Utility of Intracranial Pressure Monitoring for Diagnosis of Idiopathic Intracranial Hypertension in the Absence of Papilledema

Background

Idiopathic intracranial hypertension (IIH) is characterized by headaches, visual obscurations, and papilledema, and the diagnosis involves lumbar puncture (LP) with an elevated opening pressure (OP) ≥20 cm H₂0. When papilledema is absent, the diagnosis becomes less clear. Some physicians have argued that the absence of papilledema rules out IIH, whereas others maintain that elevated OP is sufficient for diagnosis.

Methods

The authors performed a single-institution 4-year retrospective analysis of patients who underwent invasive intracranial pressure (ICP) monitoring for presumed IIH.

Results

A total of 22 patients were reviewed, and 13 had classic symptoms of IIH, documented elevated OP, and absence of papilledema; 5/13 (38%) patients had proven intracranial hypertension as shown by invasive ICP monitoring, whereas 8/13 (62%) had normal ICP.

Conclusions

With the use of current diagnostic algorithms of clinical presentation and elevated OP, over half of patients without papilledema in our series would be falsely diagnosed with IIH, which could result in unnecessary medical and surgical intervention. Thus, elevated OP as determined by LP is insufficient to diagnose IIH. On the other hand, the absence of papilledema does not rule out intracranial hypertension.

Introduction

Idiopathic intracranial hypertension (IIH) is characterized by elevated intracranial pressure (ICP) of unknown cause.1, 2, 3 The symptoms include headaches that are typically exacerbated by lying down and by a Valsalva maneuver.⁴ Other symptoms include visual disturbances, tinnitus, and dizziness.5, 6, 7, 8 Papilledema and visual field defects are hallmark signs of the disease.3, 9, 10, 11, 12 Although the results of magnetic resonance imaging (MRI) is often normal, findings can include empty sella, flattening of the posterior globes, protrusion of the optic nerve head, optic nerve sheath distention, herniation of the cerebellar tonsils, cerebrospinal fluid (CSF) fistula, and transverse venous sinus stenosis.13, 14, 15

The diagnostic process for IIH is one of exclusion and relies on clinical symptoms and opening pressure (OP) measured by a lumbar puncture (LP).1, 2, 4, 13, 16, 17 In 2014, the IIH Treatment Trial proposed a diagnostic algorithm that used an OP of >20 cm H₂O; however, the criteria by Friedman et al.¹⁴ 2013 and the modified Dandy criteria from 198518, 19 both describe a higher threshold OP criterion of >25 cm H₂O.1, 11, 13, 20, 21 Meanwhile, OP can be difficult to assess in anxious patients and in obese patients, who make up the classic demographic of people affected by IIH.²² It can prove difficult to achieve access to the lumbar cistern, and inaccurate measurements are commonly due to incorrect positioning, partial needle obstruction, fluid loss, pharmacologic sedation, moment-to-moment fluctuations, and patient straining.²³ A Valsalva maneuver has been shown to increase OP from 14.6 cm H₂O to 32.3 cm H₂O.24, 25

In many cases, the diagnosis of IIH is straightforward. However, in some cases the optic disc signs are difficult to interpret as a result of congenital anomaly, gliosis, or pallor.²³ Meanwhile, visual field results are contingent on the patient's input, which may be unreliable.²³ In these circumstances, when papilledema is not clearly identified, intracranial ICP monitoring can prove useful in ruling in, or out, an IIH diagnosis. In a literature review, and to our knowledge, 4 articles have discussed the utility of ICP monitoring in the setting of presumed IIH, although none have looked specifically at patients without papilledema nor compared LP-obtained OP with ICP.22, 23, 26, 27 Moreover, diagnostic algorithms fail to account for patients without papilledema who experience classic IIH symptoms.

We present a series of patients with elevated OP in the absence of papilledema. We aim to corroborate past studies and emphasize a utility for ICP monitoring for selected cases of IIH. We argue that a diagnosis of IIH outside the setting of papilledema warrants more than an elevated OP on LP while also maintaining that absence of papilledema does not rule out intracranial hypertension.