Makindo Medical Notes

Related Subjects: |Subarachnoid Haemorrhage |Perimesencephalic Subarachnoid haemorrhage |Haemorrhagic stroke |Cerebellar Haemorrhage |Putaminal Haemorrhage |Thalamic Haemorrhage |ICH Classification and Severity Scores |Saccular aneurysms

Note: Any new, severe headache with onset to maximum severity within 5 minutes, lasting for at least 60 minutes, should be treated as a possible SAH. 50% of patients die within 48 hours irrespective of therapy. Early clipping or coiling, ideally within 72 hours, is now the goal for all grades of SAH. Also see Saccular aneurysms.

Initial Management of Suspected Aneurysmal SAH on CT

About

• Definition: Bleeding into the subarachnoid space from vessels on the brain's surface.
• Blood Distribution: Blood often tracks into sulci, ventricles, and basal cisterns; may involve convexity SAH on the brain's outer surface.

Incidence

• 1-2% of the population have an unruptured aneurysm.
• SAH incidence is approximately 6 cases per 100,000 patient-years, primarily in individuals under 60.

Note: Differentiating between traumatic and aneurysmal SAH can be challenging. In cases where aneurysmal SAH is suspected, a CTA and neurosurgical consultation are needed. Traumatic bleeds often involve external signs of head injury or skull fracture, have a convexity blood pattern, and are not typically preceded by headache.

Causes

• Aneurysmal SAH: Due to a berry aneurysm rupture (85% of cases).
• Non-Aneurysmal Perimesencephalic SAH: Accounts for 10%, typically in patients over 50 with less severe headache.
• Traumatic SAH: Often due to mild or moderate head injury, especially in elderly patients.
• Dissection: Vertebral artery dissections more likely to cause SAH; may present with cranial nerve palsies and lateral medullary syndrome.
• Arteriovenous Malformations (AVM): Rarely bleed only into subarachnoid space; usually associated with an intraparenchymal hematoma.
• Reversible Cerebral Vasoconstriction Syndrome: Tends to cause convexity SAH.
• Other Causes: Dural AVMs, cerebral amyloid angiopathy, vasculitis, intracranial arterial dissections, and infections.

Berry/Saccular Aneurysms Causing SAH

• Common Sites:
  • Posterior inferior cerebellar artery
  • Basilar artery tip (5%)
  • Internal carotid artery (ICA) and posterior communicating artery (35%)
  • Anterior communicating artery (35%)
  • Middle cerebral artery bifurcation (20%)
• Risk Factors: Smoking, binge drinking, illicit drug use, adult polycystic kidney disease, Marfan's syndrome, Ehlers-Danlos syndrome, SLE, sickle cell disease.

Clinical Presentation of SAH

• Sudden, severe headache (often described as the "worst ever" headache).
• Headache onset within seconds, reaching maximum intensity within one minute.
• Possible collapse followed by temporary recovery.
• Associated symptoms: photophobia, neck stiffness, coma, and sometimes third nerve palsy or monocular blindness.

Complications of SAH

• Vasospasm: Risk of delayed cerebral infarction, typically 3-12 days post-SAH; managed with Nimodipine, positive fluid balance, and preventing hyponatremia.
• Re-bleeding: Occurs in 20% of patients within the first 2 weeks, especially the day after SAH.
• Hydrocephalus: Due to obstructed CSF outflow, treatable with EVD or VP shunt.
• Seizures: Present in about 6% of cases.
• Hyponatremia: Often due to renal salt wasting or SIADH.

Differential Diagnosis

• Venous sinus thrombosis
• Migraine
• Primary intracerebral hemorrhage
• Brain tumor with hemorrhage
• Carotid or vertebral dissection

Investigations

• CT Head: Highly sensitive within 6 hours of headache onset, decreases in sensitivity after 24 hours.
• Lumbar Puncture: If CT is negative but SAH is suspected, perform LP at 6-12 hours post-onset to check for xanthochromia.
• CTA/MRA: Used for aneurysm detection; catheter angiography may still be performed if CTA is inconclusive.
• Transcranial Doppler: To monitor for vasospasm.

Treatment of SAH

• Vasospasm Prevention and Management:
  • Nimodipine: 60 mg orally every 4 hours for 21 days; prevents delayed cerebral ischaemia due to vasospasm. Regular monitoring for hypotension is necessary.
  • Triple-H Therapy: Hypertension, hypervolemia, and hemodilution to improve cerebral perfusion in cases of vasospasm. Requires close monitoring in ICU to balance risk of re-bleeding in untreated aneurysms.
  • Endovascular Treatments: Intra-arterial vasodilators (e.g., verapamil) or balloon angioplasty may be used in severe cases of vasospasm not responsive to medical therapy.
• Definitive Aneurysm Treatment:
  • Coiling: Minimally invasive endovascular coiling is generally preferred, especially in patients with high surgical risk. Platinum coils are inserted to occlude the aneurysm, reducing the risk of re-bleeding.
  • Clipping: A neurosurgical procedure involving a craniotomy to place a clip at the aneurysm's neck. Typically performed if coiling is contraindicated or anatomically difficult.
  • Timing: Early intervention (within 72 hours) is preferred to prevent re-bleeding, though the choice between clipping and coiling is based on the aneurysm’s characteristics and patient factors.
• Hydrocephalus Management:
  • External Ventricular Drain (EVD): Used for acute hydrocephalus to relieve intracranial pressure by diverting cerebrospinal fluid (CSF).
  • Ventriculoperitoneal (VP) Shunt: Considered if hydrocephalus persists; allows for long-term CSF diversion.
• Seizure Control:
  • Antiepileptic Drugs (AEDs): Typically used in patients with a history of seizures or those at high risk; levetiracetam is often preferred due to fewer drug interactions and side effects.
  • Prophylactic Use: Not routinely recommended unless seizure occurs, due to limited evidence supporting efficacy.
• Blood Pressure Management:
  • Target Range: Aim for systolic blood pressure of 140-160 mmHg before aneurysm treatment.
  • Medications: IV labetalol or nicardipine are commonly used to manage BP.
• Supportive and Preventative Care:
  • Hydration: Maintain euvolemia with IV normal saline to avoid hypovolemia and associated complications.
  • Electrolyte Monitoring: Hyponatremia is common, often due to renal salt wasting or SIADH; monitor sodium levels closely.
  • ICU Monitoring: Close observation in ICU or HDU settings for early detection of complications like re-bleeding, vasospasm, and neurological deterioration.

Complications of SAH

• Vasospasm: Delayed cerebral infarction typically at 3-12 days; manage with Nimodipine, fluid balance, and avoidance of hyponatremia.
• Re-bleeding: Occurs in 20% within the first 2 weeks; early aneurysm repair helps reduce this risk.
• Hydrocephalus: Acute or delayed; may require EVD or VP shunt placement.
• Seizures: Present in about 6% of cases; managed with AEDs if needed.
• Hyponatremia: Due to renal salt wasting or SIADH; managed with sodium supplementation and fluid balance.

References

• J. van Gijn and G. J. E. Rinkel. Subarachnoid haemorrhage: diagnosis, causes and management. Brain (2001), 124, 249-278
• Subarachnoid haemorrhage. Lancet 2007; 369: 306