THE LaryNGoscorg 91; November 1981 CENTRAL AUDITORY BATTERY TESTING IN BRAIN STEM DISEASE.* E. L. HENDERSHOT, M.D., JAMES W. Woop, M.D., and M. A, KarnvtTa, M.A., Cleveland, OH. ABSTRACT. The CAT scan and the BERA have revolutionized the practice of otology. There is a tendency to accept a negative scan report as indicating a lack of pathology. The authors have found cases where central battery testing has indicated progressing brain stem disease in the presence of a normal CAT scan, In one case, the abnormal test preceded a hemiplegia by two weeks, This raises the possibility of delaying or aborting an infarct if the correct diagnosis is made early. ——o Computerized axial tomography (CAT) and brain stem evoked response audiometry (BERA)?* have revolutionized the practice of medicine. Otology owes much to these modalities. Rubenstein, et al.,2 reported seven cases of cerebellar infarction mimicking peripheral vestibular disorders. In each case, a cerebellar infarct was diagnosed by CAT scan. So much reliance is placed on the scan that many cases of infarction are ruled out by a negative scan report. Unfortunately, there are some brain stem lesions which are not demonstrated by CAT scan, and one should not overly depend on a negative scan. Moreover, in some patients, there is a prodromal stage, which, if diagnosed early, could allow prevention of the infarct. BERA is excellent for location of retrocochlear and brain stem lesions. You are referred to any otologic journal in the past five years for confir- mation of this. However, the economics of this modality — the cost plus the limited usage — may make this diagnostic tool unavailable for the average otolaryngologist. This does not mean that the otolaryngologist should give up. Tests of central auditory functions can be performed with a minimum outlay above the two channel audiometer, impedance bridge, and a tape re- corder, The central auditory test battery, interpreted properly, gives valuable in- formation as to the site of the lesion — end organ, retrocochlear, brain stem, or cortical. The author is presenting this paper not only to point out the short comings of the CAT scan but to give the otolaryngologist a proto- col for use in diagnosing brain stem and cerebellar lesions. TEST BATTERY. Our central auditory battery (Table I) consists of seven tests: 1. stape- dial reflex testing, 2. performance intensity for phonetically balanced *Pr ited at the Meeti f the Middle Section of the Americ: Lary! logical, Li \- cal ‘and Otological Society, ‘Inc. Oiiahoma City, OK, January 2 49810 oglen}, Rhinotogt were Reprint Requests to E, L, Hendershot, M.D., 21851 Center Ridge Rd., Rocky River, OI 1801 1802 HENDERSHOT, ET AL.: BRAIN STEM TESTING. TABLE I. Central Auditory Test Battery. ‘Test Level 1 Acoustic reflex Brain stem to superior olivary complex 2 PI-PB Retrocochlear 3 SSI-ICM Brain stem 4 SSI-CCM Cortex 5 SSW Auditory reception area-cortex 6 Binaural fusion Brain stem 7 Filtered speech Cortex words (PI-PB), 3. synthetic sentence identification with ipsilateral and 4. contralateral competing messages (SSI-ICM and SSI-CCM), 5. the stag- gered spondiac word test (SSW), 6. binaural fusion and 7. the filtered speech test.* We also do electronystagmography routinely. The following describes each test: Acoustic reflex testing. The nature of the reflex arc allows for the assess- ment of the integrity of the VIIIth nerve and brain stem to the level of the superior olivary complex. PI-PB functions have been demonstrated to be sensitive to retrocochlear lesions by means of the rollover phenomenon. . SSI-ICM (synthetic sentence identification) ipsilateral competing mes- sage is based on aural overload. The patient is asked to listen concur- rently to 10 synthetic sentences in the presence of continuous discourse. His task is to identify the sentence. This is diagnostic for VIIIth nerve and brain stem disorders. SSI-CCM tests the listener’s ability to identify 10 synthetic sentences in the presence of a competing message to the opposite ear. Patients who demonstrate a deficit should be suspected of cortical dysfunction. SSW tests a patient’s ability to separate spondee words that have the second syllable of the first word and the first syllable of the second word overlapping. Each ear receives one spondee. The patient’s ability to repeat both words is dependent on cortical integrity, most particularly in the auditory reception area. The binaural fusion test assesses the brain stem’s ability to fuse a low- pass filtered spondee with a simultaneously presented high-pass filtered spondee in the other ear. Neither spondee heard alone produces a good test score. There is a published range of normal performance against which to judge the patient’s performance. The filtered speech test assesses cortical ability to understand words that have been low-pass filtered. Asymmetry between ears, especially if per- formance falls below 70%, is a significant finding. Electronystagmography is invaluable in the diagnosis of these lesions. In every case there have been ENG abnormalities indicating central nervous system involvement in the presence of normal caloric testing. ENG includes bilateral bithermal testing, positional testing, pendulum tracking and saccadic pursuit. HENDERSHOT, ET AL.: BRAIN STEM TESTING. 1803 FREQUENCY IN HZ “10 250 5001000 2000 4000 8000 SOUND IN R SOUND IN L PROBE INR PROBE IN L. (Pu ip IPSILATERAL HEARING THRESHOLD LEVEL IN DECIBELS KEY O= RIGHT EAR x= LEFT EAR 20 40 60 80 (HL IN dB) Fig. 1, Results of part of central battery test. a. Upper Left — normal puretone and speech audiogram, b. Upper Right — acoustic reflexes with absent left stapedial reflex. c, Lower Left — PI-PB showing left roll over phenomena, SYMPTOMS. Impending brain stem infarction may cause many symptoms. Tinnitus, “blocked ear,” hearing loss, instability, vertigo, and facial pain have been recorded. The author has learned to treat recent unilateral tinnitus with a great deal of respect. Actual infarction can also cause hemiplegia together with the preceding symptoms. CASE REPORT. A 62-year-old white female was seen complaining of humming in the left ear for 2 weeks. Ear, nose, and throat examination was normal, Pure tone and speech audiometry were normal; however, the stapes reflex was absent in the left ear. A central battery test was performed and the patient’s scores were abnormal (Fig. 1). Petrous pyramid X-rays were normal as was the CAT scan. An ENG (Fig. 2) showed normal peripheral caloric responses, but there was abnormal pendulum tracking and saccadic pursuit. Spontaneous nonfatigable left beating nystagmus was observed in all positions except left la- teral, Several days later, while awaiting hospitalization, she developed a left hemiparesis, A repeat scan showed a left cerebellar infarct. She improved gradually with physiotherapy and occupational therapy. DISCUSSION. Central auditory battery testing has many advantages. It is excellent when there is relatively normal hearing and the patient is mentally alert. The tests are sensitive to virtually all the levels of the central auditory pathways. It is also inexpensive. 1804 HENDERSHOT, ET AL.: BRAIN STEM TESTING. CALORICS-EYES CLOSED 44° RIGHT 44° LEFT ye igi 30° RIGHT 30° LEFT A EE NS ICE RIGHT {CE LEFT Fig. 2-A, Bithermal caloric testing, SACCADIC PURSUIT PENDULUM TRACKING POSITIONAL TESTS SITTING SUPINE HEAD HANGING RIGHT LATERAL LEFT LATERAL ——_ Fig, 2-B, BNG — Saccadle pursuit, pendulum tracking, and positional testing. One should be aware of the limitations. It is obviously not used in the very young. There is some applicability in assessing children’s auditory processing abilities, but at present it is not used for site of lesion testing. Many elderly people demonstrate pure age-related depressed performance and this is a bilateral phenomenon. A lesion producing bilateral findings clouds interpretation of the test results. It goes without saying that it is useless in testing a dead ear. HENDERSHOT, ET AL,: BRAIN STEM TESTING. 1805 SUMMARY. The CAT scan, although extremely helpful in the diagnosis of lesions, can miss small ones, The central auditory test battery is an efficient, practi- cal, and inexpensive way to diagnose the site of the lesion from the cochlea to the cortex. Although there are limitations to central battery testing, it can be very accurate in diagnosing the site of the lesion. The small cost should make it available to every otolaryngologist. Finally, a case is reported in which prodromal symptoms were present. It behooves us to be alert to these. We do not know if the course could have been altered, but given the end result, it makes sense to treat all suspected patients enthusiastically if not scientifically. BIBLIOGRAPHY. 1, GaLamnos, R. and Hecox, K. E.: Clinical Applications of Auditory Brain Stem Response. Otolaryngol. Clin. North Am., 2 (3):3, ‘709-721, 1978. 2, Rubenstew, R. L., ev au.: Cerebellar Infarction — A Presentation of Vertigo, Tam Laryncoscorg, 90:505-514, 1980. 3, Dempsey, C.: A Guide to Tests of Central Auditory Function, Otolaryngol. Clinic. North Am., 2 (3):677-700, 1978. . NEW YORK UNIVERSITY POST-GRADUATE MEDICAL SCHOOL. New York University Post-Graduate Medical School announces a course entitled “Basic Sciences of Otorhinolaryngology.” This course will be pre- sented Wednesdays: 10 a.m. to 5 p.m., September 9, 1981 to May 12, 1982. Course Directors: Noel L. Cohen, M.D., Professor and acting chairman, Department of Otorhinolaryngology. H. K. Chandra Sekhar, M.D., Asso- ciate Professor of Clinical Otorhinolaryngology. This course is designed for those who intend to specialize in otorhino- laryngology and who will complete their training with a residency. Early emphasis is placed on embryology, anatomy and physiology of the ear, head and neck, as well as the upper digestive and respiratory tracts. These are followed by surgical anatomy of the head and neck, paranasal sinuses and temporal bone, plastic and maxillofacial surgery, neurotology, audi- ology, laryngology and bronchoesophagology, allergy, disorders of the thy- roid gland, radiation biology and therapy, antibiotic management, and other allied subjects. The course is planned to give the student a solid grounding in the basic sciences as applied to otorhinolaryngology. The basic science portion of the course can be integrated with a residency training program by special arrangement with the program director. The format consists of lectures, seminars, demonstrations, cadaver dis- sections and temporal bone surgery. Accreditation: 216 AMA Category I credit hours. For further information write: NYU Post-Graduate Medical School, 550 First Ave., N.Y., NY 10016, (212) 340-5295 (24-hour telephone service).