<s>[INST] context: SAH- Thunder clap headache Cause- Rupture of berry's aneurysm If at post. communicating aery rupture-Involves oculomotor Nerve -So, Dilated pupils -Meningitis - Headache + fever + Nuchal rigidity -Brainstem encephalitis- Altered sensorium autonomic insufficiency -Acute ischemia of Brain/ Stroke - Aletred sensorium Quadri/ Para/ Hemiplegia. Prodromal symptoms suggest the location of a progressively enlarging unruptured aneurysm. A third cranial nerve palsy, paicularly when associated with pupillary dilation, loss of ipsilateral (but retained contralateral) light reflex, and focal pain above or behind the eye, may occur with an expanding aneurysm at the junction of the posterior communicating aery and the internal carotid aery. A sixth nerve palsy may indicate an aneurysm in the cavernous sinus, and visual field defects can occur with an expanding supraclinoid carotid or anterior cerebral aery (ACA) aneurysm. Occipital and posterior cervical pain may signal a posterior inferior cerebellar aery or anterior inferior cerebellar aery aneurysm ). Pain in or behind the eye and in the low temple can occur with an expanding MCA aneurysm. Thunderclap headache is a variant of migraine that simulates an SAH. Before concluding that a patient with sudden, severe headache has thunderclap migraine, a definitive workup for aneurysm or other intracranial pathology is required. [/INST] question: A patient presented with sudden onset on thunderclap headache & dilated pupils. Finding are consistent with: | options: A: Meningitis B: Brain stem encephalitis C: Acute ischemia of midbrain D: Acute aneurismal hemorrhage | answer: D </s>