Subarachnoid hemorrhage

A subarachnoid hemorrhage (SAH) is bleeding into the subarachnoid space of the brain, i.e., the area between the arachnoid and the pia mater. It is a medical emergency which, depending on severity, can lead to death or severe disability if not recognized and treated in an early stage.

Symptoms and causes

There are roughly two types of SAH. It is most often the result of head trauma. Additionally, it occurs spontaneously in the rupture of a cerebral aneurysm or cerebral arteriovenous malformation, but can also be due to angioma, thrombosis, hematoma, or a brain tumor.

In spontaneous SAH, the main symptom is sudden severe headache, described by patients as "like being hit over the head with a heavy object". Neurological symptoms (like slurred speech, paralysis, visual symptoms and meningism) are not necessarily present.

Diagnosis

The diagnosis is made on the clinical history, physical examination, and CT scanning. The scan reveals blood in the cerebral ventricles or parenchyma, dependent on the location of the blood loss. In traumatic SAH (tSAH), the scan will also identify any additional injuries to the head.

Classification

The Hunt and Hess scale (1968) of subarachnoid hemorrhage severity is:

• Grade 1: Asymptomatic; or minimal headache and slight neurologic deficit except cranial nerve hemiparesis; possibly early coma; decerebrate rigidity; moribund.

Treatment

Neurosurgical intervention is necessary in severe SAH with high or increasing Hunt-Hess scoring. This may be by craniotomy and external clipping of the bleeding artery, or by interventional radiology, which employs angiography and inserting of metal coils to stem the bleeding.

There are few evidence-based guidelines on the timing of neurosurgical interventions, and this often depends on the clinical experience and guidelines of local interventional centers. Some may favor a "wait-and-see" management in less severe cases.

A patient who recovers spontaneously may receive a follow-up angiography to identify "berry" aneurysms which may be amenable to coiling to prevent recurrent episodes of SAH.

Complications

Complications of SAH can be acute, subacute, and chronic.

• Acute:
  • coma and brainstem herniation due to increased intracerebral pressure (ICP)
  • pulmonary edema ("neurogenic pulmonary edema") as a result of the suddenly increased ICP
• Subacute:
  • vasospasm, leading to ischemia of the brain (can be prevented partially with the calcium channel antagonist Pneumonia and pulmonary embolism (due to immobility)
  • SAH recurrence (20% within two weeks)