Subarachnoid Hemorrhage

What Is Subarachnoid Hemorrhage?

Subarachnoid hemorrhage (SAH) refers to a clinical syndrome caused by the rupture of diseased blood vessels at the bottom or surface of the brain, and the direct flow of blood into the subarachnoid cavity. It is also known as primary SAH, which accounts for approximately 10% of the acute stroke. SAH is a common disease of unusual severity.

WHO surveys show that the incidence rate in China is about 2 per 100,000 people per year, and there are also reports of 6-20 per 100,000 people per year. There is also secondary subarachnoid hemorrhage caused by intracerebral hemorrhage, epidural or subdural blood vessel rupture, blood penetrating brain tissue and flowing into subarachnoid cavity.

What is the Etiology of Subarachnoid Hemorrhage?

Any cause of cerebral hemorrhage can cause subarachnoid hemorrhage. Common causes are:
1. Intracranial aneurysm: it accounts for 50-85%, and it is more likely to occur at the branch of the aorta of the cerebral artery ring;
2. Cerebral vascular malformation: mainly arteriovenous malformation, mostly seen in adolescents, accounting for about 2%. Arteriovenous malformations are mostly located in brain areas of cerebral arteries;
3. Abnormal cerebral vascular network disease (Moyamoya disease): it accounts for about 1%;
4. Others: Dissecting aneurysm, vasculitis, intracranial venous thrombosis, connective tissue disease, hematopathy, intracranial tumor, coagulation disorders, anticoagulation treatment complications, etc.
5. The cause of bleeding in some patients is unknown, such as primary peri midbrain hemorrhage.
The risk factors of subarachnoid hemorrhage are mainly factors that cause rupture of intracranial aneurysms, including hypertension, smoking, heavy drinking, previous history of ruptured aneurysm, accumulation of aneurysms, multiple aneurysms, etc. Compared to non-smokers, smokers have bigger aneurysms and they are more likely to have multiple aneurysms.

What Are the Symptoms of Subarachnoid Hemorrhage?

The typical clinical symptoms of SAH are sudden severe headache, nausea, vomiting and meningeal irritation, with or without focal signs. During or after strenuous activities, there would be burst of local or total head pain, which is intolerable. It could be persistent or continuously aggravated, and sometimes, there would be pain in upper neck.

The origin of SAH is often related to the rupture site of the aneurysm. Common accompanying symptoms are vomiting, temporary disturbance of consciousness, back or lower limbs pain, and photophobia, etc. In most cases, meningeal irritation appeared within hours after the onset of the disease, with neck rigidity being the most obvious symptom. Kernig’s and Brudzinski’s signs could be positive. The fundus examination could reveal retinal hemorrhage and papilledema. In addition, about 25% of patients may have mental symptoms, such as euphoria, delusions, hallucinations, etc.

There may also be epileptic seizures, focal neurological deficit signs such as oculomotor paralysis, aphasia, monoplegia or hemiplegia, sensory disorders, etc. Some patients, especially the elderly patients, often have atypical clinical symptoms such as headache and meningeal irritation, while the mental symptoms are obvious. Patients with primary midbrain hemorrhage have mild symptoms, shown in CT as hematocele in mesencephalon or peripontine cistern with no aneurysm or other abnormalities on angiography. Generally, no rebleeding or late-onset vasospasm would occur, and the expected clinical consequences are good.