Aneurysmal Subarachnoid Hemorrhage (SAH).

What Happens When an Aneurysm Bursts? How is the site of rupture identified?

What You Need to Know About SAH

Subarachnoid Hemorrhage (SAH), particularly due to an aneurysm, is a critical condition that demands prompt recognition and care. Here, we break down the essential information about its presentation and diagnosis in a way that’s easy to understand.

• The Hallmark Sign: Sudden Severe Headache
• The Thunderclap Onset: SAH typically announces itself with a sudden, intense headache. It’s often described as the “worst headache of my life.”
• The Isolated Nature: In many cases, this headache might be the only symptom, making it crucial to take it seriously.
• A Matter of Frequency: Research shows that out of patients who report this kind of headache, 6% were found to have SAH.
  Not Always Instantaneous
• Delayed Peak Intensity: For some, the headache doesn’t hit its peak intensity immediately. This can happen in about 5% of cases.
• Why It Matters: This delay can sometimes lead to a misdiagnosis or delayed diagnosis.

Headache Location and Type

• No Specific Location: The pain can be anywhere on the head, making it hard to pinpoint based on location alone.
• Different From Other Headaches: Those with a history of migraines or tension headaches often find the SAH headache to be uniquely severe.

Other Symptoms to Watch For

• More Than Just a Headache: Symptoms like brief fainting, vomiting, and neck pain are also common in SAH.
• Prevalence: These additional symptoms are more frequently observed in SAH patients compared to those without it.

Early Warning Signs

• The Sentinel Headache: Some patients experience severe headaches days or weeks before a major SAH event.
• The Controversy: While these could be early warnings, the evidence supporting this is not strong.

When Does SAH Occur?

• Activity or Rest: SAH can strike during physical exertion, emotional stress, or even during rest or sleep.
• Diagnosing SAH: What Clinicians Look For
• Initial Steps: A sudden severe headache should always raise suspicion for SAH. A head CT scan is a crucial first step in diagnosis.
• The Ottawa Rule: This set of criteria (age, neck pain, movement, fainting, exercise, sudden headache) helps in diagnosing SAH and avoiding unnecessary tests.

The Hidden Dangers of Misdiagnosing SAH

Diagnosing a Subarachnoid Hemorrhage (SAH), particularly when it stems from an aneurysm, is a critical yet challenging task in the medical world. Despite its severity, SAH can often be overlooked or misdiagnosed, leading to dangerous delays in treatment. Let’s explore the reasons behind these diagnostic challenges and the methods used to improve accuracy.

Why SAH Diagnosis Is Often Mistaken

• Varied Symptoms: A key mistake in SAH diagnosis is missing the wide array of symptoms it can present. Not every case of SAH looks the same, which can lead to oversight.
• Reliance on Head CT Scans: Another pitfall is either not conducting a head CT scan or not fully understanding its limits in identifying SAH.
• Lumbar Puncture Oversights: This procedure, crucial in SAH diagnosis, can be either not performed or misinterpreted, adding to the diagnostic challenges.

A Common Misconception

A major misconception in SAH diagnosis is the belief that patients will always appear visibly ill or show obvious neurological symptoms. In reality, nearly 40% of SAH patients can be awake, alert, and showing no neurological impairments, leading to potential underestimation of their condition.

Our Approach to SAH Diagnosis

• Head CT Scan: A noncontrast head CT scan is essential. Its effectiveness is highest within the first six hours after the onset of symptoms, capturing even small amounts of blood that indicate SAH.
• Lumbar Puncture: If the CT scan doesn’t reveal SAH, a lumbar puncture is typically the next step. This procedure involves collecting and analyzing spinal fluid for signs of bleeding.
• Further Imaging: In cases where CT and lumbar puncture results are inconclusive, additional imaging like CT angiography or MR angiography is considered, especially if symptoms began more than two weeks ago.

The Specifics of Lumbar Puncture in SAH Diagnosis

• What We Look For: During a lumbar puncture, doctors look for high opening pressure, an elevated red blood cell count, and xanthochromia (a pink or yellow discoloration in the spinal fluid), which are tell-tale signs of SAH.
• Differentiating Factors: It’s crucial to distinguish between blood from SAH and blood introduced during the lumbar puncture itself. This distinction is often made by comparing the red blood cell count in different samples of spinal fluid.

Reducing the Chances of Misdiagnosis

Studies suggest that if every patient experiencing a sudden, severe headache (known as thunderclap headache) underwent a head CT scan and, if necessary, a lumbar puncture, the majority of SAH cases would be correctly diagnosed. There remains a small risk of missing cases, particularly those with non-ruptured aneurysms, but this approach significantly reduces the likelihood of misdiagnosis.

The Evolving Landscape of SAH Diagnosis

Historically, the misdiagnosis rate of SAH has been alarmingly high, with studies showing rates ranging from 23 to 51%. However, more recent data suggests a decline in misdiagnosis, with rates around 7% in emergency departments.

How Doctors Identify the Cause of Bleeding in Subarachnoid Hemorrhage

• Finding the Source of a Brain Bleed: A Key Step in SAH Treatment
  Once a Subarachnoid Hemorrhage (SAH) is diagnosed, the next crucial step is to find out where the bleeding is coming from. This is typically done using special imaging techniques, and understanding these can help demystify the process.

Choosing the Right Imaging Technique

Digital Subtraction Angiography (DSA):

• Considered the most detailed test for finding brain aneurysms.
• Can also be used to treat the aneurysm at the same time.
• However, it’s more complex than other methods.

Computed Tomography Angiography (CTA):

• Faster and easier to do than DSA.
• Often the first choice in emergency situations.
• Can miss small aneurysms but is getting better with technological advances.

Magnetic Resonance Angiography (MRA):

• Another non-invasive option like CTA.
• Useful for planning surgery but not as detailed as DSA.

Why DSA Remains the Gold Standard

Despite the advances in non-invasive methods like CTA and MRA, DSA is still the most reliable way to find and understand aneurysms.
It’s particularly good at showing small or complex aneurysms that other scans might miss.

The Role of CTA and MRA

CTA and MRA:

• Great for a quick look to see if there’s an obvious aneurysm.
• Good for planning surgery.
• However, they might not catch smaller aneurysms.

When No Cause is Found: Repeat Angiography

Sometimes, the first round of imaging doesn’t show the cause of the SAH.
In these cases, doctors usually do another DSA after a couple of weeks.
Up to 24% of people with an initial negative test might have an aneurysm found on this second test.

Nonaneurysmal SAH: When There’s No Aneurysm

In about 15 to 20% of SAH cases, there’s no aneurysm causing the bleed.
These cases can be due to various other issues like perimesencephalic hemorrhage or vascular malformations.
For these patients, the bleeding source often remains a mystery.

The Importance of Detailed Imaging in SAH

Understanding the cause of SAH is crucial for effective treatment. While technologies like CTA and MRA are improving and offer quicker, non-invasive options, DSA still stands as the most thorough method, particularly for complex cases. For patients where the initial scans don’t show a clear cause, repeat angiography is essential to uncover hidden aneurysms or other sources of bleeding.

In cases of nonaneurysmal SAH, where no aneurysm is found, the journey to find the source can be challenging, and sometimes, the cause remains unknown. This underscores the complexity of diagnosing and treating brain hemorrhages and the importance of advanced imaging techniques in providing the best care for patients with SAH.