Diagnosis and Classification of aSAH
Diagnosis of aSAH is made based on the patient's history and physical examination, together with diagnostic tests. Approximately half of aSAH patients have a period of reduced consciousness, including syncope, confusion, convulsions, and/or coma. Patients are often dazed, confused, or drowsy within the first few hours after aSAH. In a middle-aged adult who complains of a headache and sudden loss of consciousness, aSAH should be a prime consideration in the differential diagnosis.
If aSAH is suspected early non-contrast head computerized tomography (CT) is the cornerstone of aSAH diagnosis. Head CTs performed within the first 3 days of aneurysm rupture are almost 100% accurate; this accuracy decreases substantially after 5-7 days post-rupture (Cortnum, Sorensen, Jorgensen, 2010).
Hunt and Hess SAH classification system is used to score patient's risk for perioperative mortality. The patient is assigned to a category on admission based on (a) intensity of meningeal inflammatory reaction, (b) severity of neurological deficit, (c) level of arousal, (d) presence of associated disease.
- Grade I - Asymptomatic or minimal headache and slight nuchal rigidity.
- Grade II - Moderate-to-severe headache, nuchal rigidity, no neurological deficit other than cranial nerve palsy.
- Grade III - Drowsy, confusion or mild focal neurologic deficits.
- Grade IV - Stupor, moderate-to-severe hemiparesis, possibly early decerebrate rigidity.
- Grade V - Deep coma, decerabrate rigidity, moribund appearence.
The Hunt and Hess classification system does not apply to SAH due to trauma, arterial or venous anomalies, venous thromboses, mycotic aneurysms, or septic emboli (Hunt, 1968).
Fisher grading scale has been used since 1980 to predict patients at risk for post aSAH cerebral vasospasm based on the amount of blood seen on initial CT scans.
Fisher Scale (Frontera modification): % risk of symptomatic vasospasm or delayed cerebral ischemia (DCI) (Frontera, 2006).
- Grade 1 - focal or diffuse, thin(<1mm) SAH, no intraventricular hemorrhage (IVH): 6-24%
- Grade 2 - focal or diffuse, thin SAH, with IVH): 33%.
- Grade 3 - focal or diffuse, thick SAH, no IVH: 33%
- Grade 4 - focal or diffuse, thick, SAH, with IVH):40
If aSAH remains suspected and the cranial CT is initially negative, or it is suspected to be several days post-rupture, a lumbar puncture may be considered to check for the presence of blood or blood byproducts (xanthochromia) in the spinal fluid (Connolly et al., 2012; Cortnum et al.,2010; Meurer 2016). Small aneurysms (less than 3mm) or poor CT visualization may warrant CT angiography or magnetic resonance imaging (MRI), particularly to guide treatment decisions based on the exact size, location, and type of aneurysm.