Communicating Hydrocephalus (fluid on the brain)

MPS I can cause hydrocephalus, a condition where fluid accumulates in the brain, causing a pressure buildup that can lead to brain damage. This is more common in individuals with severe neurological (brain and nerve) symptoms. Early detection and treatment of hydrocephalus is believed to improve qualify of life. However, neurosurgeons are often unfamiliar with the unique aspects of diagnosing communicating hydrocephalus in MPS I, creating a frustrating situation for parents.

Hydrocephalus was once known as “water on the brain.” The “water” is actually cerebrospinal fluid (CSF), a clear fluid surrounding the brain and spinal cord. The CSF protects the brain and spinal cord from injury by providing a liquid cushion, and is continually being produced, circulated and absorbed. Communicating hydrocephalus (also known as “non-obstructive hydrocephalus”) is caused when the CSF is not absorbed properly. This causes the CSF to build up, leading to an abnormal enlargement of the spaces in the brain called ventricles. This causes potentially harmful pressure on the tissues of the brain.

Hydrocephalus is diagnosed through clinical neurological evaluation (where the doctor checks the individual’s brain and nerve function); by using imaging techniques such as ultrasound, computer tomography (CT), magnetic resonance imaging (MRI); and through techniques to measure pressure, such as lumbar puncture (spinal tap). Hydrocephalus is most often treated with the surgical placement of a shunt. A shunt is a flexible plastic tube that diverts the flow of CSF from the brain to another area of the body where it can be absorbed as part of the circulatory process.

Surgical placement of a shunt
Courtesy of the National MPS Society

It is recommended that individuals with MPS I have a “baseline” head scan (CT or MRI) at the time of diagnosis with regular follow-up scans (as frequently as the doctor recommends). Measuring intracranial pressure (pressure inside the brain) allows the doctor to diagnose hydrocephalus. Intracranial pressure is measured in millimeters of mercury (mm Hg), and once the pressure is over 180–200 mm Hg, it is considered to be high. Once the fluid buildup is too severe, the doctor may recommend a shunt.