Dr. Levy Clears Things Up

Hi Ms. Huguley,

The spinal fluid is made deep in the brain and circulates around the brain and spinal cord, as you said correctly, and then ultimately gets resorbed into the veins at the top of the skull. The total volume of spinal fluid is turned over 3 times every day so you can imagine the circulation is fairly brisk. That's why a bleed anywhere in the spinal fluid leads to exposure of the whole nervous system to the blood. As the blood breaks down, the blood iron products precipitate out and eventually settle down by gravity to the back of the head while sleeping and to the bottom of the spinal cord while awake. The reason hearing is affected is because the nerve that goes from the ear to the brain spends the majority of its time in the spinal fluid. All other nerves that come directly off the brain have < 1 mm of surface exposed to the spinal fluid. So the nerve to the ear is vulnerable to blood products circulating in the spinal fluid. Since that nerve has a large surface area relative to the volume of the nerve, a large percentage of the nerve is exposed to the iron. That's why hearing is usually the first symptom of superficial siderosis. 

Michael Levy, MD, PhD
Assistant Professor, Johns Hopkins University
Director, Neuromyelitis Optica Clinic
1800 E. Orleans St.
Pathology 509
Baltimore, MD 21287
443-287-4412 phone
888-523-4168 fax