Caveats for interpreting ‘normal’ imaging
| Diagnosis | Risks of missing the diagnosis |
|---|---|
| Subarachnoid haemorrhage (SAH) | Although only ∼2% of SAH patients SAH have a normal CT head scan initially, there are risks with a missed diagnosis: case fatality rate ∼50% and mean medicolegal cost of a claim for damages in SAH in the UK stands ∼£211 00022 |
| Ischaemic stroke | Plain film CT scan can be normal in initial stages, posterior circulation strokes are difficult to visualise on CT |
| Idiopathic intracranial hypertension | Imaging normal but potential for irreversible sight loss if not managed appropriately2 |
| Neuromuscular disorders | Initial presentation of both myasthenia gravis and Guillain–Barré syndrome may (in early phases) be misdiagnosed as a brain stem stroke or possible cord compression (mortality rate of 8.7 and 7.7% respectively in those patients requiring intensive care23) |
| Functional disorders | Risk is from delayed diagnosis, over-investigation and iatrogenic harm24 |