Abstracts

Rationale: The WADA test for lateralization of cerebral dominance for speech and memory evaluation was traditionally performed with Amobarbital and is usually fundamental in the pre-surgical evaluation of medically-refractory epileptic patients. Recently a new protocol that uses Etomidate (ETO) instead of Amobarbital (ETO speech and memory eSAM) has been employed with good results. We report two cases of ophthalmological adverse events during the eSAM that had not been previously described.Methods: Two patients with medically-refractory temporal lobe epilepsy (patient A, 36 yr, fem and patient B, a 26 yr, fem), realized eSAM prior to the epilepsy surgical procedure (left anterior temporal lobectomy). We used the same dose and concentration described by Jones-Gotman et al. 2005: an initial bolus of 4 ml of ETO (0.03 mg/kg) diluted in saline solution was injected in the internal carotid artery over 1 minute and following it, a maintenance dose with injections of 1 ml of ETO solution (0.003 mg/kg) repeated every minute until all tests were done. After the infusion, testing continued until all stimulus presentation were completed and hand strength, EEG and language returned to baseline. After an interval of ten minutes memory recognition was evaluated and the patient s subjective comments were registered.Results: Except for a mild shivering-like tremor during the infusion of ETO, the whole procedure was rather unspecific in both patients. However, right after the initial left carotid bolus infusion, both patients reported severe pain in the left eye, followed by hyperemia and scintillating scotoma, which persisted for 4 days in patient A and 5 days in patient B. In both patients ophthalmologic evaluation disclosed a macular lesion approximately the same size as the papilla. Angioretinography showed arteriolar occlusion in the macular region as well as some edema in both patients. After six months of follow-up patient A persisted with mild visual impairment, reported as a shadow-like defect in the visual field, and patient B had a full recovery.Conclusions: The advantages of ETO are the subsequent infusions after the initial bolus guarantee a period of hemianesthesia during all the procedure and the worldwide availability. Previously described adverse events with ETO included an increase in the risk of adrenal insufficiency, shivering-like tremor in about half of the injections, an increase in interictal spike activity and it might also act as a seizure-inducing agent. In rabbits submitted to one hour ETO anesthesia a partly irreversible change in the external nuclear layer of retina has been reported, due to an eventual toxic effect, but not after a single IV 2 mg/kg dose (Antal, M 1981, 1982). Considering that manual infusion could have led to higher concentrations of ETO in the ocular circulation in our cases, we increased the dilution of ETO in 50%, using 8 ml of saline for the initial bolus and 2 ml for the maintenance doses, without ophthalmological adverse events in the others six patients submitted to the same procedure.