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Normal Pressure Pseudotumor—Is There Evidence for a Unique Clinical Entity?


 

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Among a cohort of patients who most likely had headache secondary to idiopathic intracranial hypertension, no patients showed the elevated levels of opening CSF pressure established as criteria for the disorder.

WASHINGTON, DC—Normal opening CSF pressures are not enough to rule out headache secondary to idiopathic intracranial hypertension, or pseudotumor, in patients with chronic daily headache, according to research presented at the 53rd Annual Scientific Meeting of the American Headache Society.

“Headache secondary to idiopathic intracranial hypertension may occur in the context of normal opening pressures,” said Bert B. Vargas, MD, Assistant Professor in the Department of Neurology at Mayo Clinic Arizona in Phoenix. “Therefore, International Classification of Headache Disorders, 2nd Edition (ICHD-II) criteria for CSF hypertension and headache attributed to idiopathic intracranial hypertension should seriously be reconsidered.”

Defining Idiopathic Intracranial Hypertension
Headache secondary to idiopathic intracranial hypertension, sometimes called pseudotumor because its symptoms mimic those of a brain tumor, is found in up to 14% of patients presenting with chronic migraine, according to some studies, Dr. Vargas noted. Idiopathic intracranial hypertension usually occurs with papilledema. The headache occurs when intracranial pressure increases for no obvious reason, and it improves after withdrawal of CSF. ICHD-II criteria for such headaches require CSF opening pressures above 200 mm H20 in nonobese patients and above 250 mm H20 in obese patients.

In a 2008 study, however, Vieira and colleagues described three patients with idiopathic intracranial hypertension without papilledema (IIHWOP), even though these patients were obese and had opening pressures lower than 250 mm H2O. The researchers expressed confidence in their diagnosis based on the patients’ response to lumbar puncture and clinical outcomes, and they concluded that all obese patients with chronic migraine should undergo lumbar puncture.

In addition, a 2010 study by Bono and colleagues found that average CSF pressures could increase during the course of an hour in many patients whose initial CSF opening pressures were normal. “Taking into consideration the presence of abnormal pressure waves and elevated mean pressures, the transitory improvement of headache after lumbar puncture, and the good response to pressure-lowering treatment, we classified these patients as having secondary headache and IIHWOP,” the researchers wrote. They added that relying on single spot opening pressure is not an accurate method of determining increased intracranial pressure.

With these factors in mind, Dr. Vargas and colleagues reviewed data on 13 patients with apparent headache secondary to idiopathic intracranial hypertension to determine whether the patients met ICHD-II criteria for the disorder.

Criteria Unmet
The sample included 13 patients with daily headache with normal CSF opening pressures that improved after lumbar puncture, suggesting the presence of idiopathic intracranial hypertension. Of the patients, 10 (77%) were women and 12 (92%) presented with headache meeting criteria for chronic migraine. Magnetic resonance venography showed either no findings or clinically insignificant findings in all but one patient, who had unilateral transverse sinus stenosis.

On average, the patients’ age was 38.7, and their BMI was 34.0. “This average was definitely above the BMI of 30 that defines obesity,” said Dr. Vargas. “But the range was pretty large—keep in mind that the lowest BMI was 18.6, meaning that this is not a disorder that affects only obese individuals.”

None of the 13 patients met ICHD-II criteria for idiopathic intracranial hypertension. Two patients had opening CSF pressures above 200 mm H2O, and both of those patients were obese and had opening pressures below 250 mm H2O. “The point that I really wish to highlight is that the mean opening pressure in this group was 182 mm H2O,” Dr. Vargas said. “And not a single one of them went above 230 mm H2O.”

With regard to treatment and outcomes, seven patients were shunted, and six were managed medically. Of the shunted patients, six showed significant improvement postoperatively, with five showing sustained improvement and one showing initial improvement followed by a postoperative complication and shunt removal. Of the medically managed patients, five were unresponsive and one had significant and sustained improvement on acetazolamide.

A New Clinical Entity
“Normal pressure pseudotumor, as we refer to it—mostly because normal pressure idiopathic intracranial hypertension doesn’t make any sense—may exist as a clinical entity,” Dr. Vargas concluded. “All patients with refractory chronic daily headache should undergo lumbar puncture. Positive response to lumbar puncture should guide diagnosis and management of refractory chronic migraine.”

Reliance on single spot checks of opening pressure to diagnose headache secondary to idiopathic intracranial hypertension is leading to under-recognition of the disorder, he added. “Many patients with chronic daily headache are therefore untreated or inadequately treated.”

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