 Welcome back to intracranial bleed part 2. In this section, we will discuss subarachnoid hemorrhage and parankumal hemorrhage. We'll discuss their presentations. As we talked about before, there are four types of intracranial bleed. It includes epidural, subduro, subarachnoid bleed, and intracerebral or parankumal bleeds. Those are the four types. We will discuss the presentation of subarachnoid hemorrhage and intracerebral or parankumal hemorrhage. First, subarachnoid hemorrhage. It can be separated into trauma and non-traumatic cause. Traumatic subarachnoid hemorrhage tends to occur with trauma. It tends to occur in combination with other traumatic bleeds. Traumatic subarachnoid bleed by itself tend to be of small volume. And therefore, besides a headache and maybe nausea and vomiting, the patient does not usually present with focal neurological signs. However, since it is usually happening in conjunction with other bleeds, those bleeding usually causes neurological signs. Those bleeding will also decrease the patient's level of consciousness and GCS. As with all bleeding, the risk of this bleed is increased by the use of anticoagulants. For non-traumatic causes of subarachnoid hemorrhage, most of them will be due to rupture of an aneurysm. The minor causes include ruptured AVM and neoplasms. We therefore will focus on aneurysmal subarachnoid hemorrhage. Aneurysms are most often found in the circle of willis. That is formed by the anterior cerebral arteries, middle cerebral arteries, posterior cerebral arteries, and the communicating arteries. The incidence of aneurysm increases with family history of aneurysms. Diseases that are associated with increased incidence of aneurysms include polycystic kidney disease and connective tissue disease such as Marfan's and Ehler-Danlos syndrome. As the aneurysm grows, the risk of ruptures increases. A rupture aneurysm causes significant blood loss into the subarachnoid space, pushing on the brain, leading to herniation and death. In some aneurysms, there are small or minor leaks from the aneurysm prior to its rupture. That is also called a sentinel bleed. Investigation of a sentinel bleed might lead us to an earlier discovery for an aneurysm that has not ruptured yet. It is therefore the sentinel bleed that we wish to pick up in the emergency department. How does an aneurysmal subarachnoid hemorrhage present? A ruptured aneurysm will cause significant mass effect on the brain, leading to headaches, vomiting, seizure, decreased level of consciousness, and coma. Sentinel bleeds, on the other hand, since it is of small volume, does not produce mass effect on the brain. Therefore, the patient's GCS should be normal and there should be no focal neurological deficits. On history, a sentinel bleed will present as a severe headache. This headache peaks at its onset, also known as a thunderclap headache. The patient might complain of neck pain, nausea, and vomiting. An expanding aneurysm can also cause symptoms before it ruptures. Craneal nerve 3 runs very close to the posterior communicating artery. An aneurysm in the posterior communicating artery will compress Craneal nerve 3. That will lead to the eye being down and out. It will also lead to the lack of pupil construction. The pupil therefore stays dilated. Whenever we see a Craneal nerve 3 deficit that involves the pupil, we have to worry that there is a posterior communicating artery aneurysm that's compressing the nerve. Now move on to interest cerebro and parenchymal hemorrhage. Again, it can be divided into trauma and non-traumatic causes. Trauma is caused by direct head injury. It is often associated with other bleeds. The extent of the bleed will determine the patient's presenting complaint and their neurological status. For non-traumatic interest cerebro bleeds, the main risk factor is hypertension. Common sites for the interest cerebro bleeds due to hypertension includes the basal ganglia and thalamus, pons and the cerebellum. The patient will present with certain onset headache, vomiting, seizure, decreased level of consciousness, vocal neurological deficits that corresponds to what part of the brain is affected. The risks of interest cerebro bleeds also increase with the use of sympathetic drugs. In summary, we discussed parenchymal hemorrhage and interest cerebro hemorrhage. Both can be caused by trauma. However, we need to worry about aneurysm that causes parenchymal hemorrhage. We would want to pick up the aneurysm before it ruptures by diagnosing sentinel bleeds. For parenchymal bleeds, the main risk factor is hypertension. In the next part, we will discuss the physical examination investigations. Thank you for watching.