A 35-year-old nondiabetic, nonhypeensive individual to casualty with a sudden bursting headache and altered sensorium. What is the most likely diagnosis?
**Core Concept**
The sudden onset of a bursting headache and altered sensorium in a nondiabetic, nonhypertensive individual suggests a vascular cause of the symptoms, likely related to a rupture or hemorrhage in the brain.
**Why the Correct Answer is Right**
The correct diagnosis is a subarachnoid hemorrhage (SAH), which is often caused by the rupture of an aneurysm in the cerebral arteries. This leads to bleeding into the subarachnoid space, causing sudden onset of severe headache, often described as a bursting or thunderclap headache, and altered sensorium due to increased intracranial pressure and potential brainstem compression. The lack of diabetes and hypertension makes atherosclerotic aneurysm less likely, but other causes such as arteriovenous malformation (AVM) or mycotic aneurysm cannot be ruled out.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it is less likely to cause a sudden onset of symptoms. A brain tumor may present with a gradual increase in symptoms over weeks or months.
**Option B:** This option is incorrect as it is more commonly associated with chronic symptoms such as seizures, cognitive decline, and focal neurological deficits.
**Option C:** This option is incorrect as it is more commonly associated with a history of trauma, hypertension, or atherosclerosis.
**Clinical Pearl / High-Yield Fact**
A sudden, severe headache described as a "bursting" or "thunderclap" headache is highly suggestive of a subarachnoid hemorrhage.
**Correct Answer:** C. Subarachnoid hemorrhage.