Chronic Headaches and Shunts
A significant number of shunt-dependent children and adults are plagued by chronic, often disabling headaches. These are usually not associated with other symptoms of increased intracranial pressure, and neuro-diagnostic studies usually do not reveal evidence of a shunt malfunction. In most cases the CAT or MR scan small ventricles. The condition of small ventricles on CAT or MR scan coupled with chronic headache complaint has been termed the Slit Ventricle Syndrome.
Small ventricles are a desirable result of shunting, but they can sometimes cause problems. There are a number of therapeutic options. In the first place it is essential that a CAT scan be carried out while the patient is symptomatic. This is because an intermittent shunt malfunction may masquerade as slit ventricle syndrome with the fluid spaces only enlarging at the time of malfunction. Scans done when the individual is asymptomatic will show the ventricles to be unchanged in comparison to scans done previously when the patient was asymptomatic. Other causes for headaches are searched for on the scan such as sinusitis.
Recent evidence has shown that shunt-dependent children with chronic headache are often suffering from a migraine equivalent. They do not experience classic migraine, but may for some reason be vulnerable to similar variations of in blood volumn within the brain. It has been found that anti-migraine therapy (Inderal, etc.) has a very dramatic result in many such cases. Therefore, we now recommend that this regime be employed with all children experiencing chronic headache in the absence of obvious shunt malfunction. Intracranial pressure monitoring and surgery can also be considered when other avenues have been exhausted.
Once it has been documented that the ventricles are unchanged during symptomatic periods and pharmacologic treatment has failed, the next step is to determine what is happening to the pressures within the head (Intracranial Pressure) during periods of headache. Intracranial pressure monitoring is exceedingly useful in evaluating chronic headache complaints in shunt-dependent children and adults. We have found that this symptom may be produced by higher-than-normal pressure (hypertension), lower-than-normal pressure (hypotension), or it may be unrelated to the shunt's function. Appropriate treatment is obviously dependent on identifying the true cause of the symptoms, and intracranial pressure should be determined in all such cases.
Intracranial hypotension may occur many years after insertion of the shunt as a result of axial growth and consequent increased siphoning through the shunt; it is treated by increasing the resistance of the system or placing an anti-siphon device in the system. Intracranial hypertension can be more problematic to deal with. First, it is confirmed that a CAT or MR scan has been obtained while the individual was maximally symptomatic to rule out an intermittent shunt malfunction. If this has been done, consideration is given to changing the shunt's valve if it is not a low resistance system. Finally, if headaches persist and pressure monitoring shows episodes of severe rise in intracranial pressure with resulting headache, either surgical expansion of the skull or establishing of bone widows under the temple's muscles can be done to allow underlying expansion of the brain to dissipate transient periods of increased pressure. In cases where pressure monitoring fails to document changes in intracranial pressure during periods of headache, the child or adult is referred to a headache clinic with the reassurance that there is no problem with the shunt's function.