WORKPLACE SAFETY AND INSURANCE APPEALS TRIBUNAL DECISION NO. 107/06

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1 WORKPLACE SAFETY AND INSURANCE APPEALS TRIBUNAL DECISION NO. 107/06 BEFORE: L. Gehrke : Vice-Chair HEARING: December 7, 2005 at Thunder Bay Oral Post-Hearing activity completed on September 13, 2006 DATE OF DECISION: November 7, 2006 NEUTRAL CITATION: 2006 ONWSIAT 2508 DECISION UNDER APPEAL: WSIB ARO decision dated 18/03/2004 APPEARANCES: For the worker: For the employer: Interpreter: J. Ranger, Consultant C. Nichols, Office of the Employer Adviser none /NAME/LANGUAGE Workplace Safety and Insurance Appeals Tribunal Tribunal d appel de la sécurité professionnelle et de l assurance contre les accidents du travail 505 University Avenue 7 th Floor 505, avenue University, 7 e étage Toronto ON M5G 2P2 Toronto ON M5G 2P2

2 Decision No. 107/06 REASONS (i) Introduction [1] The worker appeals the Appeals Resolution Officer s denial of entitlement for carpal tunnel syndrome, which she claims resulted from her duties in a hospital kitchen as a cook and a cook aide. [2] In Interim Decision No. 107/06I, I set out the background facts, including the worker s medical history and her job duties. I also set out questions to be put to a Tribunal-appointed medical assessor. As well, some additional information was gathered from the Board and from the worker s treating specialist. The medical assessor, Professor Peter Ashby, a specialist in neurology, has returned his report, and the parties have been given an opportunity to make final written submissions. This is my final decision on the worker s entitlement for carpal tunnel syndrome. [3] Having reviewed Dr. Ashby s report in the context of the other file information and the worker s testimony, I accept Dr. Ashby s opinion that the worker s job duties did not contribute to her carpal tunnel syndrome. As a result, I am not persuaded on a balance of probabilities that the worker s diagnosed condition of carpal tunnel syndrome resulted from her job duties. My reasons follow. (ii) Analysis (a) The legal test for determining whether there is a causal relationship between the work and the injury [4] It is a well-accepted principle at common law and in workers compensation law that the causal relationship between the work and the injury (in a compensation situation) is that of significant or material contribution. The issue to be addressed is whether the work contributed in a significant or material way to the development of the medical condition of carpal tunnel syndrome in this worker. A material contribution need not be the sole contribution, but must be more than a minimal contribution. Causation need not be determined with scientific precision. Medical experts ordinarily determine causation in terms of certainties, but the law requires a lesser standard. It is the function of the trier of fact, not the medical witnesses to make a legal determination of the question of causation, using a robust and pragmatic approach, where there is medical uncertainty with respect to causation. Reasonable inferences may be made from the primary facts of the case. Causation is determined on a balance of probabilities, or applying the benefit of the doubt where the evidence is equally weighted. However, a finding of causation may not be made based on mere speculation or evidence of a possibility, rather than a probability. 1 [5] Dr. Ashby confirmed the diagnosis of carpal tunnel syndrome, and discussed the possible causes of that condition. Dr. Ashby concluded that there were no specific medical conditions, such as hypothyroidism, that could contribute to the worker s carpal tunnel syndrome. 1 See the judgments of the Supreme Court of Canada in Snell v. Farrell, [1990] 2 S.C.R. 311, [1990] S.C.J. No. 73; Laferriere v. Lawson [1991] 1 S.C.R. 541 per Gonthier J.

3 Page: 2 Decision No. 107/06 Dr. Ashby also concluded the available evidence suggests that the worker s duties did not contribute. In regard to these conclusions, Dr. Ashby wrote: 3) Most cases of carpal tunnel syndrome are not related to a specific medical cause In the majority of cases of carpal tunnel syndrome, none of the above causes can be identified and the condition is said to be idiopathic (i.e. to have no known cause). Idiopathic carpal tunnel syndrome is common (average prevalence about 1-3% of the population), is more common in women than men (1.4 to 7 times more common), and, in women, is most common in those who are between 45 and 54 years of age. Thus the carpal tunnel syndrome in this worker could be idiopathic. 4) Can carpal tunnel syndrome be work related? Idiopathic carpal tunnel syndrome is so common that it is difficult to determine whether someone s work contributes to the condition. For example, Nathan et al (2005) followed 471 workers from 1984 to 2002 and found that, only female gender and greater relative weight were associated with the occurrence of carpal tunnel syndrome during follow up and that work place demands appear to bear an uncertain relationship to carpal tunnel syndrome. Gell et al (2005) followed 432 workers over a 5-year period. The predictors for the development of carpal tunnel syndrome included changes in nerve conduction at the initial assessment that suggested that a narrow tunnel was already present in those who later developed symptoms. But carpal tunnel syndrome can be related to work. Rossignol et al (1997) found that the rate of surgery for carpal tunnel syndrome in the general population was 0.9% while in manual workers it was 1.9% and Silverstein et al (1987) found that the prevalence of carpal tunnel syndrome in workers in low force low repetitive jobs was 0.6% while in high force repetitive jobs it was 5.6%. Stock (1991) reviewed studies of carpal tunnel syndrome and concluded that there was a causal relationship between repetitive, forceful work and carpal tunnel syndrome. Similarly, Hagberg et al 1992 concluded that repetitive forceful gripping is probably a risk factor for carpal tunnel syndrome and Roquelaire et al (1997) added that lack of breaks, change of task, or job rotation were additional factors. The present evidence, therefore, suggests that only repetitive forceful work is associated with carpal tunnel syndrome. Claims that light work gave rise to work-related carpal tunnel syndrome are probably unjustified. Derebery (2006) in Work-related carpal tunnel syndrome: the facts and the myths suggests that work-related carpal tunnel syndrome has become a cultural concept that has grown out of proportion to its medical justification. 5) It is important to recognize that timing of the symptoms is not related to the cause of carpal tunnel syndrome. The symptoms of idiopathic carpal tunnel syndrome are often worse at night, or when driving a car or holding a hair dryer. It should not be concluded that sleeping, driving or drying hair causes narrowing of the carpal tunnel; rather that those particular postures transiently reduce the available space in the carpal tunnel giving rise to symptoms in susceptible persons. Thus while the worker had symptoms on the job, for example while holding a mop, it does not follow the work contributed to the narrowing of the canal. 6) The worker s job The worker was employed as a part time cook or cook aide at the [employer s] Hospital from 1994 to 2003 (and as a housekeeping aide thereafter). The hours of work recorded by her supervisor were between 16 and 22 hours per week (or 3 to4 hours a day for a

4 Page: 3 Decision No. 107/06 five day week) for the years 1998 to There was no major increase in the work hours in the period prior to May 2002 when the symptoms began. The tasks she had to carry out are listed in detail in sections 8,9,13,14 of the decision 107/06I (23 March 2006) and will not be repeated here. They were quite varied and included meal preparation, moving pots, washing dishes, mopping floors, loading trays (weighing 10 lbs) feeding long term patients. These tasks were reviewed by the [WSIB] ergonomist, Malcolm Sutherland (9 March 2004), who concluded that the occupation had a low force demand and low level of repetitiveness. As such a significant or direct link to occupational cause cannot be attributed. Thus the job did not appear to involve the repetitive forceful work that has been linked to the development of the carpal tunnel syndrome. 7) Prognosis of carpal tunnel syndrome Idiopathic carpal tunnel syndrome may recover spontaneously, be helped by splinting and be permanently cured by carpal tunnel decompression. Properly treated there should be no long term disability. [6] Dr. Ashby sets out persuasive reasons for concluding that carpal tunnel syndrome can be related to work only where there is repetitive forceful work, such as repetitive forceful gripping. In this case, there is no doubt that the worker used her hands a lot in her work. However, the issue, from a causation viewpoint, is whether her work involved repetitive forceful use of her hands. [7] The worker was employed from 1994 to 2003 as a part time cook and cook aide in a hospital, with responsibility for about 17 patients, and thereafter as a housekeeping aide. Most of the time, according to her testimony, she was a cook aide. Her hours of work, recorded by her supervisor, were from 16 to 22 hours per week, working 3 or 4 hours per day, for the years 1998 to Her symptoms of carpal tunnel syndrome first appeared, according to the record, in May [8] The Board s ergonomist, M. Sutherland, concluded based on the description of her job duties, which the worker confirmed in her testimony, that her tasks were varied rather than repetitive, and involved low force rather than high force. Mr. Sutherland found that her wrist positions were varied, to perform a variety of duties, not static, or required to perform identical tasks in short cycles, and that the occupation described presented a bilateral upper extremity requirement with a low force demand and a low level of repetitiveness. I accept this assessment of the worker s job duties as consistent with how her job is described in the file documents and in her testimony. I find that while she certainly used her hands almost constantly during her work, her tasks were varied and were not repetitively forceful. [9] Having accepted that the worker s job duties did not involve repetitive, forceful use of the hands, I am unable to conclude on a balance of probabilities that the worker s job duties were a significant contributing factor to the development of her carpal tunnel syndrome. The fact that she was able to work from 1994 to 2002 in the same duties without apparent problems is more consistent with an idiopathic condition, as described by Dr. Ashby. The worker is a woman and the onset of her condition occurred between the age of 45 and 54, both of which factors are consistent with idiopathic carpal tunnel syndrome.

5 Page: 4 Decision No. 107/06 [10] Dr. T. Wilson, who performed the worker s carpal tunnel surgery, reported that it was her opinion that [the worker s] carpal tunnel syndrome is not likely related to her thyroid disease but rather to repetitive tasks that she does at work. I based this on the fact that she has no myxedema or signs of peripheral swelling which would have led to the carpal tunnel syndrome. Dr. Ashby is in agreement with Dr. Wilson that the worker s thyroid disease is not a factor, since myxedema does not occur where the thyroid condition is treated. However, Dr. Ashby also explains cogently why the worker s carpal tunnel syndrome could be idiopathic in nature, and is not related to her work because her work did not involve repetitive forceful use of the hands. Dr. Wilson s opinion is based upon an incorrect assumption regarding the repetitive forceful nature of the worker s job duties, and does not consider the possibility of idiopathic carpal tunnel syndrome. I find Dr. Ashby s opinion to be a more thorough consideration of the factors that may be involved in the development of the worker s carpal tunnel syndrome. [11] The worker s representative has provided another decision granting entitlement for carpal tunnel syndrome to a kitchen worker in a large hospital. I would only comment that each case must be decided on its specific facts, and rarely are the facts in two cases exactly alike. [12] The factual issue in this case was whether the worker was doing forceful, repetitive work in her employment. On the evidence before me, I am unable to conclude that her work was both repetitive and forceful. I therefore conclude that the causal link between her work and the development of carpal tunnel syndrome has not been established on a balance of probabilities. [13] Nor is this a case where the benefit of the doubt applies, because in my view the factors of gender and age in favour of idiopathic carpal tunnel syndrome outweigh the factors in favour of work-related carpal tunnel syndrome.

6 Page: 5 Decision No. 107/06 DISPOSITION [14] The worker s appeal is denied. DATED: November 7, 2006 SIGNED: L. Gehrke