Dr. Kirkpatrick - Independent Medical Opinion

I have had the opportunity to review the medical records and numerous documents that were sent to me and they appear to be his entire medical record since entering the RCMP in 1993. The Board sought guidance on three specific questions. Firstly - what permanent hearing disability does the claimant suffer from; secondly - does the claimant suffer disability resulting from tinnitus as a result of intermittent noise experienced while driving an RCMP car with the window open; and thirdly - is there other medical information that might be helpful to the Board in sorting out this claim.

The Appellant’s medical file since 1993 is voluminous and only a very small percentage of the documentation relates to tinnitus, which first appears in the documentation in about 2003, although it may have been there much longer than that. The tinnitus has been entirely on the left hand side, which is the side that he has a documented high frequency hearing loss on.

The first audiogram on record was one done in 1993 and shows a small high frequency notch in the left ear. It becomes much more pronounced in his 1998 audiogram, once again on the left side only with the greatest drop in hearing occurring at 4000 cycles. In the year 2000 it was less distinct but by 2003 there was a significant change with normal hearing up to 3000Hz, a drop off to a moderate sensori-neural hearing loss on the left hand side, but with excellent discrimination. Two years later in 2005 in the left ear he had normal hearing up to 3000Hz and then thereafter it sloped off to a moderately severe sensori-neural hearing loss. The audiologist giving an opinion said that "a hazardous noise typically affects both ears at the same time. The asymmetrical hearing loss in the left ear is not consistent with noise exposure". This quotation appears in a later judgment and is unfortunately misleading.

While it is true that occupational noise exposure usually is experienced in both ears simultaneously and so therefore the changes are symmetrical, there are numerous types of occupational noise exposure that result in asymmetrical exposure and therefore asymmetrical hearing changes. An example would be gunfire, use of industrial explosives such as Ramset, dentists who have the drill off to one side, or drummers who have a tendency to lose their hearing on the high hat side of their drum set.

Looking just at the audiogram from 2005, the characteristics of this hearing loss are indeed not typical of noise induced hearing loss. However, the previous audiograms do show a more typical noise notch which typically progresses to a pattern which is indistinguishable from other high frequency hearing losses. In this case the noise induced hearing loss is established by retrospectively looking at earlier audiograms. Taking all of his audiograms together, one can reasonably conclude that noise exposure was a factor in his hearing loss on the left.

The specific question though is was this caused by him driving around with his window down on the left hand side. There are references in the medical literature to hearing loss caused by driving an 18 wheel transport truck. On the other hand, race car drivers who have been studied have not been shown to have noise induced hearing loss. There is no useful information in the literature linking noise exposure to driving an automobile with the window down.

What is not part of the record is what sort of noise exposure he had experienced in his 46 years prior to entering the RCMP, as the 1993 audiogram starts to show a high frequency notch and the most typical noise notch appears just five years later in 1998.

Did his training include unprotected gun fire? Right handed rifle shooters tend to have asymmetrical hearing loss as they sight with their right eye, putting their left ear closer to the muzzle. Had he used weapons prior to his entry into the RCMP? The tinnitus was matched at 4000Hz at 50dBs in the left ear. Typically the tinnitus does match to the frequency of greatest loss, and 4000Hz is the typical maximal loss frequency in noise induced hearing loss. It should also be noted that there is no correlation between the measured loss and loudness and the self-reported severity; in other words tinnitus loudness and annoyance are not necessarily congruent.

In terms of ruling out a retrocochlear lesion, I see where a CT scan and an ABR were done. The ABR was normal. It might have been useful if distortion product otoacoustic emission levels were determined as they are frequently lower in individuals who have a peripheral auditory malfunction as the cause.

One also has to take into consideration the possible effects of some of the medications he has been on over this period of time. Altace and Celexa are medications that may either potentiate or partially alleviate tinnitus. It is also well established that sensory stimulation of other cranial nerves may potentiate tinnitus. This has been verified in many studies with respect to the trigeminal nerve. Inflammatory states involving the cervical spine and temporo-mandibular joint may have an exacerbating influence.

In conclusion:

1. Although the Appellant does indeed have a high frequency hearing loss in the left ear, it is occurring in a frequency outside the speech range so he is not experiencing a hearing related disability.
2. We can measure the degree of high frequency hearing loss and even the frequency and loudness of his tinnitus but there is such inter-individual difference in annoyance that it is not possible to say how much distress the tinnitus is causing him. There is however a paucity of evidence linking this to fluctuating noise arising from driving a police car with the window opened.
3. The only additional medical information that might be useful to your committee would be to have more detailed information about his noise exposure prior to 1993 and what, if any, noise exposure he may have had during weapons' training.

David A. Kirkpatrick, M.D., F.R.C.S.(C)
Head, Division of Otolaryngology -Head & Neck Surgery Department of Surgery
5820 University Ave., Room 3046A
Halifax, N.S. B3H 1V7
(902)473-2670
(902)473-3418FAX