Subarachnoid haemorrhage

Definition/diagnostic criteria Subarachnoid Haemorrhage (SAH) is a medical emergency characterised by bleeding into the subarachnoid space, the area between the arachnoid membrane and the pia mater, which surrounds the brain. The most common cause of SAH is the rupture of an intracranial aneurysm, although other factors such as trauma or arteriovenous malformations can also lead to SAH.

Diagnosing SAH requires a high index of suspicion due to its potentially life-threatening nature. The classic clinical presentation includes a sudden severe headache, often described as “the worst headache of my life,” accompanied by neck stiffness (meningism) and occasionally loss of consciousness. However, it is essential to note that not all patients will present with these classical symptoms.

Epidemiology SAH is relatively rare, with an estimated annual incidence in the UK of around 6 per 100,000 people. It predominantly affects adults aged 40 to 70, with a slight female preponderance. Smoking, hypertension, and a family history of SAH are known risk factors. The mortality rate of SAH remains high, with up to 50% of patients dying within the first month.

Diagnosis
Clinical features:

• Headache: The hallmark symptom of SAH is a sudden and severe ‘thunderclap’ headache. It often starts suddenly, reaches maximum intensity within minutes, and may be associated with nausea and vomiting.
• Meningism: Neck stiffness and photophobia can be present, but these signs may not be prominent in all cases.
• Neurological deficits: Depending on the extent of bleeding and the location of the aneurysm, patients may exhibit focal neurological deficits such as hemiparesis, cranial nerve palsies, or altered consciousness.

Investigations:

• CT head scan: An urgent non-contrast CT head scan is the primary imaging modality for diagnosing SAH. The presence of blood in the subarachnoid space (hyperdensity) on CT is highly suggestive of SAH.
• Lumbar puncture: If the initial CT is negative, a lumbar puncture is recommended to detect the presence of xanthochromia (yellowish discoloration of cerebrospinal fluid due to the breakdown of red blood cells), which is indicative of SAH.

Typical abnormalities found in SAH include:

• Blood in the subarachnoid space on CT head scan.
• Xanthochromia in cerebrospinal fluid (if lumbar puncture is performed).
• Cerebral angiography may reveal the presence and location of an aneurysm.

Treatment Management of SAH requires a multidisciplinary approach and often involves neurosurgeons and interventional radiologists. Key aspects of treatment include:

• Immediate stabilisation: Patients should receive supportive care, including blood pressure control to prevent re-bleeding, and management of complications such as hydrocephalus or seizures.
• Aneurysm securing: Once diagnosed, aneurysms should be secured to prevent re-bleeding. This can be achieved through surgical clipping or endovascular coiling, depending on the patient’s clinical condition and aneurysm characteristics.
• Blood pressure control: Careful blood pressure management is crucial, balancing the risk of re-bleeding with the risk of ischemia in compromised cerebral vessels.
• Nimodipine: This calcium channel blocker is recommended to improve outcomes by reducing the risk of delayed cerebral ischemia.

Prognosis The prognosis for SAH patients is variable, depending on factors such as age, grade of SAH severity, and the presence of complications. Early diagnosis and prompt treatment are associated with better outcomes. However, even with appropriate care, SAH carries a risk of long-term neurological deficits and cognitive impairments.

• SAH is a critical neurological emergency with potentially devastating consequences.
• Early recognition and accurate diagnosis, primarily through CT head scan and lumbar puncture if needed, are crucial for initiating appropriate treatment.
• Prompt intervention to secure the aneurysm, along with careful blood pressure control and supportive care, can significantly impact the prognosis of SAH patients.
• GPs should maintain a high index of suspicion for SAH in patients presenting with sudden severe headaches, and timely referral to specialist services is imperative to improve patient outcomes.