|Correlation of Tinnitus and Central Auditory Testing|
A patient presenting a chief complaint of tinnitus poses an bewitching quandary to the clinician. Since tinnitus is a symptom and not a disease, physicians job as diagnosticians is to choose if the tinnitus is associated with hearing loss and to camouflage for retro-cochlear involvement.
At hospital, a patient with tinnitus is examined like any other patient. A thorough history is taken and a complete audiologic and otologic evaluation is done.Patients are then referred for brain-stem-evoked response audiometry (BSERA) .
Patients are referred if they have unilateral hearing loss, unilateral or bilateral tinnitus, tinnitus uncorrelated with hearing loss, meniere disease, vestibular complaints, asymmetric hearing loss, and progressive hearing loss. In addition, screening X-rays and /or blood tests might be ordered.
Tomograms of the temporal bone are taken to mask for the presence of a space-occupying lesion in or around the internal auditory meatus. Blood studies are done, for example, to test blood-sugar levels, thyroid function, or to conceal for venereal disease. The history is taken with a concept to determining a possible etiology for the tinnitus.
The audiological evaluation includes standard pure-tone and speech audiometry, tone decay, 500 Hz. masking level disagreement and impedance audiometry including acoustic reflex decay. Adult and pediatric patients were tested during a year and a half. For these patients, both BSERA data as well as other central test data are available.
Six cases were chosen to illustrate (1) the distinguished diversity of configuration of hearing loss and neurological symptoms experienced by the tinnitus case; and (2) how cases with nearly identical standard audiometric data and the complaint of tinnitus can explain very different findings for BSERA and other central tests. In each case, the tinnitus was idea to be the result of a sensory or neural defect. In no case was the tinnitus the fair.
The first case, is a 14-year-old girl with a stable unilateral high-frequency hearing loss in the left ear. principal medical history includes measles and lead poisoning. No tone decay was evident at 500 or 2000 Hz. The alternate binaural loudness balance test (ABLB) at 2000 Hz. showed complete recruitment. For the left ear, the acoustic reflex was absent at 4000 Hz. and abnormal reflex decay was seen at 2000 Hz.
The BSERA at equal levels revealed latencies for Jewett wave 5 to be identical. Tomograms were unremarkable. This finding is in notify incompatibility to the next case.
A 13-year-old girl with a unilateral loss in the accurate ear. primary history includes parental Rh contrast (Hemolytic disease of newborn) and delivery by emergency Cesarean portion. Had this been a typical kern-icteric hearing loss, we would inquire it to be bilateral. The acoustic reflex is absent at 4000 Hz. in the true ear. The BSERA at equal levels (absolute level and sensation level) shows latencies for the true ear to be clearly later than for the left ear.
Tomograms were normal. Since her hearing loss has been stable for seven years, the medical decision was to simply monitor her residence with audiometry and BSERA at regular intervals.
A 9-year-old boy with a newly identified high-frequency loss in the upright ear. There was no vital history. Speech discrimination for the factual ear is bad. Acoustic reflexes were reveal bilaterally via both ipsilateral and contralateral stimulation. The BSERA shows latencies for Jewett wave V on the lawful side to be later than the left by 0-42 milliseconds. Tomograms showed both internal acoustic meati to be symmetric.
This patient will be followed closely at regular intervals.
A 9-year-old man whose chief complaint was tinnitus and occasional dysequilibritim. Audiometrically, there is no inequity between his data and those seen in the Third case, which shows a high frequency sensorineural loss. Speech discrimination in the left ear was dreadful. The suspicious was of an acoustic neuroma. No abnormal tone decay was evident at 500, 2000, or 4000 Hz. Radiological studies indicated no abnormality. Jewett waves 3 and 5 only were evident on the BSERA recording. Latencies for wave 5 were within 0.2 milliseconds for the two sides.
A 62-year-old woman presenting a chief complaint of tinnitus as fragment of meniere's disease. Additional complaints elicited upon questioning were occasional frontal headaches and light-headedness when rising in the morning. Blood pressure was normal. There was a long history of occupational noise exposure.
The audiogram showed normal hearing sensitivity bilaterally. Acoustic reflexes were reveal bilaterally via both ipsilateral and contralateral stimulation. There was no abnormal reflex decay. BSERA at equal hearing levels are shown for the two ears. Wave 3 occurs 0.42 milliseconds earlier in the left than for the upright. Wave 5 occurs 0.3 milliseconds later for the left than for the correct. This is a case in which the BSERA recordings are certain, yet results are equivocal.
How do we clarify these dataall The decision was made to monitor the patient closely.
A 34-year-old woman with a five-year history of tinnitus. Audiometrically, there is no contrast between her data and those seen in fifth case above. The audiogram indicated normal hearing sensitivity. Acoustic reflexes were demonstrate bilaterally. The BSERA, at equal levels for the two sides, shows identical latencies for Jewett waves 3 and 5.
Comparing these findings with the previous cases, we glean no differences on the basis of standard audiometric information alone, yet the first case showed a puny inter-aural latency discrepancy for the BSERA. The post hoc analysis of our data pool was simply an attempt to resolve if 'routine' tests were in any draw uniquely sensitive to the tinnitus complaint.
The usefulness of BSERA
Furthermore, we questioned the usefulness of BSERA as a differential diagnostic tool in these cases. Since tinnitus is only a symptom, this inquire of cannot be approached in quite the same manner as the usefulness of BSERA, for instance, in the detection of acoustic tumors. BSER A has been useful in a wide range of cases for both adults and children. However, we do have tinnitus cases where normal BSERA was not confirmed by radiological studies.
We must ask whether or not the abnormal BSERA is a very early indication of a retro-cochlear lesion, or have we stumbled upon another unknown predicament to which BSERA is rather sensitive?
Especially in those few cases in which there is no hearing loss, and in which tinnitus was the only symptom, would this unknown quandary be related to that giving rise to the tinnitus?
One positive scrape is using BSERA as a tool to eye tinnitus arises from the nature of the tool itself, at least as we routinely employ it. A burly complement of Jewett waves is evident only a moderate-to-high levels of stimulation. We might quiz the tinnitus to actually be masked by the test stimulus in many cases. At levels rude enough for the stimulus to hide the tinnitus in loudness, only wave 5 is typically show and not as stable and well defined as at higher levels.
When hearing loss is enthusiastic, one is always working at a relatively high level compared to normal hearing thresholds. In the unique case of the patient with normal hearing and abnormal BSERA, we again must ask if a disease exists that can cause an alteration In the timing of neural signals transmitted in the central nervous system and yet not lead to certain hearing loss.
It might be postulated that, were we to look enough such cases, we might salvage a preponderance of tinnitus and thereby have an instance in which BSERA was selective for tinnitus. Comparisons between such cases and those with normal BSERA and no complaint of tinnitus could note most revealing.