Claim dismissed where probable cause of unrecognised surgical complication not identified

Collyer v Mid-Essex Hospital Services NHS Trust [2019]

Kennedys successfully defended the Trust in this unique case where the claimant suffered a previously unreported surgical complication. Despite experts advancing a number of explanations for the injury, the court could not identify any mechanism as a probable cause.


The claimant underwent lifesaving laryngectomy to successfully treat cancer but suffered a never before reported complication of bilateral hypoglossal (tongue) nerve palsy. As a result, the claimant lost nearly all tongue function, speech and ability to swallow.

The initial evidence of the claimant’s expert was that if the onset of the claimant’s tongue palsy was immediate there had been negligent cutting of both nerves by the surgeon or incorporation of the nerves into closing sutures. At trial, there was significant disagreement on the facts as to when the claimant’s tongue palsy first set in. Further, the claimant’s expert sought to advance clarifying evidence during trial that partial (as opposed to total) resection of the nerves could still have resulted in the pattern of injury seen.

The experienced treating surgeon and his colleagues assisting during the operation, gave evidence that the procedure was performed standardly. The Trust’s expert opined that the claimant’s expert’s proposed mechanisms of injury were highly unlikely and there was no evidence of anything other than standard – acceptable - surgical technique applied. The Trust’s expert also posited the claimant’s injury was possible via the mechanism of inevitable traction applied on already vulnerable structures during the procedure. Ultimately, however, the Trust’s expert conceded that whilst this was a more probable causal mechanism than those proposed by the claimant’s expert, all the posited causal mechanisms were unlikely.


The Trust’s case was that it was not sufficient for the claimant to prove that the negligent cause (being one of many possible causes) is the most likely cause. Rather, the claimant had to go further in establishing the negligent mechanism is more likely than not to be the cause (following Rhesa Shipping Co S.A. v Edmunds and Fenton Insurance Co Ltd [1985] , and “the Popi M” & O’Connor v The Pennine Acute Hospitals NHS trust [2015].

In her judgment, Her Honour Judge Coe QC asserted that “medicine is not a precise science and there must be room for wholly unexpected result[s] notwithstanding appropriate surgical technique”. Whilst considering that “both experts were doing their best to assist the court and to try to find a logical explanation for the outcome of this surgery” HHJ Coe QC concluded that there was a lack of evidence from either party that would permit her to find the cause for the claimant’s injury on the balance of probabilities. Accordingly, no cause (let alone negligent) could be established and the claim was dismissed.


Cause of injury can frequently be unclear in clinical negligence claims with experts advancing theoretical explanations of different causal mechanisms. Some causal mechanisms will, inevitably, be more likely than others. But this does not mean those ‘more likely’ explanations will be found to be ‘more likely than not’ by the court (which, as in this case, will lead to those claims failing). We recommend parties should seek - early on - to establish realistic prospects of whether experts’ proposed causal mechanisms will be accepted as ‘more likely than not’.

Mid Essex Hospital Services NHS Trust recently merged to create Mid and South Essex NHS Foundation Trust.

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