WHAT IS IDIOPATHIC INTRACRANIAL HYPERTENSION?

Idiopathic intracranial hypertension (IIH) is a condition that is more common in women of childbearing age who are overweight. Headaches are a frequent complaint. A lumbar puncture (“spinal tap”) can show increased pressure in the spinal fluid around the brain. When the eyes are examined, swelling in the main nerve that connects the eye to the brain—the optic nerve—can often be seen. Permanent vision loss is the most feared complication of this disorder, so prompt evaluation and treatment are important.

WHY IS THIS STUDY IMPORTANT?

This study¹ is important because patients who do not have IIH may be incorrectly diagnosed. Patients may be examined by their primary care provider, emergency department staff, eye care provider, or neurologist and be told that they have swollen optic nerves. This may lead the provider to make a diagnosis of IIH when it does not exist. There are other causes for swollen optic nerves, and not everyone with this finding has IIH. Those with IIH are often treated with medicine and sometimes with surgery. People who don't have IIH should not have needless treatments that might produce side effects. This study examined the reasons for misdiagnosis of IIH.

WHAT DID THE AUTHORS STUDY?

The authors reviewed charts over an 8-month period looking for patients diagnosed with IIH or possible IIH by various providers. They separated these patients into those who had been treated and those who had not received treatment. They collected information about the patients, recorded the appearance of the optic nerves, and recorded spinal fluid pressure. They documented any medical or surgical treatment for IIH.

WHAT DID THE AUTHORS FIND?

A total of 1,249 new patients were seen in the eye clinic where this study was done. Eighty-six were referred with a preexisting diagnosis of IIH. On closer examination, 34 (39.5%) of the 86 patients did not have IIH. Most of the misdiagnosed patients were women (94%) with an average age of 38 years. Of these misdiagnosed patients, 27 had undergone at least 1 lumbar puncture and 10 had undergone 2–4 lumbar punctures. Twenty-six (76.5%) had been treated with medications for IIH, 1 had undergone a procedure to drain spinal fluid from the lower back to relieve pressure, and 4 had been referred for surgery. Twenty-two of these 34 patients had slightly elevated spinal fluid pressures, but this alone is not enough to make a diagnosis. Some findings on brain imaging can support the diagnosis, but only 3 of the 34 patients had imaging findings that would indicate increased intracranial pressure. The main reason patients were misdiagnosed was misinterpretation of the results from a single examination: the eye examination. This misinterpretation prompted unnecessary testing in about one-third of patients and led to invasive procedures in about one-third. The authors' main conclusion was that the combination of common, harmless headaches and obesity in young women often leads to costly tests for presumed IIH.

WHAT ARE THE FUTURE DIRECTIONS?

A swollen optic nerve signals a problem and suggests the diagnosis of IIH in an overweight headache patient. This study shows that many practitioners do not correctly assess the appearance of the optic nerve, which leads to unnecessary testing and treatments. Many patients had borderline elevated spinal fluid pressures, but it is unclear how the lumbar punctures were performed. It has been shown that spinal fluid pressures in normal patients can appear falsely elevated if pressure is applied to the abdomen during pressure measurement.² This “erroneously elevated” pressure can alarm practitioners into believing that the patient has IIH.

As the authors note, physicians often get very little education in viewing the optic nerve. The training of physicians in medical school and residency needs to be improved. It would also be helpful if doctors who first see these patients in the emergency department or primary care clinic had the technology to be able to “see” the back of the eye with photography. These images could be given to experts who could make better decisions about the appearance of the optic nerve. Some specialty centers are already working on these improvements.