Pediatric Idiopathic Intracranial Hypertension

Abstract

After completing this article, readers should be able to: Idiopathic intracranial hypertension (IIH), previously referred to as pseudotumor cerebri or benign intracranial hypertension, was recognized initially in adults by Quincke in 1893 as “meningitis serosa.” (1) The syndrome is characterized by elevated intracranial pressure (ICP) without any evident underlying neurologic disease. The modified Dandy criteria, which were developed based on an adult population, can assist in establishing the diagnosis of IIH (Table 1) (2).Interestingly, children who have IIH may display a greater spectrum of clinical presentations than adults, and the disorder may have special epidemiologic characteristics in children.IIH occurs most commonly in young adults and rarely is seen in those older than age 45 years. The overall annual incidence is 0.9 per 100,000 individuals, (4) and there is a strong female predilection among affected adults. The incidence of IIH increases to 3.5 per 100,000 in women ages 20 to 44 years. The association between IIH and obesity is very strong in adults. The incidence of IIH rises to 19.3 per 100,000 in women who are 20% or more above their ideal body weight. (5)IIH has different characteristics in the pediatric age group, where it is considered to be relatively rare, (6) especially in the prepubertal child. (7)(8) In one case series, more than 60% of children who had IIH were older than 10 years of age. (9) Interestingly, the unequal sex distribution of the disease appears to begin only after puberty. (9)(10)In contrast to the adult population, in which 66% of men and 90% of women presenting with IIH are obese, studies often show obesity not associated with the condition in younger children. (8)(11)(12)(13) As with the predilection for women, the association with obesity increases only after puberty, (8)(12) likely as a result of hormonal changes. There is no racial predisposition for IIH, (3) and even though familial cases have been reported, no genetic locus has been described. (14)The pathogenesis of IIH remains elusive, despite many theories emerging from neuroradiologic research and studies of cerebrospinal fluid (CSF) hydrodynamics (Table 2). (15) The absence of an increase in ventricular size despite the raised ICP in this disease also is puzzling.Vision loss in IIH is believed to be caused by transmission of high ICP to the optic nerve head (ONH). Damage may result from axoplasmic stasis and microvascular compromise. Early vision loss may be caused by macular edema, subretinal or perimacular hemorrhages, and anterior ischemic optic neuropathy. (17)(18)IIH is a diagnosis of exclusion. Following the Dandy criteria, by definition there should be no other identifiable neurologic disease. Numerous associations with IIH have been described (Table 3), and any of these related variables and potential causes of increased ICP must be excluded. Nomenclature dictates that identifiable causative factors be excluded from the diagnosis of IIH and be referred to, instead, as secondary causes of intracranial hypertension. However, many different “associations” with IIH are cited in the literature, and although many are well documented, others are based on anecdotal case reports or small case series. Pediatric ICP very often is found in association with an underlying causative factor, (40) such as ear infection, dural sinus thrombosis, steroid withdrawal, malnutrition associated with refeeding, hypervitaminosis A, minocycline, and others. (3)(9)(10)(12)(40)(41)(42)(43) It is very important to exclude any of these associated conditions or causative factors prior to commencing therapy. (44)Optic nerve drusen can be confused with papilledema. Drusen are the most common causes of disc elevation, and confirming their presence may be challenging, more so in children because drusen tend to locate deeply in the ONH at a young age, only becoming more visible later in life. (11)(45)(46) Lorentzen (47) reported the prevalence of optic nerve drusen at 0.34%, increasing by a factor of 10 in relatives of affected individuals. Although most patients who have drusen never develop visual symptoms, some have visual field abnormalities as a result of axonal compression. Fortunately, other complications, such as ischemic optic neuropathy and peripapillary neovascular membranes, are rare.Headache is the most common symptom of IIH in both children and adults. (9)(12)(41)(42) As with most headaches induced by elevated ICP, they may be worse in the morning, awaken the patient from sleep, or increase with a Valsalva maneuver. The headaches can be accompanied by nausea and vomiting. Ophthalmic symptoms, such as decreased and blurred vision, diplopia, and transient visual obscurations, also are reported frequently. (12) Transient visual obscurations are, in our experience, relatively frequent in older children but rarely reported on routine questioning. The obscurations probably result from transient ischemia of the ONH and are el