Frequency of bitemporal independent interictal epileptiform discharges in temporal lobe epilepsy.

PURPOSE: Bitemporal interictal epileptiform discharges (IEDs) occur in < or =42% of scalp EEGs in patients with temporal lobe epilepsy (TLE) studied with routine EEGs or partial analysis of long-term recordings. METHODS: Twenty-eight patients with TLE demonstrating exclusively unilateral temporal IEDs on routine EEGs underwent 24-h continuous recording. The entire record was visually inspected for epileptiform discharges. We used continuous EEG to assess the significance of long-term recording in detecting bilateral IEDs. RESULTS: Twenty-two patients had left temporal IEDs; 21 had right temporal IEDs. Seventeen (61%) patients had IEDs originating from both the right and left temporal lobes. The probability of detecting bilateral independent IEDs was correlated with the duration of continuous EEG recording. There was no correlation between the number of IEDs originating from one side and the probability of detecting independent IEDs on the other side. The frequencies of IEDs were not correlated with the length of time since onset of epilepsy. CONCLUSIONS: The findings suggest that when long-term recordings are performed, the incidence of bilateral discharges in TLE is higher than previously reported in the literature and supports the view that TLE is commonly a bilateral disease.

Mesial frontal epilepsy.

The mesiofrontal cortex comprises a number of distinct anatomic and functional areas. Structural lesions and cortical dysgenesis are recognized causes of mesial frontal epilepsy, but a specific gene defect may also be important, as seen in some forms of familial frontal lobe epilepsy. The predominant seizure manifestations, which are not necessarily strictly correlated with a specific ictal onset zone, are absence, hypermotor, and postural tonic seizures. Other seizure types also occur. The task of localization of the epileptogenic zone can be challenging, whether EEG or imaging methods are used. Successful localization can lead to a rewarding outcome after epilepsy surgery, particularly in those with an imaged lesion.

Speech and the dominant superior frontal gyrus: correlation of ictal symptoms, EEG, and results of surgical resection.

Two patients with seizures characterized by speech arrest had astrocytoma in the superior frontal gyrus (SFG) of the left hemisphere. Preoperative video EEG monitoring of seizures using subdural electrode arrays showed that comprehension, crude vocalization, and limb and tongue movements were preserved during speech arrest. One patient had difficulty writing during seizures. Ictal EEG onset was localized to the SFG without involvement of Broca's area. Electrical stimulation of SFG electrodes reproduced the speech arrest and writing difficulty. Resection of this region reduced seizures but did not result in lasting speech deficit. Cessation of speech with electrical stimulation of the superior frontal gyrus occurs by interrupting control of muscles required for speaking, which occurs independently of simple 'negative' motor effects. We postulate that functional redundancy is the basis for resection of this region without producing significant speech deficits.

The value of PET scan (and MRI and Wada test) in patients with bitemporal epileptiform abnormalities.

BACKGROUND: Lateralization remains difficult in patients with bitemporal epileptiform abnormalities. OBJECTIVE: To evaluate the reliability of the interictal fluorodeoxyglucose F18-positron emission tomographic (PET) scan in this setting. METHODS: We analyzed PET scan findings in 25 patients who required bilateral depth electrodes for lateralization of temporal lobe epilepsy. The contribution of magnetic resonance imaging and the intracarotid amobarbital procedure was also analyzed. RESULTS: Positron emission tomographic scan revealed lateralized hypometabolism in 15 patients. This was in agreement with the depth evaluation in 10 cases (67%). In five cases (33%), the PET and depth findings were in disagreement, with no predominant side of seizure origin by depth electroencephalography (EEG) in four cases and PET lateralization opposite to depth findings in one case. In 10 of the 25 patients, PET scans could not lateralize hypometabolism to one temporal lobe, of which six were confirmed by depth EEG not to have a predominant side of seizure onset. The overall sensitivity of PET for concordant lateralized seizure onset was 67%. Ten of 14 patients who underwent a lobectomy had a successful outcome, including three of four patients whose temporal lobe epilepsy was lateralized by depth EEG but not by PET. One patient had PET lateralization opposite to the depth EEG and side of surgery and failed to improve. CONCLUSIONS: In this highly selected group of patients, the lateralizing value of PET and magnetic resonance imaging was somewhat diminished, and the intracarotid amobarbital procedure was not found useful for lateralization. Positron emission tomography and magnetic resonance imaging, when pointing to the side opposite depth EEG, may indicate a poor prognosis.

Ictal scalp EEG in temporal lobe epilepsy with unitemporal versus bitemporal interictal epileptiform discharges.

We investigated the ictal scalp EEG in 228 seizures of 36 patients with unitemporal (n = 25) or bitemporal independent (n = 11) interictal epileptiform discharges (IED). All patients had proven temporal lobe epilepsy since they became seizure-free or only had auras after temporal lobectomy with a minimum follow-up of 1 year. Ictal patterns at seizure onset or later in the course of the seizure were lateralized significantly more often in patients with unitemporal IED (90%, at seizure onset and 96%, later) compared with those with bitemporal independent IED (75%, at seizure onset and 78%, later). Furthermore, scalp ictal EEGs, when lateralized at seizure onset or later in the course of the seizure, were significantly more likely to predict the correct side for surgery in patients with unitemporal (98%, at seizure onset and 100%, later) than bitemporal (64%, at seizure onset and 77%, later) IED. Bilateral independent seizure onsets, asynchrony of ictal activity over the two temporal lobes, and switch of ictal activity from one to the other hemisphere are ictal patterns that are strongly correlated with bitemporal excitability.

Atonic phenomena and partial seizures. A reappraisal.

At least three types of ictal atomic phenomena can be seen in partial seizures. Focal atomic seizures are partial seizures with ictal paresis or paralysis of one or more body parts preceding or independent of any convulsive activity. A diagnosis may be difficult without simultaneous EEG recording supplemented by video monitoring or polygraphy. Epileptic negative myoclonus manifests as brief lapses in tone in one or more muscle groups that interferes with motor coordination and postural control. Drop attacks can also occur in partial seizures, as have been well documented in patients with temporal or frontal lobe epilepsy. Different mechanisms may underlie these three phenomena. Focal atonic seizures probably result from relatively circumscribed seizure activity in one or more cortical areas that contribute to the elaboration and execution of motor functions. Whether this represents inactivation or interference in motor integration, or activation of inhibitory system, remains unresolved. The pathophysiology of epileptic negative myoclonus, like that of its positive counterpart, is probably to be found at a more local level, possibly from transiently enhanced local inhibition in the motor cortex. Drop attacks in partial seizures may be close in mechanism to that also seen in generalized seizures, possibly related to ictal activation of descending inhibitory pathways in the brainstem.

Recurrence, remission, and relapse of seizures.

BACKGROUND: Approximately 6% of the population will experience at least one afebrile seizure in their lifetime. OBJECTIVE: To review the prognostic factors and clinical implications for recurrence, remission, and relapse of seizures. SUMMARY: Antiepileptic drug treatment reduces the risk of recurrence after a first seizure by about half, but these drugs cause a variety of adverse effects. The risk of recurrence is higher in the presence of neurologic or electroencephalographic abnormalities or if the seizure is partial as opposed to generalized. Neurologic abnormalities and partial seizures also reduce the probability of remission. Gradual drug withdrawal can be considered if the patient has been in remission for 2 years in the absence of any negative prognostic indicators. CONCLUSIONS: When deciding whether to begin or discontinue antiepileptic drug therapy, clinicians should consider the risks and possible benefits for the individual patient.

Etiologic factors for unitemporal vs bitemporal epileptiform discharges.

We compared the etiologic factors and clinical characteristics of 30 patients with unitemporal vs those of 30 patients with bitemporal independent (minimum 20% from one side) interictal epileptiform discharges on extracranial electroencephalograms. Febrile seizures occurred significantly more frequently in the unitemporal (40%) than in the bitemporal (17%) group. Mass lesions were more common in the bitemporal group, and seven of 10 patients with mass lesions showed bitemporal interictal epileptiform discharges. There were no statistically significant differences in age at onset, frequency of seizures, duration of epilepsy, and history of central nervous system infection or trauma between the two groups. A history of febrile seizures or central nervous system infection that may be expected to cause diffuse cerebral injury does not appear to be the major factor predisposing to the development of bitemporal interictal epileptiform discharges.

Progressive myoclonus epilepsies: clinical and neurophysiological diagnosis.

Diagnosis and management of the progressive myoclonus epilepsies (PMEs) provides a challenge to the clinician and neurophysiologist. Over 15 specific disorders can cause the PME syndrome; all are rare, and individual physicians are unlikely to have experience in all of them. Accurate diagnosis is essential to provide a prognosis, optimal therapy, and genetic counseling. The major causes are PME of the Unverricht-Lundborg type, Lafora disease, neuronal ceroid lipofuscinoses (three forms), MERRF (myoclonus epilepsy and ragged red fibers), and sialidoses (two forms), in addition to a number of even rarer disorders. Here we review the clinical aspects and neurophysiology of these disorders, which can now be diagnosed in life by relatively simple methods in the vast majority of cases.

Acute postictal psychosis: a stereo EEG study.

An acute psychosis characterized by auditory hallucinations and paranoid delusions developed in a 19-year-old man with temporal lobe epilepsy after he had a cluster of seizures when antiepileptic drugs (AEDs) had been gradually discontinued. Continuous sterotactic depth and epidural EEG recordings confirmed that this was a postictal rather than an ictal event. Acute postictal psychosis is a self-limited condition phenomenologically distinct from ictal or postictal confusion.

Delayed leukoencephalopathy in survivors with small cell lung cancer.

Six patients with small cell lung cancer developed a slowly progressive neurologic syndrome characterized by apathy, abulia, memory loss, gait ataxia, and corticospinal tract signs 26 to 50 months (mean, 35.2 months) after prophylactic cranial irradiation and systemic chemotherapy. In each case this was accompanied by CT and/or MRI evidence of changes in the periventricular white matter. These patients are long-term survivors (41 to 69 months) and do not have CNS metastases.