Observations on verbal, pictorial and stereognostic memory in epileptic patients during intracarotid Amytal testing

Use of the intracarotid amobarbital procedure in the evaluation of memory

The intracarotid amobarbital procedure (IAP) involves the temporary inactivation of one cerebral hemisphere by the injection of sodium amobarbital, which allows independent testing of the contralateral hemisphere. Initially used for lateralization of language, IAP later found a role in the evaluation of memory function in patients with intractable temporal lobe epilepsy being considered for resective surgery. IAP technique varies widely across centers, but, in general, memory is assessed by presenting the patient with a number of items during the period of hemispheric inactivation and testing recall or recognition of these items after the effect of the drug has worn off. Because the medial temporal lobe is not directly perfused by the internal carotid artery, concerns have been raised about the ability of the IAP to test hippocampal memory function. Consequently, a variety of selective procedures have been devised. Findings on both intracranial EEG recordings and pathologic and neuroimaging studies support the association of IAP memory results with hippocampal function. The IAP memory test was originally designed to predict the risk for development of global amnesia following unilateral temporal lobectomy. More recently, it also has been used as an adjunct in lateralizing the seizure focus and for predicting postoperative selective memory deficits and seizure outcome.

Use of a brief assessment examination in a study of subacute sclerosing panencephalitis

Subacute sclerosing panencephalitis is a degenerative disease affecting children and young adults that remains a distinct and relatively frequent problem in developing countries worldwide. Recent advances in treatment prompted a study at King Faisal Specialist Hospital, Riyadh, Saudi Arabia, using oral isoprinosine and intraventricular alpha-interferon. Initially, the Neurological Disability Assessment and Index was used for tracking patient progress. However, an additional means of assessment was deemed necessary and the Brief Assessment Examination was devised. Largely cognitive based, the Brief Assessment Examination appeared to be more sensitive to mental status changes than the Neurological Disability Assessment and Index, though it correlated modestly with the Neurologic Disability Assessment and Index and more strongly with staging. In addition, the Brief Assessment Examination can be administered by technician-level staff with a minimum of training. Though more study is needed, preliminary findings suggest that the Brief Assessment Examination should be a useful tracking tool for subacute sclerosing panencephalitis, particularly in the developing world.

Cerebral hemisphere memory for manual object handling: an intracarotid Amytal study

The memory capacity of the cerebral hemisphere for manual object handling was studied during preoperative, intracarotid Amytal testing for hemisphere speech and memory in 32 patients with intractable partial epilepsy. The tactile stereognostic memory was tested non-visually before and after amobarbital injection. Two common objects, one in each hand, were given to the patient with the request to identify each by manipulation, but not to name it. Before injection, object handling was carried out correctly by both hands. After injection, while the patient was hemiplegic, the dominant hemisphere executed the object handling correctly; the non-dominant hemisphere, however, did it less properly. Free verbal recall of the object presented before the injection was correct in 85%. The free verbal recall of the postinjection objects was much lower; 22% for the speech-dominant, and only 3% for the non-dominant hemisphere. Tactile, non-visual recognition gave a memory score of 41% for the speech-dominant, and 13% for the opposite hemisphere. An epileptic lesion in the dominant hemisphere impaired the memory performance of that hemisphere compared to the non-lesioned group.

Neuropsychological aspects of learning disabilities in epilepsy

Cognitive impairment is regarded as the link between epileptic conditions and the inability to learn in school. The neuropsychological approach to learning disabilities in epilepsy, therefore, first concentrates on analyzing the differential effects of epileptic factors on cognitive function. The impact of seizure activity, localization of epileptogenic foci, and antiepileptic treatment on cognitive functioning can be evaluated based upon the results of continuous assessment with a computerized neuropsychological test system. Second, learning disabilities may be evaluated on observations made during classroom performance. Three issues seem to predominate in learning studies among disabled children with epilepsy: test-retest variability, deterioration, and the supposed specificity of the learning disabilities.

Event-related potential evidence of sex differences in verbal and nonverbal memory tasks

ERPs were recorded from 19 scalp electrodes while 48 subjects (24 females) performed visual recognition tasks for recurring verbal items and recurring abstract figures. Reaction times were longer in the figures than verbal task; the latencies of the ERP components (P2, N4, P3, P4) were also longer for the figures. A nonreversing asymmetry (R greater than L) was seen in both tasks. Significant task by electrode interactions (for P3, P4) were found, due to larger amplitudes anteriorly for the figures, but larger amplitudes posteriorly for the verbal task. All ERP latencies were longer for males than females. There were sex by task by electrode interactions in the amplitudes, due to larger ERPs (P2, N4) for females anteriorly for the figures, but slightly larger posteriorly for the verbal task. These results suggest that sex differences in cognitive abilities may be based on differences in biological mechanisms.

Short-term and long-term memory deficit following intracarotid Amytal injection: further support for the memory consolidation hypothesis

To test the three main hypotheses of the human amnesic syndrome (encoding, consolidation, retrieval), we designed an original protocol for memory assessment under Amytal that included, in addition to a retrograde memory measure, both short-term and long-term anterograde memory measures. Twenty epileptic patients with SEEG-confirmed unilateral temporal lobe foci were given right and left injections on successive days. Only the long-term memory measure for material presented under Amytal was significantly related to the presence of a temporal contralateral epileptogenic focus, even if it was assessed when the hemisphere had completely recovered from the effect of Amytal. Short-term memory deficits were observed equally often after injections ipsilateral and contralateral to the epileptogenic focus, and no retrograde amnesia was observed. These results are consistent with the consolidation hypothesis.

Selective posterior cerebral artery injection of amytal: new method of preoperative memory testing

The carotid Amytal test (Wada test) was introduced, in 1948 by Wada, to localize speech function before temporal lobectomy in patients with medically refractory epilepsy, and it remains the standard for that purpose. The same test has also been used since 1962 to evaluate memory function; however, the adequacy of the test in this application has been viewed with increasing skepticism in recent years. Therefore, we developed an alternative to the Wada test. It consists of selective injection of Amytal into the posterior cerebral artery (PCA). This PCA Amytal test is designed to test only memory function (not language). We present several anatomic and functional reasons why this approach should be superior to the Wada test for this purpose. We also present preliminary data in support of this hypothesis. To date, we have had successful results of the PCA Amytal test in 38 of 45 patients (84%), and one major complication has occurred (2%).

[Clinical treatment of resistant epilepsy]

The authors analysed 34 cases of resistant epilepsy (20 males and 14 females, mean age 23 years), treated clinically between February/1984 and May/1986. The patients underwent neurological, neuropsychological, psychological, psychiatric, cerebrospinal fluid, electroencephalographic, tomographic and/or angiographic examination. Most of the patients had complex partial seizures. The etiology was unknown in 19 patients (55.8%), probable neurocysticercosis in 6, perinatal hypoxia in 5, delivery trauma in 3 and probable sequelae of encephalitis in 2 patients. There was a clear past history of infantile febrile convulsion in 2 patients. Most patients received carbamazepine (mean dose 24.5 mg/kg/day), phenytoin (5 mg/kg and valproic acid (28 mg/kg) as monotherapy or in association. Twenty-two patients (64.7%) had more than 80% decrease of the seizure frequency. Nine resistant epilepsy cases (24.5%) were evaluated as candidates for surgical therapy. The authors concluded that the resistant epilepsy is best managed by a specialised, multidisciplinary team, and pointed out the need of a correct diagnosis of the seizure type, an adequate drug therapy and a good engagement of the patient and his family in the treatment.

Effects of amobarbital and methohexital on epileptic activity in mesial temporal structures in epileptic patients. An EEG study with depth electrodes

Bilateral intracarotidal Amytal (amobarbital) tests for evaluation of speech and memory function were performed during preoperative evaluation of 30 patients with drug-resistant epilepsy. In 8 of these patients (16 tests), having partial complex epilepsy, EEG was recorded with depth electrodes, implanted bilaterally in anterior mesial temporal structures. The EEGs during 13 tests could be quantified with regard to spike activity. A rapid increase in spike frequency was observed ipsilateral to the injection in all tests but one. No seizure activity or clinical seizures were provoked. This previously unnoticed effect of amobarbital could be due to a direct excitatory effect of the drug on epileptic temporal neurones or, alternatively, to a release of interictal inhibition, exerted upon these neurons by other structures. In 4 patients, the effect was compared with that of methohexital, another barbiturate known to have excitatory effects upon epileptic activity.

Preoperative and postoperative memory testing of epileptic patients

The present paper has four main objectives. First, it proposes a general theoretical orientation of memory functions as a basis for the research to be discussed. This framework is functionalistic/interactionistic in nature, in that memory is seen as an interaction between available cognitive capabilities of the individual and specific demands of the situation in which the individual is to remember a certain set of materials. Secondly, on the basis of this framework certain methodological requirements are discussed. These considerations take into account the need for a proper analysis of the to-be-remembered (TBR) information and those cognitive functions involved in remembering the TBR information presented. Thirdly, a preoperative and postoperative memory test is presented. This was designed on the basis of the theoretical and methodological considerations mentioned. Data from one such ongoing study is presented, taking into account various measures of memory functions; immediate free recall, final free recall, final cued recall, serial recall, final final free recall, short-term memory and long-term memory capacity as measured by the Tulving & Colotla [1] lag measure, primacy, asymptote and recency effects, and semantic memory. Finally, on the basis of the experience from this memory test a few aspects of memory testing in epileptic patients are suggested for future research.