When work and MS are on collision course

Expert evidence is critical in a case where a sufferer of Multiple Sclerosis is seeking to prove an accident at work triggered the disease, says Breige MurphyMultiple Sclerosis is a disease of which most of us are aware, and which we know to have devastating effects on sufferers and their families.

A diagnosis of MS can mean the end of employment, and if an accident at work leads to a diagnosis, it is understandable that an employee might seek to make a claim against the employer.

Until recently, scientific and judicial opinion has been divided as to whether MS is a latent pre-existing condition which can be triggered by trauma, or, alternatively, is present in susceptible people, and trauma is coincidental to the diagnosis of the disease and not a precipitating factor.

A recent case - Perry v The Post Office (18 October 2001, unreported) - has, in reliance on scientific evidence, found that the latter view has most merit.Accident circumstancesThe claimant was employed as a postwoman by the defendant and was injured in an accident at work on 18 March 1993.

Although there was some dispute as to the circumstances of the accident, essentially, the claimant walked from the sorting office to a loading platform and to reach the loading platform, had to pass through double doors.

When she pushed the doors open and passed through, she tripped over a post-bag which had been left on the floor.

She fell on to the ground.

She attended her GP that evening, who noted: 'On examination, tender over the left lumbar lower thoracic area.

No visual marks.

Good range of spinal movement.

Diagnosis muscle strain/spasm.

Also hit left side of head.

On examination, no abnormality detected.'She was treated with analgesics and was off work for five weeks.She returned to work on 19 April 1993, but her backache persisted and, with the heaviness in her legs, she had difficulty in walking.

After three days, she had to stop work and never returned.The claimant's difficulty in walking worsened and in November 1993, she was found to have mild spastic paraparesis with a spastic gait and disturbance of balance; it was recognised that this could not be related to the back injury.

Her neurological condition deteriorated and she was diagnosed as suffering from MS in May 1994.

She was medically retired on 18 June 1994.The issue of liability was resolved by consent.

The claimant accepted a deduction of 20% for contributory negligence.

Judgment on liability with an apportionment of liability of 80:20 in her favour was entered on 28 April 1997.Causation of injuriesIt was the claimant's case that the trauma sustained in the index accident triggered her pre-existing non-symptomatic MS.

As liability had been resolved, on 6 April 2001, Master Eyre ordered that there be a preliminary trial on the issue of causation with a view to answering several questions:l What were the exact nature and extent of the injuries sustained by the claimant in the accident on 18 March 1993?l Is it the case that trauma can provoke MS at all?l How severe must that trauma be?l On the facts of this particular case, did the injuries sustained by the claimant trigger symptoms of MS?l If the answer to the preceding question is yes, what have been and are likely to be the nature, extent and duration of those symptoms attributable to those injuries?There were two diametrically opposed bodies of medical opinion.

The claimant's was promulgated by Professor Peter Behan, former professor of neurology at Glasgow University.

The defendants were represented by Professor Alastair Compston of the neurology unit of Cambridge University.Prof Behan maintained that trauma may aggravate and precipitate MS in people who have a tendency to develop the disease, so trauma can convert an asymptomatic latent state into a malignant form which sets in train the progression of the disease.

However, Prof Compston maintained that the process leading to the development of MS affects genetically susceptible individuals and is triggered in childhood or adolescence, so trauma is merely a chance independent event.

He said that MS is an auto-immune disease.The judgmentMr Justice Griffiths Williams adopted the reasoning of the Lord President in Dingley v Chief Constable of Strathclyde Police (5 March 1998) who said, for the claimant to succeed, she '...requires to establish two things on the balance of probabilities: first, that the onset of symptomatic MS can be triggered by an injury of the type which [the claimant] suffered in the accident; secondly, that not only could [the claimant's] injury have triggered the onset of her condition, but it actually did so'.

Subsequent case law emphasised that it was not for the judge to resolve the medical dispute to the standard of scientific proof, but rather he had to determine the issues on the evidence of the parties, on the balance of probabilities.The judge took 'a less than favourable view' of Prof Behan as a witness.

He had overstated and mis-stated certain issues, was dismissive of the views of others and his own research was not statistically tested.

He also insisted that the trauma suffered by the claimant had to be to her spinal cord, yet this was inconsistent with other parts of his evidence where neck injury was assumed.

The judge held that 'Prof Behan demonstrated a capacity to use his interpretation of the evidence to suit his purposes which conflicts with his duty to the court as an expert witness'.The judge preferred Prof Compston's evidence.

He found that Prof Compston's explanation of the likely onset of MS was more credible than that of Prof Behan, not least because Prof Compston accepted 'the uncertainties of his own research'.He accepted the opinion of Prof Compston that on the balance of probabilities, the process of demyelisation had started before and independently of the accident.

In addition, as the claimant's expert, Prof Behan concurred with this assessment, the judge was not required to investigate the link between trauma and MS any further because it was accepted by both experts that the claimant was suffering from the condition at the time of the index accident.

Therefore, he followed that the trauma could not have 'triggered' the condition.Judgment was delivered on 18 October 2001 and the findings were:l The claimant suffered no more than a minor back injury in the accident on 18 March 1993, and this was unrelated to her MS;l On the evidence in this case, the judge was unable to conclude, on the balance of probabilities, that trauma can provoke MS.This interesting case leaves us with three points worthy of note:l There is now authority, and persuasive authority too, for the proposition that trauma cannot trigger MS.

l It is for the claimant to prove the cause of the damage on the balance of probabilities.l Expert evidence is vital in this type of case and should be carefully scrutinised at the pre-proceedings stage to avoid years of distress for the claimant and a substantial bill for legal costs.Breige Murphy is an associate at Bristol-based Osborne Clarke's regulatory unit