Hearing Disorders After Auto Injury
This study sought to shed some light on the problem of hearing loss or dysfunction after rear-end collisions. The researchers started with 153 auto injury patients and 33 healthy control subjects, and performed audiograms on these subjects. The audiogram tests the ability of patients to recognize a pure tone. All patients were also asked about the presence of hearing problems. Of the 153 injury patients, 14% were found to have a hearing impairment "exceeding the 90th percentile of the ISO standards."
The researchers did not stop here, however. Next, they took a group of 33 patients with chronic auto injury pain with a duration of 3 years or more. These patients had no hearing loss or minor hearing impairment, as based on the audiogram. They tested these subjects and the controls using a "standardized speech-in-noise test." This test is more useful, as, "Speech recognition is a perceptive-cognitive function, in contrast to pure-tone hearing, which is a threshold identification function." The speech recognition test (SRN) is more sensitive, and can provide more information to the clinician.
After performing the SRN test, the authors found that "40% of this subgroup of patients with WAD [whiplash associated disorder] reported hearing problems. As many as 30% of the patients with [auto injuries] had an abnormal SRN test result, as against 5% of the controls. Significant relations were found between the SRN test and self-assessed hearing loss..." The authors propose a number of explanations as to how whiplash injuries can cause hearing dysfunction:
- "The trauma might cause lesions other than the neck injury affecting the auditory system. Subliminal injury of the cochlea, which is so delicate that conventional tests cannot detect it, is quite possible. Lesions affecting the central auditory system, from the brainstem to the temporal lobe cortex, are also conceivable..." although less likely.
- The hearing problem may be a "auditory stress disorder." "Most patients under stress have increased tension of the neck muscles, as have patients with WAD."
- "A reflexogenic disturbance from the neck via divergent afferent proprioceptive activity to the central auditory nervous system might be an alternative explanation. Some support for this theory is the single-photon emision computed tomography (SPECT) results by Otte et al. this group found parieto-occipital hypoperfusion in a group of patients with WAD and interpreted it as caused by activation of nociceptive afferents from the upper cervical spine, sicne a group of patients with non-traumatic chronic neck pain also showed parieto-occipital hypoperfusion."
No matter what the mechanism of injury, this study demonstrates that the SRN is more accurate at uncovering hearing problems than a simple audiogram, and that a significant percentage of auto injury patients show signs of hearing dysfunction.
Tjell C, Tenenbaum A, Rosenhall U. Auditory function in whiplash-associated disorders. Scandinavian Audiology 1999;28:203-209.