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Subarachnoid hemorrhage

Subarachnoid hemorrhage. extravasation of blood into the subarachnoid space between the pial and arachnoid membranes. Etiologies. Trauma MOST COMMON cause of SAH. Spontaneous Ruptured aneurysms (75-80%) Cerebral AVMs CNS vasculitides Cerebral artery dissection Coagulation disorders

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Subarachnoid hemorrhage

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  1. Subarachnoid hemorrhage • extravasation of blood into the subarachnoid space between the pial and arachnoid membranes

  2. Etiologies • Trauma • MOST COMMON cause of SAH • Spontaneous • Ruptured aneurysms (75-80%) • Cerebral AVMs • CNS vasculitides • Cerebral artery dissection • Coagulation disorders • Dural sinus thrombosis • No cause determined

  3. Risk Factors • Hypertension • OCPs • Substance abuse—cigarette smoking, cocaine abuse, alcohol consumption • Diurnal variation ins BP • Pregnancy and parturition • During LT or cerebral angiography in those with aneurysms • Advancing age

  4. Pathophysiology • Aneurysms usually occur at the branching sites on the large cerebral arteries of the circle of Willis • Early precursors of aneurysms are small outpouchings through defects in the media of the arteries • These defects are thought to expand as a result of hydrostatic pressure from pulsatile blood flow and blood turbulence, which is greatest at the arterial bifurcations • A mature aneurysm has a paucity of media, replaced by connective tissue, and has diminished or absent elastic lamina

  5. Pathophysiology • The probability of rupture is related to the tension on the aneurysm wall • Law of La Place: tension is determined by the radius of the aneurysm and the pressure gradient across the wall of the aneurysm • The rate of rupture is directly related to the size of the aneurysm • < 5 mm: 2% risk of rupture • 6-10 mm: 40% have already ruptured upon diagnosis

  6. Pathophysiology • Brain injury from an aneurysm can occur in the absence of rupture via mass effect • Rupture: blood extravasates under arterial pressure into the subarachnoid space and quickly spreads through the CSF around the brain and spinal cord • Direct damage to local tissues • Increased ICP • Meningeal irritation

  7. Clinical Features SYMPTOMS • Headache • Most common, present in 97% of cases • Worst headache of my life • Severe and sudden • Vomiting • Syncope • Photophobia • Neck pain • Focal cranial nerve deficits (diplopia, ptosis)

  8. Clinical Features SIGNS • (+) Kernig’s or Brudzinksi’s • Coma • Increased ICP • Damage to brain tissue • Hydrocpehalus • Diffuse ischemia • Seizure • Low blood flow • Ocular hemorrhage • Due to compression of the central retinal vein and the retinochoroidalanastomoses by elevated CSF pressure causing venoud HPN and disruption of retinal veins

  9. Grading SAH

  10. Grading SAH • Grades 1 & 2: operated ASAP as soon as an aneurysm is diagnosed • Grade > 3 managed until condition improved to grade 2 or 1 • Exception: life threatening hematoma or multiple bleeds (operated on regardless of grade)

  11. Grading SAH MORTALITY • Admission Grade 1 or 2: 20% • OR Grade 1 or 2: 14% • Rebleed: major cause of death for Grade 1 or 2 • Signs of meningeal irritation increases surgical risk

  12. Grading SAH

  13. Grading SAH

  14. SAH Grading • The Hunt and Hess and the WFNS grading systems correlate well with patient outcome • The Fischer classification predicts the likelihood of symptomatic cerebral vasospasm, one of the most feared complications of SAH • All 3 grading systems are useful in determining the indications for and timing of surgical management

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