A neuropsychological study on the occurrence of auditory extinction in a case with right temporo-parietal lesion
Tanabe, H.; Nishikawa, T.; Okuda, J.; Nishimura, T.; Shiraishi, J.; Miyoshi, T.
Seishin Shinkeigaku Zasshi 84(6): 424-438
1982
ISSN/ISBN: 0033-2658 PMID: 7146180 Document Number: 196103
There have been few reports about the conditions of bilateral stimulation for the occurrence of auditory extinction. A neuropsychological study concerning the conditions of both nonverbal and verbal stimuli is presented. A 49-yr-old right-handed man was studied who showed left ear extinction by approximately simultaneous bilateral stimulation with snappings of the fingers after cerebral vascular accidents. Neurological examinations revealed that he was alert, intelligent and normally oriented. He did not show motor disturbance, but hyperreflexia and pathological reflexes were observed on the right extremities, and Barre's test showed a slight dropping of the right leg. Sensory examination revealed slight impairment on the right side of the body below the neck. Left homonymous hemianopsia was observed. He showed mild hemispatial neglect, tactile and auditory extinction on the left side. Cross-modal extinction was not observed and tactile extinction disappeared later, while auditory extinction persisted. Auditory extinction did not occur by approximately simultaneous bilateral stimulation with 2 dissimilar sounds, such as finger snapping and jangling keys. EEG showed a normal pattern. CT scan revealed a large low density area in the right temporo-parietal lobes and small low density areas inside the bilateral insulae. Pure-tone audiometry revealed a mild sensorineural hearing loss on the left ear. Fixed-frequency Bekesy audiometry showed instability of the threshold on interrupted and continuous tones, and it was difficult to classify these findings into the type I .apprx. V Bekesy patterns by Jerger. Speech discrimination test showed the impairment of intelligibility in the left ear in spite of rather well-preserved pure tone threshold. Auditory brain stem responses revealed normal configuration. Influence of onset delay and qualities of dichotically presented stimuli on the occurrence of auditory extinction were studied. Finger snapping and pure tones were used as nonverbal stimuli, and single vowels and different 3-syllabic words pronounced by men and women as verbal stimuli. The frequency of occurrence of auditory extinction was high in less than a certain delay time (boundary delay time) on both nonverbal and verbal stimuli, no matter whether the left ear (L-precede) or the right ear stimuli preceded (R-precede). On finger snappings, single vowels and different words, the average boundary delay times in L-precede and R-precede were 118 and 135 ms; 103 and 81 ms; 197 and 197 ms, respectively. It was presumed that the boundary delay time would correspond to cognitive processing time of auditory stimuli from unilateral ear and that during the period the extinctive competition might occur between the cognitive processes of bilateral ear stimuli. There were no significant differences between the average boundary delay times in L-precede and in R-precede on all kinds of stimuli. Within each boundary delay time, on nonverbal stimuli and same words, the frequency of occurrence of auditory extinction was high when the qualities of bilateral stimuli were similar acoustically and phonetically. On different words, auditory extinction occurred irrespective of the difference in phonetic quality between bilateral voices. On verbal stimuli, the patient's replies in auditory extinction were classified into 2 types: i.e., type 1 indicates that the patient heard nothing in the left ear, and type 2, that he could not discriminate verbal stimuli to the left ear. When identical stimuli were presented to both ears simultaneously, auditory extinction did not occur on both nonverbal and verbal stimuli; e.g., when putting a stethoscope in a patient's ears and tapping the diaphragm, the patient could hear the sounds in bilateral ears or localized the sound inside his head consistently.