MISTAKE @5:06: CN3 Palsy causes pupil dilation, not constriction!
In this video we will be covering of Cerebral Hemorrhages such as epidural hemorrhage, subdural hemorrhage, subarachnoid hemorrhage, and intracerebral hemorrhage in preparation for USMLE Step 1. We will be covering the neuroanatomy and pathophysiology, diagnosis of these conditions for the purposes of USMLE Step 1
ANATOMY
The meninges is made up of the skull, dura mater which is made up of periosteal and meningeal layer. Then the arachnoid mater and pia mater. In between these two there is cerebrospinal fluid (CSF) known as the subarachnoid space
EPIDURAL HEMATOMA or EPIDURAL HEMORRHAGE
Caused by rupture of the middle meningeal artery in between the two layers of the duramater. When this ruptures it seperates the two layers of the dura mater. The middle meningeal artery comes from the foramen spinosum and moves laterally where it then splits anteriorly and posteriorly. Therefore trauma to the lateral side of the head there can be rupture of the middle meningeal artery and blood will flow between the two duramater layers. Therefore epidural hemorrhage is caused by trauma to the lateral part of the head causing rupture of middle meningeal artery. Symptoms are interesting. They will be unconcious for awhile due to trauma. Then there is a lucid interval where they are okay for a few hours and then they will go into coma. Also there is Cranial Nerve three palsy. On CT findings there is something called the lens shapred on the side of the head. This lens shape is created by the presence of fissures that it can't pass. However, it can pass the falx cereberi and tentorium cereberi.
SUBDURAL HEMATOMA or SUBDURAL HEMORRHAGE
Here the hematoma is immediately under the duramater. Briding vessels also known as superior cerebral vessels rupture. These veins are between the cerebrum and the skull. When there is shaking of the brain severe enough it will lead to rupture of the vein and blood will flow. Brain atrophy caused by old age and alcohol can predispose to Subdural hematoma or subdural hemorrhage. Symptoms are delayed because of the slow bleeding. Also there is some history of trauma such as fall, epilepsy or motor vehicle accident. Investigations you would want to perform is the CT Scan. On CT Scan subdural hematoma will show in a more elliptical pattern. This crosses the fissures, but does not cross the falx or tentorium cereberi.
SUBARACHNOID HEMATOMA or SUBARACHNOID HEMORRHAGE
Here there is hemorrhage into the subarachnoid space. Here there is CSF and the LP will show blood. Subarachnoid hematoma is caused by berry aneurysm around the circle of willis. This is caused by Ehlor Danlos/Marfan's, ADPKD, and finally subarachnoid hematoma is caused by AV malformation. Symptoms are classically described as "worst headache ever". Very sudden onset and there is no history of trauma. Often times there is vasospasm which is not seen by CT scan and the treatment is the nimedipine which is a calcium channel blocker.
INTRACEREBRAL HEMORRHAGE
This hemorrhage is within the brain, not in the meninges. Caused primarily by system hypertension that leads to microaneurysm in the the lenticular straite aslso known as Charcot Couchard. Also found in the Basal Ganglia. There are some condition associated with this condition. Amyloid angiopahty, vasculitis and neoplasms.