What is the primary cause of neurological deterioration in patients after an initial subarachnoid hemorrhage (SAH)?

The main cause of neurological deterioration after an initial SAH is cerebral infarction due to arterial vasospasm. Key diagnostic features include new focal neurological deficits and changes in mental status, often occurring 3-14 days post-SAH. Clinical pearls include monitoring with transcranial Doppler ultrasound for early detection of vasospasm. A common pitfall is mistaking rebleeding for vasospasm; however, rebleeding typically presents with a sudden severe headache and rapid decline.