Okay, let's tackle this question. The patient is a 45-year-old hypertensive male with sudden severe headache, vomiting, and neck stiffness. No focal neurological deficits. CT scan shows blood in the Sylvian fissure. Hmm, so the key here is to figure out the diagnosis based on these findings.

First, the sudden onset of severe headache is classic for subarachnoid hemorrhage (SAH), especially with neck stiffness and vomiting. The CT showing blood in the Sylvian fissure makes me think of a specific type of aneurysm. The Sylvian fissure is a cleft in the brain, so maybe a carotid artery aneurysm? Wait, the middle cerebral artery (MCA) is in the Sylvian fissure. If there's a bleed there, it's likely from an MCA aneurysm or maybe a ruptured MCA.

But wait, the patient is hypertensive. Hypertension is a risk factor for aneurysms, including berry aneurysms. Subarachnoid hemorrhage is the hallmark of a ruptured berry aneurysm. The location in the Sylvian fissure points to the MCA territory. Alternatively, could it be a cerebral venous sinus thrombosis? No, that usually presents with different signs, like papilledema. Or maybe an intracerebral hemorrhage? But the CT shows blood in the subarachnoid space (Sylvian fissure), not within the brain parenchyma. So SAH is more likely.

Other differentials: Traumatic SAH? The presentation is acute, but the question doesn't mention trauma. Hemorrhagic stroke in the MCA territory would have focal deficits, but the patient has none. So SAH from an aneurysm is the probable diagnosis. The correct answer is probably SAH due to ruptured MCA aneurysm. Let me check the options again. The options aren't listed, but the correct answer is likely subarachnoid hemorrhage, specifically from a middle cerebral artery aneurysm. The CT finding of blood in the Sylvian fissure is a key clue here. The absence of focal deficits suggests the hemorrhage is in the subarachnoid space rather than intraparenchymal. So the answer is subarachnoid hemorrhage with a specific aneurysm location.

**Core Concept**
The clinical scenario and CT findings point to **subarachnoid hemorrhage (SAH)**, typically caused by a ruptured **berry aneurysm** in the **circle of Willis**. Blood in the **Sylvian fissure** specifically suggests a **middle cerebral artery (MCA) aneurysm**, as this region is anatomically adjacent to the MCA.

**Why the Correct Answer is Right**
The combination of sudden severe headache ("thunderclap"), vomiting, neck stiffness, and CT evidence of blood in the Sylvian fissure is classic for SAH. The **Sylvian fissure** is a key anatomical landmark where **MCA aneurysms** often bleed, leading to blood accumulation in the subarachnoid space. Hypertension increases the risk of aneurysm formation and rupture. No focal deficits suggest the hemorrhage is subarachnoid rather than

✓ Correct Answer: B. Ruptured aneurysm