Arch. Psychiat. Nen,enkr. 224, 213--220 (1977) Archiv ffir Psychiatrie und Nervenkrankheiten Archives of Psychiatry and Neurological Sciences 9 by Springer.Verlag 1977 A Case of Cortical Deafness A. E. Adams 1, K. Rosenberger 1, H. Winter t, and Ch. Z611ner 2 I Neurologische Klinik im Krankenhaus Nordwest, Steinbacher Hohl 2--26, D-6000 Frankfurt a. M., Federal Republic of Germany 2Universit~itsklinik for Hals-, Nasen- und Ohrenkranke, Killianstra6e 5, D-7800 Freiburg i. Br., Federal Republic of Germany Summary. At the age of 42 Lothar H. suffered a left-sided ischaemic brain lesion with transient aphasia, followed at the age of 49 by a right-sided ischemic infarction, which caused a continuous inability to understand spoken language and to identify tones and noises. He was still able to discriminate between single qualities of pure tones. The ERA-results showed the central acoustic pathways of the brain-stem to be intact. The occurrence of cortical deafness following bilateral lesions of the acoustic cortex and adjoining cortical centres supports the view that human auditory recognition is represented in both temporoparietal areas. Key words: Word deafness - Auditory agnosia - ERA-results - Bitemporal lesions. Zusammenfassung. Ein Mann erlitt mit 42 Jahren einen linksseitigen isch~imischen Hirninsult mit vortibergehender Aphasic. Mit 49 Jahren erkrankte er durch eine rechtsseitige Infarzierung, die nun eine dauernde Unf~ihigkeit zum Verstehen gesprochener Sprache und zum Erkennen yon T6nen oder Ger~iuschen hervorrief. Einfache alternative Unterscheidungen zwischen den Reizqualitgten reiner T6ne konnte er noch treffen. ERA-Befunde zeigten, dab die zentralen H 6 r b a h n e n des Hirnstamms intakt waren. Diese Rindentaubheit im Gefolge bilateraler Lgsionen des akustischen Cortex und angrenzender corticaler Zentren ftihrt zu der Annahme, das auditive Erkennen sei beim Menschen beiderseits in den temporo-parietalen Regionen repr~isentiert. Schliisselw6rter: Worttaubheit - Auditive Agnosie - ERA-Befunde - Bitempotale L~isionen. Introduction Classical case histories [5, 15] suggest the concept of a purely verbal agnosia, which may be compared to pure visual-agnostic alexia or word blindness [1, 6, Sonderdruckanforderungen an: Prof. A. E. Adams 214 A Case of Cortical Deafness 11]. In v a r i o u s clinical studies no differences were m a d e between a u d i t o r y o r a c o u s t i c a g n o s i a a n d central h e a r i n g deficit. The m a j o r i t y o f the p r e d o m i n a n t l y a u d i t o r y agnosias also include i m p a i r e d identification o f a v e r b a l signals [12, 18]. A l t h o u g h ' p u r e ' w o r d deafness a n d w o r d blindness were conceived as d i a g n o s t i c entities, the p a t h o l o g i c a l findings in the b r a i n h a r d l y c o n f i r m this. The present r e p o r t a d d s to this evidence. It is n o t o u r i n t e n t i o n to dwell on the persisting u n s a t i s f a c t o r y views a n d t e r m i n o l o g i e s p a r t i c u l a r l y since this has recently been d o n e [14]. Case Report Lothar H., employee. In earlier years he had been essentially healthy. On December 12, 1967, he suddenly became unable to speak and to understand spoken words and was therefore admitted to a neurological clinic. The only findings in this right-handed patient were 'sensory' aphasia, left-sided focal EEG-changes, and stenosis of the left angular artery. In addition it was stated that the patient suffered from diabetes mellitus. The aphasia and EEG-changes cleared completely within two weeks. Subsequently H. had no more complaints until December 1, 1974, when he suffered a new stroke, this time on the right side of the brain, with a sudden left-sided hemiparesis and a neuropsychological syndrome in two other clinics; this was again interpreted as aphasia. On April 23, 1975, H. was sent to us. Physical Evaluation Left arm and leg were only slightly paretic, so H. was practically not handicapped. The flexor muscles of the left arm and the extensor muscles of the left leg showed mild spasticity. All myotatic reflexes were preponderant on this side, without clonus or Babinski response. Fig. 1. Computerized axial tomography (Siemens "Siretom" scanner) with bilateral temporoparietal softening. Dilated ventricular system in mid-position. Considerably reduced density of both temporal lobes and adjoining parietal areas, more extensive on the right than on the left. The basal ganglia stand out clearly A Case of Cortical Deafness 215 Repeated EEG recordings showed temporal and temporo-parietal focal changes in the theta and delta waves on the right side. This localisation was also established by isotope brain scanning with 99m-Tc. Combined angiography of the right internal carotid and vertebral arteries showed a moderate stenosis in the proximal section of the right middle cerebral artery, with retarded arterial flow, especially within the area of the posterior temporal artery. Furthermore, the extracranial part of the right vertebral artery was seen as a hypoplastic vessel. On puncture of the left brachial artery the left vertebral artery and its branches were found to be normal. The contrast medium flowed retrograde, from the basilar artery into an approx. 5 mm long stump of the right vertebral artery. This was completely blocked within its intracranial section. The pneumo-encephalography showed moderate dilatation of all ventricles of the brain, and atrophy of the insular region which was more pronounced on the left than on the right side. The cisterno-scintiscanning with 4 mCi 99m-Tc (by the Deutsche Klinik far Diagnostik in Wiesbaden, Dr. P. Pfannenstiel) showed no disturbances of liquor passage, but there was evidence of marked widening of the fissurae Sylvii mainly on the left side. The clearest picture of the extension of a bilateral, mostly temporal but also parietal, atrophy of the cerebral cortex was provided by computerized axial tomography carried out by the Department of Neuroradiology of the Frankfurt University, Dr. H. Hacker (Fig. I). Neuropsychological Evaluation Examinations were made of the audiophonetic, audiomanual, visuophonetic, and visuomanual abilities and of simple discrimination as well as the identification of non-verbal sounds and noises. Since verbal intelligence tests were not possible, the patient's general intellectual level was evaluated on the basis of his reactions and attitudes during these examinations. The three examiners classified him as of average capacity and education. His spontaneous speaking and loud reading of texts was fluent, of proper sound intensity and normal pitch, and with faultless articulation, phrasing and choice of word. On written demand he recited familiar series of numbers or word sequences (for instance, rhymes and proverbs) without paraphasic or other errors. He also gave the correct names of objects, geometrical figures and colours. Verbal perseverations were only rarely noticed. On the other hand, we found a slight agraphy; his writing showed a tendency to run upwards. Some letters were printed instead of written in normal italics. Others were mutilated, or two letters were joined to form some almost unrecognizable shapes. The quota of mistakes--compared with earlier samples of writing from the time before December, 1967--was between 10% and 20% of the number of written letters. Simple, usual movement patterns and familiar expressive and mimical or buccofacial innervations were executed without fault in response to written demand but difficulties such as helpless hesitating, tedious correcting and wrong sequences arose in systematic, complex actions. These were the signs of a so-called ideomotor apraxia. H. had no auditory understanding of even simple spoken words, sentences, or numbers. He became observant when somebody spoke, and he recognized from the mimic and gestures used that he was being addressed. Then he would sometimes look shy and say something like: 'I can hear you, but I don't know what you are saying.' This made him different from a person suffering from deafness. Sometimes he guessed single words which he could lip-read by visuomotor recognition. But he could not state with certainty from the phonetic differences whether he was addressed in German, French, or Italian, or whether the words sounded like a question, a threat, or an affront. On the other hand, he could discern pure tones quite well. He usually gave the right answer as to how many notes were touched on an instrument ('cantele,' range c'--e"), whether the second note was higher or lower, longer or shorter, louder or softer than the first. And he made fewer mistakes when the intervals were thirds or sixths than when they were fourths of fifths. When listening to tape recordings he once even identified the voices of a man, a woman, and a child. However, apart from this he was hardly able to identify averbal noises. He once recognized a bird's call on tapes, but not the horn of an automobile, a bell, laughing, a locomotive, the 216 A.E. Adams et al. noises of a harbour, an aeroplane, a singing voice, piano or violin playing, nor the differences between classical music and jazz. He neither recognized simple melodies of folk-songs nor could he repeat the beat of a sequence oI tones nor the rhythm of a melody by Knocking. He could not reproduce given notes phonetically in his own voice. He succeeded in this repeating only sometimes by lip-reading vowels from the testing person. He was also unsure in distinguishing between single tones and chords or between spoken language and singing. However, he usually succeeded in locating the source of a tone or sound in the r o o m - - o r at least in giving the direction from whence the sound had come. o'H. L. 50J. Sprachaudiogramm r e . + li. 100 20 0 10 Tonaudiogramm 20 ~2s ~so soo ~ooo 29oo ~ooo ~1000Hz 30 /-0 SO >( 60 7O SO ~< ,~o 8o go loo 190 110 120 12o dEI 1/.0 dB SPL130 3~ 2/. 1S 10 10 K .... ERA -Schwelle re. x--x ERA-Schwel(e li. 1/, 20 dg SPL 125 250 SO0 1000 2000 60 /-0 0 % DV Impedanz - Messung Stopedius - Reflex - Audiogramm 63 go /-000 8000 HZ dEISPL am 2ccm Kuppter 9O ~I _ ',/?N ~, tJ' ~' eo x/" ""t. 120, dg 1r 38 2r I 15 75 10 10 1r 1/- 20 dB~:~. -/,IX) -200 0 +200 +/-00 mm H20 Fig. 2. Audiometric findings. Tone-audiogram including the threshold values of late potential component N1 between 500 Hz and 4 kHz for the right and the left ear: speech-audiogram; stapedius-reflex-audiogram and impedance measurement (tympanogram) A Case of Cortical Deafness 217 Au~omet~ Figure 2 summarizes the results of tone-, speech- and stapedius-reflex-audiograms as well as the impedance measurement (tympanogram). The tone-audiogram shows a symmetrical bilateral hearing loss reaching 60 dB at 500 Hz, 80 dB at 1 kHz and 85 dB at 2 and 4 kHz. The toneaudiogram includes in addition the ERA-threshold values of the acoustically evoked late potential component N~ for the four frequencies 0.5, 1.0, 2.0, 4.0 kHz. The ERA-threshold lies bilaterally just under the tone-audiogram threshold. No speech-audiogram could be obtained because of the patient's failure to understand numbers and words even at high intensity levels. 3?he B6k6sy-audiogram (here not reporduced) showed bilaterally no dissociation of the tracings for interrupted and continuous signals. A normal tympanogram on both sides could be plotted; thus pathological changes in the middle ear can be excluded. The stapedius-reflex-audiogram threshold lies within the normal range on both sides at frequencies from 250Hz to 4kHz. Electrical Response Audimetry (ERA) The early and late acoustically evoked potentials were recorded. Deriving the early potentials (comprising the compound nerve action potential and the brain-stem potentials) the acoustic stimulus consisted of an alternating rectangular wave of 2001xs duration at a rate of 10/s, which were monaurally delivered by a headphone (Beyer DT 48). The electrode position was earlobe-vertex, with ground at the forehead. The amplification amounted to 120dB and bandpass filtering was used with cutoff-frequencies at 200 Hz and 2 kHz. By means of a computer (CAT 1024A) 2000 sweeps at high and middle intensities, and 3000 sweeps at low intensities were analysed with 62.51as/addr. at each 10dB step. For the registration of the late potential component N1 the stimulation was a 500 ms long tone-burst with a rise- and decay-time of 10 ms and the frequencies of 0.5 kHz, 1 kHz, 2 kHz and 4 kHz. The tone-bursts were presented with randomized interstimulus intervals (ISI = 1.3--3.6s) by the headphone. The electrode position was vertex-contralateral mastoid, an electrode on the neck served as earth ground. The signals were here amplified by 94 dB and with filter-settings at 0.2Hz and 150Hz 100 EEG-sweeps were summed up and analysed with 2ms/addr. by the computer at each 10dB step. During the measurements the patient was lying on a bed in an electrically shielded and sound-proof room. He was sedated only for the registration of the early potentials in order to avoid muscle artefacts. Sedation was not applied while the potential component N1 was registered; at intervals of 30 to 40 rain the measurements were interrupted in order to prevent fatique. The sound pressure in dB SPL was controlled by the coupler NBS 9a (Briiel and Kjaer Type4152) both for rectangular waves and for sine-bursts. The threshold of the brain-stem potantial IV in our normal population lies in the region of 30 dB SPL + 10 dB, while that of the late component N~ is about 20 dB SPL; the subjective threshold for rectangular pulses is 20 dB SPL, for sine-bursts 10dB SPL. Figure 3 reproduces the results of the late c o m p o n e n t N1 m e a s u r e m e n t s . S u p r a l i m i n a l d o w n to threshold registration at the four frequencies are d r a w n for the right a n d the left ear. The c o r r e s p o n d i n g threshold values are plotted in the t o n e - a u d i o g r a m (see Fig. 2). The late potential N1 could obviously be registered only a t high intensities with small amplitudes at the four frequencies. The results o b t a i n e d o n registering the early potentials are s u m m a r i z e d in Figure 4. A t a s o u n d pressure level of 90 dB a complete potential p a t t e r n with n o r m a l latencies is received. The threshold for the b r a i n - s t e m potential IV lies bilaterally at 4 0 d B SPL, i.e., at the u p p e r n o r m a l limit. I n o u r case, the a u d i o m e t r i c results indicate for two reasons rather a central t h a n a cochlear damage: 1) because the threshold of the stapedius-reflex-audiog r a m in c o m p a r i s o n to that of the t o n e - a u d i o g r a m is n o r m a l a n d 2) because a o"H.L. 50.1. 2ms/Adr. n=lO0 2mslAdr. n=lO0 N1 P2 500 Hz 5 1 ~ ~ N1 P2 N1 P2 2000 HZ HI P2 120dBSPL~ 110dBSPL 100dBSPL I ~ _ _ 90 dBSPL~ N ' 0 200 t,00ms 0 1000Hz 200 t,00ms 0 200 /,00ms 0 ~,000Hz 200 /,00 ms 130dBSPL _ ~ ' ~ , , a , . l ~ ' ~ 110dBSPL -, , . ~ 110dBSPt. ~ 100dBSPL ~ 0 120dBSPL ,u~r. ~ 90dBSPL" ~ 200 rechts /,00ms 0 200 /,00ms links 0 200 /,00ms 0 200 /~00ms links rechts Fig. 3. Electric response audiometry. Registration of acoustically evoked late potential component N1 for the right and the left ear stimulated with sine-bursts of 500 ms duration and different intensities and frequencies (500Hz, 1 kHz, 2 kHz, 4 kHz) ~H.L. 50s 256 Adr. 62,5 pslAdr 10Is ~I II • l n= 2000 V rechts =~ ., I IV 256 Adr. 62,5 JJs/Adr. n =3000 10Is ][ m .,~v~ ~J [inks ~..;~ 90 dB SPL 70 dBSPL t00nVI ~ ~ 5070dBdBsPLSPL ~ 0 2 4 6 8 10 /,0 dB SPL ~ 30 dB SPL ' ~ ~ 0 2 /, 12 ms / 50 dB SPL ~ /,0 dBSPL . ~ 6 30 dBSPL 6 10 12 ms Fig. 4. Electric response audiometry. Registrations of the early acoustically evoked potentials (brainstem potentials) for the right and the left ear stimulated with alternating rectangular pulses with a stimulus rate of 10/s and with varying intensities A Case of Cortical Deafness 219 discrepancy exists between tone- and speech-audiograms insofar as according to the tone-audiogram threshold an understanding of numbers and some words ought to be present at least at higher intensity-levels. Stapedius-reflex-audiometry tests the central auditory pathways up to the olivary nuclei [8]. Hence in our patient the central acoustic pathways up to the third neuron appear to be intact. The discrepancy between the tone- and speechaudiograms would confirm a lesion in the cortical centres. Discussion Except for a stenosis of the left angular artery, neither in 1967 nor later could further corticovascular changes be proved by left-sided angiography. This stenosis cannot therefore be the only explanation of the extent of the left-sided brain atrophy. After the second stroke had injured the right brain hemisphere, in 1975 we found a stenosis of the proximal section of the right middle cerebral artery and an intracranial occlusion of the right vertebral artery. It would only be conjecture to assume that part of the left cerebral symptoms and atrophy was caused by a haemodynamic steal effect from the right. The outstanding tomographic finding is now considerable brain atrophy, mainly of both temporal lobes, which also extends bilaterally to the parietal lobes, the fissurae Sylvii and the insular regions. This is interpreted as supporting the view that cortical deafness may occur after bilateral lesions of the temporo-parietal cortex. As shown by experiments in the cat [3, 9, 13] the brain-stem potentials are probably generated by neurons of the central acoustic pathways situated in the brain-stem. The late potential component N~ seems to originate in the primary and secondary auditory cortex [4, 19, 17]. In the case of our patient, therefore, the central acoustic pathways of the brain-stem appear to be intact according to the ERA-results, since the registrations of early potentials yielded approximately normal values on both sides. But since the late potential component N1 could be bilateral elicited at the four frequencies only at very high intensities with small amplitudes, it follows that the damage must be situated in acoustic cortical areas. There is a considerable difference whether in the described case it is a question of the meaning of various perceptions or only of alternative decisions between some sensory qualities. Our patient showed a complete inability to understand the spoken word. Furthermore, he was to a great extent unable to identify kind or meaning, or to obtain semantic information from tones and noises. On the other hand, only in the high intensity range could he discriminate pure tones quite well: not only their number but also the relative differences in duration, pitch, intensity, and the direction of sound. We do not advocate any further hypotheses on findings of this kind, which cannot be correlated to experimental results in lower vertebrates, valuable though such investigations may be [2, 7, 19]. 'Agnosia' appears to be an unsatisfactory expression to indicate a functional impairment of sensory recognition after cortical lesions. It should be used only as a means for simplified diagnostic understanding. The situation described here is largely similar to the findings of Mahoudeau et al. [16] and of Lhermitte et al. 220 A.E. Adams et al. [14]. W e are also o f the o p i n i o n t h a t in the r i g h t - h a n d e d p e r s o n ' s cortex the expressive speech ability is r e p r e s e n t e d m o r e u n i l a t e r a l l y on the left side t h a n a u d i t o r y p e r c e p t i o n a n d r e c o g n i t i o n , which are r e p r e s e n t e d m o r e bilaterally b u t also in the right t e m p o r a l cortex. 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