Journal of Neurology, Neurosurgery, and Psychiatry 1988;51:1-9 Cortical auditory disorders: clinical and psychoacoustic features MARIO F MENDEZ,* GEORGE R GEEHAN,Jr.t From the Department of Neurology, Case Western Reserve University, Cleveland, Ohio,* and the Hearing and Speech Center, Rhode Island Hospitalt, Providence, Rhode Island, USA SUMMARY The symptoms of two patients with bilateral cortical auditory lesions evolved from cortical deafness to other auditory syndromes: generalised auditory agnosia, amusia and/or pure word deafness, and a residual impairment of temporal sequencing. On investigation, both had dysacusis, absent middle latency evoked responses, acoustic errors in sound recognition and matching, inconsistent auditory behaviours, and similarly disturbed psychoacoustic discrimination tasks. These findings indicate that the different clinical syndromes caused by cortical auditory lesions form a spectrum of related auditory processing disorders. Differences between syndromes may depend on the degree of involvement of a primary cortical processing system, the more diffuse accessory system, and possibly the efferent auditory system. Since the original description in the late nineteenth century, a variety of disorders has been reported from bilateral lesions of the auditory cortex and its radiations. The clinical syndrome of cortical deafness in a woman with bitemporal infarction was described by Wernicke and Friedlander in 1883.' The term auditory agnosia was used by Freud in 1891,2 and has been used alternately for two observed syndromes: a selective decrease in recognition of non-verbal sounds and a generalised decrease in recognition of both verbal and non-verbal sounds. Lissauer (1890) proposed the existence of an apperceptive agnosia resulting from inability to synthesise sensory information into an adequate percept.3 Kussmaul (1877) first described a patient with pure word deafness,4 and Bernard (1889) noted an amusia where melodies lose their musical character. I Since that time, many other cases have been reported and attributed to lesions involving the cortical auditory areas.6-10 It is still not fully understood how dysfunction of the cortex results in these diverse syndromes and whether they are functionally related or truly distinct.3 Investigators disagree as to whether true deafness can result from cortical lesions.6 1112 Case Address for reprint requests: Mario F Mendez, M.D., Department of Neurology, University Hospitals of Cleveland. 2074 Abington Road, Cleveland, Ohio 44106, USA. Received 6 March 1987 and in revised form 19 June 1987. Accepted 26 June 1987 reports of auditory "agnosias" suggest that these are not genuine agnosias in the classic Teuber definition of an intact percept "stripped of its meaning".'3 14 Other studies indicate that pure word deafness and the auditory agnosias may be functionally related auditory perceptual disturbances. "5 l 7In addition, the clinical evolution and substantial overlap between these disorders suggest that these are related disorders and should have similar underlying psychoacoustic abnormalities. A review of the clinical characteristics and psychoacoustic findings of the cortical auditory disorders clarifies whether these are a spectrum of related disorders. We investigated two new patients whose condition evolved from "cortical deafness", absent response to sound with decreased hearing thresholds, to disturbances of sound recognition. We used evoked responses and psychoacoustic tests and compared our findings with all similarly studied cases in the literature. These findings suggested a model of dysfunction of the auditory cortex. Case reports Case I A 60 year old, right-handed male with previously normal hearing, was reported to have a sudden onset of deafness of 2 weeks duration. On admission, he did not respond to verbal questions or environmental sounds and did not startle to loud noises. He was an alert patient with fluent speech and occasional literal paraphasias. He spoke in a hypophonic monotone. Testing of recent memory, constructions, and calculations was within normal limits. .k 2 IL : H ~' Mendez, Geehan ..- ~~I .41 z,: &I 4 Cortical auditory disorders: clinical and psychoacoustic features Initial evaluation was consistent with the impression of cortical deafness. Past medical history included hypertension, a myocardial infarction, and a right hemisphere lacunar stroke 4 years previously. Examination was remarkable for left-sided increased tone, hyperreflexia, and an extensor plantar response all dating from his prior stroke. He had multiple small necrotic lesions on his fingertips of possible embolic origin. The non-contrast CT scan showed bilateral haemorrhagic infarcts in both temporal lobes involving the superior temporal gyri and surrounding hypodensity from temporal tips to parietal lobes (fig la, b, c). Echocardiography demonstrated a dyskinetic ventricular segment, and the patient was subsequently given anticoagulants for a possible cardiac embolic source. During his first 2 weeks in the hospital, there was contradictory evidence of deafness. Audiological testing found pure tone thresholds to be 70 dB HL, above which responses were inconsistent. The patient appeared to be unaware of sound; however, he occasionally and unexpectedly reacted to sounds that he could not hear later. This phenomenon was unreproducible on testing. Furthermore, he stated that he could not hear, but did not behave like other deaf patients by requesting the speaker to speak louder, repeat himself, write things down, nor did he tilt an ear toward the speaker as in intent listening. These reactions did not correlate with sounds that were soft or loud, simple or complex. After 2 weeks, his awareness of sounds was consistent. Pure tone thresholds were 30-40 dB in the right ear, and 20-25 dB in the left ear, but with continued variability in his responses. He did not differentiate voices, music, and environmental sounds. Everything sounded like a disagreeable noise, a "hurr," including the pure tone signals. He did not startle to loud noises or localise sound. Efforts to hear led to the erroneous interpretation of sounds from concurrent environmental cues. 3 At 6 weeks he had a mild fluent aphasia with acoustically similar paraphasic errors on naming: chisners/scissors, whiskle/whistle, trifloss/tripod. Verbal repetition was severely defective with phonemic substitutions and selfcorrections by acoustic approximations. Reading and writing were relatively preserved. After resolution of the haemorrhage and oedema, a CT scan at 3 months showed smaller lesions involving the superior temporal gyri bilater- ally (fig 2a, b). Case 2 A 23 year old ambidextrous male, after an episode of altered awareness, was brought to the emergency room where he had a generalised tonic-clonic seizure. After becoming alert, he behaved as if totally deaf. He attended visually, but did not follow oral commands or respond to environmental sounds. Verbal output was loud and fluent with literal paraphasias, perseveration, and word-finding difficulty. He comprehended written and gestural communication. Recent memory, constructions, or calculations were normal. Seventeen months previously, he had suffered a stroke resulting in left hemiparesis. He had left arm weakness, spasticity, hyperreflexia, and an extensor plantar response. The CT scan showed an old right frontoparietotemporal infarct and a new left parietotemporal lesion (fig Id, e, f). Echocardiogram revealed an unusual configuration of the posterior mitral valve leaflet with vegetations and a dilated left ventricle. The patient was heparinised and eventually discharged on phenytoin and coumadin for a presumed cardiac embolic source. During the first 3 weeks of his hospitalisation, there was evidence of deafness. He had no response at output limits of audiometry and showed no discomfort to high sound intensities. However, he occasionally had inconsistent and unexpected responses to environmental sounds. He did not Fig 2 (a) CT scan of case I three months after his strokes. (b) Schematic drawing at the same horizontal level of the brain showing the central auditoryv structures involved. 4 ask examiners to raise their voices, or repeat their messa ge, write things down, nor did he appear concerned about his inability to hear. After 3 weeks he began to hear sound consistently. Audihograms showed a mild sensorineural hearing loss but wvith much variability in his responses (fig 3a). All sounds wvere ,&L _ like a "buzzing noise." Melodies were not recognised, me startle response was decreased and sound localisation vwas poor. At 2 months, he recognised many environmenntal sounds, but not speech or music; at 3 months, music rec ognition returned but speech lagged; and after 7 months, there was significant language comprehension. Language evaluation a year later revealed a mild hil level deficit in auditory comprehension and relatively pireserved fluency, reading, and writing. An initial anomia bhad (9)10 Left ear Right ear 10 0 10: 20 3040- 1 I dB 50607080- JII' 90- 100 110 125 500 2000'8000 125 500 2000 Boo)0 Frequency (Hz) 0 PO V Right Left 0 50 10( Time (ms) Fig 3 (a) Summary of pure tone audiograms of case 2 from 2-18 months after his second stroke and after he stopped showing progressive improvement in hearing thresholds. The audiograms showed a variable and fluctuating hearing loss. Hearing levels are in dB (ANSI, 1969). (b) Middle latency response testing of case 2 showing complete absence of responses after 20 ms. The characteristic Pa wave should occur at 30-35 ms. The Po response is probably myogenic from the-postauricular muscle. Mendez, Geehan improved to near normal, and repetition showed occasional phonemic substitutions with self-correction with acoustic approximations. Methods Evoked responses Stimuli were presented at approximately 90 dB HL via shielded headphones. (1) Case I Brainstem auditory evoked response (BAER) variables were: 10 ms epoch, 102 js rarefaction clicks, rate of 10 Hz, 2048 repetitions and bandpass of 160-3200 Hz. Middle latency response (MLR) variables were: 50 ms epoch, 1 KHz tone bursts of 5 ms, rate of 10 Hz, 1024 repetitions and bandpass of 0-8-3200 Hz. Late vertex auditory evoked response (LVAER) variables were: 300 ms epoch, 1 KHz tone bursts of 50 ms, rate of 0 5 Hz, 300 repetitions and bandpass of 0-8-160 Hz. (2) Case 2 BAER variables were: 10 ms epoch, 102 is rarefaction clicks, rate of 3 1 Hz, 2048 repetitions and bandpass of 300-1500 Hz. MLR variables were: 100 ms epoch, 102 js rarefaction clicks, rate of 11 1 Hz, 2000 repetitions and bandpass of 0-8-1500 Hz. The evoked responses were recorded from Cz ("10-20" System) referred to the ipsilateral mastoid with the contralateral mastoid electrode used as a ground. Psychoacoustic tests Pilot controls were tested at the identical settings described below for the patients and scored 100% correct on these psychoacoustic tests. Examination of attention span, language, visual fields, and hearing acuity did not reveal abnormalities that would interfere with these tasks. The testing sessions were limited to 30 minutes. Instructions were given in writing, and two or more trials were administered until the patients understood the tasks. All auditory stimuli were presented binaurally by loudspeakers located 2 feet from the patient. The patients were asked to: (1) Listen to 48 pre-recorded environmental sounds and point to the corresponding picture, based on similar testing by Vignolo.18 Four pictures were presented with each environmental sound. The four choices were either correct, acoustically related, semantically related, or totally unrelated. (2) Discriminate two environmental sounds as same or different by pointing to one of two response cards marked SAME or DIFFERENT. There were 10 trials. (3) Discriminate pre-recorded pure tones as same or different with respect to large differences in frequency, intensity, or duration. The same response cards were used, and there were 10 trials on each task. Parameters, when not an independent variable, were held at 60 dB, 1000 Hz, and 250 ms. Frequencies ranged from 250 to 3000 Hz with a minimum difference of 1000 Hz, intensity test used 70 to 90 dB with a minimum difference of 10 dB, and duration test used 75 to 300 ms with a minimum difference of 150 ms. (4) Discriminate as same or different between 10 phoneme pairs. (5) Discriminate as same or different between pairs of sequences of three sounds which varied in regularity, in frequency pattern, or in vowel sequence. In the first 10 trials, the three sounds were spaced apart at regular intervals of from 50-300 ms. The patients had to distinguish between sequences varyingonly in a regular interstimulus interval. In Cortical auditory disorders: clinical and psychoacoustic features 5 the second 10 trials, the patients had to distinguish between Case 1 distinguished pure tones with constant intersequences with variable interstimulus intervals between the stimulus intervals (10/10), but failed to distinguish three stimuli. In the third and fourth sets, they were spaced them when the intervals varied (5/10). Scores on a at regular intervals of 150 ms but were composed of different frequency pattern and a sequence of vowels were 5/10 frequencies or different vowel sounds. and 6/10, respectively. Case 2 had the Pinhiero Pitch Pattern Sequence'9 (verbal part) administered at 7 months with a 30% correct response, and at 18 Results months with 30% in the left ear and 60% in the right Evoked responses In Case 1, evoked response testing (20% is chance level). When temporal sequencing at 6 weeks showed normal BAER but absent MLR skills were tested at 2 years, he answered 10/10 for and LVAER. In Case 2, evoked responses showed pure tones with constant interstimulus intervals and normal BAER and an absent Pa wave of the MLR on 7/10 for tones with variable intervals. On a frequency sequence test he answered 6/10, and on a vowel seven occasions (fig 3b). Psychoacoustic tests Case 1 was tested at 3 thonths sequence test he answered 7/10 correctly. after stroke and Case 2 two years after the onset of his cortical auditory disturbance. Discussion (1) Identification of pre-recorded environmental sounds: Case I identified 19 of 48 sounds correctly, We studied two new cases of auditory cortical disorthat is, no better than chance. Of the 29 error res- der which differed in degree of recovery. Our first ponses, 14 were acoustically related (48%), seven were patient went from cortical deafness to a generalised semantically related (24%), and eight were totally auditory agnosia, and our second patient evolved furunrelated (27%). Case 2 did significantly better but ther into a word deafness plus amusia stage, a pure still missed seven out of the 48 environmental sounds. word deaf stage, and finally a mild disturbance priMost of his errors were also acoustically related (five marily in temporal pattern analysis. On clinical examout of seven). His acoustic errors were mistaking ination, both had marked overlap of features between church bells for a telephone, an airplane for a motor- the different cortical auditory syndromes, dysacusis or cycle, water for "slurping," clapping for someone run- the experience of sound as distorted and/or disagreening, and a hand bell for a telephone. These patients able, and absent middle latency evoked potentials. On responded best to cuing that clarified characteristics psychoacoustic tests they showed predominant acousof the sound: Case 1 identified five of the previously tic errors or evidence that sounds were mistaken missed environmental sounds when given silent lip because of disturbance of their auditory characterreading cues. Written class cues such as "an animal," istics, inconsistent auditory behaviours such as "a musical instrument," etc., did not help on a single unexpected responses to specific isolated sounds occasion. Silent lip reading also facilitated sound despite otherwise compromised auditory functioning, recognition in Case 2 while written class cues allowed and a similar pattern of decreased discrimination of him to "figure it out" and did not provide a sense of acoustic parameters, particularly in temporal familiarity for the sound. sequencing. (2) Discrimination between two environmental Other patients with cortical auditory disorders have sounds: Case 1 succeeded in only four out of 10 trials, comparable findings. Reports show a similar pattern no better than chance. Case 2 was able to match envi- of evolution starting with a transient cortical deafness ronmental sounds to each other in all 10 trials but did and evolving through various stages to the other cortical auditory disorders.'5I-20 There is significant so with uncertainty and hesitations. (3) Discrimination of pure tones based on fre- clinical overlap across these syndromes, that is, they quency, intensity, or duration: Case 1 performed no are rarely "pure" disturbances.'5 Some decrease in better than chance: 5/10, 5/10, 5/10, respectively; auditory acuity is found in patients with agnosia or however, Case 2 did well on these tasks: 10/10 on bilateral word deafness, "' 12 21 22 and environmental frequency discrimination, 8/10 on intensity discrimi- sound agnosia is present, to a degree, in cortical deaf nation (binomial p = 0 044), and 8/10 on duration and bilateral word deaf cases.6 2326 In bilateral pure word deaf cases there may be psychoacoustic deficits discrimination (p = 0-044). (4) Differentiation between phonemes: Case I did like those of the auditory agnosias.'6 17 28 29 Finally, poorly on both vowels (5/10) and voiced versus voice- amusia is rarely reported to occur alone and is freless consonants (4/10), but Case 2 did poorly only on quently combined with pure word deafness.30 the latter (7/10). Case 2 got 10/10 for vowels. Many authors have reported dysacusis. Sounds (5) Discrimination between different sequences of may be experienced as altered and may even sound sounds: both patients did significantly worse on like a foreign language. Our patients described sequences varying in regularity, frequency, or vowels. sound as a disagreeable "hurr" or a buzzing noise. 6 Table I Mendez, Geehan Middle latency evoked potentials Case reports Diagnosis Audiogram BAER MLR LVAER Graham et al, 19806 Parving et al, 198033 Shindo et al, 198139 Ozdamar et al, 198237 Rosati et al, 198240 cortical deafness agnosia agnosia agnosia agnosia 110 dB without response 20 dB LE: 37 dB; RE: 41 dB LE: 73 dB; RE: 65 dB 40 dB + + + + + absent Pa absent + absent LeChevalier et al, 19844' Marshall et al, 198542 Motomura et al, 198643 Case I agnosia agnosia deaf onset Case 2 agnosia deaf onset agnosia agnosia + absent Pa absent Pa Left: + prolonged latencies esp. left absent Right: Po-Pa latency prolonged LE: 36 dB; RE: 67 dB "normal" LE: 20 dB; RE: 30 dB LE: 23 dB; RE: 37 dB variable response LE: 37 dB; RE: 31 dB variable response + absent Pa absent Pa absent Pa absent Pa + absent Pa + + absent absent + = present;- = absent; LE = left ear; RE = right ear; where given separately for each ear, audiogram values correspond to pure tone averages for the speech range (500, 1000, 2000 Hz); agnosia refers to all sound recognition disorders such as auditory sound agnosia, word deafness, or amusia. The characteristic Pa wave should occur at 30-35 ms. The Po response is probably myogenic from the postauricular muscle. Sound has been described as "banging of tin cans",31 from thalamic nuclei, lemniscal pathways, or the "rattles and squeaks",32 "buzzing and roaring",33 accessory cortical auditory areas,35 was absent in "far away",23 "doubled",34 "excessively loud' ,25 or both of our cases. It was also absent in most other sometimes so bothersome as to require wearing patients reported in the literature regardless of specific earplugs. 1c cortical auditory disorder or audiographic findings Recently, diagnostic tests have focused on the audi- (table 1)633 37 39-43 including a case with bilateral tory middle latency evoked responses, occurring subcortical lesions43 and does not clearly discriminate between 10 and 50 ms after the auditory stimulus, as between the cortical auditory disorders. a possible discriminative test for these synOn psychoacoustic testing a similar pattern of dromes.35 36 While most patients with cortical audi- deficits is found among the different cortical auditory tory disorders have normal brainstem evoked syndromes. First, errors in sound recognition occur responses and abnormal late vertex or "cortical" because acoustic characteristics are not deciphered. evoked responses,37 it is suggested that the absence of This is evidenced by the inconsistency in matching the Pa wave of the MLR is uniquely characteristic of identical environmental sounds and the presence of cortical deafness and not seen in agnosic sound dis- phonemic substitutions on attempting to reproduce turbances.38 However, the Pa wave, which may come sounds. On repeating sounds there may be a conduite Table 2 Perceptualfindings in cortical auditory disorders Case reports Audiogram Lhermitte et al, 197144 Lhermitte et al, 197144 Albert et al, 197227 Assal & Despland PA, 197345 Kanshepolsky et al, 197351 Chocolle et al, 197553 Goldstein et at, 19752 Michel et al, 197628 Adams et al, 197754 LE: 11 dB RE: 17 dB LE: 63 dB RE: 53 dB LE: 24 dB RE: 20 dB no significant deficit LE: 37 dB RE: 33 dB LE: 28 dB RE: 27 dB 70 dB LE: 40 dB RE: 10 dB LE: 73 dB RE: 69 dB inconsistent LE: 40 dB RE: 12 dB LE: 37 dB RE: 41 dB 40 dB LE: 36 dB RE: 67 dB LE: 20 dB RE: 30 dB LE: 23 dB RE: 37 dB LE: 37 dB RE: 31 dB Ulrich, 197750 Michel & Peronnet, 198038 Shindo et al, 198139 Rosati et al, 198240 LeChevalier et al, 19844' Motomura et al, 198643 Case I Case 2 Consistency Acoustic Acoustictype errors of sound percept matching discrimination fteq. int. dur. sequencing + + + + - + + - - - - - + + - + + + + + - + + + - + + + + + + + - - + + + - + + + - Temporal +' - + - + + - - - + + = present;- = absent; LE = left ear; RE = right ear; freq. = frequency; int. = intensity; dur. = duration; where given separately for each ear, audiogram values correspond to pure tone averages for the speech range (500, 1000, 2000 Hz). 'This positive result may be a function of the task. Temporal order was determined from measures of intersignal delay time between onset of a second tone superimposed on a first one. Cortical auditory disorders: clinical and psychoacoustic features 7 d'approche of successive acoustic approximations Disturbed auditory processing is evidenced by the until the word is recognised. Foreign words and non- perception of sounds as distorted and variable. sense words are reproduced with difficulty. Lip read- Furthermore, acoustic cues and other clarifications of ing, with its added information about the acoustic the sound signal may help in sound recognition; characteristics of a sound, was superior to semantic semantic cues do not. Disturbed auditory attentional cues about sound class or context. mechanisms are suggested by the presence of auditory Secondly, patients with cortical auditory disorders behavioural inconsistencies. Unexpected reactions to have inconsistent auditory behaviour. Cortically sounds indicate at least subliminal or intermittent sig"deaf' patients have had unexpected reactions to nal reception. The lack of requests for clarification of environmental sounds. 11 12 2442 44-47 For example, unrecognised sounds, compromised startle response, our first patient reported being disturbed by the noc- and poor sound localisation may also be maniturnal conversations of unseen people in the hall festations of selective auditory inattention. Disturbed despite concurrent absence of any reaction to loud temporal processing is a specific cortical auditory disnoise. He also displayed no reaction to a ringing tele- turbance. A hierarchy of psychoacoustic disturbances phone in a small room. Afterwards, when asked if he occur, and the most vulnerable psychoacoustic proheard the telephone, he showed some recognition cesses are those which are a function of time, particureminiscent of the blindsight recognition seen in corti- larly sequencing and duration. Even stop consonants, cal blindness. Mahoudeau reported a patient who did which require temporal transitional analysis, are more not experience discomfort to a 100 dB stimulus but likely to be abnormal compared to vowels. could hear the soft jangling of keys or snapping of When correlated with the pathology, the clinical fingers,48 and LeChevalier had an unusual patient and psychoacoustic findings suggest certain funcwho retained a pleasure sensation to music.4' Fur- tional relationships to the auditory cortex. Cases of thermore, as patients recovered from cortical deaf- cortical deafness involve extensive lesions which ness, many still regarded themselves as deaf and extend subcortically,24 46 47 5 5and true "cortical" denied hearing sounds that they reacted to or, con- deafness from isolated lesions of the cortex probably versely, lacked the startle response to unexpected does not exist. Interhemispheric differences are not sounds. I 1 12 38 49Another instance of auditory behav- totally clear, but verbal or semantic comprehension ioural inconsistency has been the absence of behav- may be mediated more by the left hemisphere and iours seen in those who are hard of hearing, for exam- certain auditory perceptual properties more by the ple, requests for clarification or attempts to right.' 8 56- 59 Clearly, pure word deafness may occur understand the speaker better. with isolated left hemisphere lesions,3 and amusia Finally, a summary of studies that have looked at may be more pronounced with right hemisphere psychoacoustic characteristics shows a similar pattern lesions.30 However, in most auditory cortical disorof disturbances across all auditory cortical syndromes ders a part of both the right and the left auditory (table 2). 12 27 28 38-41 44 45 50-54 Ulrich in his review cortex must be damaged for the syndrome to of 29 cases of auditory agnosia was impressed with appear. 21 51 subjects' inability to perform on specific psychoThe remaining functional relationships may be acoustic features.50 Regardless of specific cortical explained by the extent of involvement of the primary auditory disorder, the most common disturbances auditory cortical system, the accessory auditory cortiwere in discriminating sound sequences, followed by cal system, and possibly disturbances of the efferent sound duration. Basic frequency and intensity auditory system as well. The more complex temporal discrimination were better preserved. analysis needed for language and music may require The present findings and a review of the literature the primary auditory cortex (Heschl's gyrus, area 41) suggest that the different clinical syndromes resulting and its main radiations from the medial geniculate from lesions in the cortical auditory areas constitute a bodies. Bilateral lesions in this main route into and spectrum of related auditory processing disorders from the primary auditory cortex could result in pure with similar clinical features and common underlying word deafness, amusia, or the frequent combination psychoacoustic abnormalities. This has not been pre- of pure word deafness plus amusia.30 60 This more viously established. The clinical course may reveal a complex temporal pattern analysis is not a requirepattern of improvement from a usually transient ment for the processing of most environmental cortical deafness to generalised auditory agnosia; sounds. Their analysis can bypass the primary audiselective auditory agnosia, pure word deafness and/or tory cortex and take place in secondary auditory amusia; and ultimately a residual disorder of temporal association areas reached through the accessory sequencing. These are not truly distinct disorders. pathways.61 62 This dual organisation has been sugThere is much clinical overlap across syndromes, and gested to explain how primary cortex lesions can there are absent MLRs regardless of diagnosis. result in word deafness with relative sparing of envi- 8 ronmental sound recognition,63 and, conversely, the existence of cases with abnormal environmental sound recognition but preserved language comprehension.27 64 The efferent auditory system may also play a role in these disorders. Through multiple reciprocal connections with subcortical structures, it mediates specific auditory attention by suppression of unwanted sound and enhancement of the signal of choice. This system may result in much of the auditory behavioural inconsistency through exaggeration of sound suppression, for example, Miceli's and Lhermitte's patients also had no reactions to sound when engaged in other tasks.1445 In summary, patients with bilateral lesions in the cortical auditory regions manifest a spectrum of disorders ranging from cortically deaf to generalised auditory agnosia, selective auditory agnosia, pure word deafness and/or amusia, and a milder disturbance in the temporal pattern analysis of sound. The clinical evolution and overlap, the presence of dysacusis, the lack of discrimination of the MLR findings, and the similar pattern of psychoacoustic deficits indicate that these are related disturbances of auditory processing. It is suggested that clinical differences between these syndromes may depend on the degree of involvement of the primary temporal processing system, the more diffuse accessory system, the left and right hemisphere, and possibly the auditory efferent system. References I Wernicke C, Friedlander C. Ein Fall von Taubheit in Folge von doppelseitiger Lasionen des Schlafenlappens. Fortschritte der Medizin 1883;1:177-85. 2 Freud S. Zur Auffassung der Aphasien. Vienna: Deuticke, 1981 (English translation, On Aphasia, London, Imago, 1953). 3 Bauer RM, Rubens AB. Agnosia. In: Heilman KM, Valenstein E, eds. Clinical Neuropsychology. New York: Oxford Univ Press 1985:209-17. 4 Kussmaul A. Disturbances of speech. In: von Ziemssen H, ed. Cyclopedia of the Practice of Medicine. New York: William Wood 1877:581-875. S Bernard P. De l'aphasie et de ses diverses.formes. Paris: Lecrosnier et Babe, 1889. 6 Graham J, Greenwood R, Lecky B. Cortical deafness. A case report and review of the literature. J Neurol Sci 1980;48:35-49. 7 Ulrich G. Interhemispheric functional relationships in auditory agnosia. Brain Lang 1978;5:286-300. 8 Vignolo LA. Auditory agnosia: A review and report of recent evidence. In: Benton AL, ed. Contributions to Clinical Neuropsychology. Chicago: Aldine 1969:172-231. 9 Oppenheimer DR, Newcombe F. Clinical and anatomic findings in a case of auditory agnosia. Arch Neurol 1978;35:712-19. 10 Rousseaux M, Devos P. Deafness, mutism and behavioral problems caused by bitemporal cerebral lesion. Cortex 1983;4: 557-68. 11 Leicester J. Central deafness and subcortical motor aphasia. Brain Lang 1980;10:224-42. 12 Goldstein MN, Brown M, Hollander J. Auditory agnosia and cortical deafness: analysis of a case with a three-year follow-up. Brain Lang 1975;2:324-32. 13 Goldstein MN. Auditory agnosia for speech ("pure word deafness"): a historical review with current implications. Brain Mendez, Geehan Lang 1974;1:195-204. 14 Miceli G. The processing of speech sounds in a patient with cortical auditory disorder. Neuropsychologia 1982;20:5-20. 15 Buchman AS, Garron DC, Trost-Cardamone JE, Wichter MD, Schwartz M. Word deafness: One hundred years later. J Neurol Neurosurg Psychiatry 1986;49:489-99. 16 Auerbach SH, Allard T, Naeser M, et a,4 pure word deafness. Analysis of a case with bilateral lesions and a defect at the prephonemic level. Brain 1982;105:271-300. 17 Albert ML, Bear D. Time to understand. A case study of word deafness with reference to the role of time in auditory comprehension. Brain 1974;97:373-84. 18 Vignolo LA. Auditory agnosia. Phil Trans R Soc Lond 1982;B298:49-57. 19 Pinheiro ML, Musiek FE. Sequencing and temporal ordering in the auditory system. In: Pinheiro ML, Musiek FE, eds. Assessment of Central Auditory Dysfunction. Baltimore: William and Wilkins 1985:219-38. 20 Tabira T, Tsuji S, Nagoshima T, et al. Cortical deafness in multiple sclerosis. J Neurol Neurosurg Psychiatry 1981;44:433-36. 21 Wohlfart G, Lingren A, Jernelius B. Clinical picture and morbid anatomy in a case with "pure word deafness". J Nerv Ment Dis 1952;116:818-27. 22 Tanaka Y, Taquchi K, Sakabe N, et al. Pure auditory agnosia associated with alteration of voice and personal character. Folia Phoniat 1964;17:185-94. 23 Klein R, Harper J. The problem of agnosia in light of a case of pure word deafness. J Ment Sci 1956;102:112-20. 24 Earnest MP, Monroe PA, Yarnell PR. Cortical deafness: Demonstration of the pathologic anatomy by CT scan. Neurology 1977;27:1 172-5. 25 Hemphill RE, Stengel E. A study on pure word-deafness. J Neurol Neurosurg Psychiatry 1940;3:251-62. 26 Shoumaker RD, Ajax ET, Schenkenberg T. Pure word deafness (Auditory verbal agnosia). Dis Nerv Syst 1977;38:213-99. 27 Albert ML, Sparks R, von Strockert T, et al. A case study of auditory agnosia: Linguistic and non-linguistic processing. Cortex 1972;8:427-43. 28 Michel F, Martin MM, Peronnet F. A propos d'un cas clinique de surdite verbale. Lyon Med 1976;236:691-8. 29 Chan JL, Hsi MS. Auditory agnosia-a case report. Taiwan I Hsueh Hui Tsa Chih 1983;7:718-23. 30 Sidtis JJ. Music, pitch perception, and the mechanism of cortical hearing. In: Gazzaniga M, ed. Cognitive Neuroscience. 1984: 91-114. 31 Quensel F, Pfeifer RA. Ein Fall von reiner sensorischer Amusie. Ztschr Neurol Psychiatr 1923;81:31 1-30. 32 Reinhold M. A case of auditory agnosia. Brain 1950;73:203-23. 33 Parving A. Solomon G, Elberling C, et al. Middle components of the auditory evoked response in bilateral temporal lobe lesions. Scand Audiol 1980;9:161-7. 34 Masnetoil MMR, Messimy R, Serrotte D. Un cas de surdite centrale. Ann Otolaryngol (Paris) 1959;76: 1103-5. 35 Kileny P. Middle latency (MLR) and late vertex auditory evoked responses (LVAER) in central auditory dysfunction. In: Pinheiro ML, Musiek FE, eds. Assessment of Central Auditory Dysfunction. Baltimore: William and Wilkins 1985:87-102. 36 Woods DL, Knight RT, Neville HJ. Bitemporal lesions dissociate auditory evoked potentials and perception. Electroencephalogr Clin Neurophysiol 1984;57:208-20. 37 Ozdamar D, Kraus N, Curry F. Auditory brainstem and middle latency responses in a patient with cortical deafness. Electroenc ephalogr Clin Neurophysiol 1 982;53:224-30. 38 Michel F, Peronnet F, Schott B. A case of cortical deafness: Clinical and electrophysiological data. Brain Lang 1980;10:367-77. 39 Shindo M, Kaga K, Tanaka Y. Auditory agnosia following bilateral temporal lobe lesions. No To Shinkei 1981;33:139-47. 40 Rosati G, Bastiani P De, Paolino E, Prosser S, Arslan E, Artioli M. Clinical and audiological findings in a case of auditory agnosia. J Neurol 1982;227:21-7. Cortical auditory disorders: clinical and psychoacoustic features 41 LeChevalier B, Rossa Y, Eustache F. Un cas de surdite corticale epargnant en partie la musique. Rev Neurol (Paris) 1984;140: 190-201. 42 Marshall RC, Rapport BZ, Garcia-Bunuel L. Self-monitoring behavior in a case of severe auditory agnosia with aphasia. Brain Lang 1985;24:297-313. 43 Motomura N, Yamadori A, Mori E, Tamaru F. Auditory agnosia: Analysis of a case with bilateral subcortical lesions. Brain 1986;109:379-91. 44 L'Hermitte F, Chain F, Escourolle R, et al. Etude des troubles perceptifs auditifs dans les lesions temporales bilaterales (a propos de trois observations dont deux anatomo-cliniques). Rev Neurol (Paris) 1971;124:327-51. 45 Assal G, Despland PA. Presentation d'un cas d'agnosie auditive. Rev Otoneuroophtalmol 1973;45:353-55. 46 Clark WE, Russell WR. Cortical deafness without aphasia. Brain 1938;61:375-83. 47 Metz-Lutz MN, North P, Dutour P, et al. Troubles auditifs d'origine corticale. A propos de deux cas. Rev Otoneuro- ophtalmol 1980;52:231-8. 48 Mahoudeau D, Lemoyne J, Foncin JF, et al. Considerations sur l'agnosie auditive (a propos d'un cas anatomo-clinique). Rev Neurol (Paris) 1958;99:454-71. 49 Ziegler DK. Word deafness and Wernicke's aphasia. Arch Neurol 1952;67:323-3 1. 50 Ulrich G. Das Syndrom der akustischen Agnosie. Fallbericht und Versuch einer neuropsychologischen Qualifizierung. Arch Psy hiat Nersvenkr 1977;224:221-33. 51 Kanshepolsky J, Kelley JJ, Waggener JD. A cortical auditory disorder. Neurology 1973;23:699-705. 52 Jerger J, Lovering L, Wertz M. Auditory disorder following bilateral temporal lobe insult. Report of a case. J Speech Hear 1972;37:523-35. c 9 53 Chocolle R, Chedru FR, Botte MC, et al. Etude psychoacoustique d'un cas de 'surdite corticale". Neuropsychologia 1975;13:163-72. 54 Adams AE, Rosenberger K, Winter H, Zollner CH. A case of cortical deafness. Arch Psvschiat Nervenkr 1977;224:213-20. 55 Mendez MF. Cortical auditory disorders: Functional correlation with the auditory cortex. In: Daroff RB, Conomy JP, eds. Contributions to Contemporary Neurolog:. A Tribute to Joseph M. Foley, M.D. Boston: Butterworth (in press). 56 Lassen NA, Larsen B. Cortical activity in the left and right hemispheres during language related brain functions. Phonetica 1980;37:27-37. 57 LeMoyne J, Mahoudeau D. A propos d'un cas d'agnosie auditive avec surdite corticale associee a une dysphonie fonctionnelle. Ann Otolars ngol Chir Cervicqfac 1959;76:293-310. 58 Gazzaniga MS, Glass AV, Sarno MT, et al. Pure word deafness and hemispheric dynamics: a case history. Cortex 1973;9: 136-43. 59 Nagafuchi M, Suzuki J. Auditory agnosia due to incision of splenium corporis callosi. Acta Otolars ng 1973;76:109-13. 60 Guard 0, Couiller JF, Dumas R, et Agnosie auditive. Lyon Med 1980:243:211-317. 61 Noback CR. Neuroanatomical correlates of central auditory function. In: Pinheiro ML, Musiek FE, eds. Assessment of Central Auditors Dysfunction. Baltimore: William and Wilkins 1985:7-21. 62 Celesia GG. Organization of auditory cortical areas in man. Brain 1976;99:403-14. 63 Coslett HB, Brashear HR, Heilman KM. Pure word deafness after bilateral primary auditory cortex infarcts. Neurology at. 1984;34:347-52. 64 Spreen 0, Benton AL, Fincham RW. Auditory agnosia without aphasia. Arc-h Neurol 1965;13:84-92.