Visual loss and a bitemporal field defect indicate pressure on the optic chiasm. Pressure on the optic tract produces noncongruent homonymous hemianopia. When the aneurysm ruptures, headache is usually acute and severe. Patients may present with only a headache or may have varying degrees of neurologic deficits or changes in consciousness. The mixture of escaping blood and CSF irritates the meninges and increases intracranial pressure, producing headache, vomiting, dizziness, and alterations in pulse and respiratory rates.
Seizures occasionally occur.
The neck is usually not stiff initially unless the cerebellar tonsils are herniated downward. However, within 24 h, moderate to marked stiffness of the neck, Kernig's sign, and bilateral Babinski's signs develop. Rebleeding is common in patients with aneurysms who are not treated surgically. The diagnosis can often be made from CT scans, reducing the need for lumbar puncture. After 6 h or more, a xanthochromic supernatant is found.