How neurologists assess causation when stroke thrombolysis is missed due to A&E triage delays

In stroke litigation, the window for effective thrombolysis is narrow—and when A&E triage delays prevent timely treatment, the question of causation becomes central to the claim. For solicitors handling such cases, understanding how a neurology expert assesses causation in the context of missed thrombolysis is essential to building a robust legal argument.

This article explains the clinical and medico-legal framework neurologists apply when evaluating whether a delayed diagnosis caused a worse neurological outcome, and what legal practitioners should expect from expert evidence.

The critical 4.5-hour thrombolysis window

Intravenous thrombolysis with alteplase is the standard emergency treatment for acute ischaemic stroke. Current NICE guidance recommends administration within 4.5 hours of symptom onset, with earlier treatment associated with better outcomes. After this window, the risk of intracranial haemorrhage increases and efficacy declines.

Neurologists assess the exact time of symptom onset, not arrival at hospital, when evaluating eligibility. This distinction is often pivotal in causation arguments where triage delays push patients beyond the therapeutic window.

Clinical assessment of causation in delayed thrombolysis cases

In neurology medico-legal practice, causation is assessed by comparing the likely outcome with timely thrombolysis against the actual outcome. This involves:

• Review of imaging (CT or MRI) to confirm ischaemic stroke and exclude haemorrhage
• Assessment of NIHSS (National Institutes of Health Stroke Scale) scores at baseline and discharge
• Consideration of ASPECTS (Alberta Stroke Programme Early CT Score) to quantify salvageable brain tissue
• Evaluation of time from symptom onset to hospital arrival, and from arrival to assessment

Neurologists may also consider whether extended window eligibility existed (up to 9 hours with perfusion imaging) and whether such imaging was performed or available.

Legal tests for causation in stroke delay claims

In clinical negligence claims, the test for causation is but for the breach, would the claimant have suffered the damage? In stroke thrombolysis cases, this often requires the expert to opine that timely treatment would have materially improved the outcome—not necessarily that the stroke would have been prevented entirely.

The Bolitho test applies where causation is disputed: the expert’s opinion must be logically defensible and based on sound reasoning. In stroke cases, this includes consideration of stroke mimics, diagnostic uncertainty, and the standard of care expected of A&E clinicians.

Common pitfalls in causation assessment

Several issues commonly arise in stroke delay litigation:

Misinterpretation of time windows

Some reports focus on door-to-needle time rather than symptom-to-needle time. Neurologists must clarify that the critical period begins at symptom onset, not hospital arrival.

Overestimation of thrombolysis benefit

Experts must avoid overstating the likelihood of a good outcome with timely thrombolysis, particularly in large vessel occlusions where thrombectomy may be the more appropriate intervention.

Failure to consider stroke mimics

Not all suspected strokes are true ischaemic events. Neurologists must assess whether the diagnosis was correct and whether thrombolysis was appropriate, even if delayed.

The role of the neurology expert witness

A neurology expert witness in stroke delay claims provides opinion on:

• Whether thrombolysis was indicated and would have been beneficial
• Whether the delay fell below the standard of care
• The likely difference in outcome with timely treatment
• The accuracy of the initial diagnosis and appropriateness of management

The report must comply with CPR Part 35, addressing breach and causation separately, and stating the degree of certainty in probabilistic terms.

Practical guidance for solicitors

When instructing a neurology expert in stroke delay cases, consider the following:

• Provide full clinical records, including ambulance handover notes, triage documentation, and imaging reports
• Clarify the exact timeline of symptom onset, arrival, assessment, and treatment
• Ask the expert to comment on both breach and causation, and to distinguish between them clearly
• Consider whether a neuroradiologist should also be instructed for complex imaging interpretation
• Request opinion on whether thrombectomy was also a missed opportunity, particularly in large vessel occlusion

Early expert instruction can help identify whether the claim has merit before substantial costs are incurred, and can guide the scope of Part 35 questions.

Conclusion

In stroke thrombolysis delay claims, causation assessment requires careful integration of clinical timing, imaging findings, and outcome prediction. Neurologists must apply both medical expertise and legal principles to provide opinion that is robust under cross-examination. For solicitors, understanding this framework is key to effective case preparation and expert instruction.

Specialist neurological assessment from an experienced expert witness can be pivotal in cases involving causation, prognosis, or capacity.