Biomedical subjects

M Javidan

Publications and source records attributed to M Javidan.

7 recordsLinked to original sources

PubMed2001

Identification of the temporal components of seizure onset in the scalp EEG.

BACKGROUND: The identification of the earliest indication of rhythmical oscillations and paroxysmal events associated with an epileptic seizure is paramount in identifying the location of the seizure onset in the scalp EEG. In this work, data-dependent filters are designed that can help reveal obscure activity at the onset of seizures in problematic EEGs. METHODS: Data-dependent filters were designed using temporal patterns common to selected segments from pre-ictal and ictal portions of the scalp EEG. Temporal patterns that accounted for more variance in the ictal segment than in the pre-ictal segment of the scalp EEG were used to form the filters. RESULTS: Application of the filters to the scalp EEG revealed temporal components in the seizure onset in the scalp recording that were not obvious in the unfiltered EEG. Examination of the filtered EEG enabled the onset of the seizure to be recognized earlier in the recording. The utility of the filters was confirmed qualitatively by comparing the scalp recording to the intracranial recording and quantitatively by calculating correlation coefficients between the scalp and intracranial recordings before and after filtering. CONCLUSION: The data-dependent approach to EEG filter design allows automatic detection of the basic frequencies present in the seizure onset. This approach is more effective than narrow band-pass filtering for eliminating artifactual and other interference that can obscure the onset of a seizure. Therefore, temporal-pattern filtering facilitates the identification of seizure onsets in challenging scalp EEGs.

Algorithms↗

PubMed1997

Significance of spikes recorded on intraoperative electrocorticography in patients with brain tumor and epilepsy.

PURPOSE: Patients with medically intractable epilepsy due to brain tumors may undergo resective surgery for treatment of both the tumor and the epilepsy. In this instance, the extent of surgical resection is sometimes guided by spikes recorded on intraoperative electrocorticography (ECoG). Whether spikes recorded by electrocorticography imply active epileptogenicity has not been addressed adequately. METHODS: We performed preresection and postresection electrocorticography on 36 patients with brain tumor and seizures. There were 31 low-grade gliomas, 4 high grade gliomas, and 1 dysembryonic neuroepithelial tumor. Patients had resection of the tumor to normal tissue margins only. No additional surgery was performed, based on electrocorticography findings. Patients were divided into 2 groups: Group I (no seizures or rare seizures after resection) and Group II (recurrent seizures). Recorded spikes were analyzed for spike distribution and spike discharge rate. RESULTS: On preresection ECoG, 85% of patients in Group I and 88% of patients in Group II had spikes. In Group I, 70% of patients had spikes over the tumor bed, and 63% of patients had spikes in the surrounding tissue. In Group II, 55% of patients had spikes over the tumor bed and 89% of patients had spikes in the surrounding tissue. Spike distribution and discharge rate did not correlate with outcome. On postresection ECoG, 60% of patients in Group I and 67% of patients in Group II had residual spikes. In Group I, 46% of patients had spikes along the margin of resection and 26% of patients had extramarginal spikes. In Group II, 50% had spikes along the margin of resection and 67% of patients had extramarginal spikes. CONCLUSIONS: The difference in spike distribution in the extramarginal area between the 2 groups was not statistically significant, but showed a trend toward a relationship between postresection spikes and seizure recurrence.

Brain Neoplasms↗

PubMed1995

Significance of spikes recorded on electrocorticography in nonlesional medial temporal lobe epilepsy.

Whether spikes recorded by intraoperative electrocorticography imply active epileptogenicity has not been adequately addressed. We performed preresection and postresection electrocorticography on 47 patients with nonlesional medial temporal lobe epilepsy who were undergoing surgery for the treatment of medically refractory epilepsy. A standard anteromedial temporal lobectomy was performed on all patients, with no additional resection, regardless of electrocorticographic findings. Patients were divided into two groups: Group I (no seizures or rare seizures) and Group II (recurrent seizures). Recorded spikes were analyzed for distribution and spike discharge rate. On preresection electrocorticography, 83% of Group I and 82% of Group II had spikes in the anterior temporal lobe. The spike discharge rate was equally distributed between high frequency and low frequency for both groups (not significant). Although spikes localized to the posterior temporal neocortex were seen more in Group II (64%) than Group I (39%), this was not a significant difference (p > 0.1). Most of these patients had a low-frequency spike discharge rate. On postresection electrocorticography, 80% of Group I and 75% of Group II had residual spikes. The majority of these had a low-frequency spike discharge rate and were localized to the margin of resection. We found no correlation between residual spikes on preresection and postresection electrocorticography and outcome. These findings do not support the role of intraoperative electrocorticography in guiding mesial temporal lobe resection.

Adolescent↗

PubMed1992

Attenuation of pathological tremors by functional electrical stimulation. I: Method.

In this study we explored the possibility of suppressing pathological tremors using closed-loop functional electrical stimulation (FES) to activate the tremorogenic muscles out-of-phase. A displacement signal monitored with a transducer was filtered so as to be "tuned" to the tremor frequency at the wrist or elbow. The filtered signal was used to amplitude-modulate the electrical stimulation. The design process was based on measurements of the open-loop frequency response characteristics of the forearm and hand to stimulation of the elbow and wrist flexors and extensors in a number of subjects. These data allowed us to identify closed-loop configurations, which attenuated 2-5 Hz tremors substantially, while only minimally attenuating functional movements in the 0-1 Hz range. There was a fairly delicate balance between efficacy and the risk of instability. However, designs were identified that offered enough tremor suppression and adequate immunity to muscle/load variations for the technique to be considered seriously for clinical application.

Electric Stimulation↗

PubMed1992

Attenuation of pathological tremors by functional electrical stimulation. II: Clinical evaluation.

In this study we evaluated a technique for tremor suppression with functional electrical stimulation (FES), the technical details of which were described in the previous paper. Three groups of patients were investigated: those with essential tremor, parkinsonian tremor, and cerebellar tremor associated with multiple sclerosis. In each group, tremor was attenuated by significant amounts (essential tremor: 73%; parkinsonian tremor: 62%; cerebellar tremor: 38%). These attenuations were in good accord with predictions based on the dynamic analyses and filter designs derived in the previous paper. With filters "tuned" to the lower mean tremor frequency encountered in the cerebellar patients, more attenuation was possible in this group as well. We identified some practical limitations in the clinical application of the technique in its present form. The most important was that in daily use, only one antagonist pair of muscles can realistically be controlled. At first sight, this restricts the usefulness of the system to patients with single-joint tremors. However, the concomitant use of mechanical orthoses may broaden the scope of application.

Adult↗

PubMed1991

Leading a high-commitment high-performance organization.

This article conducts a thorough review of the extensive literature on executive leadership. It provides a definition for the concept of superior executive leadership and then presents a model explaining the key roles and attributes required to perform effectively in top management ranks. The article then discusses the implications of this model for senior executives and describes how it can be used to assess the quality of executive performance.

Administrative Personnel↗

PubMed1986

Cerebral evoked potentials in multiple sclerosis.

Multimodal evoked potentials were analyzed from 58 possible, 62 probable and 100 definite (total 220) multiple sclerosis (MS) patients. Visual evoked potentials (VEP) were most frequently abnormal yielding 39%, 69%, 84% in the three diagnostic groups respectively. Median nerve sensory evoked potentials (SEP) yielded abnormalities in 26%, 65%, 79% respectively. Brainstem auditory evoked responses (BAER) were abnormal in 17%, 39%, 66% respectively. We measured the combined amplitude (CA) of waves III, IV, V in the BAER of these patients as an objective measure of amplitude asymmetry. The CA was considered abnormal if it was 1SD below the lowest CA value in the control group. The CA was abnormal in 9.2% of BAER with normal central conduction time. The BAER diagnostic yield in MS patients increased 11% by using CA analysis.

Adult↗