Transient epileptic foci associated with intracranial hemorrhage in patients with subdural and epidural electrode placement.

We report two cases of transient epileptic foci in humans associated with placement of intracranial electrodes. The abnormalities consisted of restricted areas of active, almost continuous, rhythmic spiking, intermittently evolving into electrographic seizure activity, which resolved spontaneously within 3-4 days. The first occurred after placement of a subdural electrode grid and the second following insertion of epidural peg electrodes. Neuroimaging demonstrated a small subdural hematoma overlying the grid and a focal intraparenchymal hemorrhage underlying the affected epidural electrodes. The insertion of intracranial electrodes may be complicated by the induction of transient epileptic foci unrelated to a patient's typical epileptic generator.

Electrocorticography and outcome in frontal lobe epilepsy.

The prognostic significance of epileptiform activity (EA) recorded at electrocorticography (ECOG) was examined in a group of 60 consecutive non-tumoral patients with intractable frontal lobe epilepsy (FLE). Pre-excision EA was documented as absent, focal (one gyrus), regional (two gyri), lobar (3 gyri) or multilobar (frontal + temporal gyri). Post-excision EA was documented as absent, restricted to the resection border, or recorded distant to the resection border, and was quantitated by spike frequency. Pre-excision EA from < or = 2 gyri and absence of post-resection EA correlated with Class I or II (Engel classification) outcome while pre-excision EA from > or = 3 gyri and persistent post-resection EA, especially distant to the resection border, correlated with Class III or IV outcome (P < 0.001). A significant correlation between poorer outcomes and increased abundance of distant post-resection EA was observed (P < 0.001). EA restricted to the resection border was not significantly correlated with outcome. Presence of a circumscribed lesion correlated with Class I outcome (P < 0.01) and absence of pathological abnormality correlated with Class IV outcome (P < 0.05). Neither side nor extent of surgical excision correlated with outcome. EA recorded at ECOG is of prognostic significance in FLE. A lobar or multilobar distribution of pre-excision EA and persistent post-excision EA distant to the resection border, especially when abundant, are highly unfavorable prognostic indicators. In contrast, a restricted distribution of pre-excision EA and absence of post-resection EA both herald a favorable outcome.

Mesial temporal versus lateral temporal interictal epileptiform activity: comparison of chronic and acute intracranial recordings.

Intracranial interictal epileptiform activity (EA) was recorded by chronic stereotactic depth electroencephalography (SDEEG) and acute electrocorticography (ECOG) in 22 patients with complex partial seizures of temporal lobe origin. Chronic SDEEG recordings defined two groups of patients with respect to the presence or absence of lateral temporal EA; 13 patients showed independent lateral temporal EA during chronic recordings and 9 patients did not. All patients had EA recorded from mesial temporal structures during SDEEG. The presence of lateral temporal EA was correlated with a higher pre-operative seizure frequency but not with ictal onset zones, structural pathology, age at onset of epilepsy, or duration of epilepsy. Results of acute ECOG recordings performed on the same patients 1-24 months after SDEEG accurately reproduced the mesial versus lateral distribution of EA within patients (P < 0.0003). Though ECOG was less sensitive than SDEEG in demonstrating EA confined to mesial structures, positive findings at ECOG were 100% specific with respect to SDEEG. These results suggest that, at least with respect to mesial temporal versus lateral temporal structures, there is a constancy within patients in the distribution of interictal EA recorded with chronic intracranial electrodes. In addition, acute ECOG provides an accurate representation of individual patients' interictal EA.

Induction of burst-suppression and activation of epileptiform activity after methohexital and selective amygdalo-hippocampectomy.

Electrocorticography (ECOG) compared the effects of methohexital (MTH) and selective amygdalo-hippocampectomy (selAH) upon lateral temporal neocortical epileptiform activity (EA) in 31 patients with mesial temporal epilepsy. Pre-excision ECOG showed independent neocortical EA before MTH in 12/31 and after MTH in 18/31. MTH (20-50 mg) activated neocortical EA in 12 cases and induced burst-suppression (BS) over temporal neocortex in 14/31. Post-excision ECOG showed neocortical EA in 21/31 and BS in 27/31: compared with pre-excision ECOG before MTH, selAH activated neocortical EA in 15 cases. Significant correlations were found between presence of pre-excisional neocortical EA and presence of post-excisional neocortical EA (P < 0.001) and between activation of pre-excisional neocortical EA by MTH and activation of (post-excisional) neocortical EA by selAH (P < 0.006). Presence or severity of BS in the post-excision ECOG was not correlated with presence, absence or activation of post-excisional EA. Presence of neocortical EA was significantly correlated with a higher pre-operative seizure frequency (P < 0.001) but not with duration of epilepsy nor surgical outcome. Both MTH and selAH can induce neocortical BS, likely through chemical and surgical disconnection of cortex, respectively. Unrelated to induction of BS, MTH and selAH appear to decrease threshold for expression of neocortical EA in a similar fashion.

Intrinsic epileptogenicity of human dysplastic cortex as suggested by corticography and surgical results.

Cortical dysplastic lesions (CDyLs) are often associated with severe partial epilepsies. We describe the electrographic counterpart of this high degree of epileptogenicity, manifested by continuous or frequent rhythmic epileptogenic discharges recorded directly from CDyLs during intraoperative electrocorticography (ECoG). These ictal or continuous epileptogenic discharges (I/CEDs) assumed one of the following three patterns: (1) repetitive electrographic seizures, (2) repetitive bursting discharges, or (3) continuous or quasicontinuous rhythmic spiking. One or more of these patterns were present in 23 of 34 patients (67%) with intractable partial epilepsy associated with CDyLs, and in only 1 of 40 patients (2.5%) with intractable partial epilepsy associated with other types of structural lesions. I/CEDs were usually spatially restricted, thus contrasting with the more widespread interictal ECoG epileptic activity, and tended to colocalize with the magnetic resonance imaging-defined lesion. Completeness of excision of cortical tissue displaying I/CEDs correlated positively with surgical outcome in patients with medically intractable seizures; i.e., three-fourths of the patients in whom it was entirely excised had favorable surgical outcome; in contrast, uniformly poor outcome was observed in those patients in whom areas containing I/CEDs remained in situ. We conclude that CDyLs are highly and intrinsically epileptogenic, and that intraoperative ECoG identification of this intrinsically epileptogenic dysplastic cortical tissue is crucial to decide the extent of excision for best seizure control.

Morbidity of chronic recording with intracranial depth electrodes in 170 patients.

A consecutive series of 170 patients who have been submitted to intracranial depth electrode recordings is reviewed to assess the overall morbidity of the technique. Most patients had bitemporal and frontal electrodes inserted and were monitored for an average period of 18 days. A surgically amenable focus was found in 85% of the cases. There were 4 cases of infection including 2 cerebral abscesses which required surgical evacuation. One patient with frontal lobe atrophy developed an acute subdural hematoma after electrode implantation. There was no death or neurological deficit in the entire series. Morbidity was encountered mainly in the neuropsychological sphere, several patients having developed transient postictal psychosis after repetitive seizures. Our recording technique has been associated with low surgical morbidity. Patients undergoing depth electrode recordings should be closely monitored to minimize the occurrence of psychotic episodes associated with drug withdrawal and increased seizure frequency.

Clinical responses to electrical brain stimulation of the temporal and frontal lobes in patients with epilepsy. Pathophysiological implications.

The clinical responses elicited by electrical stimulation of discrete cerebral structures in the temporal and frontal lobes were studied in 75 patients undergoing pre-surgical evaluation using chronic intracerebral electroencephalographic recordings. Responses without after-discharge spreading beyond the site of stimulation included somatosensory, autonomic, thermoregulatory and viscerosensory phenomena, simple motor responses, some simple automatisms, changes in facial expression or voice tone, vocalizations, conscious confusion and experiential phenomena. Except for oro-alimentary automatisms, these responses were similar to the initial responses elicited by stimulations followed by a spreading after-discharge. Responses were most often obtained from limbic structures, sometimes from the temporal isocortex, and rarely from frontal sites (except for simple motor activity and some simple automatisms). Specific clinical responses could often be elicited from more than one site (74 out of 147), frequently even from non-contiguous areas in the same or both hemispheres. This suggests that the neuronal substrates responsible for the production of some of these phenomena are widespread neuronal matrices linked through connections which have become strengthened through repeated use as hypothesized by one of us [Gloor (1990), Brain, 113, 1673-1694]. Such a hypothesis could also account for the individually idiosyncratic nature of many of these responses.

Excitatory amino acids are elevated in human epileptic cerebral cortex.

We used intraoperative electrocorticography to identify and compare specimens from two groups of patients undergoing temporal lobectomy: (1) spiking cortex (12 patients)--epileptic activity recorded over much of the temporal convexity; and (2) nonspiking cortex (9 patients)--temporal convexity free of interictal spiking, epileptic activity confined to the hippocampus and/or amygdala. Comparative amino acid levels were (mumol/g protein, mean +/- SEM): glutamate--spiking 109.8 +/- 1.8, nonspiking 87.4 +/- 2.0 (p less than 0.001); aspartate--spiking 15.2 +/- 0.9, nonspiking 12.2 +/- 0.5 (p less than 0.05); GABA--spiking 15.0 +/- 1.0, nonspiking 13.9 +/- 1.4 (NS); taurine--spiking 14.5 +/- 0.8, nonspiking 12.2 +/- 0.8 (NS); and glycine--spiking 11.5 +/- 0.8, nonspiking 7.4 +/- 0.6 (p less than 0.01). Cortical epileptic activity appears to be associated with elevated concentrations of glutamate, aspartate, and glycine, but not GABA and taurine, perhaps indicating a relative imbalance between putative excitatory and inhibitory amino acid neurotransmitters.

Acute rheumatic fever and poststreptococcal glomerulonephritis in an open population: comparative studies of epidemiology and bacteriology.

We conducted epidemiologic and bacteriologic studies of 104 cases of acute rheumatic fever (ARF) and 84 cases of poststreptococcal acute glomerulonephritis (AGN) occurring in the southeast health district of Santiago, Chile, between March 1978, and February 1982. The AGN cases were both postpharyngeal and postpyodermal in origin. Despite the fact that ARF and AGN were occurring in the same neighborhoods and among families of equivalent size and socioeconomic status, the pharyngeal isolation rates of group A streptococci were significantly lower among patients with ARF and their household contacts than among patients with AGN and their contacts. Moreover, the streptococcal throat colonization rates and geometric mean anti-streptolysin O titers were similar in ARF families and the families of noninfected controls. Streptococci of M-type 5, a highly rheumatogenic type, were isolated from three patients with ARF (representing 36% of group A isolates from this group) and one ARF contact but never from patients with AGN, control subjects, or their respective contacts. These observations suggest possible differences in the streptococcal milieus from which ARF and AGN cases emerge. The nature of such differences requires further exploration.

Are all recurrences of "pure" Sydenham chorea true recurrences of acute rheumatic fever?

We are conducting prospective studies of patients in Santiago, Chile, who have had an attack of rheumatic fever and are receiving continuous secondary prophylaxis with monthly injections of benzathine penicillin G. Throat cultures are obtained just prior to injection each month, and serum antistreptococcal antibody titers (antistreptolysin O and antideoxyribonuclease B) are performed at least every 3 months. During the course of these studies we have observed 17 recurrences of "pure" chorea in 10 patients (six girls). In four recurrences the timing of serologic studies and onset of chorea appeared to exclude the occurrence of an immunologically significant group A streptococcal infection within the preceding 6 to 9 months. In one case the period of serologic follow-up was too brief to allow a definite determination. In the remaining 12 recurrences serologic evidence was suggestive or confirmatory of recent streptococcal infection; however, in several instances the titer elevations were quite modest. Our data suggest that in certain chorea-prone patients, Sydenham chorea may recur after streptococcal infections too weak and transient to be readily detectable or, alternatively, after stimuli other than streptococcal infection.

Enzyme changes in actively spiking areas of human epileptic cerebral cortex.

Five enzymes involved in glutamic acid, GABA, and catecholamine metabolism were measured in epileptic human brain. Electrocorticographically defined areas of focal spiking were compared with samples from surrounding nonspiking cortex. Comparative enzyme activities were as follows (mumol/h/g wet wt): glutamic acid dehydrogenase (GDH)--spiking 135.77 +/- 10.22 (mean +/- SEM), nonspiking 118.58 +/- 9.42 (p less than 0.001, N = 17); glutamic acid decarboxylase--spiking 10.63 +/- 0.95, nonspiking 9.96 +/- 1.10 (NS, N = 13); GABA-aminotransferase--spiking 36.49 +/- 1.05, nonspiking 36.46 +/- 1.48 (NS, N = 12); glutamine synthetase--spiking 96.94 +/- 3.81, nonspiking 96.52 +/- 4.10 (NS, N = 20); and tyrosine hydroxylase (TH; nmol/h/g)--spiking 16.23 +/- 2.39, nonspiking 10.67 +/- 1.95 (p less than 0.001, N = 14). Increased activity of GDH and TH may prove useful to characterize further areas of active spiking in human focal epilepsy.

Does head-turning during a seizure have lateralizing or localizing significance?

Forced lateralized head-turning, occurring as the first clinical sign in 106 epileptic seizures in 43 patients, was recorded on videotape simultaneously with the EEG. Forty-five ictal EEGs were obtained with stereotaxically implanted intracerebral electrodes. Forced head-turning was seen with seizures that had a frontal, temporal, unilateral diffuse, or a generalized onset in the EEG. Ipsilateral was as common as contralateral head-turning in all groups, including the seizures with frontal lobe onset. Initial head-turning in a seizure has no localizing or lateralizing significance.