Idiopathic intracranial hypertension (IIH) is a disorder of unknown etiology affecting predominantly obese women of childbearing age (1) The diagnosis is established according to the modified Dandy criteria (2).
Scarce information exists as to the psychosocial impact and quality of life (QoL) of individuals with IIH. Consistently, a higher incidence of depression and anxiety has been reported in IIH patients compared with age- or weight-matched controls or neuro-ophthalmologic controls (3–5). Patients with IIH may complain of thought and concentration difficulty. However, there have been few studies of formal cognitive evaluation of this population. Sørensen et al (6) found a mild general intellectual impairment, mostly on verbal tests (6). Kaplan et al (7) published a case study showing depression and subjective complaints of concentration and memory deficits despite normal neuropsychological scores. A retrospective study reported impaired function in memory, learning, visuospatial skills, and language in 10 patients with IIH (8). Yri et al (9) conducted a prospective study showing cognitive impairment in newly diagnosed IIH patients.
Considering the results of these reports and our impression that IIH influences cognitive functions, we evaluated cognitive functions in IIH patients who were not in the acute phase of the disease.
Participants were recruited from the Neuroophthalmology Unit, at the Tel Aviv Medical Center, Tel Aviv, Israel. Thirty consecutive adult male and female patients diagnosed with IIH scheduled for routine clinical follow-up were offered to participate in this prospective study. Patients in the acute phase of the disease were not enrolled; the time of diagnosis or of a relapse had to be at least 2 months before cognitive testing. Patients with history of a major psychiatric disorder, major depression, any neurological disorder except IIH or use of psychotropic drugs were excluded.
All participants completed a NeuroTrax battery of tests for mild cognitive impairment, which uses custom software installed on the testing computer (10).
The computerized battery of tests used in this study (testing time: 30 minutes) sampled non-verbal memory, executive function, visual spatial processing, attention, motor skills, problem solving, and information processing speed. Outcome parameters for tests or test levels included accuracy, reaction time (RT), standard deviation (SD) of RT, and a composite score ([accuracy/RT] × 100). Normalized subsets of outcome parameters were averaged to produce 7 summary scores. The outcome parameters contributing to each index score were included. The Global Cognitive Score (GCS) was computed as the average of the index scores. NeuroTrax index scores and GCS, computed using the same methodology, have been used in other studies (11–13).
The test results of the participants were compared with normative data in the NeuroTrax database. The normative sample is stratified according to age and education, and normalization of patient scores is according to the appropriate stratification. Normalization occurs automatically with upload of the test results to the NeuroTrax server. All individuals in the normative sample were tested in their primary language and diagnosed as cognitively healthy—as diagnosed by experienced clinicians as part of academic research studies using MindStreams performed at a variety of research sites (14–17).
The following are brief descriptions of the NeuroTrax tests included in our study.
Eight pictures of simple geometric objects were presented, followed by a recognition test, in which 4 versions of each object were presented, each oriented in a different direction (Fig. 1A). Participants were required to remember the orientations of the originally presented objects.
Go–No Go Test
A series of large colored stimuli were presented at pseudorandom intervals (Fig. 1B). Participants were instructed to respond as quickly as possible by pressing a mouse button if the color of the stimulus was any color except red, for which no response was made.
The Stroop is a well-established test of response inhibition (18) (Fig. 1C). The NeuroTrax Stroop test consists of 3 phases. Participants were presented with a pair of large colored squares, one on the left and the other on the right side of the screen. In each phase, the participants were instructed to choose as quickly as possible which of the 2 squares was a particular color by pressing either the left or right mouse button, depending on which of the 2 squares is the correct color.
Visual Spatial Processing
Computer-generated scenes containing a red pillar were presented (Fig. 1D). Participants were instructed to imagine viewing the scene from the vantage point of the red pillar. Four alternative views of the scene were shown as choices.
Staged Information Processing Speed
This test comprises 3 levels of information processing load: single digits, 2-digit arithmetic problems (e.g., 5−1), and 3-digit arithmetic problems (e.g., 3+2−1). For each of the 3 levels, stimuli were presented at 3 different fixed rates, incrementally increasing as testing continues. Participants were instructed to respond as quickly as possible by pressing the left mouse button if the digit or result was less than or equal to 4 and the right mouse button if it was greater than 4.
The Catch game is a motor screen assessing cognitive domains distinct from those in other NeuroTrax tests (Fig. 1E). Participants had to “catch” a rectangular white object falling vertically from the top of the screen before it reached the bottom of the screen. Pressing on the mouse button moved a rectangular green “paddle” horizontally so that it could be positioned directly in the path of the falling object. The test required hand–eye coordination, scanning, and rapid responses.
Pictorial puzzles of gradually increasing difficulty were presented (Fig. 1F). Each puzzle consisted of a 2 × 2 array containing 3 black and white line drawings and a missing element. Participants had to choose the best fit for the fourth (missing) element of the puzzle from among 6 possible alternatives.
NeuroTrax Summary Measures
To minimize differences in age and education and to permit averaging performance across different types of outcome parameters (e.g., accuracy, RT), each NeuroTrax outcome parameter was normalized and fitted to an IQ-style scale (mean: 100, SD: 15) in an age- and education-specific fashion. Normative data consisted of test data stored on the NeuroTrax central server for individuals classified as cognitively healthy in controlled clinical trials conducted at academic centers. Normalized subsets of outcome parameters were averaged to produce 7 summary scores as follows, each indexing a different cognitive domain.
All statistics were computed with SPSS statistical package version 15.0. Neurocognitive test scores were converted into z-scores and compared with 0 (i.e., average) using a one-sample t test to evaluate whether performance differed from average for age and education. An independent sample t test was run comparing treated patients with non-treated. Pearson correlations were used to evaluate the relationship of neurocognitive test scores with years of education and duration of disease. Statistical analysis was performed by the Statistical Laboratory School of Mathematics, Tel Aviv University, Tel Aviv, Israel.
Standard Protocol Approvals and Patient Consent
This prospective study was approved by the local institutional review board. Written informed consent was obtained from all patients participating in the study.
Thirty consecutive IIH patients participated, 3 men and 27 women. Mean age at the time of testing was 34.4 ± 10.6 years (range, 19–68 years). Mean disease duration was 5.7 ± 4.1 years. Body mass index (BMI) was available for 27 patients; mean BMI was 32.1 ± 5.8 kg/m2. At the time of testing, all patients were at least 2 months from diagnosis, a relapse or a lumbar puncture. Eight patients were being treated with acetazolamide; 22 patients did not receive treatment to lower intracranial pressure (ICP). None of the patients had persistent impairment of visual acuity or visual fields. Mean years of education was 14.2 ± 2.0. Demographic data are shown in Table E1, Supplemental Digital Content, https://links.lww.com/WNO/A118. All patients denied suffering from severe or chronic headache when they were included in the study.
When informed consent was obtained from the participants, the test supervisor explained the objective of the study. As part of the pre-study screening, all 30 patients confirmed that they had noticed some cognitive decline after having been diagnosed with IIH. However, they had not mentioned it to the treating physician, as they attributed it to daily circumstances of life rather than IIH. None of our patients took medication for anxiety or depression and none of them complained about an anxiety state or disturbances of sleep, depressed mood, lack of appetite, loss of weight, or other signs of depression. None of the patients suffered from sleep apnea.
Mean scores for all domain index scores were below average for age and education (See Supplemental Digital Content, Table E2, https://links.lww.com/WNO/A119 and Fig. 2). The GCS, attention, and visual spatial indices had the lowest scores with −0.63 to −0.73 SDs below average.
A t test showed statistically significant differences from average for all domains but memory, which did not reach statistical significance (P = 0.162). The GCS and attention index were most impaired (P = 0.01). Results of all domains are shown in Table E3, Supplemental Digital Content, https://links.lww.com/WNO/A120.
Results did not differ between patients who did or did not take acetazolamide at the time of testing (for Global score P = 0.1870). The cognitive domain measures and GCS were not correlated with age, years of education, BMI, or duration of disease (See Supplemental Digital Content, Table E4, https://links.lww.com/WNO/A121).
Our results indicate that patients with IIH have mild cognitive impairment. All domain measures apart from memory showed a statistically significant difference from normal individuals, indicating a form of multidomain cognitive impairment in IIH.
Study of cognition in IIH patients is limited (6,8,9,12). Kharkar et al (8) reported retrospective results of 10 IIH patients and, similar to our results, found borderline deficits in memory, learning, executive function, and visuospatial skills and language were impaired. Yri et al (9) evaluated patients within 7 days of diagnosis of IIH, who were tested the second time after 3 months of treatment. Similar to our results, they found a multidomain impairment. Processing speed and RT were most profoundly impaired. In the study of Yri et al, attention scores and visuospatial memory improved at follow-up, whereas the others stayed unchanged. This improvement was mainly explained by the test–retest effect. Our results also support Yri's findings, which showed no overall deficits in working memory, both in the acute and treated phase. Remarkably, Yri et al did not find a correlation between change in cognitive performance and difference in ICP from baseline. Arseni et al (19) found impaired memory in 24% of 85 IIH patients when tested with the Wechsler Memory Scale. Details of the nature and degree of memory impairment were not described nor were other cognitive functions measured. Sørensen et al (6) reported normal neuropsychological test performance in 5 IIH patients with a protracted clinical course.
In a prospective study of 20 IIH patients, 10 with chronic headaches and 9 healthy controls, Kesler et al (20) used brief psychological instruments to assess hostility (8-item New-Buss scale), anxiety (State-Trait Anxiety Inventory), and depression (autobiographical memory test). Patients with IIH scored higher on anxiety and showed reduced recall of specific autobiographical memories compared with weight-matched controls. No difference was found within the IIH group between patients taking or not taking acetazolamide.
Information regarding QoL and cognitive functions in IIH patients is limited: The impact of IIH on health-related QoL has been studied by Kleinschmidt et al (3) who reported a higher incidence of depression and anxiety in IIH patients compared with weight- and age-matched control groups. Vision-specific health-related QoL was significantly lower in newly diagnosed IIH patients compared with neuro-ophthalmologic controls. Kesler et al (5) found high levels of anxiety and stress in IIH patients. Depression and anxiety themselves are known to cause cognitive decline, impairing memory, executive functions, and learning (21). Accordingly, Airaksinen et al (22) found significant impairment in episodic memory and executive functions in anxious patients.
The relationship between IIH and cognitive impairment is unclear. Neither structural change nor change in brain volume has been identified in IIH patients. Brain dysfunction may be related to axonal flow as in optic nerve swelling or to mechanical compression as in normal pressure hydrocephalus (23,24).
We speculated that elevated ICP may cause diffuse effects in a broad array of brain areas. We found poorer performance in all cognitive domains tested. Attention and visual spatial processing scores were lowest. Even though memory was below average, it did not reach statistical significance. Our results demonstrated that cognitive decline was not related to patient age, disease duration, BMI, or acetazolamide treatment. The absence of correlation with these other variables implicates that IIH itself may cause cognitive impairment.
A limitation of our study is that we did not test patients for anxiety and depression, although none of the participants had a diagnosis of a psychiatric disorder. Yet, it is well known that anxious and depressive disorders are often unrecognized in the population. Hence, there may be a portion of patients that suffered from undiagnosed anxiety or depression and a possible impact on cognitive results cannot be ruled out.
STATEMENT OF AUTHORSHIP
Category 1: a. Conception and design (D. Zur, A. Kesler); b. Acquisition of data (D. Zur, E. Naftaliev, A. Kesler); c. Analysis and interpretation of data (D. Zur, E. Naftaliev). Category 2: a. Drafting the manuscript (D. Zur, E. Naftaliev, A. Kesler); b. Revising it for intellectual content (D. Zur, E. Naftaliev, A. Kesler). Category 3: a. Final approval of the completed manuscript (D. Zur, E. Naftaliev, A. Kesler).
Statistical analysis was performed by the Statistical Laboratory School of Mathematics, Tel Aviv University, Tel Aviv, Israel.
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