Subarachnoid Hemorrhage is a type of stroke. Subarachnoid hemorrhage is bleeding into the space in the cranium called the subarachnoid. The subarachnoid space is also referred to as the subarachnoid cavity. This is the area in the cranium or skull between the first membrane covering the brain (pia matar) and the second membrane (meninges) covering the brain (arachnoid mater). The subarachnoid cavity contains a sponge like tissue made up of trabeculae and interconnecting channels which communicate and contain cerebrospinal fluid.
This type of stroke is a medical emergency, happening either from trauma, injury or spontaneously. Subarachnoid hemorrhage can lead to death or severe disability, even if diagnosed treated quickly.
There are two ways in which a subarachnoid hemorrhage can occur, spontaneously and as the result of head trauma. The head trauma inducing SAH is most common and usually occurs when a patient is in a car accident or serious fall. This is called a traumatic subarachnoid hemorrhage. The patient becomes less responsive and develops a weakness on one side of the body called either a hemi paresis or hemiplegia. Headache is not always a symptom of this stroke. The patient can also have changes in pupil reflexes and the scores for the Glasgow Coma Score test decrease dramatically.
A spontaneous subarachnoid hemorrhage begins with what has been called a ‘thunderclap headache.’ It is often described by victims as the worst headache ever. Other symptoms are slurred speech, paralysis, vision impairments and meningism, which are not always present. The most common symptoms are vomiting, nausea and loss of consciousness.
Aneurysms which can cause SAH have a 50% pre-hospital admission mortality rate.
A diagnosis is made by a complete physical exam, including a clinical history and medical imaging such as a CT scan. A CT scan that reveals blood in the subarachnoid space, cerebral ventricles or brain parenchyma indicates a subarachnoid hemorrhage. The scan may also reveal any abnormalities or injuries to the brain.
Some times an ophthalmologist may detect a pre-retinal hemorrhage, which is a sign of a subarachnoid bleed or that one is coming.
Lumbar punctures or spinal taps are also used to determine if a subarachnoid bleed or hemorrhage has occurred in the patient, especially if it is not detected on the medical imaging. Cerebral spinal fluid that has a yellowish tinge indicates a breakdown of blood. This yellowish tinge is also described by as the term xanthochroma and is best detected 12 hours after the initial symptoms. The xanthocrhoma is usually caused by a small bleed or slow progression bleed due to a lesion. A test called a spectrophotometry is used to detect xanthochroma in the cerebral spinal fluid.
A cerebral angiography is used to determine the source of the bleed before beginning surgical corrections, if they are possible.
Subarachnoid hemorrhage is classified into grades of severity.
The Hunt and Hess Scale has five grades:
Grade 1 no symptoms, minimal headache and slight nuchal rigidity – survival rate is 70%.
Grade 2 moderate to severe headache, nuchal rigidity is present, no extreme neurological impairments – except cranial nerve palsy (head shaking) – survival rate is 60%.
Grade 3 patient is drowsy with minimal nerological deficit – survival rate is 50%
Gradient 4 patient is stuporous with moderate to severe hemi paresis, displaying possible decerebrate rigidity and vegetative behavior – survival rate is 20%.
Gradient 5 patient is in deep coma, decerebrate rigidity is present and he or she is moribund – 10% survival rate.
Another classification is called the Fischer Grade and it classifies the appearance of the hemorrhage on a CT scan:
Grade 1 – no hemorrhage detected visibly
Grade 2 – hemorrhage is less than 1 mm thick
Grade 3 - hemorrhage is more than 1 mm
Grade 4 – Subarachnoid hemorrhage with intraventricular hemorrhage or parenchymal extension. Hemorrhage be any sized or thickness
Treatment for SAH is neurosurgery for severe or traumatic cases, especially with a high or escalating Hunt-Hess grading. Neurosurgery can be a craniotomy in which external in which a bleeding vessel or aneurysm is clipped. Interventional neuroradiology is another procedure in which metal coils are inserted to stop bleeding. This is preformed with the guided image of the transfermoral angiography and is useful an aneurysmatic hemorrhage.
If a spontaneous rupture of aneurysm occurs, intervention will be based no the guidelines and experience of the hospital or medical center. A risk of rupture will indicate surgical intervention as soon as possible.
Medical treatment is aimed at reducing a repeat bleeding and treating a potentially serious complication called a vasospasm.
Vasospasm defines a sudden constriction or spasm of blood vessels. This is a serious complication that can occur with a subarachnoid hemorrhage. This can cause permanent brain damage, ischemic brain injury and death. Vasospasm occurs if 50% of patients with angiography and is a symptom in 30% of patients with SAH. An oral calcium channel blocker, called nimodipine can reduce the risk of a poor outcome.
Besides vasospasm there are other complications associated with subarachnoid hemorrhage and they are classified as acute, subacute and chronic.
Chronic complications are pneumonia and pulmonary embolism due to immobility, recurrence of SAH, unrelenting neurology impairments and long term immobility or paralysis.
Sub-acute complications are vasospasm, hydrocephalus and hyponatremia (low sodium levels). Hyponatremia can be caused by SIADH or cerebral salt wasting syndrome.
Acute complications are coma, brainstem herniation, pulmonary edema, cardiac arrhythmias, myocardial damage, hydrocephalus, vasospasm and hyponatremia.
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