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INTRACRANIAL HYPERTENSION CSF pressure is pulsatile at 2 frequencies: *Synchrony with beat by beat change of intracranial blodd volume *Synchrony with respiration (at a slower fre quency as result from changes in intrathora- cic and central venous pressure)
INTRACRANIAL HYPERTENSION(cont) *Normal CSF pressure: -0-140 mm H2O(0-10mmHg=0-1.3kPa) *Intracranial hypertension(ICP): >200 mm H2O (15 mmHg =2kPa) *SLOW elevations up to 200-300 mmH2O (15-22.5 mmHg = 2-3 kPa) may be well tole rated in patients with intracranial expanding lesions
INTRACRANIAL HYPERTENSION(cont) *Values up to and above 500 mmH2O(37.5- 38 mmHg or 5 kPa) are associated with sig nificant cerebral edema *ICP >800 mmH2O (60 mmHg or 8 kPa) is almost always a prelude to death in patients with expanding lesions or head injury
INTRACRANIAL HYPERTENSION(cont) Increased intracranial pressure occurs in 2 main circumstances: 1. Due to the presence of an EXPANDING LESION A.Intracerebral(hemorrhages/hematomas, traumatic or spontaneous; infarction and tumors) B.Meningeal(hemorrhages/hematomas, usually traumatic: extradural, subdural or subarach noidal; tumors vgr. Meningiomas)
INTRACRANIAL HYPERTENSION(cont) Clinical symptoms and signs: -headache -nausea and vomiting -diplopia -papilledema -focal neurologic signs related to intracranial expanding lesions or brain shifts w/herniation -alteration in level of consciousness
CEREBRAL PERFUSION PRESSURE *This is the difference between arterial and intracranial pressure *Compensatory arterial/arteriolar vasodilation mantain cerebral flow AUTOREGULATION -Effective only in conditions of mild to moderate reduction in CPP *CPP =zero= brain death *Intracranial hypertension(CSF pres >200mmH2O and brain edema commonly occur together BUT DO NOT neccesarily coexist
HYDROCEPHALUS...(cont.) CAUSES... *Congenital stenosis or atresic aqueduct *Obstruction of 3rd ventricle/aqueduct by cysts or neoplasia, gliosis/chronic inflamm. of aqueduct, obstruction of 4th ventricle, or ganized subarachnoidal hemorrhage w/obs truction at the base of encephalus.
*Herniation under the falx – mainly involving the cingulate gyrus -anterior cerebral artery occlusion leading to infarction of paracentral lobule -spastic paralysis and a cortical sensory disorder in the contralateral leg
FORAMEN MAGNUM(TONSILLAR) HERNIATION. *Associated with expanding supratentorial or infratentorial masses *Characterized by: -cerebellar tonsillar herniation and necrosis -compression of the pyramids motor signs -compression of RAS changes in level of consciousness -compression of cardiac/respiratory centers sudden cardiac/respiratory failure