Commonly diagnosed as bleeding within the subarachnoid cavity (the area of the skull around the brain), a subarachnoid hemorrhage is often the result of an arteriovenous malformation, a knot of malformed or otherwise abnormal blood vessels. The bleeding can also result from a cerebral aneurysm (caused by weak blood vessels that rupture), from a head injury resulting from a fall or accident or from the use of blood thinning medications prescribed to treat bleeding disorders.

The onset of a sudden and severe headache is one warning sign that a subarachnoid hemorrhage exists. The pain is typically worse at the back of the head and may be accompanied by a loss of consciousness preceded by dizzy spells, changes in mood or behavior, confusion, seizures, stiffness in the neck and vision problems.

To diagnosis a subarachnoid hemorrhage, a physician will check for stiffness in the neck and test the patient’s brain and nervous system function. An examination of any vision problems (especially reduced eye movement) will also be considered, and if the condition is suspected a CT scan of the head will be ordered along with cerebral and magnetic resonance angiography, a lumbar puncture to check the state of cerebrospinal fluid, an MRI and perhaps a transcranial Doppler ultrasound.

Because a subarachnoid hemorrhage can be fatal, treatment focuses on relief of the symptoms. Surgery will most likely be performed to remove blood located in the subarachnoid cavity or repair a rupture blood vessel, both of which will also relieve pressure on the brain. And post-surgery recovery will require complete bed rest until the condition leading to hemorrhage is completely resolved.