Secondarily generalized seizures in mesial temporal epilepsy: clinical characteristics, lateralizing signs, and association with sleep-wake cycle.

PURPOSE: Secondarily generalized seizures (SGSs) are often considered to be stereotyped, presumably sharing a common electrical pathway. We examined whether SGSs are uniform in a homogeneous group of patients with mesial temporal epilepsy, and whether certain clinical signs associated with generalization are lateralizing with regard to seizure origin. METHODS: A comprehensive, standardized video/EEG analysis was performed of the clinical characteristics of 29 patients (69 SGSs) with mesial temporal seizure onset. RESULTS: The sequence of tonic postures, as well as the sequence of tonic and clonic activity, was variable in SGSs of mesial temporal origin. The sequence of tonic activity, followed by vibratory and then clonic activity alone, was seen only in 51.7% of patients. Tonic and clonic activity could occur simultaneously. The most common clinical signs were forced head deviation (89.7%) and vocalization (75.9%). The most common tonic posture was bilateral arm extension (72.4%). All other clinical signs occurred in <60% of patients. Among these, early forced head deviation, asymmetric tonic facial contraction, tonic arm abduction with elbow flexion, and tonic arm extension combined with opposite arm flexion had lateralizing significance. The preceding partial seizure in SGSs (mean, 43.6 s) was significantly shorter than partial seizures without generalization (mean, 105.2 s; p < 0.001). SGSs occurred more often out of sleep (p < 0.01). CONCLUSION: Secondarily generalized seizures of mesial temporal origin are not uniform in their clinical presentation. The final phases of SGSs are more stereotyped than the initial clinical signs of generalization. This suggests variable electrical spread patterns, which may end in a common pathway. Some asymmetric motor signs have lateralizing significance. SGSs were associated with sleep and abbreviated partial seizures.

Medically intractable, localization-related epilepsy with normal MRI: presurgical evaluation and surgical outcome in 43 patients.

PURPOSE: High-resolution magnetic resonance imaging (MRI) plays a crucial role in the presurgical evaluation of patients with medically refractory partial epilepsy. Although MRI detects a morphologic abnormality as the cause of the epilepsy in the majority of patients, some patients have a normal MRI. This study was undertaken to explore the hypothesis that in patients with normal MRI, invasive monitoring can lead to localization of the seizure-onset zone and successful epilepsy surgery. METHODS: A series of 115 patients with partial epilepsy who had undergone intracranial electrode evaluation (subdural strip, subdural grid, and/or depth electrodes) between February 1992 and February 1999 was analyzed retrospectively. Of these, 43 patients (37%) had a normal MRI. RESULTS: Invasive monitoring detected a focal seizure onset in 25 (58%) patients, multifocal seizure origin in 12 (28%) patients, and in six patients, no focal seizure origin was found. Of the 25 patients with a focal seizure origin, cortical resection was performed in 24, of whom 20 (83%) had a good surgical outcome with respect to seizure control. Six of the 12 patients with multifocal seizure origin underwent other forms of epilepsy surgery (palliative cortical resection in two, anterior callosotomy in two, and vagal nerve stimulator placement in two). CONCLUSIONS: Successful epilepsy surgery is possible in patients with normal MRIs, but appropriate presurgical evaluations are necessary. In patients with evidence of multifocal seizure origin during noninvasive evaluation, invasive monitoring should generally be avoided.

Responses of human auditory association cortex to the omission of an expected acoustic event.

Unexpected auditory events initiate a complex set of event-related potentials (ERPs) that vary in their latency and anatomical localization. Such "mismatch" responses include active responses to the omission of an expected event or the omission of elements in expected stimulus composites. Here we describe intracranial recordings of middle-latency ERPs elicited by the omission of an auditory event. We first presented a sequence of tones at regular temporal intervals and the tone was omitted 20% of the time. In a second condition, we presented a sequence of tone pairs and the second tone of the pair was omitted 20% of the time. These two conditions are complementary in that the single tone conformed to the expectancy in one condition, but violated the expectancy in the other. All patients demonstrated localized cortical responses to missing tones that were topographically similar to the responses evoked by actual tones. Responses to both actual and omitted tones were observed bilaterally in the vicinity of the temporal--parietal junction, where we also obtained midlatency ERPs to a variety of other auditory stimuli. Responses that appeared to be selective for the nonoccurrence of expected tones were also observed in a number of subjects. We interpret these effects in terms of processes associated with the comparison of sensory inputs to the contents of a short-term auditory memory. Such a system could automatically detect deviant auditory events, and provide input to higher-level, task-dependent cognitive processes.

Investigation of extra-temporal epilepsy.

Medically intractable epilepsy of extra-temporal origin can represent a difficult therapeutic challenge. Our Epilepsy Service has managed these patients using standard investigative methods as well as ictal SPECT and intracranial electrode recording. In the present series of patients, image-guided surgery was used for all electrode implantation and resective surgery. Seizure localization and successful resection were achieved in 70-80% of 42 patients with follow-up of at least one year. Normal MRI and previous failed intracranial investigation were not associated with poorer outcome.

Parietal lobe epilepsy.

When symptoms such as lateralized paresthesias or pain occur prominently and early in partial seizures, parietal lobe seizure origin should be suspected. Most patients with parietal lobe seizures, however, have no symptoms or signs suggesting the parietal lobe. In the absence of detectable epileptogenic lesions, these patients without clinical seizure characteristics suggesting parietal lobe origin can present with misleading findings, resulting in erroneous localization, which can, in turn, lead to ineffective surgical intervention (23,25). Although ictal SPECT might provide vital evidence of parietal lobe seizure origin (25), as noted previously, this technology also can produce misleading data in some patients (52). Even when parietal lobe seizure origin is suspected, in the absence of a structural lesion, documenting this with invasive monitoring can be difficult. The parietal lobes, like the frontal lobes, are large, diffuse structures, and the potential for sampling error is high (19). Spread patterns are unpredictable and can result in false localization (23). Even with extensive and repetitive invasive studies, localization can prove elusive (53). No well-documented series of patients with non-lesional parietal lobe epilepsy in the modern literature who have been cured by surgery have been reported as a result of a combination of the rarity of the condition, the lack of correct recognition, as well as the difficulty of localization. Patients with medically intractable parietal lobe seizures, however, can experience excellent surgical results (23,24). Postoperative parietal lobe symptoms and signs, even when extreme, are usually not enduring (patient 3). One of our patients, however, did develop a chronic pain syndrome (48).

Does performing image registration and subtraction in ictal brain SPECT help localize neocortical seizures?

UNLABELLED: Ictal brain SPECT (IS) findings in neocortical epilepsy (patients without mesiotemporal sclerosis) can be subtle. This study is aimed at assessing how the seizure focus identification was improved by the inclusion of individual IS and interictal brain SPECT (ITS)-MRI image registration as well as performing IS - ITS image subtraction. METHODS: The study involved the posthoc analysis of 64 IS scans using 99mTc-ethyl cysteinate dimer that were obtained in 38 patients without mesiotemporal sclerosis but with or without other abnormalities on MRI. Radiotracer injection occurred during video-electroencephalographic (EEG) monitoring. Patients were injected 2-80 s (median time, 13 s) after clinical or EEG seizure onset. All patients had sufficient follow-up to correlate findings with the SPECT results. All patients had ITS and MRI, including a coronal volume sequence used for registration. Image registration (IS and ITS to MRI) was performed using automated software. After normalization, IS - ITS subtraction was performed. The IS, ITS, and subtraction studies were read by 2 experienced observers who were unaware of the clinical data and who assessed the presence and localization of an identifiable seizure focus before and after image registration and subtraction. Correlation was made with video-EEG (surface and invasive) and clinical and surgical follow-up. RESULTS: Probable or definite foci were identified in 38 (59%) studies in 33 (87%) patients. In 52% of the studies, the image registration aided localization, and in 58% the subtraction images contributed additional information. In 9%, the subtraction images confused the interpretation. In follow-up after surgery, intracranial EEG or video-EEG monitoring (or both) has confirmed close or reasonable localization in 28 (74%) patients. In 6 (16%) patients, SPECT indicated false seizure localization. CONCLUSION: Image registration and image subtraction improve the localization of neocortical seizure foci using IS, but close correlation with the original images is required. False localizations occur in a minority of patients.

Intractable seizures of frontal lobe origin: clinical characteristics, localizing signs, and results of surgery.

PURPOSE: We analyzed the clinical characteristics of seizures of frontal lobe (FL) origin with particular emphasis on establishing different categories and determining if these categories had any localizing or lateralizing value. In addition, results of surgery are reported. METHODS: Seizure characteristics were established by historical review and electroencephalographic/videotape analysis of 449 seizures in 26 adult patients with refractory seizures of FL origin. RESULTS: No outstanding risk factor was identified for seizures of FL origin. Seizures were frequent (7.1 per week), brief (mean duration, 48.3 seconds), and had a nocturnal preponderance in 58% of the patients. Status epilepticus was reported in 54%, and generalized convulsions as a prominent seizure type were reported in 26% of patients. The most common reported aura was a nonspecific sensation, often localized to the head (35%). Early forced head and eye deviation was not a consistent lateralizing sign, whereas late head and eye deviation always occurred contralateral to the site of seizure origin. Early asymmetric tonic posturing occurred consistently contralateral to the side of seizure origin. Clinical seizure patterns did not consistently localize to specific regions of the frontal lobe, although there were some noticeable trends: focal clonic seizures were associated with seizure origin in the frontal convexity; tonic seizures were most often associated with origin in the supplementary motor area but also occurred with origin in other parts of the frontal lobe; seizures resembling typical temporal lobe seizures with oroalimentary automatisms were observed with seizure origin in the orbitofrontal region; and seizures with hyperactive, frenetic automatisms were not associated with any specific region within the frontal lobes. Eighty percent of patients had favorable seizure outcome after surgery (class I/II). CONCLUSION: Although certain clinical features are characteristic for seizures of frontal lobe origin and some have lateralizing value, they do not localize to specific areas within the FL. After careful presurgical evaluation, both lesional and nonlesional patients benefit from epilepsy surgery.

Epilepsy surgery in developing countries.

Epilepsy surgery (ES) is a well-accepted treatment for medically intractable epilepsy patients in developed countries, but it is highly technology dependent. Such technology is not usually available in developing countries. For presurgical evaluation, magnetic resonance imaging (MRI) and electroencephalogram recording while videotaping the patient have been important. High technology equipment will, in conjunction with MRI, identify approximately 70% of ES candidates. Introducing ES into developing countries will require determining the candidates that are appropriate for the existing medical infrastructure. This article reviews ES and its possible introduction into conditions existing in developing countries. The authors address (a) the types of patients to be considered for resective ES (some patients require a fairly standard series of noninvasive studies: others will require extensive invasive studies), (b) ways to determine which patients might be appropriate for the existing situation (unilateral mesial temporal lobe epilepsy detected with MRI, epilepsy with a circumscribed MRI lesion, hemispheric lesions, circumscribed MRI detected neuronal migration, and development disorders), (c) surgical procedures (local resection, functional hemispherectomy, multiple subpial transections, corpus callosotomy, and implantation of a vagal nerve stimulator), (d) special considerations for introducing ES into developing countries (medical infrastructure, technology, seizure monitoring systems, selective intracarotid/carotid Amytal testing, and surgical equipment), and (e) the limitations, realistic expectations, personnel requirements, and educational function for selected professionals. Delivery of the technology and expertise to perform ES in developing regions of the world is a realizable project, but it would be limited by available technology and existing medical infrastructure. It should be possible in most areas to train local personnel and thereby leave a lasting legacy.

Pure lesionectomy versus tailored epilepsy surgery in treatment of cavernous malformations presenting with epilepsy.

Cerebral cavernous malformations (CM) are well-circumscribed vascular malformations that often present with epileptic seizures. Although patients may initially benefit from antiepileptic drugs, surgical treatment may become necessary due to medically intractable seizures. However, it is unclear whether lesionectomy alone or tailored epilepsy surgery with previous invasive monitoring is the optimal strategy in such cases. We report two patients with epileptic seizures due to CM. One patient with few seizures prior to surgery became seizure-free following resection of the CM and the surrounding tissue. In the second patient with long-lasting epilepsy, lesionectomy was performed because of the proximity to a functioning left hippocampus. This limited resection failed and the patient still had seizures. Subsequently, invasive monitoring with intracranial depth and strip electrodes was performed in order to localize the epileptogenic area and determine whether the left hippocampus could be spared. The invasive study showed the seizure origin in the tissue around the former CM but no epileptic discharges in the hippocampus. In a second operation, an anterior temporal resection was performed with removal of the epileptogenic surrounding tissue and the patient became seizure-free without cognitive deficits. The optimal surgical strategy for CM presenting with epileptic seizures must take into account various factors such as underlying mechanisms and duration of epilepsy, and location of the lesion.

An unusual complication of intracranial electrodes.

This report describes two patients who developed persistent neurologic deficits during intracranial EEG recording without clear evidence of intracranial edema or infarction. Both patients had previously received high-dose brain radiation therapy and chemotherapy. Because of this experience, we strongly caution the use of intracranial electrodes in patients with similar profiles.

The role of intracranial electrode reevaluation in epilepsy patients after failed initial invasive monitoring.

PURPOSE: Intracranial electrode recording often provides localization of the site of seizure onset to allow epilepsy surgery. In patients whose invasive evaluation fails to localize seizure origin, the utility of further invasive monitoring is unknown. This study was undertaken to explore the hypothesis that a second intracranial investigation is selected patients warrants consideration and can lead to successful epilepsy surgery. METHODS: A series of 110 consecutive patients with partial epilepsy who had undergone intracranial electrode evaluation (by subdural strip, subdural grid, and/or depth electrodes) between February 1992 and October 1998 was retrospectively analyzed. Of these, failed localization of seizure origin was thought to be due to sampling error in 13 patients. Nine of these 13 patients underwent a second intracranial investigation. RESULTS: Reevaluation with intracranial electrodes resulted in satisfactory seizure-onset localization in seven of nine patients, and these seven had epilepsy surgery. Three frontal, two temporal, and one occipital resection as well as one multiple subpial transection were performed. Six patients have become seizure free, and one was not significantly improved. The mean follow-up is 2.8 years. There was no permanent morbidity. CONCLUSIONS: In selected patients in whom invasive monitoring fails to identify the site of seizure origin, reinvestigation with intracranial electrodes can achieve localization of the region of seizure onset and allow successful surgical treatment.

A comparative study of trauma and posttraumatic stress disorder prevalence in epilepsy patients and psychogenic nonepileptic seizure patients.

PURPOSE: This study tests the hypothesis that trauma histories, including histories of physical and sexual abuse, and posttraumatic stress disorder (PTSD) are more prevalent in psychogenic non-epileptic seizure (NES) patients than in epilepsy patients. METHODS: Thirty-five inpatients with intractable seizures were evaluated for trauma history and PTSD. After these assessments, patients were diagnosed as having either epileptic or nonepileptic seizures through EEG monitoring. RESULTS: NES diagnosis correlated with PTSD and total number of lifetime traumas, adult traumas, and abuse traumas. Contrary to previous hypotheses, reported childhood sexual abuse (CSA) did not correlate significantly with NES diagnosis. However, CSA predicted PTSD in a discriminant analysis. CONCLUSIONS: We found evidence for the hypothesized relations between trauma, abuse, PTSD, and NES diagnosis. However, elevated levels in both seizure-disorder groups suggest that routine assessment for abuse, trauma, and PTSD might facilitate medical care and treatment for all intractable seizure patients.

Localized pain associated with seizures originating in the parietal lobe.

PURPOSE: Ictal pain is a rare symptom of seizures. Epileptic pain may be experienced unilaterally (lateral/ peripheral), cephalically, or in the abdomen. Painful seizures have been associated with seizure origin in both the parietal and the temporal lobes. We report on the different types of epileptic pain and discuss its etiology and possible localizing value. METHODS: We reviewed the records of patients referred to our epilepsy program over the last 6 years. Eight (1.4%) of 573 patients had pain as an early prominent symptom of their seizures. RESULTS: Pain was predominantly unilateral in three patients, cephalic in two, and abdominal in three patients. Seizure onset was in or involving the parietal lobe in all patients, and when the painful symptoms were lateralized, they were contralateral to the side of seizure origin. Parietal lobe seizure origin was determined by both intracranial EEG recording and neuroimaging [magnetic resonance imaging (MRI), ictal single photon emission computed tomography (SPECT)] in five patients, and by both scalp EEG and neuroimaging in three patients. CONCLUSIONS: We conclude that ictal pain is a rare symptom of parietal lobe seizure origin with lateralizing potential.

Long-term seizure outcome following corpus callosotomy in children.

INTRODUCTION: The long-term outcome of pediatric patients undergoing corpus callosotomy (CC) for palliative control of medically intractable seizures is presented. METHODS: During a 27-year period, 43 patients, 20 years of age or younger, underwent CC for seizure palliation and had a minimum of 1 year follow-up. Seizure reduction and stability of that outcome for individual seizure types and for most disabling seizure were reviewed. RESULTS: Overall, 63% of the seizures documented showed a good response. For the most disabling seizure, 56% of the patients had good outcomes. Changes in outcome status occurred within the first 6 months, and outcome was largely maintained after that point. CONCLUSION: Callosotomy achieves the goal of seizure palliation in more than half of the patients, with stable, good outcomes being maintained in the majority of patients.

Medial temporal lobe epilepsy: videotape analysis of objective clinical seizure characteristics.

PURPOSE: The syndrome of temporal lobe epilepsy has been described in great detail. Here we focus specifically on the clinical manifestations of seizures originating in the hippocampus and surrounding mesial temporal structures. METHODS: Seizure origin was confirmed in 67 cases by depth EEG recording and surgical cure after mesial temporal resection. RESULTS: Among nonlateralized manifestations, we commonly found oral automatisms, pupillary dilatation, impaired consciousness, and generalized rigidity. Appendicular automatisms were often ipsilateral to the seizure focus, whereas dystonia and postictal hemiparesis were usually contralateral. Head deviation, when it occurred early in the seizure, was an ipsilateral finding, but was contralateral to the seizure focus when it occurred late. Clear ictal speech and quick recovery were found when seizures originated in the non-language-dominant hemisphere, but postictal aphasia and prolonged recovery time were characteristic of seizure origin in the language-dominant hemisphere. CONCLUSIONS: These signs help to define the mesial temporal lobe epilepsy (MTLE) syndrome and often provide information as to the side of seizure origin.

Nonconvulsive status epilepticus after intravenous contrast medium administration.

PURPOSE: We describe a 52-year-old man with a glioblastoma multiforme who had a prolonged partial seizure immediately after undergoing a computed tomography (CT) scan of the head with intravenous contrast medium. METHODS: Earlier computed tomography (CT) had demonstrated a ring-enhancing hypodense mass. The patient was treated with a regimen of intravenous Tirapazamine and brain irradiation. After CT scan performed on the day of his second hospitalization, the patient became aphasic. EEG showed continuous high-voltage semirhythmic sharp and slow waves in the left posterior temporal and parietal regions consistent with status epilepticus (SE). Intravenous lorazepam and a loading dose of phenytoin were administered. RESULTS: On the next morning, the patient's condition had improved almost to baseline. He had no recurrent seizures. EEG at 2-month follow-up showed no epileptiform discharges. CONCLUSION: This appears to be the first reported case of contrast medium-induced status epilepticus.

Familial paroxysmal dystonic choreoathetosis revisited.

A case of familial paroxysmal dystonic choreoathetosis (PDC) documented by video/EEG monitoring is described. The father of the proband is affected by exertional cramping but not PDC, lending support to the previous hypothesis that exertional cramping may represent a "forme fruste" or the incomplete expression of PDC. Other family members affected by PDC are women, with exercise-induced cramping alone found in two men. Two of the women report prolonged exertion as a precipitant of lengthy spells consistent with typical PDC rather than the previously described "intermediate," exercise-induced form of PDC. Exertional cramping in families affected by PDC may represent the variable expression of the "dystonia gene" in male members. Conversely, exercise-induced PDC, both of the intermediate and longer form described here, may have a predilection to manifest in women.