Subarachnoid Hemorrhage Causing Communicating Hydrocephalus

What Is Subarachnoid Hemorrhage?

Brain Model Showing Blood In The Subarachnoid Space

Where is the bleeding in subarachnoid hemorrhage? On top of the surface of the brain tissue is a layer called the arachnoid. It looks like cellophane. It is clear in young individuals, can become a little opaque as we all get older. Between this layer and the brain is cerebrospinal fluid which is circulating around the brain tissue. Blood vessels are also along the surface of the brain. These blood vessels can form an aneurysm and bleed. When they bleed, the blood will mix and spread with the cerebral spinal fluid along the surfaces of the brain. Since it is below the arachnoid, it is called a subarachnoid hemorrhage. Other relatively common causes of subarachnoid hemorrhage include trauma and arterial venous malformations.

Bleeding Into The Brain From An Aneurysm Rupture May Cause Communicating Hydrocephalus

CT Head Showing Subarachnoid Hemorrhage With Hydrocephalus

For more information specifically about Communicating Hydrocephalus, see Hydrocephalus:Communicating Type. The CT Scan to the left shows blood mixed with cerebral spinal fluid associated with an enlarging ventricular system. Blood can be very irritating to the brain and can be thought of causing a "chemical meningitis". This inflammation results in decreased absorption of the CSF (cerebral spinal fluid). The production of CSF continues so a net increase of CSF occurs. Thus, the ventricles begin to enlarge. About 10% of people who suffer SAH (subarachnoid hemorrhage) develop hydrocephalus.

Delayed Communicating Hydrocephalus From Subarachnoid Hemorrhage

CT Scan Showing Aneurysm Clip and Hydrocephalus

Sometimes hydrocephalus is not apparent during the acute treatment of an aneurysm rupture. It may present itself several months later. Follow-up CT scans are important to diagnose delayed hydrocephalus if clinically indicated.