Intracarotid Amobarbital Procedure and Prediction of Postoperative Memory in Patients with Left Temporal Lobe Epilepsy and Hippocampal Sclerosis

Abstract

Summary:Purpose: Although temporal lobe epilepsy (TLE) patients with dominant hemisphere hippocampal sclerosis generally have good cognitive outcome after anterior temporal lobectomy (ATL), a minority of patients experience at least mild post-ATL decline on one or more standardized measures of episodic and semantic memory. The goal of this investigation was to determine whether memory outcome in this group could be predicted from preoperative intracarotid amobarbital procedure (IAP) recognition memory scores.Methods: Data from 22 left TLE patients were studied retrospectively. All were left hemisphere language dominant and had IAP scores for each hemisphere, a significant degree of pathology-confirmed left hippocampal sclerosis (HS+), and no positive MRI findings other than atrophy. Cognitive outcome status was represented by the number of pre-to post-ATL declines across three tests, as defined by 90th percentile Reliable Change Index (RCI) criteria.Results: Only 14% of the sample exhibited decline on more than one memory test. Low right IAP (left hemisphere injection) scores and relatively high preoperative cognitive ability and age at surgery predicted a greater risk of post-ATL memory decline.Conclusions: A minority of left TLE HS+ patients experience at least a mild degree of RCI-defined decline in episodic or semantic memory after ATL. The right hemisphere IAP memory score, which reflects the functional reserve of the contralateral hemisphere, can help predict the risk of postoperative memory decline for TLE patients in whom HS+ is likely based on the presence of hippocampal atrophy on MRI or early age of seizure onset. Key Words: Memory-NeuropsychologyIntracarotid amobarbital procedure-Anterior temporal lobectomy-Temporal lobe epilepsy.There are many variables that help predict vulnerability to verbal memory decline after anterior temporal lobectomy (ATL) for the treatment of intractable temporal lobe epilepsy (TLE). These include dominant hemisphere seizure onset, absence of ipsilateral hippocampal atrophy, high preoperative psychometric memory ability, and a relatively late age at the time of the initial precipitating injury (IPI), the onset of seizures, or surgery (1-8).Recently, in a small number of studies, intracarotid amobarbital procedure (IAP) recognition memory results in groups of TLE patients also have been used retrospectively in attempts to predict memory outcome after ATL

Functional MRI is a valid noninvasive alternative to Wada testing

“…The Wada memory test was originally developed for the purpose of predicting global amnesia after ATL resection [91]. Studies of its ability to predict material-specific verbal memory decline have been inconsistent, with several suggesting good predictive value [41, 87-89, 92] and others showing little or none, particularly when used in combination with non-invasive tests [42, 45, 46, 93-95]. Some authors have questioned the general validity and reliability of Wada memory results [96-102].…”

fMRI assessment of language lateralization: An objective approach

“…Robust assessment of the side of language dominance and whether it is normally organized is particularly important when planning neurosurgery close to putative language regions (Binder et al, 1996). Postsurgery language and memory deficits have been linked to presurgical lateralization of language (Bell et al, 2000;Powell et al, 2008;Sabsevitz et al, 2003). The intracarotid amobarbitol, or Wada, test (Wada and Rasmussen, 1960) or electro-cortical stimulation intraoperatively or with implanted electrodes is a traditional method for determining whether language is normally organized but is highly invasive, and involves risks to the patient.…”

Prediction of neuropsychological outcome after resection of temporal and extratemporal seizure foci

“…Functional integrity of the mesial temporal lobe can be estimated in a number of ways, including greater left medial temporal lobe activation during presurgical fMRI, 6 the absence of structural MRI abnormalities such as mesial temporal sclerosis, 63 a lack of significant asymmetry in temporal lobe activation on FDG-PET, 22 and intact presurgical verbal memory ability on neuropsychological 9 or Wada testing. 3 Later age at seizure onset is also associated with greater risk for memory decline following ATR, because individuals who have seizures that began in adulthood have a greater likelihood of developing adequate verbal memory abilities prior to the onset of seizures. Resection of seizure foci is an effective treatment for the control of medically intractable epilepsy.…”