Radiologic findings in idiopathic intracranial hypertension

Introduction

Idiopathic intracranial hypertension (IIH), previously known as pseudotumor cerebri and benign intracranial hypertension, is characterized by elevated intracranial pressure (ICP) without a known etiology. The Modified Dandy Criteria, updated in 2002, defined IIH as (1) symptoms of generalized intracranial hypertension or papilledema; (2) signs of generalized intracranial hypertension or papilledema; (3) documented elevated ICPs in lateral decubitus position; (4) normal cerebrospinal fluid (CSF) composition; (5) no evidence of hydrocephalus, mass, structural, or vascular lesion on magnetic resonance imaging (MRI) or computed tomography (CT); and (6) no other cause of intracranial hypertension identified.

Longstanding evidence suggests that IIH is associated with spontaneous CSF rhinorrhea. ^, Imaging plays an integral role in the diagnosis of IIH and identification of the site of CSF leak. Identifying patients with elevated ICP (normal CSF pressure ranging from 5–15 cm H ₂ O) is necessary for successful management of patients with spontaneous CSF rhinorrhea and to prevent recurrences. Specific radiographic findings of IIH and CSF leak may be found in patients with specific risk factors such as women in childbearing age group and those with a body mass index greater than 30 kg/m ² . Magnetic resonance imaging (MRI) and computed tomography (CT) are the most important imaging techniques for IIH and spontaneous CSF leak. This chapter details imaging findings and recent advances applicable to IIH and spontaneous CSF rhinorrhea.

Imaging techniques

Magnetic resonance imaging is the imaging of choice for IIH in diagnosing and excluding other causes of increased ICP. Recent studies have shown that the identification of three or four findings on MRI in patients with a clinical suspicion of IIH is highly specific (100% specific and 64% sensitive) for the diagnosis. Various salient findings have been determined on MRI that are indicative of IIH when correlated clinically. Although MRI provides conclusive evidence of IIH, CT is useful in detecting the long-term effects of IIH like skull base erosions and CSF rhinorrhea. CT is noninvasive and accessible and provides outstanding bony detail. Even small defects can be detected using CT with high sensitivity (92%) and specificity (100%).