Study uses MRI to assess mechanisms in IIH

May 8, 2012

Measures of total cranial, ventricular, and extraventricular cerebrospinal fluid (CSF) volumes in idiopathic intracranial hypertension (IIH) provide strong evidence that at least two mechanisms are involved in this condition, said Byron L. Lam, MD.

Fort Lauderdale, FL-Measures of total cranial, ventricular, and extraventricular cerebrospinal fluid (CSF) volumes in idiopathic intracranial hypertension (IIH) provide strong evidence that at least two mechanisms are involved in this condition, said Byron L. Lam, MD.

In a prospective study, magnetic resonance imaging (MRI) of 14 newly diagnosed, untreated IIH patients and 11 healthy controls, all women, showed that the mean intracranial CSF volume of IIH patients was significantly greater compared with controls and that the extraventricular space, in particular, was larger in the patient group, said Dr. Lam, professor of ophthalmology, Bascom Palmer Eye Institute, Miami.

The significantly greater extraventricular CSF volume found in the patient group accounted for the increase in the intracranial CSF in that group, a figure that was also significant. However, the ventricular CSF volume was the same between the IIH and control groups.

These findings suggest that decreased CSF absorption and altered venous outflow, both previously suggested as mechanisms of action, coexist in obesity-related IIH.

“If IIH is associated with decreased CSF absorption, increased CSF volume is expected,” Dr. Lam said.

Previous studies suggest that ventricular spaces are larger in IIH, but these reports are limited and inconsistent.

The larger quantitated global cranial CSF volumes in patients compared with controls confirm previous reports that IIH is associated with impaired CSF absorption, while the higher extraventricular volume in the patient group is in line with prior findings on CSF accumulation in the optic nerve sheath as well as lower spinal canal compliance in IIH.

For more articles in this issue of Ophthalmology Times Conference Briefclick here.