A University of Iowa Health Care team is participating in a $16 million grant from the National Institutes of Health to investigate the case of elevated pressure within the skull that, left untreated, may cause blindness. Michael Wall, MD, neuro-ophthalmologist at University of Iowa Hospitals and Clinics, talks about the study:
What causes idiopathic intracranial hypertension, or elevated pressures within the skull?
Idiopathic intracranial hypertension (we abbreviate it to IIH) is elevated pressure of unknown cause in the fluid-filled spaces around the brain and spinal chord. It has many parallels to high blood pressures—hypertension—which is high pressure within our arteries. That, too, is most often of unknown cause. There are many causes for increased intracranial pressure, including brain tumors and overuse of vitamin A.
When we see patients with symptoms of intracranial hypertension, we evaluate them for these other causes, and if none are found, we evaluate them for IIH.
What are the symptoms of elevated pressure in the skull?
A daily headache is the most common symptom. Most patients also have something called pulsatory tinnitus, which they describe as a whooshing sound in their ear in sync with their heartbeat.
Patients also commonly report visual loss, which is either transient—lasting seconds to a minute—or permanent, and can be progressive if treatment is not instituted. Lastly, double vision can occur as a symptom of elevated intracranial pressure.
What is the current treatment for elevated pressure?
The current treatments for IIH are use of a low-sodium, weight-reduction diet. A diuretic called acetazolamide or Diamox is commonly used, but its efficacy has not been proven by a clinical trial. That is one of the goals of our randomized, double-blinded, placebo-controlled clinical trial.
Is idiopathic intracranial hypertension genetic?
That’s a very good question. There is some evidence that IIH runs in families, but the genetics behind the disease has not been worked out. That’s another goal of our study.
How many centers will be involved in this study?
Our study will be performed by 40 sites across the United States and Canada, including a site here at The University of Iowa. Most of these sites are academic medical centers, but some are private practices.
What will study patients be asked to do as part of the study?
First, study patients will be educated about the disease and its treatment. They will need to know that optimal treatment to prevent visual loss is unknown and they’ll be asked to undergo a low-sodium, weight-reduction diet and lose about five percent total body weight and maintain this modest amount of weight loss.
They will also need to consent to being randomized to one of two groups, either daily Diamox or a placebo. They will need to return for examinations approximately monthly for the first six month, and then yearly for five years.
How long will the study last?
An overall index of visual field function will be obtained after six moths of treatment. We will then continue to follow the patient for five years to determine the long-term outcome.
What do you hope this study will show?
We anticipate our study will give us evidence-based treatment strategies for idiopathic intracranial hypertension.
Secondly, we hope to determine the cause of the disease as we’re doing a genetic study and investigating various biomarkers, so that more targeted treatments can be developed. And lastly, we hope to learn about the long-term outcomes of therapy. |
