Expanding the clinical spectrum of idiopathic intracranial hypertension

Abstract

Purpose of review: Idiopathic intracranial hypertension (IIH) is a disorder of raised intracranial pressure (ICP). Although the majority of patients with IIH present classically with headache and papilledema, some patients may have unusual presentations or manifestations. Recent advancements in neuroimaging have facilitated the identification of other presentations associated with IIH. This review provides an overview of the expanding clinical spectrum of IIH.

Recent findings: Presentations of IIH that are considered unusual include highly asymmetric or unilateral papilledema, IIH without papilledema, and IIH associated with cranial nerve involvement. These presentations likely reflect differences in the way cerebrospinal fluid (CSF) pressure is transmitted intracranially. Radiological signs of intracranial hypertension are increasingly recognized in patients with IIH and provide further insights into the effects of raised ICP on intracranial structures. Osseous changes in the skull base leading to formation of meningoceles and encephaloceles have been identified in patients with IIH, spontaneous skull base CSF leak, and drug-resistant temporal lobe epilepsy, suggesting a possible association.

Summary: Clinicians should be familiar with the expanding clinical spectrum of IIH and the implications for the management of these presentations.

Box 1

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FIGURE 1

The clinical spectrum of idiopathic intracranial hypertension. Typical IIH presents with headache (indicated by lines inside the head) and papilledema (indicated by enlarged eyes), often accompanied by other symptoms of raised intracranial pressure and normal neurological examination. This is the most common presentation (roughly indicated by size of head). A subset of patients with IIH are relatively asymptomatic or have mild IIH. These patients are often incidentally found to have papilledema and, compared with patients with typical IIH, have fewer headaches, less severe papilledema, and lower cerebrospinal fluid opening pressure on lumbar puncture. Patients with IIH without papilledema (IIHWOP) have a chronic refractory headache syndrome. It is unclear if IIHWOP represents a variant of IIH where ICP is not elevated enough for papilledema to develop or a separate disorder of intracranial hypertension. IIH can also present with highly asymmetric or unilateral papilledema and other cranial nerve manifestations, including ocular motor nerve palsies, trigeminal neuropathy or neuralgia, and facial nerve dysfunction. With chronic intracranial hypertension, osseous changes can occur in the skull base predisposing to spontaneous skull base CSF leak, which presents with CSF rhinorrhea and headache. Osseous changes can also lead to formation of temporal meningoceles and encephaloceles, potentially acting as a nidus for temporal lobe epilepsy. CSF, cerebrospinal fluid; CT, computed tomography; ICP, intracranial pressure; IIH, idiopathic intracranial hypertension.

FIGURE 2

Imaging examples of radiological signs of intracranial hypertension. (a) Sagittal postcontrast T1-weighted image demonstrating an expanded, cerebrospinal fluid (CSF)-filled ‘empty’ sella turcica (arrow) and flattened appearance of the pituitary gland against the floor of the sella turcica (arrowhead). (b) Coronal T2-weighted image demonstrating abnormally enlarged Meckel caves bilaterally, filled with CSF (arrows). (c) Coronal T2-weighted image through the right temporal lobe demonstrating a meningoencephalocele. Defects in the tegmen mastoideum (margin indicated by arrowheads) transmit CSF and a portion of the right inferior temporal lobe (arrow). Fluid within adjacent mastoid air cells indicates associated CSF leak. (d) Sagittal postcontrast T1-weighted image demonstrating cerebellar tonsillar ectopia. The cerebellar tonsils, with normal rounded morphology (arrow), are in a low-lying position 5 mm below the foramen magnum (white line). (e) Oblique sagittal reconstruction of volumetric T2-weighted image in the plane of the optic nerve demonstrates posterior scleral flattening (arrowhead) and increased vertical tortuosity of the intra-orbital optic nerve sheath complex (arrow). (f) Axial T2-weighted image shows protrusion of the optic nerve head (arrows) and distention of the optic nerve sheaths by CSF (arrowheads) bilaterally. (g) Axial postcontrast T1-weighted image demonstrates enhancement of the optic nerve head bilaterally (arrows). (h) Cranio-caudal maximum intensity projection (MIP) of a postcontrast MR venogram. Arrows demonstrate smooth tapered severe stenosis of the distal transverse sinuses bilaterally.