Kalarickal J. Oommen

Electrical stimulation of the anterior nucleus of thalamus for treatment of refractory epilepsy.

Purpose:  We report a multicenter, double‐blind, randomized trial of bilateral stimulation of the anterior nuclei of the thalamus for localization‐related epilepsy.

Long-term Surface Cortical Cerebral Blood Flow Monitoring in Temporal Lobe Epilepsy

Long-term subdural surface cortical cerebral blood flow (CBF) and electrocorticographic monitoring was performed in 12 patients with complex partial seizures. A total of 40 seizures were analyzed. Baseline CBF values from nonepileptic and epileptic temporal lobe (mean +/- standard error) were 60.0 +/- 1.0 and 50.2 +/- 1.8 ml/100 g per minute, respectively (P < 0.05). In general, clinical seizure onset was preceded by a 20-minute preictal CBF increase from baseline in the epileptic temporal lobe. Peak early postictal CBF values of nonepileptic and epileptic temporal lobes were 57.7 +/- 13.3 and 89.0 +/- 21.7 ml/100 g per minute (P > 0.05) at 5.2 +/- 2.2 and 2.4 +/- 1.0 minutes (P > 0.05) after clinical seizure onset, respectively. Statistically significant differences between nonepileptic and epileptic temporal lobe CBF were detected at 50 minutes (74.0 +/- 14.2 and 37.5 +/- 9.2 ml/100 g per minute, respectively; P < 0.05) and 60 minutes (75.6 +/- 13.6 and 36.1 +/- 8.5 ml/100 g per minute, respectively; P < 0.05) postictal. The data suggest that the optimal times for CBF analysis to differentiate epileptic from nonepileptic temporal lobe are 1) during the interictal period and 2) late (50 to 60 minutes) postictal. The results of this study should improve the understanding of the dynamic cerebral perfusion patterns in the epileptic human brain.

Long-Term Subdural Strip Electrocorticographic Monitoring of Ictal Déjà Vu

Summary: We report a series of 8 patients with ictal déjà vu. Subdural strip electrocorticographic (ECoG) monitoring localized the ictal epileptogenic focus as follows: right (n = 6) and left (n = 2) mesiotemporal lobe. In all 8 patients, the left hemisphere was dominant for language function based on intracarotid amytal testing. In 6 right‐handed patients, ictal déjà vu was associated with a right temporal lobe focus. However, in the 2 left‐handed patients, the ictal focus was left temporal lobe. Although ictal déjà vu localizes the epileptic focus to temporal lobe, this experiential phenomenon appears to lateralize to the hemisphere nondominant for handedness.

Quantitative analysis of the EEG in the intracarotid amobarbital procedure. I. Amplitude analysis

Thirty-seven subjects underwent bilateral internal carotid artery injections of amobarbital prior to surgery for intractable epilepsy. The electroencephalogram (EEG) of these patients was continuously monitored during these 74 procedures and was later subjected to quantitative analysis. Topographic mapping of these data suggested that the areas of inactivation were largely restricted to the anterior 2/3 of the hemisphere injected, corresponding to the vascular distributions of the anterior and middle cerebral arteries. Graphical representation of the data demonstrated that delta and theta band activity peaked in the first 2 min post injection and decreased gradually thereafter, becoming stable at around 12 min post injection. Examination of the alpha, beta 1, and beta 2 bands suggested that activity increased and decreased more gradually than that for delta and theta, with perhaps a longer latency. Although EEG changes were most prominent in the anterior 2/3 of the inactivated hemisphere, similar (though smaller) changes were also observed in both ipsilateral and contralateral zones thought to be outside of the vascular distribution of the internal carotid artery.

Cerebral Blood Flow (CBF) Monitoring in Intensive Care by Thermal Diffusion

Continuous monitoring of cortical blood flow (CoBF) in the intensive care unit is possible with thermal diffusion techniques. The normal brain flow limits have been established when electrical activity ceases and when infarction is likely to occur. With continuous monitoring of CoBF one can see immediate changes in flow and approaching these levels may be anticipated. The thermal diffusion system we have employed is based on the thermal conductivity of cortical tissue. As blood flow increases through the tissue, the conduction of energy away from the flow probe allows the sensor to detect changes in flow. This form of monitoring has been carried out in patients with subarachnoid hemorrhage, resection of cerebral mass lesions, severe craniotrauma, and intractable epilepsy. In subarachnoid hemorrhage, vasospasm can be identified and the efficacy of treatment determined with continuous monitoring of CoBF. During resection of mass lesions, increases in blood flow can be readily detected to document the recovery of brain tissue. Continuous monitoring of CoBF in epilepsy patients is now possible with the implantation of subdural electrodes. The increase in blood flow can be documented and it is apparent that a period of elevation of blood flow is quite short. Therefore, this may be helpful in determining when other forms of CBF determination, such as Single Photon Emission Computed Tomographic (SPECT) scanning should be performed. In patients with cranial trauma, different patterns of CoBF changes are apparent. Some patients may develop increased CoBF prior to elevation of intracranial pressure (ICP); other patients demonstrate a drop in CoBF as a response to increased ICP.(ABSTRACT TRUNCATED AT 250 WORDS)

Affective self-report during the intracarotid sodium amobarbital test

Changes in internal affective state were investigated in patients undergoing the intracarotid sodium amobarbital test. It was found that when the left hemisphere was inactivated, patients rated their mood as significantly more negative than during baseline conditions. No significant change in affective state was observed during the inactivation of the right hemisphere. The findings are interpreted in terms of a differential lateralization model of emotion, in which the right hemisphere is more involved in the more powerful and salient negative affects.

Lumbar cerebral spinal fluid drainage during long-term electrocorticographic monitoring with subdural strip electrodes: elimination of cerebral spinal fluid leak

We performed this study to determine the efficacy of continuous lumbar cerebral spinal fluid (CSF) drainage in controlling CSF leak during subdural strip electrode monitoring of epilepsy patients. Subdural strip electrodes were placed in 14 patients. In seven patients, a lumbar sub-arachnoid catheter was placed for continuous CSF drainage. In seven patients, no lumbar drain was placed. The duration of scalp CSF leak during strip electrode monitoring was significantly reduced in patients undergoing lumbar CSF drainage compared to those without lumbar drains (chi 2 = 40.9, P < 0.05). In one patient spinal headache developed which resolved with lumbar drain removal. Lumbar drainage eliminates scalp CSF leakage and can improve patient comfort. This technique should be further studied to determine if it reduces infection risk during long-term invasive monitoring.

Response of human epileptic temporal lobe cortical blood flow to hyperventilation

Bilateral long-term surface cortical cerebral blood flow (CBF) and electrocorticographic (ECoG) monitoring were performed in eight patients with complex partial seizures. In each patient, the epileptic temporal lobe was localized using ictal ECoG. Mean seizure interval (frequency-1) off anticonvulsant medication, a clinical measure of epileptogenicity, was 1.0 +/- 0.3 h (range: 0.4 to 2.5 h). During 13 interictal hyperventilation periods, 3.6 +/- 0.6 min in duration, the mean decrease in epileptic and nonepileptic temporal cortical CBF was 13.7 +/- 2.3 versus 6.4 +/- 1.9 ml/(100 g min) (t = 2.230, d.f. = 16, P < 0.05), representing 20.9% and 10.8% reduction from baseline CBF during hyperventilation, respectively. Seizure interval decreased (i.e. frequency increased) with increasing magnitude of seizure focus CBF reduction during hyperventilation. Seizure interval was significantly correlated with epileptic temporal lobe CBF decrease during hyperventilation (R = 0.763, d.f. = 5, P < 0.05). The data suggest that, compared to nonepileptic brain, epileptic temporal lobe is particularly prone to hypoperfusion during hyperventilation. Epileptogenicity is a function of this seizure focus susceptibility to ischemia. The finding of abnormal seizure focus autoregulation during hyperventilation has implication for epileptic focus localization with cerebral blood flow analysis.

Abnormal vasomotor response of human epileptogenic cortex to reversal of hyperventilation A long-term surface cerebral blood flow monitoring study

Abstract Human epileptogenic and nonepileptogenic surface cerebral blood flow (CBF) was studied during hyperventilation (HV) recovery. Bilateral subdural temporal lobe CBF probes were placed for long-term monitoring. Epileptic cortex became ischemic as an inverse linear function of HV duration ( r = 0.923, df=9, P P r = 0.890, df=9, P r = 0.784, df=5, P r = 0.782, df=9, P