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
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- Spring '14
- head injury, Intracranial pressure, Traumatic brain injury, brain tissue