Biomedical subjects

Charles E Polkey

Publications and source records attributed to Charles E Polkey.

12 recordsLinked to original sources

PubMed2005

Single pulse electrical stimulation for identification of structural abnormalities and prediction of seizure outcome after epilepsy surgery: a prospective study.

BACKGROUND: Abnormal late responses to single pulse electrical stimulation (SPES) in patients with intracranial recordings can identify epileptogenic cortex. We aimed to investigate the presence of neuropathological abnormalities in abnormal SPES areas and to establish if removal of these areas improved postsurgical seizure control. METHODS: We studied abnormal responses to SPES during chronic intracranial recordings in 40 consecutive patients who were thereafter operated on because of refractory epilepsy and had a follow-up period of at least 12 months. FINDINGS: 22 patients had abnormal responses to SPES exclusively located in resected regions (96% with favourable outcome), seven had abnormal responses to SPES located in resected and non-resected regions (71% with favourable outcome), three had abnormal responses to SPES exclusively outside the resected region (none with favourable outcome), and eight did not have abnormal responses to SPES (62.5% with favourable outcome). Surgical outcome was significantly better when areas with abnormal responses to SPES were completely resected compared with partial or no removal of abnormal SPES areas (p=0.006). Neuropathological examination showed structural abnormalities in the abnormal SPES areas in 26 of the 29 patients in whom these regions were resected, despite the absence of clear MRI abnormalities in nine patients. INTERPRETATION: Abnormal responses to SPES are functional markers of epileptogenic structural abnormalities, and can identify epileptogenic cortex and predict surgical outcome, especially when a frontal or temporal focus is suspected.

Adolescent↗

PubMed2004

Material-specific recognition memory deficits elicited by unilateral hippocampal electrical stimulation.

Although the medial temporal lobe is thought to be critical for recognition memory (RM), the specific role of the hippocampus in RM remains uncertain. We investigated the effects of transient unilateral hippocampal electrical stimulation (ES), subthreshold for afterdischarge, on delayed item RM in epilepsy patients implanted with bilateral hippocampal depth electrodes. RM was assessed using a novel computer-controlled test paradigm in which ES to left or right hippocampus was either absent (baseline) or synchronized with item presentation. Subsequent yes-no RM performance revealed a double dissociation between material-specific RM and the lateralization of ES. Left hippocampal ES produced word RM deficits, whereas right hippocampal ES produced face RM deficits. Our findings provide the first demonstration in humans that selective unilateral stimulation-induced hippocampal disruption is sufficient to produce impairments on delayed RM tasks and provide support for the material-specific laterality of hippocampal function with respect to RM.

Adult↗

PubMed2004

Characteristics of scalp electrical fields associated with deep medial temporal epileptiform discharges.

OBJECTIVE: To determine scalp characteristics of epileptiform discharges arising from medial temporal structures (MT). METHODS: Signal-to-noise ratio was increased by averaging simultaneous recordings from intracranial and scalp electrodes synchronised on discharges recorded by foramen ovale (FO) electrodes. The topography, amplitude and distribution of averaged scalp signals were analysed. RESULTS: Four thousand three hundred and twenty-seven discharges from 20 patients were averaged into 77 patterns. Before averaging, only 9% of discharges were detectable on the scalp without the need of simultaneous FO recordings (SED). A further 72.3% of discharges fell into averaged patterns that could be detected on the scalp as small transients before or after averaging (STBA or STAA). In 18.7% of discharges, no scalp signal was seen after averaging. Whereas most SED patterns had largest amplitude on the scalp at anterior temporal electrodes, STBA and STAA patterns showed greater variability and more widespread scalp fields, suggesting a deeper source. Dipole source localisation modelled the majority of SED patterns as radial dipoles located just behind the eye. In contrast, dipoles corresponding to STBA or STAA patterns showed greater variability in location and orientation and tended to be located at MT. CONCLUSIONS: SED patterns seem to arise from widespread subtemporal and/or superficial neocortical activation, generating EEG fields that are distorted by the high electrical conductivity of anterior cranial foramina. In contrast, STBA and STAA patterns represent electrical fields from neuronal activity more restricted to MT, that reach the scalp highly attenuated by volume-conduction and less distorted by cranial foramina. SIGNIFICANCE: Low amplitude scalp signals can be related to MT activity and must be taken into consideration for the diagnosis of temporal lobe epilepsy, pre-surgical assessment and for valid modelling of deep sources from the scalp EEG and magnetoencephalogram.

Adolescent↗

PubMed2004

Clinical outcome of epilepsy surgery.

PURPOSE OF REVIEW: The outcome from current surgical methods of treating drug-resistant epilepsy will be considered, looking at changes in classical resective surgery and new methodology being introduced in the functional treatment of these patients. RECENT FINDINGS: There is now class I evidence that temporal lobe surgery is effective. Sophisticated and appropriate magnetic resonance imaging sequences, together with an assessment of the electroclinical syndrome, allow patients to be assessed for resective surgery. The concept of 'surgically remediable syndromes' determines the type of procedure that is effective for particular patients. Technical advances such as neuronavigation techniques and intra-operative magnetic resonance imaging have improved the effectiveness of these procedures. Other techniques of disconnection, such as multiple subpial transection, and stimulation both indirectly using the vagus nerve and directly using various intracranial targets, are currently effective and have potential for future development. SUMMARY: This review will demonstrate that current surgical techniques are safe and effective in relieving drug-resistant epilepsy.

Anterior Temporal Lobectomy↗

PubMed2004

Interictal temporal delta activity in temporal lobe epilepsy: correlations with pathology and outcome.

PURPOSE: To determine the characteristics and the clinical significance of focal slow activity and its association with focal epileptogenesis in patients with temporal lobe epilepsy (TLE). METHODS: We analyzed the interictal EEGs of 141 patients who had temporal lobe resections for intractable focal seizures and correlated the findings with pathologic changes and outcome. The pathologic changes were categorized into medial temporal sclerosis, tumors, and nonspecific changes. RESULTS: Lateralized slow activity was found in 66% of the patients, and it was mainly temporal, of delta frequency and irregular morphology. None of its characteristics, including quantity and reactivity to eye opening, was substrate specific. It was highly concordant with temporal spiking (60%), without any difference across the three groups, but provided additional information in 19 (15%) patients who had no lateralizing spikes. The effect of sleep also was similar in all three groups and included transition of slow waves into spikes. Lateralized slow activity to the side of the operation was significantly associated with favorable outcome only in the group with nonspecific pathology (p = 0.008), regardless of the presence, laterality, or topography of spikes. CONCLUSIONS: Our findings suggest that in patients with TLE whose brain magnetic resonance imaging (MRI) is either normal or suggestive of medial temporal sclerosis, interictal temporal slow activity has a lateralizing value similar to that of temporal spiking. Its association with a favorable outcome in patients with nonspecific pathology also suggests that candidates with lateralizing temporal delta and normal MRI should not be barred from further preoperative assessment.

Adolescent↗

PubMed2004

Brain stimulation in the treatment of epilepsy.

Stimulation of the brain for the treatment of epilepsy, indirectly via the vagus nerve and directly through intracranial targets, is feasible and has increased in use and complexity over the past 10 years. Vagus nerve stimulation is widely applied and the present indications and outcomes together with possible ways in which the treatment could be refined are reviewed. The application of stimulation to deep-brain targets is also reviewed along with present practice and results. Possible developments in the use of direct intracranial stimulation are also considered.

Animals↗

PubMed2003

Quantitative magnetic resonance imaging of the amygdala in temporal lobe epilepsy-clinico-pathological correlations (a pilot study).

PURPOSE: We carried out a pilot study of quantitative volumetric MRI of the amygdala in patients undergoing surgery for intractable temporal lobe epilepsy. We wished to explore whether amygdala volume correlated with pre-operative clinical variables and post-operative outcome. METHODS: Ten patients had detailed volumetric measurements of their amygdala and hippocampus according to operationalised anatomical criteria from an optimised MRI imaging sequence. A ratio of volumes from the unoperated to operated side was calculated. Surgical specimens were examined histologically for astrocytosis. RESULTS: The volumes of the amygdala and hippocampus on the operated side were significantly smaller than on the unoperated side. More severe astrocytosis appeared to go along with smaller volume ratios but the relationship was not significant. There were few significant correlations between volumes measures and clinical or outcome variables. CONCLUSION: Reductions in amygdala volume in the to-be-operated temporal lobe in patients with medically intractable epilepsy can be reliably detected using volumetric MRI. Accurate amygdala volume measures do not appear to exert a significant effect on clinical presentation and outcome in the presence of hippocampal volumes reductions, but may be useful in confirming bilateral pathology. Larger studies examining clinico-pathological correlations are recommended.

Amygdala↗

PubMed2003

Lateralising value of neuropsychological protocols for presurgical assessment of temporal lobe epilepsy.

PURPOSE: To estimate the value of neuropsychological measurements in determining the side of seizure onset for presurgical assessment in patients with temporal lobe epilepsy. The lateralising value of neuropsychological protocols was evaluated for all patients and in subpopulations depending on surgical outcome with regard to seizure control, speech dominance, neuropathology, and need for intracranial EEG recordings. METHODS: A battery of neuropsychological procedures was carried out preoperatively in 125 patients who underwent left (n = 66) or right (n = 59) temporal lobectomies. Binary logistic regression analysis was performed to find sets of variables that allowed the best prediction of the side of seizure onset (assumed to be the operated-on side). RESULTS: Combinations of noninvasive neuropsychological tests and Wada subscores showed the highest lateralising values: 80.8% for all patients, 79.4% in seizure-free patients, 86.0% in patients not rendered seizure free, 85.7% in left speech patients, 77.8% in non-left speech patients, 89.3% in patients with mesial temporal sclerosis (MTS), 78.1% in non-MTS patients, 80.3% in patients who underwent intracranial EEG recordings, and 77.3% in those who did not. CONCLUSIONS: The lateralising value (80-90%) of neuropsychological protocols appears similar to that of other tests widely accepted for lateralisation (ictal and interictal scalp EEG and neuroimaging). Attention should be paid to neuropsychological results, particularly from the Wada test, during presurgical assessment of temporal lobe epilepsy, as they can provide strong support for findings from other lateralising tests, particularly in patients with presumed MTS or in left-speech patients.

Adult↗

PubMed2003

Alternative surgical procedures to help drug-resistant epilepsy - a review.

The concepts of pathophysiology of epilepsy which underly the non-resective surgical treatment of epilepsy are reviewed. The available techniques, lesioning, disconnection and stimulation are described and reviewed critically. Stereotactic lesioning, popular in the 1950's has been largely abandoned but stereotactic radiosurgery emerges as a useful technique, especially in the treatment of mesial temporal sclerosis. Disconnection by callosotomy has fewer applications than previously and multiple subpial transection (MST) has limited applications. Stimulation is a technique with increasing usefulness. Vagus nerve stimulation(VNS) is an accepted method of treatment with low morbidity and mortality, which improves seizure control in at least 30% of patients, together with concomitant improvements in QOL and economic advantages. Stimulation of deep brain targets in the thalamus, subthalamus and mesial temporal structures is practical. There are indications that this improves seizure control in groups of patients previously un helped by surgery, and this methodology has enormous potential.

Brain↗

PubMed2003

Resective surgery for hypothalamic hamartoma.

Hypothalamic hamartoma presents with precocious puberty, epilepsy or both. There are two epileptic syndromes, one presenting initially in infancy with gelastic seizures evolving rapidly into a syndrome with multiple seizures, developmental delay and a moderate to severe behaviour disorder. The other presents later with a milder epileptic syndrome, again usually including gelastic seizures, but with normal intellect and behaviour. Magnetic resonance imaging identifies and gives a detailed anatomical picture of these lesions. Direct surgery, using microsurgical techniques and neuronavigation guidance has been used for these lesions. Three surgical approaches have been used, one lateral pterional, another midline frontal through the lamina terminalis and a third is a transcallosal interforniceal approach. In addition a disconnection procedure, usually pterional, aims to disconnect the lesion without the risks of major resection. The transcallosal interforniceal approach is the most successful with 69% of patients seizure-free. There are complications in about 24% of patients, the same as other approaches, but the complications are milder and include fewer neurological deficits than the other routes. Alternate strategies include stereotactic radiosurgery and radiofrequency ablation under stereotactic control.

Adolescent↗

PubMed2002

Internal carotid-inferior petrosal sinus fistula complicating foramen ovale telemetry: successful treatment with detachable coils: case report and review.

OBJECTIVE AND IMPORTANCE: Iatrogenic internal carotid artery-cavernous sinus fistula complicating percutaneous foramen ovale (FO) instrumentation (e.g., retrogasserian rhizotomy for trigeminal neuralgia) has been reported in only four patients to date. To our knowledge, no case of fistula has previously been reported either to complicate FO telemetry or to involve the inferior petrosal sinus (IPS); moreover, most patients have presented within 48 hours. We present a case of internal carotid artery-IPS fistula that complicated FO telemetry in which the clinical syndrome was delayed by 4 weeks. CLINICAL PRESENTATION: Four weeks after undergoing bilateral FO telemetry during Phase 2 investigations for surgery for epilepsy, a 37-year-old man suddenly developed a painful bilateral pupil-sparing oculomotor palsy, poor visual acuity, proptosis, conjunctival suffusion, and an audible bruit over the right frontotemporal region. INTERVENTION: Cerebral angiography demonstrated a high-flow arteriovenous fistula between the junction of the petrous and laceral portions of the right internal carotid artery and right IPS, with rapid filling of both cavernous sinuses. Successful obliteration was obtained with Guglielmi detachable coils, followed by complete resolution of the bilateral ocular abnormality. CONCLUSION: This is the first reported case of iatrogenic fistula formation to either involve the IPS or to complicate FO telemetry. In addition, symptomatology was anomalously delayed. This case highlights the importance of noting FO anatomic asymmetries before FO instrumentation and of routinely inquiring for "swooshing" noises after electrode withdrawal.

Adult↗

PubMedDate not supplied

Registered computed tomography images as an alternative to postimplantation magnetic resonance imaging in the assessment of subthalamic electrode placement.

Magnetic resonance imaging (MRI) after implantation of electrodes in the subthalamic nuclei is currently performed at a number of sites, but a recent adverse incident and changes in MRI technology may heighten safety concerns. In this report, it is demonstrated that given whole-head image data, registration of postimplantation computed tomography to preimplantation MRI can enable verification of the position of electrodes to an accuracy of 2 mm. This registration technique can remove the need for potentially risky postoperative MRI.

Electric Stimulation Therapy↗