Assessing Peripheral Nerve Injury: Distinguishing Iatrogenic Complications from Disease Progression

The Medico-Legal Challenge of Nerve Injury Attribution

In neurology medico-legal practice, determining whether a peripheral nerve deficit arose from a specific operative event or the natural history of an underlying disease is a fundamental requirement for assessing breach of duty and causation. This distinction is rarely binary, often requiring a granular analysis of pre-operative clinical records, electrophysiological baseline data, and the temporal proximity of symptoms to an intervention. Establishing a reliable causal link requires careful scrutiny of potential iatrogenic trauma to peripheral nerves within the context of the patient’s known comorbidities, such as diabetes, compression neuropathies, or chronic inflammatory conditions.

Clinical Assessment and Differential Diagnosis

To distinguish between iatrogenic damage and disease progression, the neurology expert must synthesise clinical history with objective diagnostic testing. Peripheral nerve injury following surgery may present with symptoms that mimic pre-existing pathology, such as focal weakness, sensory loss, or neuropathic pain. Experts consider: Dental Expert Witnesses’s guidance on nerve injury examines the same instruction questions in more depth.

• Temporal correlation: Evidence of immediate postoperative deficit versus the documentation of insidious progression prior to intervention.
• Anatomical localisation: Identifying whether the injury corresponds to the surgical field or follows a distribution inconsistent with the intervention.
• Electrophysiological baseline: Comparing pre-operative Nerve Conduction Studies (NCS) and Electromyography (EMG) with post-injury results to quantify change in nerve conduction velocity or amplitude.
• Secondary factors: Considering the role of non-surgical contributors, including patient positioning, tourniquet use, or systemic metabolic factors that may influence nerve fragility.

Where the presentation involves functional motor symptoms with inconsistent clinical signs, experts evaluate the consistency of findings relative to known neuroanatomical pathways to assist the court in assessing the clinical picture.

Applying Legal Tests to Neurological Causation

Under the Civil Procedure Rules (CPR) Part 35, the expert’s primary duty is to the court. In clinical negligence claims, the Bolam and Bolitho tests remain central to assessing whether the surgical technique was defensible. The Bolitho refinement clarifies that if a professional opinion is not capable of withstanding logical analysis, the court may conclude that it is not responsible or reasonable, even if supported by a body of clinical opinion.

Causation analysis often involves the ‘but-for’ test—determining whether, in the absence of the alleged breach (e.g., poor surgical technique or inadequate informed consent under Montgomery v Lanarkshire Health Board), the injury would still have occurred. This is particularly complex when dealing with pre-existing degenerative conditions where baseline function may have been declining independently of the surgery. Experts are expected to ground their opinions in available diagnostic evidence rather than speculative attribution.

The Role of the Expert Witness in Litigation

The expert witness provides the court with necessary insight into complex biological processes. Reports must clearly distinguish between facts, assumed facts, and clinical opinions. In cases where proceedings are advanced, the court may direct a discussion between experts under CPR 35.12 to narrow the issues and produce a joint statement. It is critical to distinguish this from the role of a single joint expert (SJE), who may be appointed by the court under CPR 35.7. Where an SJE is appointed, instructions should be provided in accordance with CPR 35.8, and the expert does not engage in a joint statement process with another expert, as they represent the sole source of expert evidence for the court.

Practical Considerations for Solicitors

When instructing a neurologist, the quality of the evidentiary brief is paramount. Solicitors should ensure the following documentation is secured early:

• Complete medical records, including pre-operative neurological assessments and baseline NCS/EMG reports.
• Anaesthetic charts, which provide essential context regarding patient positioning during the procedure.
• Discharge summaries and subsequent physiotherapy notes documenting the evolution of symptoms.

If the case involves potential capacity issues—for example, if the claimant’s cognitive status affects their ability to provide evidence or their future care needs—the expert must be qualified to apply the functional test of capacity under the Mental Capacity Act 2005. Reliable medico-legal outcomes depend on high-quality clinical evidence and strict adherence to the procedural requirements of the court. By focusing on objective data and maintaining professional independence, neurology experts provide the clarity required to assist the court in resolving complex claims.