G45.9 — Transient Ischaemic Attack

Denied

68M · investigation — MRI Brain with DWI

IncorrectHigh

Insurer Rationale

CT head is normal with no evidence of haemorrhage or acute infarction. Neurological symptoms have fully resolved within 24 hours, consistent with transient ischaemic attack. MRI is not indicated for confirmed TIA. Commence antiplatelet therapy and outpatient TIA clinic follow-up.

Clinical Contradiction

Insurer states

“CT head is normal and symptoms resolved, confirming TIA — MRI is not indicated”

Clinical evidence shows

CT cannot detect acute ischaemic infarction in the first 12 hours — only MRI with diffusion-weighted imaging can distinguish TIA from minor stroke with resolved symptoms

Patient risk

Up to 30% of patients labelled TIA have DWI-positive infarction requiring more aggressive secondary prevention

Reasoning Chain

CT head rules out haemorrhage but cannot detect early ischaemic infarction. Resolved symptoms do not exclude stroke — up to 30% of clinical TIAs show DWI-positive infarction on MRI. Without MRI, the patient may be undertreated for a minor stroke, missing the window for optimal secondary prevention and recurrence risk stratification.

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Reasoning Chain

Findings

Left-sided weakness (resolved), Slurred speech (resolved), Facial droop (resolved), Onset-to-resolution 45 minutes, AF on ECG

Differential

TIA (clinical diagnosis) vs Minor Ischaemic Stroke (not excluded)

Shared findings

Limb weakness, Speech problems, Facial weakness, Altered sensation

Discriminating investigation — DENIED

MRI Brain with DWI

Detects acute ischaemic infarction invisible on CT — the only way to distinguish TIA from minor stroke when symptoms have resolved

Verdict

Denial is clinically unsafe. A normal CT head does not exclude ischaemic stroke in the acute phase, and resolved symptoms do not confirm TIA. Denying MRI blocks the only investigation that can discriminate between these two diagnoses and determine the correct secondary prevention strategy.

Clinical Evidence

NICE Guideline NG128 — Stroke and transient ischaemic attack in over 16s

1.1 — Rapid specialist assessment

MRI with DWI is recommended for all patients with suspected TIA to detect infarction not visible on CT.

Royal College of Physicians National Clinical Guideline for Stroke (2023)

Imaging in TIA

DWI-MRI should be performed within 24 hours of symptom onset for suspected TIA to guide secondary prevention intensity.