There are different types of hydrocephalus and some are more challenging to diagnose than others. Your doctor will choose from a range of tools or techniques to confirm the diagnosis and enable preparation of a treatment plan.
STANDARD DIAGNOSTIC TOOLS
Using similar technology to that used for monitoring babies’ health in pregnant women, this device uses high-frequency sound waves to image the structures within the skull. Ultrasound is often used for the initial assessment of infants because it requires a simple technique, the device being placed over the soft spot (fontanel) on top of the baby’s head.
It can also be used to detect hydrocephalus prior to birth during routine prenatal or antenatal examinations. Prenatal ultrasound scans have no known side effects on mothers or babies and can show telltale features such as enlarged ventricles and thinning of brain tissue. The clinician would be able to see if the choroid plexus, a ‘seaweed-like’ structure that produces CSF, is floating within the ventricle. Often a separation of more than 3mm between the choroid plexus and the margin of the ventricle is considered abnormal.
Computerized Tomography uses X-rays to produce cross-sectional views of the brain. The scans are quick and painless but require the patient to lie still and so children may need a mild sedative. CT scans for hydrocephalus can show the size of the ventricles but produce less detailed images than MRI scans and are usually reserved for emergency examinations.
Magnetic Resonance Imaging uses radio signals and a powerful magnetic field to form pictures of the brain that allow the size and shape of the ventricles to be determined. The patient can also be injected with dyes that enable cerebrospinal fluid (CSF) flow patterns to be studied.
MRI scans can show enlarged ventricles caused by excess CSF. They may also be used to identify underlying causes of hydrocephalus or other conditions contributing to the symptoms. Imaging is painless but noisy and requires lying still. Children may need a mild sedative for certain scans but some hospitals use a very fast version of MRI that generally doesn’t require sedation.
ADDITIONAL DIAGNOSTIC TOOLS FOR NORMAL PRESSURE HYDROCEPHALUS (NPH)
NPH is the most difficult type of hydrocephalus to diagnose. One of its features is a slowdown of brain function similar to that found in Alzheimer’s disease. Consequently, the patient’s mental ability is carefully assessed using cognitive testing in which the patient is asked a series of questions. This provides a cognitive profile for NPH that assists differential diagnosis, tracks the disorder’s progression, and helps measure the efficacy of treatment.
These are used to check shunt responsiveness or determine shunt pressure. They include lumbar puncture, external lumbar drainage, measurement of CSF outﬂow resistance, intracranial pressure (ICP) monitoring and isotopic cisternography.
A lumbar puncture, sometimes called a tap test, is a procedure where a sample of CSF is taken from the lower spine. Removing some CSF during a lumbar puncture may help improve symptoms. The doctor will assess your gait and balance both before and after the procedure to see if removal of CSF results in a significant improvement. These tests will help guide treatment decisions. If the symptoms improve then you may benefit from having surgery.
During a lumbar infusion test, fluid is slowly injected into the lower part of your spine while measuring the pressure. Your body should absorb the extra fluid and the pressure should stay low. If your body cannot absorb the extra fluid, the pressure will rise. This could indicate that you have NPH and surgery will be helpful.