 Hz, the amplitude of the N13 potential decreases whereas the P14 remains stable. The amplitude of the N20 is not changed significantly whereas the P22, the P27 and the N30 decrease significantly. In 50% of the subjects 2 components can be seen within the frontal negativity that follows the P22: an early 'N24' component, which is not affected by the stimulus rate, and the later N30, which is highly sensitive to the stimulus frequency. The distinct amplitude changes of the N20 and P22 with increasing stimulus frequency is one among other arguments to show that these potentials arise from separate generators.

Adult↗
PubMedDate not supplied

Dissociation of P13-P14 far-field potentials: clinical and MRI correlation.

P13 and P14 far-field potentials are recorded over the scalp with median nerve stimulation when non-cephalic reference is used to measure somatosensory evoked potentials. The dissociation of these 2 potentials is exceptional. Only 2 cases subsequent to pontine lesions have been described hitherto. We report the case of a 31-year-old woman with a low grade glioma located at the spino-medullary junction who presented a P13-P14 far-field dissociation. This case fully supports the independent nature of the P13 and P14 potential generators.

Adult↗
PubMedDate not supplied

Topographic analysis of the effects of isoflurane anesthesia on SEP.

Isoflurane anesthesia induces a striking increase in the P22 potential recorded over the precentral scalp whereas the amplitude of the N20 is reduced. It is not known whether the increased "P22" enhanced by isoflurane arises from the same generator as the small precentral P22 potential recorded in the normal awake subject. Multi-channel recordings of SEP before and during isoflurane anesthesia were performed in 13 normal subjects. Isopotential topographic maps showed that isoflurane did not change the distribution of the precentral "P22" despite its clear amplitude increase. Our data confirm that isoflurane enhances the precentral P22 and that the enhanced "P22" arises from the same generator as the P22 recorded before isoflurane anesthesia.

Adult↗
PubMedDate not supplied

Hepatic myelopathy after splenorenal shunting: report of one case and review of the literature.

Hepatic myelopathy is a rare complication of cirrhosis, usually associated with surgical or spontaneous porto-systemic shunts. Its pathophysiology is unknown. It is characterized by a motor involvement of the lower limbs without clinical sensory abnormality, leading to spastic paraparesis. These neurological features are related to a symmetric loss of myelin in the lateral corticospinal tracts. Usefulness of liver transplantation in this setting is not yet determined. We describe here the case of a 29-year-old male who presented with progressive spastic paraparesis of the lower limbs 3 years after a spleno-renal shunt.

Adult↗