Prior to rupture, saccular aneurysms are usually asymptomatic. Exceptionally, if large enough to compress pain-sensitive structures, they may cause localized cranial pain. With a cavernous or anterolaterally situated aneurysm on the first part of the middle cerebral artery, the pain may be projected to the orbit. An aneurysm on the posteroinferior or anteroinferior cerebellar artery may cause unilateral occipital or cervical pain. The presence of a partial oculomotor palsy with dilated pupil may be indicative of an aneurysm of the posterior communicating–internal carotid junction or at the posterior communicating– posterior cerebral junction. Occasionally, large aneurysms just anterior to the cavernous sinus compress the optic nerves or chiasm, third nerve, hypothalamus, or pituitary gland. A monocular visual field defect may also develop with a supraclinoid aneurysm near the anterior and middle cerebral bifurcation or the ophthalmic–carotid bifurcation. In the cavernous sinus, they may compress the third, fourth, or sixth nerve, or the ophthalmic division of the fifth nerve.
Whether a small leak of blood from an aneurysm may serve as a warning sign of a subsequent more catastrophic rupture (“warning leak”) has been disputed. An entity known as “sentinel headache” has been used in an imprecise way to refer to both a headache that precedes subarachnoid hemorrhage and to a small leakage prior to a major rupture. Headaches are so ubiquitous that many, even severe ones, are coincidental in relation to subarachnoid hemorrhage. The frequency of true warming leaks is unknown but is not likely to be high. We have seen several cases where an acute and severe exertional or spontaneous headache was found to be associated with a small subarachnoid hemorrhage that was discovered by lumbar puncture; more often the headache is unrelated to hemorrhage and is attributable to migraine. This type of “thunderclap headache,” may be a variant of migraine, or less often, cerebral venous thrombosis, diffuse vasospasm (reversible cerebral vasoconstriction syndrome [RCVS], formerly called Call-Fleming syndrome), or even less often, pituitary apoplexy, hypertensive encephalopathy, intracranial hypotension, and intracranial or extracranial arterial dissection.
Before deciding on a course of action, it has been useful to assess the patient with reference to the widely employed scale introduced by Botterell and colleagues and refined by Hunt and Hess, as follows:
Grade I. Asymptomatic or with slight headache and stiff neck
Grade II. Moderate to severe headache and nuchal rigidity but no focal or lateralizing neurologic signs
Grade III. Drowsiness, confusion, and mild focal deficit
Grade IV. Persistent stupor or semicoma, early decerebrate rigidity and vegetative disturbances
Grade V. Deep coma and decerebrate rigidity