Diagnostic strategy in subarachnoid hemorrhage

1. Big picture

Subarachnoid hemorrhage, SAH, is a neurological emergency. Diagnosis must be fast because the patient may deteriorate from rebleeding, hydrocephalus, raised intracranial pressure, vasospasm, delayed cerebral ischemia, arrhythmia, or herniation.

The diagnostic strategy has two separate goals:

1. Confirm that subarachnoid hemorrhage is present

2. Find the bleeding source, usually a ruptured intracranial aneurysm

The key exam sentence:

**Suspected SAH → urgent non-contrast cranial CT first. If CT is negative but clinical suspicion remains, do lumbar puncture. After SAH is confirmed, identify the source with CT angiography and/or digital subtraction angi