Causation in stroke case not demonstrated: Choudhury v South Central Ambulance Service NHS Trust and Portsmouth Hospitals NHS Trust (High Court,13 May 2015—Cox J)

Introduction

On 16th March 2010 the claimant, then aged 42, suffered an ischaemic stroke. He developed “locked-in syndrome” due to infarction in the brain stem and cerebellum, secondary to basilar artery thrombosis. He is now virtually totally paralysed, doubly incontinent, and is fed through a PEG (Percutaneous Endoscopic Gastrostomy) tube. His ability to communicate is extremely limited and he is dependent on 24 hour nursing care. His life expectancy is markedly reduced.

On his behalf it was alleged that delays in taking him to hospital and in diagnosing his condition while there and providing the necessary treatment gave rise to the development of locked-in syndrome. In particular, it was maintained that failure promptly to start the claimant on Aspirin caused his deterioration. The trusts denied that such treatment would have resulted in a better outcome, although they admitted various breaches of duty as noted below.

Facts

The claimant was a generally fit, healthy, and active man. At around 01:00 on 16th March 2010, he began to feel seriously unwell and called an ambulance at 01:24. This arrived at 01:29. A paramedic noted raised respiratory rate, but a normal Glasgow Coma Scale (GCS) score and normal oxygen saturation. No formal diagnosis was recorded and the paramedic advised rehydration. At 03:11, Mr Choudhury telephoned the GP Out-of-Hours service. He explained that he was having problems breathing, was feeling sick and dizzy, and had vomited several times and passed out. The doctor advised by telephone that he should call 999 with a view to admission to hospital.

The claimant then called the ambulance service for the second time, at 03:20. An ambulance arrived at 03:27, but the attending paramedic did not take him to hospital, instead advising Mr Choudhury to sip fluids and go to bed.

The ambulance trust accepted that failure to take the claimant to hospital without delay following his second 999 call was a breach of duty.

At around 04:30 on 16 March, Mr Choudhury suffered a serious collapse. He was not discovered until lunchtime and was then taken to hospital, where he arrived at Accident and Emergency at 13:48.

He was assessed initially by a nurse and then by a doctor who ordered a CT scan. This was performed at 15:30, but was reported as showing no abnormality. The hospital trust admitted that this was incorrect, and that the scan in fact demonstrated an abnormal high density in the upper part of the basilar artery, consistent with acute thrombosis, and patchy low densities, consistent with nonhaemorrhagic infarctions in the cerebellar hemispheres.

A lumbar puncture at 22:30 was clear. However, overnight the claimant’s condition suddenly deteriorated further. At 02:30, his GCS had dropped to 6/15 and then to 3/15 by 04:00. He was admitted to intensive care, but the attending doctor was unable to make a diagnosis.

It was not until 08:20 on 18th March that a doctor considered that Mr Choudhury might be suffering from a “pontine locked-in type vascular event.” At 15:12 on the 18th, the claimant was examined by a consultant neurologist who correctly interpreted the CT as abnormal. He concluded that Mr Choudhury had suffered an infarct in the upper left cerebellum, and that he was suffering from locked-in syndrome. Aspirin was first given at this point.

The hospital trust admitted the following: delay in performing the CT scan; incorrectly interpreting the scan as normal; consequent delay in providing treatment with Aspirin; unnecessary performance of a lumbar puncture.

Causation

The parties agreed a chronology of the events which would have happened but for the negligence of both defendants:

The paramedic who arrived 03:27 on 16th March would have taken him to hospital;

The role of Aspirin in stroke prevention was to inhibit platelet stickiness and thereby to inhibit clot formation or propagation.

The claimant accepted that the serious collapse he suffered at 04:30 on 16th March could not have been prevented by either defendant. He also acknowledged that irreversible brain damage causing permanent disability would have been caused. However, he maintained that the locked-in syndrome would have been prevented had the defendants not been negligent, and that his present level of disability would have been lower.

Professor Brown, the claimant’s expert, considered that the most likely cause of Mr Choudhury’s basilar artery symptoms was embolism of thrombus from the vertebral artery. Dr Giallombardo, the trusts’ expert, agreed that the claimant had a recurrent stroke when a further embolism from the vertebral artery suddenly broke away in the early hours of 17th March and added to the thrombus in the basilar artery, “back-filling” the artery completely and blocking the remaining branches. The judge found, on the balance of probabilities, that this occurred.

While stroke is the third most common cause of death and the most common cause of disability in the UK adult population, the experts agreed that basilar artery thrombosis was relatively uncommon, accounting for only 1% of all strokes. Moreover, it has a different pathology from other strokes, with a tendency to show stepwise deterioration of the kind that occurred in this case. Given this propensity, the normal approach toward a mild stroke, namely that it will remain mild and the patient will not deteriorate, does not apply. The prognosis for patients with basilar artery thrombosis is worse than for those afflicted by other strokes. Both experts agreed that the further sudden deterioration suffered by the claimant in the early hours of 17th March was entirely consistent with what is known of the natural history of this relatively rare condition.

The experts, however, were at odds as to the effect of the admitted negligence. Professor Brown, for the claimant, was an eminent authority on stroke and a highly experienced expert witness. He is Professor of Stroke Medicine at the Institute of Neurology, University College London.

Dr Giallombardo is consultant stroke and general physician at North Hampshire Hospital in Basingstoke and also the principal investigator in a number of multicentre trials supported by the UK Research network. His work has involved spending considerable time in accident and emergency assessing and treating stroke patients.

The judge considered that there was force in the criticism mounted by the defendants against Professor Brown that in his report he described a “devastating pontine infarction,” whereas in cross-examination he sought to rely on the fact that the CT scan showed that there had been no extensive damage to the brain at 15:30 on 18th March, stating that “the infarcts we could see developing were not extensive.”

Professor Brown considered that the lumbar puncture performed at 22:30 on 16th March was causative, at least in part, of the claimant’s subsequent deterioration and of additional, unnecessary brain damage. Dr Giallombardo believed there was no evidence that the puncture contributed in any way to the final outcome.

At the joint meeting of experts in October 2014, Professor Brown accepted that the claimant’s clinical progression could simply have been caused by the thrombosis, unrelated to the lumbar puncture.

Held: the lumbar puncture had no effect on the claimant’s condition or on his deterioration in the early hours of 17th March.

Professor Brown argued that the benefits of giving Aspirin should not be seen in isolation. For it to work, the patient should be in optimum condition, as Mr Choudhury should and would have been if he had been admitted to hospital by 04:00 on 16th March and treated appropriately.

Dr Giallombardo agreed that there was compelling evidence that organised stroke care can reduce mortality and severe disability. He also accepted that early use of Aspirin can, in general, increase a patient’s chances of surviving a stroke with better functional outcome. However, he disagreed that the research relied upon by Professor Brown assisted the claimant in this case.

Professor Brown referred to a report entitled “Treatment and Outcomes of Acute Basilar Artery Occlusion in the Basilar Artery International Co-Operation Study (BASICS),” published in The Lancet in August 2009. Dr Giallombardo considered that BASICS, as an observational study, was not designed to consider the efficacy of different forms of treatment as against no treatment at all, or as against delayed treatment. Further, as the authors stated, “the time to treatment in patients treated only with AT [Aspirin or Heparin] was not recorded accurately.” He relied upon the findings of two major randomised controlled stroke trials carried out in 1997, covering around 40,000 patients in total: the Chinese Stroke Trial and the International Stroke Trial. Neither of these trials was referred to by Professor Brown in his causation report. Dr Giallombardo considered both trials to show that early use of Aspirin prevented death or stroke recurrence by only 1%, when treated against the placebo group. In his report, Dr Giallombardo increased Mr Choudhury’s chances of a better outcome to 10% on the basis that intervention in patients with evolving symptoms, and optimal management, could be more efficacious, although he acknowledged that there was no specific scientific or statistical basis for this conclusion.

Discussion and conclusion

Deciding what, if any, conclusions could properly be drawn from the studies was no easy task. There was no doubt that basilar artery thrombosis was a rare condition and that therefore only relatively low numbers of patients were within the studies. For example, such patients accounted for only 1% of the Chinese study and 12% of the International study. However, BASICS was not concerned with the efficacy of Aspirin versus no Aspirin. It did not relate the outcomes for basilar artery thrombosis to their causes. On the other hand, the Chinese and International studies were clearly relevant. As an investigator himself in the International trial, it was inexplicable that Professor Brown failed to refer to it.

The Chinese and International studies were reviewed in 2015 by the Cochrane Collaboration, which is widely regarded as the gold standard in the assessment of randomised controlled trials. This review considered that studies were methodologically sound and that they had continuing relevance. The omission by Professor Brown was unsatisfactory, and his reference only to the BASICS findings was influenced by his strongly held personal views as to the general potency of Aspirin for patients with ischaemic stroke.

Professor Brown fairly accepted that, on the basis of the results obtained from the Chinese and International studies alone, it could not be said that giving Aspirin to patients with basilar artery thrombosis would, on the balance of probabilities, prevent their further deterioration.

It was important to keep in mind that BASICS was an observational study, aimed at comparing the efficacy of different types of treatment relative to each other. The figures reported did not provide a proper basis for proving, to the relevant civil standard and comparing like with like, that starting this claimant on Aspirin at 06:00 on 16th March would have prevented his further deterioration.

The claimant had not demonstrated, on the balance of probabilities, that if Aspirin and good stroke care had been provided to him in hospital between 06:00 on 16th March and 02:30 on 17th March, he would have avoided the further catastrophic deterioration and locked-in syndrome that occurred. Indeed, locked-in syndrome was the outcome for a large number of patients in the BASICS study, in the mild to moderate category, even though they had the benefit of antithrombotic therapy and good stroke management.

On all the evidence, the opinion of Dr Giallombardo was the more persuasive. Judgment would therefore be given in favour of the defendants on the issue of causation.

Michael Kent QC (instructed by Blake Lapthorn) appeared for the claimant. Sir Robert Francis QC and Katie Gollop (instructed by DAC Beachcroft) appeared for the defendants.

Comment

This was a very complex case from the perspective of causation. The fact that the defendants had admitted numerous breaches of duty meant that they entered the trial firmly on the back foot, but the judge nevertheless concluded that the evidence of their causation expert was the more persuasive. Inexplicably, the claimant’s expert had not referred to a major International study, to which he himself contributed, in his own report. Accordingly, even though the claimant’s expert was an extremely eminent Professor, whereas the trusts’ equivalent was a consultant at a general hospital, nevertheless the judge considered the latter’s conclusions from the scientific literature were more sound in relation to the facts of this case than were those of the Professor. It is understood, however, that those advising the claimant are proposing an appeal.

Learning points

It is possible to defend a claim successfully on the absence of causation even though numerous breaches of duty have been admitted.