I. Overview
Subarachnoid hemorrhage (SAH) is a collective term for sudden rupture of cerebral blood vessels caused by various reasons and blood flow to the subarachnoid space, which can be divided into spontaneous (accounting for about 15% of cerebrovascular accidents, mostly seen in 30-70 years old) and traumatic subarachnoid hemorrhage.
II. Etiology
The most common causes are cerebral aneurysm and cerebral (spinal cord) vascular malformation, which together account for about 70% of subarachnoid hemorrhage.
Other causes include hypertensive atherosclerosis, smog, hematologic disease, arterial occlusion, intracranial tumor stroke hemorrhage and mixed causes.
3. Other rare causes include leptospirosis, subacute endocarditis, fibromuscular dysplasia, Ehlers-Danlos syndrome, aortic arch stenosis, polycystic kidney, and Amphtamine arteritis, which can also be caused by oral contraceptives and drug abuse.
III. Clinical manifestations
1. triad of subarachnoid hemorrhage headache and vomiting, meningeal irritation signs and bloody cerebrospinal fluid.
2. The aura symptoms before subarachnoid hemorrhage (especially before aneurysm rupture) may include headache, drowsiness, eye movement disorder (oculomotor nerve palsy), pain in the trigeminal nerve distribution area and pain in the back of the neck.
The typical presentation of subarachnoid hemorrhage is a sudden, severe headache of indeterminate nature (the worst headache ever) with or without transient loss of consciousness, nausea and vomiting, neurological dysfunction (including cerebral nerve palsy), and cervical rigidity.
4. The symptoms at the time of hemorrhage may include severe headache, photophobia, nausea and vomiting, pallor, generalized cold sweat, vertigo, collar and back pain or lower limb pain, half of them have mental symptoms such as irritability, blurred consciousness, disorientation, etc., with transient disorders of consciousness being the most common. 20%~30 combined with hydrocephalus, meningeal irritation signs may appear 1~2 days after hemorrhage.
5. Neurological impairment is common with one side of the arterial nerve palsy, mostly suggesting ipsilateral internal carotid-posterior communicating artery aneurysm or posterior cerebral artery aneurysm; 20% may have hemiparesis.
6. Epilepsy is common after MCA aneurysm surgery.
The signs of cerebral vasospasm are more common in the first week after the onset of disease, and may include transient limited localization signs, progressive impairment of consciousness, obvious signs of meningeal irritation and cerebral angiography showing vasospastic thinning.
About half of the patients with subarachnoid hemorrhage have electrocardiographic changes.
Intracranial murmurs may be present in 9.1%.
10. Some patients may have hypothermia for several days.
IV. Diagnosis
1. CT head examination is feasible in patients with the above clinical manifestations and suspected subarachnoid hemorrhage, and lumbar puncture can be performed cautiously if CT is negative and cranial pressure is not too high.
2. CT shows increased density in the cerebral sulcus and brain pool, intracerebral (ventricular) hematoma, hydrocephalus, cerebral infarction and edema, and enhanced CT can show AVM, cavernous hemangioma and brain tumor.
3. MRI is difficult to detect subarachnoid hemorrhage within 24-48 hours of onset, but helps to exclude AVM, cavernous hemangioma and brain tumor.
4. MRA can be used to screen for carotid stenosis, intracranial vascular malformations and aneurysms.
5. Cerebral angiography is the gold standard for the diagnosis of cerebral aneurysm and helps to clarify the cause of subarachnoid hemorrhage. Bilateral internal carotid arteries, bilateral vertebral arteries and spinal arteriogram are routinely performed when necessary.
6. Lumbar puncture is suitable for those who have negative CT, typical clinical manifestations, and expected less high cranial pressure can be cautiously performed, and uniform light blood cerebrospinal fluid can be seen.
7. TCD is a non-surgical, non-invasive test that can detect blood flow velocity in the proximal segment of ICA, MCA, ACA, VA and BA; in general, blood flow velocity higher than 120 cm/s is considered moderate vasospasm and higher than 200 cm/s is considered severe vasospasm.
V. Differential diagnosis
1. Cerebral aneurysm is common in 40-60 years old, asymptomatic before bleeding, a few have arteriovenous nerve palsy, normal or increased blood pressure, recurrent bleeding is common and regular, consciousness impairment is more serious, cerebral nerve palsy is common in II-VI, hemiparesis is rare, vitreous hemorrhage may be present, high density of subarachnoid space is seen in CT, aneurysm and vasospasm are seen in cerebral angiography.
2. Arteriovenous malformation is more common under 35 years old, often with seizures before bleeding, normal blood pressure, recurrent bleeding rate of about 2%/year, more severe consciousness impairment, no cerebral nerve palsy, more common hemiparesis, may have isotropic hemianopia, enhancement CT sees malformed vascular mass, cerebral angiography sees AVM.
3. Atherosclerosis is more common in people over 50 years of age, with a history of hypertension before bleeding, increased blood pressure, recurrent bleeding, more severe impairment of consciousness, rare cerebral nerve palsy, more common hemiparesis, possible fundus arteriosclerosis, cerebral atrophy or cerebral infarction on CT, and uneven thickness of cerebral arteries on cerebral angiography.
4. Smoke disease is common in adolescents, with hemiparesis before bleeding, normal blood pressure, recurrent hemorrhage, mild or severe consciousness impairment, rare cerebral nerve palsy, common hemiparesis, rare ocular changes, ventricular hemorrhage casts or infarct foci on CT, and abnormal vascular clusters on cerebral angiography.
5. Tumor stroke is common in 30-60 years old, with symptoms of cranial hypertension and foci before hemorrhage, normal blood pressure, recurrent hemorrhage is rare, consciousness impairment is more severe, ventricular nerve palsy is common with skull base tumor, hemiparesis is common, optic papilledema may be present, tumor shadow is seen on (enhanced) CT, tumor staining is sometimes seen on cerebral angiography.
VI. Treatment
1. In the acute stage of hemorrhage, the patient should be absolutely bedridden, closely monitor the vital signs, apply hemostatic agents, analgesics and sedatives, and keep the bowel movement smooth.
2. Apply mannitol dehydration treatment for those with increased intracranial pressure, dexamethasone can be given to reduce cerebral edema, and extraventricular drainage is feasible for those with combined intraventricular hemorrhage or hydrocephalus.
If the patient’s condition allows, cerebral angiography should be performed as soon as possible to identify the cause of bleeding and treat it early.
4. Maintain electrolyte balance, paying special attention to low blood sodium.
5. Anti-fibrinolytic drugs can reduce the rate of rebleeding, but increase the incidence of cerebral infarction.
6. Prevention of epilepsy recommends prophylactic application of antiepileptic drugs early in the hemorrhage, but long-term antiepileptic therapy is recommended only for patients who have had epilepsy, hematoma, infarction and middle cerebral aneurysm.
7. Treatment of cerebral vasospasm
(1) “3H” therapy, i.e. hypervolemia, hypertension and hemodilution therapy, is the main treatment for cerebral underperfusion and cerebral ischemia after vasospasm, but it can also cause cerebral edema, myocardial ischemia, hyponatremia and other aneurysm rupture risks in multiple aneurysms
②The main effect of calcium channel blockers is to inhibit the entry of calcium ions into vascular smooth muscle cells, inhibit the release of vasoactive substances from platelets and endothelial cells, improve microcirculation, and promote the establishment of collateral circulation; the main adverse effect is hypotension
(iii) Fasudil Hydrochloride (Elidel) is mainly used to inhibit the phosphorylation of myosin in the final stage of smooth muscle contraction, causing vasodilation, thus preventing and relieving cerebral vasospasm, improving cerebral blood flow and the utilization of glucose in brain tissue, and inhibiting neuronal cell degeneration; the main adverse effects are intracranial hemorrhage, gastrointestinal bleeding, hypotension and anemia
(iv) Intracerebral fibrinolysis by intracerebral injection of recombinant tissue fibrinogen activator can dissolve fibrin clumps and reduce the incidence of asymptomatic and symptomatic vasospasm
⑤ Others, such as endothelin antagonists, endothelium-dependent relaxation mechanisms and intracerebroventricular slow release systems are still in the experimental stage.
VII. Prognosis
Approximately 70% to 80% of subarachnoid hemorrhages are surgical in nature and require surgical intervention (e.g., cerebral aneurysm clamping, cerebral aneurysm intervention embolization) as soon as possible after the cause is identified. The overall prognosis of subarachnoid hemorrhage is poor, with an overall mortality rate of 25% and a disability rate of nearly 50% for survivors.