**2. Diagnosis**

#### **2.1. Clinical presentation**

The classic presentation of a patient with aneurysmal SAH is thunderclap headache, often described as the "worst headache of my life." It is generally abrupt in onset and reaches maximal intensity instantly. However, this classic description is seen in only 50% of patients presenting with aneurysmal SAH [8]. Conversely, in those patients prospectively screened for acute severe headache, only 6-17% were demonstrated to have SAH [9,10]. Common features at presentation can include seizure, loss of consciousness, and nausea and emesis preceding onset of headache [9]. The concept of 'sentinel headache' remains controversial; it is thought to be related to changes in the wall of the aneurysm versus a microbleed. A sentinel headache generally presents as a severe headache lasting greater than an hour, but diagnostic evaluation does not lead to the confirmation of SAH. These patients are at higher risk for early re-bleeding and aneurysmal SAH. The estimated relative odds ratio is 2.5-3.8 increase in early re-bleeding in patients who present initially with a sentinel headache [11].

### **2.2. Physical examination**

384 Aneurysm

Medicine. 352: 121-124

**2. Diagnosis** 

**2.1. Clinical presentation** 

provide definitive treatment of the aneurysm (Panel E).

with collagen vascular diseases, such as Marfan's Syndrome, Ehlor's-Danlos Disease,

Neurofibromatosis Type 1, and Autosomal dominant polycystic kidney disease [7].

Borrowed with permission: Ellegala D, Day A. (2005) Ruptured Cerebral Aneurysms. New England Journal of

**Figure 1.** The arterial blood supply to the brain is located primarily in the subarachnoid space (Panel B). Aneurysm formation occurs in the subarachnoid space (Panel C), which must be surgically accessed to

The classic presentation of a patient with aneurysmal SAH is thunderclap headache, often described as the "worst headache of my life." It is generally abrupt in onset and reaches maximal intensity instantly. However, this classic description is seen in only 50% of patients presenting with aneurysmal SAH [8]. Conversely, in those patients prospectively screened for acute severe headache, only 6-17% were demonstrated to have SAH [9,10]. Common Patients with aneurysmal SAH can have a variety of examination findings at presentation. These may range from a headache without focal neurologic deficits to being comatose. Most commonly, patients may have a depressed level of consciousness or confusional state. Cranial nerve palsies are also frequently seen as a direct result of an aneurysm; though cranial nerve 6 palsy may be a sign of elevated intracranial pressure. Focal weakness is also noted in a small percentage of patients. Fundoscopic examination may reveal subhyaloid hemorrhages and papilledema. Clinical correlation with outcome is best defined by the Hunt & Hess grading scale (see Table 1) [12].

#### **2.3. Neuro-imaging**

In addition to clinical presentation, the vast majority of SAH is diagnosed with correlating neuro-imaging. Non-contrast Head CT is the preferred modality of choice for the initial evaluation. Retrospective analysis has reported a sensitivity of 91-100% [13]. The sensitivity of non-contrast head CT diminishes as time elapses from the time of onset. It is best during the first 24 hours and diminishes to 85% at 5 days and subsequently to 50% at 1 week [14]. False negatives may occur in patients with anemia and is dependent upon the experience of the reading neuroradiologist [15]. MRI offers a higher sensitivity to detect SAH in patients presenting outside of first 48 hours after onset; however MRI is not readily available at most institutions and some patients may not be suitable for MRI. The FLAIR (fluid attenuated inversion recovery) and GRE (gradient echo) sequences are the most reliable method for detection of SAH in MRI [16].

Detection of aneurysms is best with catheter digital subtraction angiography, which remains the gold standard. In our practice, we perform a CT angiogram at admission, which carries a 85-98% sensitivity in comparison to catheter angiography. On average, 10-20% of patients with non-traumatic SAH will have a non-diagnostic catheter angiogram [17]. Practice varies in terms of repeat angiography; our current practice is to repeat an angiogram between 10- 14 days.

#### **2.4. Lumbar puncture**

Cerebro-spinal fluid (CSF) analysis remains an essential aid in diagnosis in CT-Negative patients presenting with acute onset of severe thunderclap headache. Lumbar puncture should ideally occur 6-12 hours after onset of symptoms to optimize sensitivity. Lysis of red cells and the formation of oxyhemoglobin and bilirubin produce xanthochromia, ideally detected visually by inspection and confirmed by spectophotometry. CSF can remain positive for up to 7 days following ictus [18].

#### **2.5. Classification**

Various classifications exist for SAH. These range from clinical grading systems to radiographic scales. The most commonly used scales are Hunt & Hess, and World Federation of Neurological Surgeons (WFNS) scales [19]. (See Table 1)


Adapted from - Rosen et al. (2005) Subarachnoid Hemorrhage Grading Scales: A Systemic Review. Neurocrit Care. 2: 110-118.

**Table 1.** Clinical grading scales for aneurysmal SAH and percent survival correlated with Hunt & Hess.

#### **2.6. Differential diagnosis**

Not all non-traumatic SAH is necessarily aneurysmal; however all non-traumatic SAH is treated as aneurysmal unless it is evident from clinical history or radiographic imaging that it is low risk. Most commonly, angiographic negative SAH is secondary to perimesencephalic hemorrhages. These compromise 10% of all SAH and two-thirds of nontraumatic SAH with negative angiograms. Blood is generally located ventral to brainstem in the prepontine and perimesencephalic cisterns. Generally, intraventricular hemorrhage (IVH) is rare. The average patient with perimesencephalic SAH is above the age of 50 and has less severe deficits. Rebleeding and vasospasm are infrequent in these patients [17].

Most SAH is in fact traumatic; however a collaborating history is not always obtained. Of those patients that have non-traumatic, non-aneurysmal SAH, intradural dissection is a concern; this is typically of the vertebral artery. Rupture of arteriovenous malformations (AVM) can occasionally extravasate blood into the cisternal space. Additionally, Arteriovenous Dural fistulas, mycotic aneurysms, pituitary apoplexy, and moya moya disease should remain on the differential, though there is generally additional history to suggest these. Cerebral vasculitis should remain a diagnosis of exclusion in patients with unexplained subarachnoid hemorrhage. The pattern of SAH on neuroimaging directs further work up. A non-classic pattern of cisternal hemorrhage suggests perimesencephalic or AVM related SAH. Blood present in the cortical sulci is generally thought to be traumatic, though can be associated with AVM rupture and vasculitis [17].
