Subarachnoid hemorrhage caused by injury is often seen in the elderly who have fallen and hit their head. Among the young, the most common injury leading to subarachnoid hemorrhage is motor vehicle crashes.

The main symptom is a severe headache that starts suddenly (often called thunderclap headache). It is often worse near the back of the head. Many persons often describe it as the "worst headache ever" and unlike any other type of headache pain. The headache may start after a popping or snapping feeling in the head.

Sudden stiffening of back and neck, with arching of the back (opisthotonos ; not very common)

Exams and Tests:

Signs include:

A physical exam may show a stiff neck

A brain and nervous system exam may show signs of decreased nerve and brain function (focal neurologic deficit )

An eye exam may show decreased eye movements -- a sign of damage to the cranial nerves (in milder cases, no problems may be seen on an eye exam)

If your doctor thinks you have a subarachnoid hemorrhage, a head CT scan (without contrast dye) will be done right away. In some cases, the scan is normal, especially if there is only been a small bleed. If the CT scan is normal, a lumbar puncture (spinal tap ) must be done.