Obesity does not induce abnormal CSF pressure in subjects with normal cerebral MR venography

The Pseudotumor Cerebri Syndrome

Pseudotumor cerebri syndrome is a syndrome of increased cerebrospinal fluid pressure without ventriculomegaly, mass lesion, or meningeal abnormality. It is either primary (idiopathic intracranial hypertension, IIH) or secondary. A secondary cause is unlikely when adhering to the diagnostic criteria. Permanent visual loss occurs if undetected or untreated, and the associated headaches may be debilitating. Fulminant disease may result in blindness despite aggressive treatment. This study addresses the diagnosis and management of IIH including new insights into the pathobiology of IIH, updates in therapeutics and causes of overdiagnosis.

Idiopathic intracranial hypertension: a step change in understanding the disease mechanisms

The understanding of idiopathic intracranial hypertension (IIH) has evolved over the past few years. Previously, IIH was considered a disease exclusively affecting the neuro-ophthalmic axis, characterized by raised intracranial pressure, headache and papilloedema, and resulting in the risk of severe and permanent visual loss and life-changing disabling headaches. Recent advances have begun to redefine IIH as a probable metabolic disease involving a range of systemic manifestations. More than 95% of individuals affected by the disease are women of reproductive age with obesity. The incidence is rapidly rising and parallels the escalating worldwide obesity rates. Contemporary insights identify associations with insulin resistance, type 2 diabetes and a twofold increased risk of cardiovascular disease in excess of that driven by obesity alone. Adipose distribution in people with IIH, like that in other metabolic diseases, is preferentially centripetal and is associated with changes in intracranial pressure. Evidence now demonstrates adipose tissue dysfunction in people with IIH, involving transcriptional and metabolic priming for lipogenesis and weight gain. Hormonal perturbations are also observed, including a unique phenotype of androgen excess that promotes cerebrospinal fluid secretion. Knowledge of these additional disease features is driving research into novel therapeutic targets and altering the approach to multidisciplinary care.

The Relationship between Intracranial Pressure and Visual Field Zones in Normal-Tension Glaucoma Patients

Growing evidence suggests that intracranial pressure (ICP) plays an important role in the pathophysiology of glaucoma, especially in normal-tension glaucoma (NTG) patients. Controversial results exist about ICP’s relationship to visual field (VF) changes. With the aim to assess the relationship between ICP and VF zones in NTG patients, 80 NTG patients (age 59.5 (11.6) years) with early-stage glaucoma were included in this prospective study. Intraocular pressure (IOP) (Goldmann), visual perimetry (Humphrey) and non-invasive ICP (via a two-depth Transcranial Doppler, Vittamed UAB, Lithuania) were evaluated. Translaminar pressure difference (TPD) was calculated according to the formula TPD = IOP − ICP. The VFs of each patient were divided into five zones: nasal, temporal, peripheral, central, and paracentral. The average pattern deviation (PD) scores were calculated in each zone. The level of significance p < 0.05 was considered significant. NTG patients had a mean ICP of 8.5 (2.4) mmHg. Higher TPD was related with lower mean deviation (MD) (p = 0.01) and higher pattern standard deviation (PSD) (p = 0.01). ICP was significantly associated with the lowest averaged PD scores in the nasal VF zone (p < 0.001). There were no significant correlations between ICP and other VF zones with the most negative mean PD value. (p > 0.05). Further studies are needed to analyze the involvement of ICP in NTG management.

Lumbar puncture position influences intracranial pressure

BACKGROUND

The standard lumbar puncture position involves maximum flexion of both lumbar and cervical spine. The cerebrospinal fluid opening pressure (CSF_op) is measured in a horizontal position. This study investigated if flexion of hip and neck both separately and simultaneously influence intracranial pressure (ICP) to a clinically relevant extent.

METHODS

Thirty-nine patients, undergoing invasive ICP monitoring as part of diagnostic work-up, were included. The patients underwent either a vertical postural examination (n = 24) or a horizontal postural examination (n = 15) to examine a varying degree of spine flexion.

RESULTS

The vertical examination showed that ICP decreased by 15.2 mmHg when straightening the neck in a sitting lumbar puncture position (n = 24, IQR - 20.1 to - 9.7). In the horizontal examination, ICP increased in all but one patient when changing from supine position to lateral recumbent position (n = 15, median increase of 6.9 mmHg, IQR 3.1 to 9.9). Straightening the hips alone decreased ICP with 0.2 mmHg (n = 15, IQR - 0.5 to 2.0), while straightening the neck alone decreased ICP by 4.0 mmHg (n = 15, IQR - 5.9 to - 1.7). However, when straightening the hip and neck simultaneously ICP decreased by 6.4 mmHg (n = 6, IQR - 9.5 to - 4.4).

CONCLUSIONS

Neck flexion alone, and neck flexion and hip flexion in combination, has significant confounding influence on ICP. This may cause patients to shift from a normal ICP range to a pathological ICP range, which will potentially affect treatment decisions. Consensus on guidelines for body position including neck and hip flexion measuring CSF_op may be needed.

Cerebrospinal fluid opening pressure in clinical practice - a prospective study

Background

Measurement of CSF opening pressure (CSFOP) is valuable and much used in the investigation of several neurological conditions. However, there are different opinions regarding reference values and influence of age, gender and body mass index (BMI). We have, in a previous study, noted possible differences in CSFOP between gender and age groups. Here the aim was to collect information regarding normal distribution of CSFOP in an out-patient sample and also include BMI.

Methods

We collected CSFOP from a lumbar puncture, following a standardized procedure, performed in an ordinary neurological out-patient sample. Age, gender and BMI was also registered. Descriptive statistics and linear regression was used.

Results

339 patients with a normal distribution of age and BMI were included consecutively (60% females). We found a mean CSFOP of 17.5 H₂O (range 4.0–30.0). In multivariable linear regression, age, gender and BMI all independently affected CSFOP. Male gender (β = 1.5, p = 0.002), lower age (β =  – 0.095, p < 0.001) and higher BMI (β = 0.42, p < 0.001) were all associated with higher CSFOP.

Conclusion

Using two standard deviations, we provide suggestions for CSFOP limits with respect to gender, age and BMI. Our results suggest that CSFOP cut-offs for pathological intracranial hypertension should be raised with these factors taken into consideration. As a “rule-of-thumb” we suggest the following cut-offs: for males < 30 cm H₂O (< 25 if over age 70), and for females < 25 cm H₂O (27.5 if over 30 BMI). A diagnosis of intracranial hypertension should not be given without such considerations.

Population-Based Evaluation of Lumbar Puncture Opening Pressures

Importance: Prior studies evaluating opening pressure (OP) have mostly involved lumbar puncture (LP) for diagnosis of neurologic disease or small cohorts of healthy volunteers and therefore the normal OP is not well-defined.

Objective: The goal of this study was to establish the normal range of OP in a community-based population using the Mayo Clinic Study of Aging (MCSA) and to evaluate factors that contribute to OP variability.

Design: LP OP were obtained from participants aged 32–95 years between 11/1/07 and 10/1/17, as part of routine data collection for the MCSA, a longitudinal, population-based study of residents of Olmsted County, Minnesota.

Setting: A longitudinal, population-based study of residents of Olmsted County, Minnesota.

Participants: There were 639 participants (56.8% male; 98.5% white) who underwent LP with recorded OP as part of the MCSA.

Intervention: LP.

Main Outcome(s) and Measure(s): LP OP was recorded along with variables that could possibly influence its variability, including age, body mass index (BMI), and obstructive sleep apnea (OSA).

Results: Six hundred thirty-nine participants (56.8% men) underwent LP with recorded OP; average age was 71.0 years (SD 10.9) with a mean BMI of 28.0 (SD 4.6). Mean OP was 155.4 mmH₂O (SD 41.9) with a 95% reference interval of 82–242 mmH₂O (range 60–314; Q1, Q3: 124, 182). Increasing age was associated with lower OP (p < 0.001), while increasing BMI was associated with higher OP (p < 0.001). Twelve (2%) participants had OP ≥ 250 mmH₂O; they were younger [58.5 (SD 8.2), p < 0.001], had higher BMI [33.6 (SD 4.6), p < 0.001], and were more likely to have OSA (75%, p < 0.001). Among the 79 participants with repeat LPs within 2.5 years, the coefficient of repeatability (CR) was 64.9. Ten (12.7%) had an OP difference ≥50 mmH₂O between serial LPs.

Conclusions and Relevance: This large population-based study showed that LP OP can vary significantly among individuals. Higher OPs were associated with higher BMI and younger age.

Cerebrospinal Fluid Pressure-Related Features in Chronic Headache: A Prospective Study and Potential Diagnostic Implications

Objective: To identify the pressure-related features of isolated cerebrospinal fluid hypertension (ICH) in order to differentiate headache sufferers with ICH from those with primary headache disorder. Methods: In this prospective study, patients with refractory chronic headaches and suspected of having cerebrospinal fluid-pressure elevation without papilledema or sixth nerve palsy, together with controls, underwent 1-h lumbar cerebrospinal fluid pressure monitoring via a spinal puncture needle. Results: We recruited 148 consecutive headache patients and 16 controls. Lumbar cerebrospinal fluid pressure monitoring showed high pressure and abnormal pressure pulsations in 93 (63 %) patients with headache: 37 of these patients with the most abnormal pressure parameters (opening pressure above 250 mm H₂O, mean pressure 301 mm H₂O, mean peak pressure 398 mm H₂O, and severe abnormal pressure pulsations) had the most severe headaches and associated symptoms (nocturnal headache, postural headache, transient visual obscuration); 56 patients with the less abnormal pressure parameters (opening pressure between 200 and 250 mm H₂O, mean pressure 228 mm H₂O, mean peak pressure 316 mm H₂O, and abnormal pressure pulsations) had less severe headaches and associated symptoms. Conclusions: Nocturnal and postural headache, and abnormal pressure pulsations are the more common pressure-related features of ICH in patients with chronic headache. Abnormal pressure pulsations may be considered a marker of ICH in chronic headache.

Idiopathic Intracranial Hypertension: Prognostic Factors and Multidisciplinary Management

BACKGROUND

Idiopathic intracranial hypertension (IIH) mostly affects young obese women and can lead to permanent visual impairment. However, prognostic factors and therapeutic strategy remain unclear.

METHODS

We retrospectively collected data from all patients diagnosed and managed for IIH in our university center from January 2001 to December 2016.

RESULTS

Seventy-nine patients were diagnosed with IIH. Bilateral transverse sinus stenosis (TSS) was found in 74% of the population. Visual outcome at 6 months was poor for 46% of patients, including all patients presenting weight gain of at least 5% since diagnosis (p < 0.001), whereas mean body mass index at diagnosis was not different between patients with poor versus good outcome (32.9 ± 7.7 versus 34.6 ± 9.4 kg·m^-2). Other significant factors of poor prognosis were bilateral TSS (OR = 5.2; 95 CI: 1.24-24.9; p = 0.024). Thirteen patients with poor outcome after 6-month assessment underwent unilateral TSS stenting leading to visual improvement in 11 cases.

CONCLUSION

Weight gain, rather than initial weight, emerged as the leading factor of poor visual outcome in patients with IIH, followed by presence of bilateral TSS. Consequently, first-line treatment must include dietary measures to control weight. Unilateral stenting appears to be a safe second-line treatment option for patients with bilateral TSS.

Pediatric Intracranial Hypertension

Primary (idiopathic) intracranial hypertension has been considered to be a rare entity, but with no precise estimates of the pediatric incidence in the United States. There have been attempts to revise the criteria over the years and adapt the adult criteria for use in pediatrics. The clinical presentation varies with age, and symptoms tending to be less obvious in younger individuals. In the prepubertal population, incidentally discovered optic disc edema is relatively common. By far the most consistent symptom is headache; other symptoms include nausea, vomiting tinnitus, and diplopia. Treatment mainstays include weight loss when appropriate and acetazolamide. Furosemide may exhibit a synergistic benefit when used in conjunction with acetazolamide. Surgical interventions are required relatively infrequently, but include optic nerve sheath fenestration and cerebrospinal fluid shunting. Pain and permanent vision loss are the two major complications of this disorder and these manifestations justify aggressive treatment. Once intracranial hypertension has resolved, up to two thirds of patients develop a new or chronic headache type that is different from their initial presenting headache.

How common is normal cerebrospinal fluid pressure in spontaneous intracranial hypotension?

Objectives

To determine the proportion of patients with spontaneous intracranial hypotension (SIH) who had a cerebrospinal fluid (CSF) pressure >6 cm H2O and to investigate the clinical and imaging variables associated with CSF pressure ( PCSF) in this condition.

Methods

We retrospectively reviewed 106 patients with SIH. PCSF was measured by lumbar puncture prior to treatment. Clinical and imaging variables – including demographic data, brain imaging results, symptom duration, and abdominal circumference – were collected. Univariate and multivariate analyses were performed to determine the correlation of these variables with PCSF.

Results

Sixty-one percent of patients had a PCSF between 6 and 20 cm H2O; only 34% had a PCSF ≤6 cm H2O. The factors associated with increased PCSF included abdominal circumference ( p < 0.001), symptom duration ( p = 0.015), and the absence of brain magnetic resonance imaging findings of SIH ( p = 0.003). A wide variability in PCSF was observed among all patients, which was not completely accounted for by the variables included in the model.

Conclusions

Normal CSF pressure is common in patients with SIH; the absence of a low opening pressure should not exclude this condition. Body habitus, symptom duration, and brain imaging are correlated with PCSF measurements, but these factors alone do not entirely explain the wide variability in observed pressures in this condition and this suggests the influence of other factors.

Intracranial pressure in unresponsive chronic migraine

To assess the prevalence and possible pathogenetic involvement of raised intracranial pressure in patients presenting with unresponsive chronic migraine (CM), we evaluated the intracranial opening pressure (OP) and clinical outcome of a single cerebrospinal fluid withdrawal by lumbar puncture in 44 consecutive patients diagnosed with unresponsive chronic/transformed migraine and evidence of sinus stenosis at magnetic resonance venography. The large majority of patients complained of daily or near-daily headache. Thirty-eight (86.4 %) had an OP >200 mmH₂O. Lumbar puncture-induced normalization of intracranial pressure resulted in prompt remission of chronic pain in 34/44 patients (77.3 %); and an episodic pattern of headache was maintained for 2, 3 and 4 months in 24 (54.6 %), 20 (45.4 %) and 17 (38.6 %) patients, respectively. The medians of overall headache days/month and of disabling headache days/month significantly decreased (p < 0.0001) at each follow-up versus baseline. Despite the absence of papilledema, 31/44 (70.5 %) patients fulfilled the ICHD-II criteria for “Headache attributed to Intracranial Hypertension”. Our findings indicate that most patients diagnosed with unresponsive CM in specialized headache clinics may present an increased intracranial pressure involved in the progression and refractoriness of pain. Moreover, a single lumbar puncture with cerebrospinal fluid withdrawal results in sustained remission of chronic pain in many cases. Prospective controlled studies are needed before this procedure can be translated into clinical practice. Nonetheless, we suggest that intracranial hypertension without papilledema should be considered in all patients with almost daily migraine pain, with evidence of sinus stenosis, and unresponsive to medical treatment referred to specialized headache clinics.

Body mass index has a linear relationship with cerebrospinal fluid pressure

PURPOSE

To examine the relationship between body mass index (BMI) and cerebrospinal fluid pressure (CSFP), as low BMI and low CSFP have recently been described as risk factors for primary open-angle glaucoma (POAG).

METHODS

This was a retrospective review of the electronic medical records of patients who had CSFP measured by lumbar puncture and data to calculate BMI at the Mayo Clinic (Rochester, MN). Exclusion criteria included diagnoses, surgical procedures and medications known to affect CSFP. Mean CSFP for each unit BMI was calculated. The probabilities were two-tailed, and the α level was set at P < 0.05. Patients with documented BMI, CSFP, and intraocular pressure (IOP) were analyzed for the relationship between IOP and BMI.

RESULTS

A total of 4235 patients, primarily of Caucasian descent, met the entry criteria. Median BMI was 26 and the mean CSFP was 10.9 ± 2.6 mm Hg. The increase in CSFP with increasing BMI was linear with an r(2) = 0.20 (P < 0.001). CSFP increased by 37.7% from BMI 18 (8.6 ± 2.1 mm Hg) to BMI 39 (14.1 ± 2.5 mm Hg). The r(2) (0.21) of the model of BMI and sex was similar to the r(2) of a BMI-only model (0.20). There was no relation between IOP and BMI within a subgroup of the study population (r (2) = 0.005; P = 0.14).

CONCLUSIONS

CSFP has a positive, linear relationship with BMI. IOP is not influenced by BMI. If CSFP influences the risk for POAG, then individuals with a lower BMI may have an increased risk for developing POAG. Similarly, a higher BMI may be protective.

Idiopathic intracranial hypertension

Idiopathic intracranial hypertension ((IIH) is characterized by increased cerebrospinal fluid pressure of unknown cause. It is predominantly a disease of women in the childbearing years. Although the cause of IIH remains obscure, it has become clear that loss of visual function is common and patients may progress to blindness if untreated. Diagnosis should adhere to the modified Dandy criteria and other causes of intracranial hypertension sought. IIH patient management should include serial perimetry and optic disc grading or photography. The proper therapy can then be selected and visual loss prevented or reversed. Although there are no evidence-based data to guide therapy, there is an ongoing randomized double-blind controlled treatment trial of IIH investigating diet and medical therapy.

Cerebrospinal fluid opening pressure measurements in acute headache patients and in patients with either chronic or no pain

OBJECTIVE

To observe cerebrospinal fluid opening pressure (CSFOP) in different clinical settings and in patients with acute, chronic and no pain and to observe possible differences because of age and sex.

METHOD

In this prospective study, CSFOP was measured in lumbar puncture in three different settings of clinical investigations; patients with acute headache investigated for subarachnoidal haemorrhage (n = 222), patients with sciatica undergoing myelography (n = 61), and patients in an outpatient neurological clinic (n = 65).

RESULTS

The mean CSFOP in cm H(2)O was 17.3 for the myelography patients, 19.1 for the outpatients, 19.3 for the primary headache patients and 22.4 for the patients with secondary headache. Large proportions of patients in all groups had CSFOP above 20 cm H(2)O. The female patients in all groups had lower mean CSFOP than the male patients.

CONCLUSION

The CSFOP levels found in clinical practice among patients without intracranial lesions or infectious conditions were broader than expected. Measurement of CSFOP is of limited value as diagnostic procedure if not closely linked to clinical symptoms and finds.

Abnormal pressure waves in headache sufferers with bilateral transverse sinus stenosis

Introduction: Bilateral transverse sinus stenosis (BTSS) has been reported to be associated with idiopathic intracranial hypertension without papilloedema in headache sufferers.

Subjects and methods: To test the accuracy of short-term cerebrospinal fluid (CSF) pressure monitoring through a lumbar needle for detection of elevated intracranial pressure in headache sufferers with BTSS, we prospectively performed lumbar puncture in order to measure lumbar CSF opening pressures and to monitor, for 1 h, the CSF pressure in 48 consecutive headache sufferers with BTSS and in 50 consecutive headache sufferers with normal appearance of transverse sinuses or stenosis of one transverse sinus.

Results: Of the 48 headache sufferers with BTSS, 18 (37.5%) had elevated CSF opening pressure and abnormal pressure waveforms, but short-term CSF pressure monitoring revealed abnormal pressure waves associated with elevated mean CSF pressure also in 26 (86.6%) out of 30 patients who had normal opening pressures. None of the 50 headache sufferers with normal appearance of transverse sinuses or stenosis of one transverse sinus had abnormal pressure waves and elevated CSF pressures.

Conclusions: In this study, short-term CSF pressure monitoring through a lumbar needle revealed abnormal pressure waves and elevated mean CSF pressures in the majority of headache sufferers with BTSS who had normal CSF opening pressures. These findings demonstrate the accuracy of short-term CSF pressure monitoring through a lumbar needle in estimating CSF pressure; they also highlight that a single-spot opening pressure measurement has a low accuracy for recognition of increased intracranial pressure in headache sufferers with BTSS.

The upper limit of normal CSF opening pressure is related to bilateral transverse sinus stenosis in headache sufferers

There are limited data on the relationship between normal cerebrospinal fluid (CSF) opening pressure and bilateral transverse sinus stenosis (BTSS); there are also several conflicting reports about the upper limit of normal CSF opening pressure. To evaluate the influence of BTSS on the upper limit of normal CSF opening pressure, we prospectively recorded lumbar CSF opening pressures in 217 adult patients with neurological symptoms who underwent cerebral magnetic resonance venography (MRV). The CSF opening pressures ranged between 65 and 286 mmH2O (mean = 149.3, s.d. = 47.5). The upper limit of opening pressure in patients with both normal appearance of transverse sinuses and unilateral transverse sinus stenosis on MRV ( n = 167) was 195 mmH2O with a range of 65–195 mmH2O. All patients with BTSS were headache sufferers, and the upper limit of opening pressure in patients with BTSS ( n = 50) was 286 mmH2O with a range of 91–286 mmH2O. All patients with opening pressures > 200 mmH2O displayed BTSS, whereas only 13% of patients with a pressure < 200 mmH2O displayed BTSS. Our findings demonstrate that the upper limit of normal CSF opening pressure is related to BTSS, and they also highlight that headache sufferers with opening pressures > 200 mmH2O should be tested for BTSS by MRV.

Idiopathic intracranial hypertension with and without papilloedema in a consecutive series of patients with chronic migraine

Chronic migraine (CM) has been associated with idiopathic intracranial hypertension without papilloedema (IIHWOP), a significant percentage of these cases occurring in obese patients with intractable headache. A prospective study from February 2005 to June 2006 was made of 62 CM patients who fulfilled International Headache Society diagnostic criteria and had cerebral magnetic resonance venography (MRV) and lumbar puncture (LP) done. Two patients were excluded, six (10%) with elevated cerebrospinal fluid (CSF) open pressure (OP), five with body mass index (BMI) > 25. None of the patients had papilloedema or abnormal MRV. BMI and CSF OP were significantly correlated (r = 0.476, P < 0.001, Pearson's correlation test). Obesity (defined as BMI > 30) was a predictor of increase in intracranial pressure (defined as OP > 200 mmH(2)O) (f = 17.26, 95% confidence interval 6.0, 8.6; P < 0.001). From our study we strongly recommend that not only intractable CM patients with high BMI, but also first diagnosed patients with BMI > 30 should be systematically evaluated by a LP to rule out IIHWOP.

Laser scanning tomography measurement of the extent of papilledema in the follow-up examination of patients with idiopathic intracranial hypertension

Object

The authors evaluated the characteristics of patients with idiopathic intracranial hypertension (IIH), and compared laser scanning tomography (LST) measurements of papilledema with the clinical parameters and cerebrospinal fluid (CSF) opening pressures obtained.

Methods

Twenty-four patients were included in this study; these individuals included 21 women and three men with a mean age of 35.5 ± 9.7 years and a mean body mass index (BMI) of 35.4 ± 8.3 kg/m2. The authors conducted a prospective follow-up study over a period of 12 months through a series of four consultations with each patient. These patients had a mean time to treatment of 6.2 ± 7.9 months and, at the time of diagnosis, suffered a mean of 2.8 ± 1.3 symptoms each. Laser scanning tomography of the optic disc revealed a mean global rim volume of 1.693 ± 1.662 mm3 and a mean height of 0.604 ± 0.306 mm. The mean CSF opening pressure was 31.3 ± 6.3 cm H20.

Results

During the follow-up period, all patients improved significantly with regard to clinical parameters (p < 0.001), BMI reduction (p < 0.001), and reduction of visual field deficits (p = 0.007); visual acuity remained unchanged. In all patients at each successive consultation, the CSF opening pressure was lower than it had been at the previous consultation (p = 0.001). Laser scanning tomography measurements demonstrated a statistically significant reduction in both optic disc parameters over the follow-up period (global rim volume, p = 0.044; mean height, p = 0.019). The CSF opening pressure and the LST measurements correlated significantly with the number of symptoms (CSF opening pressure, p < 0.001; global rim volume, p = 0.001; mean height, p < 0.001). The mean area under the receiver operating characteristic curve in detecting the presence of clinical symptoms was 0.87 for CSF opening pressure, 0.7 for rim volume, and 0.81 for mean optic disc height.

Conclusions

Laser scanning tomography measurements are useful for evaluating the degree of papilledema in patients with IIH and correspond well with clinical data and measurements of CSF opening pressure. If a diagnosis of IIH is established, LST measurements may replace repeated CSF opening pressure measurements in follow-up monitoring.

What is new about idiopathic intracranial hypertension? An updated review of mechanism and treatment

Idiopathic intracranial hypertension (IIH) is the syndrome of raised intracranial pressure without clinical, laboratory or radiological evidence of intracranial pathology. IIH is a relatively rare disease but rapidly increasing incidence is reported due to a global increasing incidence of obesity. Disease course is generally said to be self-limiting within a few months. However, some patients experience a disabling condition of chronic severe headache and visual disturbances for years that limit their capacity to work. Permanent visual defects are serious and not infrequent complications. The pathophysiology of IIH is still not fully understood. Advances in neuroimaging techniques have facilitated the exclusion of associated conditions that may mimic IIH. No causal treatment is yet known for IIH and existing treatment is symptomatic and rarely sufficient. The aim of this review is to provide an updated overview of this potentially disabling disease which may show a future escalating incidence due to obesity. Theories of pathogenesis, diagnostic criteria and treatment strategies are discussed.

Idiopathic intracranial hypertension

Idiopathic intracranial hypertension is common in obese women and can lead to significant visual impairment. First described more than 100 years ago, the cause of the disorder remains unknown. Despite a multitude of proposed links, the aetiology has never been established. Impairment of cerebrospinal-fluid reabsorption is the most likely underlying pathophysiological cause of the raised pressure, but this notion has yet to be proven. Cerebral venous sinus abnormalities associated with the disorder need further exploration. Although the major symptoms of headache and visual disturbance are well documented, most data for disease outcome have been from small retrospective case series. No randomised controlled trials of treatment have been done and the management is controversial. The importance of weight loss needs clarification, the role of diuretics is uncertain, and which surgical intervention is the most effective and safe is unknown. Prospective trials to examine these issues are urgently needed.

Diagnosing idiopathic normal-pressure hydrocephalus

OBJECTIVE

The precise incidence and prevalence of idiopathic normal-pressure hydrocephalus (INPH) is not known, and evidence-based clinical diagnostic criteria have not been developed previously. This report contains evidence-based guidelines for clinical diagnosis of INPH that are intended to facilitate future epidemiological studies of INPH, promote earlier and more accurate diagnosis, and ultimately improve treatment outcome.

METHODS

The criteria for the diagnosis of INPH are based on evidence from the medical literature, supplemented as necessary by expert opinion. From 1966 to 2003, 653 publications on "normal-pressure hydrocephalus" were cited in MEDLINE, including 29 articles that met the more stringent criteria of including "idiopathic normal-pressure hydrocephalus" in their title. Additional studies were considered that explicitly identified INPH cases and/or specified the criteria for a diagnosis of INPH. Studies were graded according to the class of evidence and results summarized in evidentiary tables. For issues of clinical relevance that lacked substantive evidence from the medical literature, the opinions of consulting experts were considered and contributed to "Options."

RESULTS

Evidence-based guidelines for the clinical diagnosis of INPH have been developed. A detailed understanding of the range of clinical manifestations of this disorder and adherence to practice guidelines should improve the timely and accurate recognition of this disorder.

CONCLUSION

It is recommended that INPH be classified into probable, possible, and unlikely categories. We hope that these criteria will be widely applied in clinical practice and will promote greater consistency in patient selection in future clinical investigations involving INPH.