Circle of willis

• Age more than 50
• Family history of intracranial hemorrhage
• Aneurysms more than 10mm
• Uncontrolled hypertension

• Mitral valve prolapse and aortic regurgitation
• Hepatic cysts
• Colonic diverticula
• Abdominal wall and inguinal hernias

Sudden onset of severe occipital headache, with drowsiness, neck stiffness indicate that the patient has developed subarachnoid hemorrhage. Excluding head trauma, rupture of saccular aneurysm of circle of willis is the commonest cause of SAH. The three most common locations are the terminal internal carotid artery, middle cerebral artery (MCA) bifurcation, and top of the basilar artery. Vasospasm is the leading cause of morbidity and mortality following aneurysmal SAH. Treatment with nimodipine improves outcome, by preventing ischemic injury rather than reducing the risk of vasospasm.

The suboccipital triangle lies in the neck at the base of the skull. The suboccipital triangle is bounded by the inferior oblique, rectus major, and superior oblique muscles. The vertebral artery can be found within the suboccipital triangle, lying on the posterior arch of the atlas, lateral to the midline, typically at about the level of the lower portion of the ear lobe. Care should be taken in accessing the vessel, since the first cervical nerve lies between the vertebral artery and the posterior arch of the atlas.

• The anterior triangle of the neck  is in the anterior neck, and is bounded by the neck midline, the mandible, and the sternocleidomastoid muscle. The anterior triangle of the neck is subdivided into the muscular, carotid, submandibular, and submental triangles.
• The posterior triangle of the neck is on the side of the neck, and is bounded by the sternocleidomastoid muscle, trapezius, and the middle third of the clavicle.
• The submental triangle, also called the suprahyoid triangle, is found below the lower jaw, and is bounded by the hyoid bone and anterior bellies of the digastric muscles.

The suboccipital triangle lies in the neck at the base of the skull. The suboccipital triangle is bounded by the inferior oblique, rectus major, and superior oblique muscles. The vertebral artery can be found within the suboccipital triangle, lying on the posterior arch of the atlas, lateral to the midline, typically at about the level of the lower portion of the ear lobe. Care should be taken in accessing the vessel, since the first cervical nerve lies between the vertebral artery and the posterior arch of the atlas.

The circulus arteriosus (circle of Willis) is a large arterial anastomosis which unites the internal carotid and vertebrobasilar systems. It lies in the subarachnoid space within the deep interpeduncular cistern, and surrounds the optic chiasma, the infundibulum and other structures of the interpeduncular fossa.

The circulus arteriosus (circle of Willis) is a large arterial anastomosis which unites the internal carotid and vertebrobasilar systems. Anteriorly, the anterior cerebral arteries, which are derived from the internal carotid arteries, are joined by the small anterior communicating artery. Posteriorly, the two posterior cerebral arteries, which are formed by the division of the basilar artery, are joined to the ipsilateral internal carotid artery by a posterior communicating artery.

Answer is A (Rupture of circle of Willis aneurysm):

Most common cause of subarachnoid haemorrhage is ruptured saccular aneurysms.

Most common site of saccular aneurysms is the anterior circulation on the circle of Willis

Ans. Anterior choroidal artery