Biomedical subjects

A Beydoun

Publications and source records attributed to A Beydoun.

47 records · Page 3Linked to original sources

PubMed1993

Correlation of evoked potential and MRI findings in Wilson's disease.

We recorded brainstem auditory evoked potentials (BAEPs) and somatosensory evoked potentials to median nerve stimulation (MSEPs) within 10 days of brain MRI in 20 patients with Wilson's disease (WD). MRI was abnormal in 90% of patients, demonstrating symmetric striatum and brainstem lesions with or without thalamic lesions. MSEPs were abnormal in 65% of patients, usually showing bilaterally prolonged N/P13-N20 latencies. BAEPs were abnormal in 40%, most often with bilateral prolongation of the III-V latency. The III-V and N/P13-N20 interpeak latencies correlated significantly with the severity of MRI lesions in the caudal pons, rostral pons, and caudal midbrain. Our results indicate that subclinical sensory dysfunction is common in WD, and that auditory and somatosensory pathways are most severely affected at the brainstem level. Both the localization and severity of evoked potential abnormalities correspond closely to the morphologic changes in the pons and caudal midbrain shown by MRI.

Adult↗

PubMed1993

Pitfalls of EEG interpretation in epilepsy.

Electroencephalogram remains the single most valuable investigation in patients with known or suspected seizure disorders. Errors made in the interpretation of electroencephalogram studies are common and have significant consequences for the patient. This article presents a logical approach to the analysis of electroencephalograms, illustrating the principle pitfalls in each step of this analysis.

Electroencephalography↗

PubMed1993

Seizure disorders of aging: differential diagnosis and patient management.

The incidence of seizures increases significantly after age 60, mainly because of an associated rise in the prevalence of such etiologies as stroke, brain tumors, and toxic-metabolic disturbances, including alcohol or drug misuse and diabetes. The differential diagnosis must rule out transient ischemic attacks, syncope, and psychiatric disorders, among other conditions. Treatment is based on the underlying cause. Seizures caused by toxic-metabolic disturbances are treated by correcting the underlying condition. Those with other etiologies require single-drug therapy with an anticonvulsant, such as phenytoin, valproic acid, or carbamazepine.

Age Factors↗

PubMed1992

Unilateral 14 and 6 Hz positive bursts.

We describe the unilateral occurrence of 14 and 6 Hz positive bursts in successive EEGs in a 25-year-old woman following surgical resection of a left parietal arteriovenous malformation which had caused a left parieto-temporal intracerebral hematoma. This is only the second reported case of unilateral 14 and 6 Hz positive bursts. This could represent either a normal pattern seen unilaterally because of a skull defect or be a manifestation of neuronal damage.

Adult↗

PubMed1991

Variance of interburst intervals in burst suppression.

Each EEG performed over a 3 year period at the University of Michigan with a diagnosis of generalized burst-suppression (BS) was reviewed. Ten EEGs from 10 patients with hypoxic-ischemic encephalopathy (HIE-BS) and 21 records from 8 patients with pentobarbital induced burst-suppression for treatment of status epilepticus (SE-BS) were reviewed. For each EEG, the mean duration of 40 interburst intervals (IBIs) as well as their coefficient of variability were calculated. We found that in the SE-BS group the coefficient of variability of IBI duration was highly correlated with the logarithm of mean IBI duration while in the HIE-BS group, there was no significant correlation between these 2 variables. This suggests that the underlying mechanism causing BS is different in the 2 groups and might be related to a uniform and progressive affection of similar brain structures in the SE-BS group and a more patchy and variable pathology in the HIE-BS group.

Adolescent↗

PubMedDate not supplied

Variability of laser-evoked potentials: attention, arousal and lateralized differences.

We recorded laser-evoked potentials (LEPs) from 20 normal subjects by stimulating the skin with pulses from an infrared CO2 laser. The conduction velocity of the peripheral afferent fibers mediating the LEPs averaged 14.9 m/sec. The amplitude of the LEP components correlated significantly with perceived stimulus intensity. During repetitive constant intensity stimulation, the peak-to-peak LEP amplitude decreased 38% during a distraction task and 42% during drowsiness and was absent during stage 2 sleep, indicating a modulation of responsiveness to laser stimulation during distraction and decreased states of arousal. Normative data revealed considerable intersubject variability in LEP latencies and amplitudes. Analysis of intrasubject lateralized (side-to-side) differences revealed that the relative peak-to-peak amplitude was less variable than that of the N or P components. For clinical applications using 3 S.D.s to define the normal range, a lateral interpeak amplitude difference greater than 28% would suggest focal or lateralized sensory abnormality in an individual patient. Vigilance and attentiveness to the stimuli should be monitored during the acquisition of LEPs.

Adult↗

PubMedDate not supplied

Topical capsaicin selectively attenuates heat pain and A delta fiber-mediated laser-evoked potentials.

Cutaneous stimulation with CO2 laser pulses activates A delta of nociceptive afferents and evokes late cerebral potentials (LEPs), the amplitude of which correlates parametrically with the perceived magnitude estimation of laser pulses. Capsaicin is known to desensitize the nociceptive terminals of C fibers. In this double-blind, vehicle-controlled experiment, we tested the hypothesis that topical capsaicin would inactivate A delta afferents and lead to an attenuation of the LEPs. Subjects applied capsaicin cream to the dorsum of one hand and vehicle cream to the other 3 times daily for a period of 5 weeks. At weekly intervals before starting, during administration and after discontinuation of capsaicin, LEPs were recorded and psychophysical thresholds and magnitude estimation for several sensory modalities were determined. The results of this study showed that topical capsaicin significantly and reversibly decreased the magnitude estimation of suprathreshold heat pain, laser pulses and amplitude of the LEPs. There was no statistically significant difference in light touch, deep pain and mechanical pain detection thresholds between the capsaicin- and vehicle-treated hands. It indicated that topical capsaicin caused a definite functional and reversible inactivation of A delta nociceptive afferent transmission. The decline in the magnitude estimation of laser pulses concomitantly with the attenuation of LEP amplitudes supports the hypothesis that some A delta afferents mediate noxious heat in humans. These findings demonstrate the usefulness of LEP in the physiological evaluation of nociceptive pathways and its potential usefulness in objectively documenting the effect of pharmacological treatment on pain perception.

Adolescent↗

PubMedDate not supplied

Benign partial epilepsy of childhood with monomorphic sharp waves in centrotemporal and other locations.

We reviewed EEGs from children whose history and clinical course was compatible with benign partial epilepsy of childhood with centrotemporal spikes. In 21% of patients with a single EEG focus, the discharge was outside the centrotemporal area. In 37.5% of patients with more than one focus, one was in the centrotemporal area while the other was not. We suggest that the typical EEG features of this syndrome are the normal background, the stereotypic morphology of the sharp waves, and their activation by drowsiness and sleep, not their exclusive location in the centrotemporal regions. Insistence on a centrotemporal location for the EEG discharges in this syndrome may lead to a misclassification of the type of epilepsy in some children with implications for therapeutic decisions and prognostic statements.

Adolescent↗

PubMedDate not supplied

Longitudinal EEG studies in a kindred with Lafora disease.

We reviewed 18 EEG studies in four members of a family with the Lafora form of progressive myoclonic epilepsy. Each patient was the product of a consanguinous marriage and presented as a teenager with progressive seizures, myoclonus, dementia, and ataxia, and had biopsy proven disease. The EEG early in Lafora disease has spike-wave activity resembling that seen in a primary generalized epilepsy; the background slowing is more typical of a secondary generalized epilepsy. With disease progression, there is increased epileptiform activity, and a striking change in the spike-wave complexes, with a marked increase in frequency up to 6-12 Hz, and many more short duration polyspike components. Unlike some other forms of secondarily generalized epilepsy, the EEG in Lafora disease is distinguished by an increased frequency of the spike-wave complexes with disease progression.

Adolescent↗

PubMedDate not supplied

Generalized spike-waves, multiple loci, and clinical course in children with EEG features of benign epilepsy of childhood with centrotemporal spikes.

In 41 patients with EEG features of benign epilepsy of childhood with centrotemporal spikes (BECCT), we noted associated generalized spike-wave discharges (GSWD) in 14.6% and multiple independent sharp wave foci in 9.8%. The presence or absence of these EEG features was not predictive of the clinical course. The high incidence of GSWD in children with BECCT suggests a possible relation in the expression of these two EEG traits.

Adolescent↗

PubMedDate not supplied

Focal cerebral magnetic resonance changes associated with partial status epilepticus.

We report 2 patients with transient abnormalities on magnetic resonance imaging (MRI) associated with partial status epilepticus (SE). A man with a 4-month history of partial seizures had complex partial SE for 9 days, with left temporal maximum on ictal EEG. Left temporal lobe T2 signal was increased on MRI during SE, but cerebral MRI was normal 9 weeks later. A woman with "cryptogenic" temporal lobe epilepsy for 16 years had complex partial SE for 1 week, with right temporal maximum on ictal EEG. T2 Signal was increased over the entire right temporal lobe, extending into the insula, without mass effect, on MRI 1 month after SE ended. Repeat MRI 1 month later showed marked decrease in volume of increased T2 intensity, without gadolinium enhancement, but with mild mass effect over the right anterioinferomesial temporal areas. A gemistocytic astrocytoma was resected. Focal cerebral MRI abnormalities consistent with cerebral edema may be due to partial SE but also may indicate underlying glioma, even in long-standing partial epilepsy. Focal structural imaging changes consistent with neoplasm should be followed to full resolution after partial SE.

Adult↗