Anosognosia and the intracarotid amobarbital procedure (Wada test)

Anosognosia is the inability of a person to recognize that they have a disease or defect. Babinskil originally used the term in relation to hemiplegia. Anosognosia is reported clinically more often after right than left cerebral lesions.2 However, this asymmetry might be an artifact due to aphasia, to sample selection, or to increased susceptibility of the right brain to focal lesions. These problems can be circumvented using the Wada test, since subjects can be queried as to their prior deficits after resolution of matched transient dysfunction of the left and right brain for each subject. Employing this technique, Gilmore et a13 reported that anosognosia for hemiplegia occurred exclusively after righthemisphere anesthesia in eight patients undergoing the Wada test using methohexital. In contrast, Terzian4 reported that when amobarbital is employed, patients do not remember their deficits regardless of the side of the Wada injection. The present study reexamines this controversy. Methods. From records of intractable epilepsy patients evaluated at the Medical College of Georgia from 1985 to 1991, 187 charts were randomly selected. These subjects had undergone the intracarotid amobarbital test as part of their preoperative evaluation for epilepsy surgery. After recovery to baseline from each injection, subjects were asked, “Did you experience any weakness? ” A total of 37 patients were eliminated because the records were incomplete. The remaining 150 patients included 82 men and 68 women, 115 of whom were dextrals with lefthemisphere dominance for language. Details of the Wada language assessment are given in Loring et al.5 The mean age of subjects was 30 years, ranging from ten to 39 years. There was a left-hemisphere seizure focus in 50 subjects (47 mesial temporal lobe), a right-hemisphere focus in 43 (30 mesial temporal lobe), and an undetermined focus in fifty-seven. The patients were classified into four groups according to their recall of contralateral weakness after the injections: (1) those recalling contralateral weakness after both injections; (2) those recalling contralateral weakness after neither injection; (3) those recalling contralateral weakness only after the left injection; and (4) those recalling contralateral weakness only after the right injection. One s o u p chi-square analysis was carried out on those recalling contralateral weakness only after one injection. Responses of bilateral or ipsilateral arm weakness following a single injection were omitted from the analysis because it was difficult to interpret if they were due to global confusion, Iefthight confusion, pseudoneglect, or allochiria. Results. The initial analysis was limited to dextrals with pure left cerebral language representation (115 patients, 230 injections), since these individuals would be most likely to demonstrate typical cerebral lateralization of cognitive functions. A significant difference in occurrence of anosognosia was noted between the left and right Wada amobarbital injections ( x 2 = 4.263; p 5 0.039). Five patients (4%) recalled contralateral weakness only after the right Wada, 14 patients (12%) recalled weakness only after the left Wada, two patients (2%) recalled weakness after each injection, and 94 patients (82%) did not recall weakness after either injection. When the entire sample of 150 patients (300 injections) was analyzed, a trend for differences between left and right amobarbital injections was noted ( x 2 = 3.200; p = 0.07). Six patients (4%) recalled contralateral weakness only after the right Wada, 14 patients (9%) recalled weakness only after the left Wada, two patients (1%) recalled weakness after each injection, and 128 patients (85%) did not recall weakness after either injection. Only one patient recalled bilateral arm weakness after a single injection. Eleven patients recalled ipsilateral weakness following one of their Wada injections, seven after leftand four after right-hemispheric injections. Thus, the leftlright asymme-