Missed Diagnosis of Subarachnoid Haemorrhage.

A 79-year-old woman presented with left retro-orbital pain, headache and blurred vision. Based on negative radiological tests, life-threatening conditions like subarachnoid haemorrhage (SAH) were ruled out and outpatient follow-up was planned. However, the patient returned to the hospital that night because of progressively declining consciousness and was diagnosed with SAH by head computed tomography. The diagnosis of SAH is often challenging, especially in cases with negative radiological results. We describe some strategies, other than radiological examination, for ruling out SAH, such as performing a lumbar puncture and repeating tests to take account of disease progression, and describe biases which can affect clinical decision-making. LEARNING POINTS A high diagnostic error rate highlights the difficulty in diagnosing subarachnoid haemorrhage (SAH).Headache together with oculomotor nerve palsy is an important symptom of SAH.If SAH is suspected, further diagnostic measures including lumber puncture are warranted.A strategy of repeating tests to take account of disease progression would also be effective.