PubMed Health⌕ Search

Biomedical subjects

N Mavroudakis

Publications and source records attributed to N Mavroudakis.

At least 19 recordsLinked to original sources
PubMed1998

Electroencephalographic abnormalities in borderline personality disorder.

Epilepsy and non-localized brain dysfunction have been invoked, among others, as underlying factors in borderline personality disorder. We have recorded 58 electroencephalograms in 20 borderline patients, first after complete drug washout and then under carbamazepine or placebo double-blind treatment. Taking into account only definite abnormal tracings, we found a 40% incidence of abnormal diffuse slow activity. No patient disclosed focal or epileptiform EEG features. Carbamazepine did not appear to modify the electroencephalogram.

Adult↗
PubMed1997

Effects of vigabatrin on motor potentials evoked with magnetic stimulation.

We studied the effect of an acute loading dose of vigabatrin on threshold of motor responses and duration of silent period elicited with cortical magnetic stimulation in normal subjects. In contrast to phenytoin, vigabatrin does not increase the motor threshold of first dorsal interosseus muscle. We also show that, although vigabatrin increases GABA concentrations in the central nervous system, duration of silent period studied at various stimulus intensities is not modified after vigabatrin administration.

Adult↗
PubMed1997

Central nervous system lesions associated with Crohn's disease.

Central nervous system vasculitis is an exceptional extraintestinal manifestation of Crohn's disease. Reported here are 2 cases, highlighting the difficulty of differential-diagnosis with multiple sclerosis and stressing the importance of early immuno-suppressive therapy.

Adult↗
PubMed1997

Audiogenic startle reflex in acute hemiplegia.

The generators of the audiogenic startle reflex (ASR) are located in the bulbopontine reticular formation. We studied the influence of acute vascular supratentorial lesions on ASR. Ten patients with hemiplegia due to hemispheric cerebral infarct were studied within 5 days of stroke onset. ASR and magnetic cortical stimulation were performed the same day. A muscle response to magnetic stimulation was not elicited over the plegic side in any patient. In four of seven patients, ASR was enhanced over the plegic side. We suggest that enhanced ASR is due to the loss of a predominantly inhibitory hemispheric drive on ASR generators.

Acoustic Stimulation↗
PubMed1996

[Alzheimer's disease in 1995].

Alzheimer's disease is the most common cause of dementia in our society. Recent progress in the understanding of the mechanisms leading to the central nervous system abnormalities produced by this disease will lead soon to new strategies of treatment and new diagnostic approaches.

Aged↗
PubMed1995

Abnormal motor evoked responses to transcranial magnetic stimulation in focal dystonia.

We evaluated motor responses evoked after magnetic cortical stimulation in dystonia, emphasizing the relationship between resting and facilitation state. We studied 15 normal controls (mean age, 37.9 years; range, 23 to 63) and 13 dystonic patients (mean age, 43.4 years; range, 20 to 56). Surface electrodes were placed over the right first dorsal interosseous muscle to measure motor evoked potentials and inhibitory silent periods obtained with magnetic stimulation. The amplitude ratio of motor evoked potentials measured during facilitation and at rest with low-intensity magnetic stimulation was significantly higher in dystonic patients (15.09) when compared with normal subjects (5.43; p = 0.04). The ratio of duration of silent periods evoked with 120% motor threshold (MT) and MT + 25% magnetic stimulus intensity was significantly higher in dystonic patients (78.4%) when compared with normal subjects (69.7%; p = 0.04). We conclude that with low-intensity magnetic stimulation the relationship between amplitudes of motor potentials evoked at rest and during facilitation, as well as the responses of pathways that mediate silent periods, are disturbed in focal dystonia.

Adult↗
PubMed1994

Spinal and brain-stem SEPs and H reflex during enflurane anesthesia.

Whereas cortical SEPs are altered by halogenated anesthetics, spinal and subcortical SEPs are thought to be hardly affected. In this study the spinal N13 potential (recorded with anterior neck reference) showed a significant delay with enflurane anesthesia. The P13 and P14 far-field potentials, however, remained unchanged. Our results indicate that oligosynaptic as well as polysynaptic pathways are influenced by halogenated anesthetics and that enflurane has different effects on spinal gray matter and cuneate synapses. Our data also demonstrate that earlobe reference recordings are not adequate to measure pharmacologic effects on subcortical SEPs.

Adult↗
PubMed1994

Effects of diphenylhydantoin on motor potentials evoked with magnetic stimulation.

We studied the effect of an acute loading dose of diphenylhydantoin (DPH) on motor responses elicited with cortical magnetic stimulation in normal subjects. DPH increased significantly the motor threshold activation of ADM, APB, FDI and biceps. The motor threshold increase was of greater magnitude for the proximal muscle. Spinal soleus alpha-motoneuron pool excitability assessed by H-reflex was increased significantly suggesting that the motor threshold increase is related to a supraspinal effect of the drug. Our study demonstrates that the motor threshold increase observed after DPH administration occurs not only in epileptic patients but also in normal subjects.

Adult↗
PubMed1994

Effects of routine hyperventilation on PCO2 and PO2 in normal subjects: implications for EEG interpretations.

There are few data in the EEG literature describing the time course of hyperventilation-(HV) induced changes in blood gases, despite this being a routine activating procedure. We studied changes in blood gases and EEG in nine normal adult subjects before, during, and after HV. The mean PCO2 fell 18 mm Hg from the baseline during HV and recovered in 7 min. The mean PO2 rose 7 mmHg during HV and fell to 25 mm Hg below baseline 5 min after HV. The PCO2 recovery period is longer than is usually assumed in clinical EEG. The PO2 fall to a nadir at 5 min after the end of HV suggests that close attention should be paid to this period, as is confirmed by the re-buildup seen in moyamoya disease. Despite uniform changes in blood gases, the EEG median power frequency change showed marked variability; on average, it dropped by 1 Hz during HV and returned to baseline within 2 min of resumption of normal respiration. The EEG root-mean-square power showed a 200% increase during HV and also had returned to normal within 2 min.

Adolescent↗
PubMed1994

Somatosensory central conduction time after sural and tibial nerve stimulation.

We recorded spinal and cortical somatosensory evoked potentials (SEPs) after sural and tibial nerve stimulation at the ankle in 34 normal subjects. Spinal SEPs were reproducible with sural nerve stimulation in only 65% of normal subjects. The spinal amplitudes were significantly smaller after sural nerve stimulation. Central conduction time (CCT) was significantly shorter when measured from onset instead of peak latencies. There was a significant difference between CCT with tibial nerve and sural nerve stimulation. Our results are consistent with the idea that CCT measures from onset and peak latencies do reflect the travel of the afferent volley in different spinal fiber populations.

Adult↗
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↗