Does the Intracarotid Amobarbital Procedure Predict Global Amnesia After Temporal Lobectomy?

Abstract

Summary: Purpose: The intracarotid amobarbital procedure (IAP) is widely used to help predict who might be at risk for postoperative amnesia after unilateral temporal lobectomy for intractable seizures. We describe the memory outcome in 10 patients who underwent standard temporal lobectomy, including mesial temporal structures, despite failing the memory portion of the IAP after injections both ipsilateral and contralateral to the resected seizure focus.Methods: Data for seven of the study subjects were obtained through a retrospective review of patients assessed on a surgical epilepsy unit during a 15-year period who failed the Montreal Neurological Institute IAP memory protocol after both ipsilateral and contralateral injections and subsequently underwent unilateral temporal lobectomy. More recently, we have studied temporal lobectomy patients who failed the Medical College of Georgia memory protocol after both ipsilateral and contralateral injections (n = 3). Preoperative and postoperative memory test scores were compared, and data regarding seizure outcome and self-perception of postoperative memory were collected.Results: At follow-up, none of the patients presented with a pattern indicative of a global amnesia, and 80% demonstrated >90% improvement in their seizure disorder or were seizure-free.Conclusions: These findings indicate that bilateral memory failure on the IAP does not preclude the removal of an epileptogenic temporal lobe or a successful surgical outcome. In addition, the findings raise questions regarding the validity of the IAP and the possibility that memory may be reorganized in patients with a long history of temporal lobe epilepsy.

Selective or Superselective Wada Test for Postoperative Memory Prediction?

“…The superselective Wada test via the anterior choroid artery with its functional inactivation of only mesial parts of the temporal lobe without accompanying aphasia, attentional, and behavioral disturbances allows a valid prediction of postoper- ative global memory performance. In agreement with other authors [7] we conclude that this better memory prediction in our case was possible because the patient was not impaired by aphasia and attentional disturbances during the superselective Wada test.…”

“…Some authors pointed to the incomplete perfusion of the hippocampus [5], and there are empirical findings of false positive and false negative identifications of patients at risk for postoperative anterograde amnesia [1,2,7,8]. In a recent study with intrahippocampal depth electrodes and SPECT, Urbach et al [17] demonstrated that increased EEG delta activity in the posterior hippocampus could be observed even if only the anterior part of the hippocampus is perfused by amobarbital.…”

Memory outcome following left anterior temporal lobectomy in patients with a failed Wada test

“…Kubu et al [22] reported 10 patients with bilateral failure on Wada testing who did not develop amnesia following ATL. Lacruz et al [11] reported that the patients with a failed Wada test did not develop significant memory decline after temporal lobectomy or selective amygdalohippocampectomy.…”

“…While many studies have shown that the Wada test was helpful in predicting the decline in material-specific memory following unilateral ATL [6,11,12,[18][19][20], others have not been able to substantiate its usefulness in this respect [8,[21][22][23][24]. Several factors contribute to the lack of consensus in the literature regarding the predictive value of the Wada memory test.…”

Localizing Cortical Function Is Occasionally Impossible

“…3 Such patients illustrate that localization of cortical function may not be as precise as we might suppose, especially in individuals whose brain function is altered by disease. Often not considered when predicting the effect of surgery is the effect of a successful operation on cortical function.…”