(From the January 2014 Issue of PediatricsOnline)
Identifying intracranial hypertension in children is often a process of excluding which conditions it isn’t, a task complicated by disagreement among physicians over a key diagnostic element. New criteria proposed by neurologists at Nationwide Children’s Hospital could solve this problem, increasing diagnostic accuracy and helping physicians better determine the best course of treatment.
Intracranial hypertension occurs when the pressure exerted by the cerebral spinal fluid (CSF) is increased. This buildup of pressure can cause headaches and, in some cases, vision problems. Without treatment, pressure on the optic nerve can lead to permanent vision loss.
Once believed to be rare in children, many neurologists now say that intracranial hypertension may be more common than previously thought. The rise in awareness among pediatric neurologists has prompted a closer scrutiny of the diagnostic criteria by experts such as Shawn C. Aylward, MD, director of the Intracranial Hypertension Clinic at Nationwide Children’s, a collaboration among neurologists and ophthalmologists and the first program in the nation to focus specifically on children with this disorder.
In a recent article in the journal Pediatric Neurology, Dr. Aylward addressed the diagnostic difficulties and proposed several new guidelines for identifying intracranial hypertension in children. The recommendations are based on several small studies in children and Dr. Aylward’s work in the field. Since the clinic opened in 2010, there have been more than 800 clinic visits.
When a patient presents with possible intracranial hypertension, an MRI or CT scan of the brain is ordered to rule out a clot, tumor or abnormalities. If the scan is normal and an ophthalmological exam reveals swelling of the optic nerve, the patient undergoes a lumbar puncture to measure the CSF pressure and look for infection in the fluid.
Following conventional guidelines, patients have intracranial hypertension if their CSF pressure is greater than 25 cm of water. The problem is that this reading is based on studies of normal CSF pressures in adults.
“The disagreement in the literature comes from what pressure is too high in kids and the problem is, we really don’t know what is normal for kids,” says Dr. Aylward. Determining the normal limit for kids would require physicians to perform lumbar punctures on hundreds of healthy children, a study no institution would approve.
Among the guidelines Dr. Aylward has proposed is a lower pressure level for children under the age of 8. Although there is no large study of normal CSF pressure in children, several small studies and case reports involving children in whom lumbar punctures were done to rule out meningitis suggest that, for children younger than 8 years, normal CSF pressure is somewhere around 18 cm of water—far lower than the pressure followed for adults.
“Anyone under the age of 8 who presents to our clinic with the other warning signs and has a CSF pressure higher than 18 cm of water is diagnosed with intracranial hypertension,” Dr. Aylward says. In clear-cut cases, physicians prescribe medications to help reduce the pressure. Not surprisingly, many cases are not clear-cut.
To address this issue, Dr. Aylward has proposed a system to categorize intracranial hypertension as either “primary” or “secondary,” based on what is known about the underlying cause of the increased pressure. In most cases, a definitive cause is unknown. At Nationwide Children’s, these patients are diagnosed with primary intracranial hypertension and usually given a drug called Diamox.
But in some patients, the increased pressure can be linked to an infection, underlying neurological condition or a negative reaction to certain medications. In these cases, which Dr. Aylward calls secondary intracranial hypertension, the first line of defense would be to treat that underlying condition, in addition to prescribing Diamox in some cases.
“There is the potential the duration of treatment is shorter, and the patient may require further tests,” Dr. Aylward says. “That’s why we think the ‘primary’ and ‘secondary’ classifications are so important, because it can help physicians determine which is the best course of treatment.”
Patients in the clinic are usually followed for a year after their original diagnosis. For patients with primary intracranial hypertension, resolution of symptoms can take up to six months after they begin medication. Primary cases also have a 20 percent relapse rate within the first year, another reason for the lengthy follow up. Patients with secondary intracranial hypertension can get relief from symptoms much sooner, especially if the increased pressure was due to a reaction from such drugs as steroids, acne medicines, growth hormone and some chemotherapeutic medications.
Dr. Aylward and colleagues in the clinic are launching a new study designed to not only get a better handle on the incidence of intracranial hypertension in children, but also the rates of primary versus secondary cases and how the groups respond differently to therapy and follow up.
“Despite all we’ve learned about this problem, there is still so much we don’t understand,” says Dr. Aylward, who is an assistant professor of clinical pediatrics at The Ohio State University College of Medicine. “We are hoping our future studies will answer some of those questions.”
Aylward SC. Pediatric idiopathic intracranial hypertension: a need for clarification. Pediatric Neurology. 2013 Nov, 49(5):303-4. Epub 2013 Aug 16.