**4.3 Initial imaging**

With such a large number of patients presenting to the ED with a chief complaint of headache [79–84], the description of headache can help differentiating those with a benign cause from those with an emergent etiology such as SAH. The diagnosis of SAH should be considered in any patient with a severe and sudden onset or rapidly escalating headache (**Figure 5**).

## *New Insight into Cerebrovascular Diseases - An Updated Comprehensive Review*


**Table 1.**

*World Federation of Neurological Surgeons Grading System for Subarachnoid Hemorrhage - (WFNS) scale.*


#### **Table 2.**

*Hunt and Hess scale.*


#### **Table 3.**

*Modified fisher grading system [82].*
