Establishing probable cause in cerebral palsyBMJ 2000; 320 doi: https://doi.org/10.1136/bmj.320.7241.1075/a (Published 15 April 2000) Cite this as: BMJ 2000;320:1075
How much certainty is enough?
- Peter Dear, consultant in neonatal medicine,
- Simon Newell, consultant in neonatal medicine
- St James's University Hospital, Leeds LS9 7TF
- Alder Hey Children's Hospital, Liverpool L12 2AP
- King's College Hospital, London SE5 9RS
- Department of Obstetrics and Gynaecology, University of Adelaide Women's and Children's Hospital, North Adelaide, South Australia 5006, Australia
EDITOR—The thesis set out by Little in 1862 that cerebral palsy was primarily due to perinatal cerebral injury did not meet with approval from the London Obstetrical Society—it was an obvious conflict of interests.1 Almost 14 decades later the echoes of those opposing voices still resonate, most recently in a statement from a group calling itself the International Cerebral Palsy Task Force.2 This statement makes some useful points, but there are aspects that need further debate.
One is the need to recognise that it is usually possible to form a view on what caused cerebral palsy only in probabilistic terms. The question then is, how much certainty is enough? In the medicolegal context the answer is clear—more than 50% certainty (that is, P<0.5). It is irrelevant that birth asphyxia causes cerebral palsy rarely and that cerebral palsy is due to birth asphyxia rarely, as long as it is accepted that cerebral palsy is caused by birth asphyxia sometimes. In that case, when confronted with a case of cerebral palsy that could be due to birth asphyxia and in which there is evidence of birth asphyxia of potentially damaging severity, the relevant question to ask is, are these events probably causally related or are they probably coincidental? The answer is that they are more likely to be causally related, as long as no better explanation for the …