Chapter 37 notes 3 cranial perfusion pressure

Chapter 37 Notes 3
 Cranial Perfusion Pressure = Pressure required in the brain to maintain perfusion of brain tissue
 CCP = Mean Arterial BP (MABP) – Intracranial Pressure (ICP, normally 0 – 15 mmHg)
 CCP is normally 70 – 100 mmHg, but if falls below 40 mmHg; ischemia and potential brain
damage results
 Compartment Syndrome (in the skull):
o If intracranial pressure becomes greater than arterial blood pressure, arteries collapse;
blood flow to brain is cut of
 Brain Herniation:
 Increased intracranial pressure pushed the brain out of position with respect to supporting
fibrous septa that normally separate regions
 Neurologic symptoms depend on the region that is displaced
 Compression of the oculomotor nerve is an early sign
 Hydrocephalus:
 Abnormal increase in CSF volume with progressive enlargement of ventricular system
 Treat with a shunt to drain the fluid
 Noncommunicating (obstructive) :
o Congenital malformations
o Tumors
o Inflammation
o Hemorrhage
 Communicating :
o Impaired reabsorption
o Inadequate number of villa formed
o Post-infective scarring (meningitis)
o Obstruction of villi by blood or debris
o Normal pressure hydrocephalus – seen in elderly, often confused with other dementias
 If hydrocephaly occurs before skull bone sutures have fused (neonatal or infancy):
o Head expands and bulging fontanels but little increase in ICP so intelligence is spared
o S&S:
 Seizures
 Weakness
 Uncoordinated movement are common
o Treat with surgical placement of shunt
 If occurs after sutures fuse, then head cannot expand so increased ICP
o S&S:
 Headache
 Vomiting
 Papilledema
 Deviation of eye movements
 Due to pressure on cranial nerves
o Can lead to herniation.
o Treat with surgical decompression & shunting
o Traumatic Brain Injury:

Chapter 37 Notes 4
 Primary Injuries :
o Due to direct impact
o Difuse axonal injury due to shearing & tearing
o Focal lesions of lacerations, contusion, & hemorrhage
 Secondary Injuries :
o Due to swelling, infection, or hypoxia
o Difuse & multifocal
o Concussion, infection, hypoxic brain injury
o Ischemia is most common cause of hypotension & hypoxia
 Mild Head Injury :
o Momentary loss of consciousness
o No residual damage except amnesia
o No neurological signs and symptoms
o Postconcussion Syndrome :
 Headache
 Irritable
 Insomnia
 Poor concentration
 Memory issue
o Not seen on MRI or CT
 Moderate Head Injury:
o Small hemorrhages and some swelling of brain tissue
 Usually frontal or temporal lobes
o LOC
o Focal manifestations:
 Hemiparesis
 Aphasia
 Cranial nerve palsy
 Severe Head Injury:
o Irreversible damage
o Extensive mechanical and secondary damage
o Hematoma:
 Broke blood vessels
 Epidural Hematoma:
o Between bone and dura
o Blow to temporal lobe  rupture meningeal arteries
o Rapid bleeding
o