Abstracts

RATIONALE: The Wada test is often accompanied by neglect for contralateral neurological deficits and aphasia but conflicting reports exist on the conditions that predispose to this phenomenon. Gillmore et al. (Neurology 1992;42:925) reported in 8 patients that neglect was seen with right sided methohexital injections. In another report by Adair et al. (Neurology 1992;45:241) with 52 left hemisphere dominant patients, 52% of left sided methohexital injected (Linj) cases recalled the hemiparesis Vs 3% after right injection (Rinj). Durkin et al. reported a much higher prevalence of anosognosia with the intracarotid amobarbital test in 150 patients with mixed dominance (Neurology 1994;44:978).
METHODS: This is a prospective study of anosognosia during the Wada test from 1997 to 2002. Patients evaluated by one examiner (PCVN) were included in the study. There were 182 intracarotid amobarbital injections (ICA) of which 152 were in 75 right handed localization related epilepsy patients. 90-120 mg amobarbital was used for each study. After recovery from amobarbital and after memory testing was completed, patients were asked if they recalled having any problems with vision, weakness, language, or speech to assess awareness of the neurologic deficits. Memory recall was reviewed to see if poor memory performance correlated with anosognosia. Lateralization of the epileptogenic zone was examined for effect on anosognosia.
RESULTS: Aphasia occurred in 76 ICA tests; 62 patients were amnestic for the deficits, one was not asked, 13 recalled the aphasia. The 13 cases were all left dominant and 8 failed the memory portion of the test. Hemianopia occurred during 91 ICA tests. In 77, there was amnesia for the visual deficit (37 Linj and 40 Rinj), 12 were not asked, 2 recalled the hemianopia and both of these were dominant hemisphere Linj studies with failing scores on memory testing. Hemiplegia occurred in all 152 ICA tests; 133 were associated with amnesia for the deficit, 12 were not asked, and 7, all left dominant for language, recalled the hemiplegia including 5 with the left ICA test. Of the 7 cases that recalled the hemiplegia, 4 failed the memory portion of the Wada test. The presence of anosognosia for aphasia, hemianopia, or hemiplegia was unrelated to whether the patient passed the memory portion of the Wada test, the side of injection or lateralization of the epileptogenic zone (Fisher[ssquote]s Exact test).
CONCLUSIONS: The amobarbital Wada test is usually associated with anosognosia for amobarbital associated neurologic deficits. Anosognosia for hemianopia or hemiplegia was not significantly more likely with Rinj ICA than Linj ICA (Fisher[ssquote]s exact test) and is not dependent on the localization of the epileptogenic zone. Additionally, anosognosia is independent of the memory score on the Wada test. It is possible that methohexital and amobarbital are not equivalent in their effect on cognition during the Wada test. These data emphasize the importance of developing a standardized Wada test and raise concerns about drug substitution when amobarbital is unavailable as has occurred in recent years.