Headache arising from idiopathic changes in CSF pressure

Spontaneous intracranial hypotension: review and expert opinion

Spontaneous intracranial hypotension (SIH) results from spinal cerebrospinal fluid (CSF) leaking. An underlying connective tissue disorder that predisposes to weakness of the dura is implicated in spontaneous spinal CSF leaks. During the last decades, a much larger number of spontaneous cases are identified and a far broader clinical SIH spectrum is recognized. Orthostatic headache is the main presentation symptom of SIH; some patients also have other manifestations, mainly cochlear-vestibular signs and symptoms. Differential diagnosis with other syndromes presenting with orthostatic headache is crucial. Brain CT, brain MR, spine MRI, and MRI myelography are the imaging modalities of first choice for SIH diagnosis. Invasive imaging techniques, such as myelography, CT myelography, and radioisotopic cisternography, are progressively being abandoned. No randomized clinical trials have assessed the treatment of SIH. In a minority of cases, SIH resolved spontaneously or with only conservative treatment. If orthostatic headache persists after conservative treatment, a lumbar epidural blood patch (EBP) without previous leak identification (so-called "blind" EBP) is a widely used initial intervention and may be repeated several times. If EBPs fail, after the CSF leak sites identification using invasive imaging techniques, other therapeutic approaches include: a targeted epidural patch, surgical reduction of dural sac volume, or direct surgical closure. The prognosis is generally good after intervention, but serious complications may occur. More research is needed to better understand SIH pathophysiology to refine imaging modalities and treatment approaches and to evaluate clinical outcomes.

Spontaneous spinal CSF-venous fistulas associated with venous/venolymphatic vascular malformations: report of 3 cases

Spontaneous CSF-venous fistulas may be present in up to one-fourth of patients with spontaneous intracranial hypotension. This is a recently discovered type of CSF leak, and much remains unknown about these fistulas. Spinal CSF-venous fistulas are usually seen in coexistence with a spinal meningeal diverticulum, suggesting the presence of an underlying structural dural weakness at the proximal portion of the fistula. The authors now report the presence of soft-tissue venous/venolymphatic malformations associated with spontaneous spinal CSF-venous fistulas in 2 patients with spontaneous intracranial hypotension, suggesting a role for distal venous pathology. In a third patient with spontaneous intracranial hypotension and a venolymphatic malformation, such a CSF-venous fistula is strongly suspected.

Variability of Consecutive Lumbar Puncture Opening Pressures

BACKGROUND

Lumbar puncture (LP) opening pressures (OPs) are known to fluctuate based on diurnal, environmental, and pathologic conditions. Despite their dynamic nature, single OPs are often deemed sufficient for diagnosis of elevated intracranial pressures (ICPs) in nonspecialists' hands. The purpose of this study was to determine the variability of consecutive LP OPs at a large referral center to determine the potential range of variability for a given LP OP.

METHODS

In this retrospective cohort study, medical records of all patients seen at Mayo Clinic, Rochester, MN, from January 1, 2001, through June 1, 2016, were screened for ≥2 LP OPs within 30 days of each other. Patients with pathologic conditions known to influence ICP were excluded.

RESULTS

There were 148 eligible patients (39.2% female) with mean age of 63.5 ± 15.5 years and mean body mass index (BMI) 28.0 ± 6.0. The LPs were a mean of 10 ± 9 days apart. Mean OP for the first and second LP was 149 ± 51 mm H2O and 148 ± 48 mm H2O (P = 0.78), respectively, with a mean difference of 1 mm H2O, providing an overall coefficient of repeatability (CR) of 86.4 between consecutive LPs. There was a significant correlation between initial OP and BMI (r = 0.39, P < 0.001). OP >200 mm H2O had a significantly higher CR of 111.4, compared to OP <200 mm H2O, with CR 74.6 (P = 0.006). CRs were also higher for patients with diagnoses of headache (P = 0.002) or anxiety (P = 0.03).

CONCLUSIONS

Higher initial LP OP, headache, and anxiety were associated with greater variability on subsequent LPs. OPs that are not consistent with the patients' clinical signs and symptoms should therefore be interpreted with caution.

Comparing the Efficiency of Two Treatment Methods of Hydrocephalus: Shunt Implantation and Endoscopic Third Ventriculostomy

Introduction:

Hydrocephalus is one of the most common diseases in children, and its treatment requires brain operation. However, the pathophysiology of the disease is very complicated and still unknown.

Methods:

Endoscopic Third Ventriculostomy (ETV) and Ventriculoperitoneal Shunt (VPS) implantation are among the common treatments of hydrocephalus. In this study, Cerebrospinal Fluid (CSF) hydrodynamic parameters and efficiency of the treatment methods were compared with numerical simulation and clinical follow-up of the treated patients.

Results:

Studies have shown that in patients under 19 years of age suffering from hydrocephalus related to a Posterior Fossa Brain Tumor (PFBT), the cumulative failure rate was 21% and 29% in ETV and VPS operation, respectively. At first, the ETV survival curve shows a sharp decrease and after two months it gets fixed while VPS curve makes a gradual decrease and reaches to a level lower than ETV curve after 5.7 months. Post-operative complications in ETV and VPS methods are 17% and 31%, respectively. In infants younger than 12 months with hydrocephalus due to congenital Aqueduct Stenosis (AS), and also in the elderly patients suffering from Normal Pressure Hydrocephalus (NPH), ETV is a better treatment option. Computer simulations show that the maximum CSF pressure is the most reliable hydrodynamic index for the evaluation of the treatment efficacy in these patients. After treatment by ETV and shunt methods, CSF pressure decreases about 9 and 5.3 times, respectively and 2.5 years after shunt implantation, this number returns to normal range.

Conclusion:

In infants with hydrocephalus, initial treatment by ETV was more reasonable than implanting the shunt. In adult with hydrocephalus, the initial failure in ETV occurred sooner compared to shunt therapy; however, ETV was more efficient.

Characteristics of Diffuse Leptomeningeal Glioneuronal Tumor With First-Episode Headache and Rapid Blindness Misdiagnosed as Viral Meningoencephalitis

Diffuse leptomeningeal glioneuronal tumor has a high degree of malignancy and high mortality. The purpose of this paper is to describe the characteristics of atypical diffuse leptomeningeal glioneuronal tumor and analyze the causes of misdiagnosis as viral meningoencephalitis. An adolescent female patient presented with headache, nausea, vomiting, sharp vision loss and cognitive dysfunction. After poor therapeutic effect of standard antiviral treatment, further inspection found that malignant cells were detected by cerebrospinal fluid (CSF) cytology; and enhanced magnetic resonance imaging (MRI) showed extensive enhancement of the leptomeningeal. In conclusions, when patient with unexplained high intracranial pressure, it is necessary to be alert to the diagnosis of diffuse leptomeningeal glioneuronal tumor. Multiple examinations of fresh CSF are helpful to increase the positive detection rate of tumor cells. Early diagnosis and active treatment are conducive to improving survival rate.

Intradural non-calcified thoracic disc herniation causing spontaneous intracranial hypotension: a case report

Background

Spontaneous intracranial hypotension (SIH) is a rare pathology caused by a cerebrospinal fluid (CSF) leak. If intractable by conventional methods (i.e. bedrest, analgesics, or epidural blood patching) it may lead to the inability of the patient to cope with daily life and eventually to life-threatening complications. Recently, calcified discogenic microspurs or dorsal osteophytes were identified as a major cause for ventral CSF loss through vertical longitudinal dural slits. We report a rare case of intractable SIH due to an intradural disc herniation at the thoracolumbar junction (without signs of calcification) and its management.

Case presentation

A 46-year old woman suffered from orthostatic headache (sudden onset, no history of trauma) due to intractable SIH for over 2 month (without neurologic deficits). There was no clinical amelioration by conservative measures (analgesics, bedrest) and serial unspecific epidural blood patches (repeated for 3 times). She was diagnosed with an intradural disc herniation at the thoracolumbar junction causing a CSF leak. Surgical exploration by a translaminar and transdural approach with removal of the disc herniation and closure of the CSF leak was performed with immediate cessation of orthostatic symptoms. Histological workup revealed non-calcified intervertebral disc material. After 3 months of follow-up and no evidence for clinical relapse the patient returned to work.

Conclusions

We report the rare phenomenon of an intradural non-calcified disc sequester at the thoracolumbar junction as the cause of a ventral dural tear leading to a CSF leak with intractable SIH. This is of particular interest as the major cause of ventral dural leakage is thought to arise from calcified discogenic microspurs or dorsal osteophytes. Furthermore, we comprehensively describe a short and reasonable diagnostic and surgical approach of this rare pathology, which may particularly be of use in daily clinical routine in neurological wards and general surgical spine centers not facing such pathologies on a regular basis.

Electronic supplementary material

The online version of this article (10.1186/s12893-019-0527-3) contains supplementary material, which is available to authorized users.

Rebound high-pressure headache after treatment of spontaneous intracranial hypotension: MRV study

BACKGROUND

Rebound high-pressure headaches may complicate treatment of spontaneous intracranial hypotension (SIH), but no comprehensive study of such patients has been reported and little is known about its frequency and risk factors. We therefore studied patients undergoing treatment for SIH and performed magnetic resonance venography (MRV) to assess for cerebral venous sinus stenosis, a risk factor for idiopathic intracranial hypertension.

METHODS

We studied a consecutive group of patients who underwent treatment for SIH. Rebound high-pressure headache was defined as a reverse orthostatic headache responsive to acetazolamide. MRV was obtained in all patients and lateral sinus stenosis was scored according to the system published by Higgins et al., with 0 being normal and 4 signifying bilateral signal gaps.

RESULTS

The mean age of the 46 men and 67 women was 45.9 years (range 13-71 years) at the time of onset of SIH. Rebound high-pressure headache was diagnosed in 31 patients (27.4%); 14% of patients with an MRV score of 0, 24% with a score of 1, and 46% with a score of 2 or 3 (p = 0.0092). Also, compared to SIH patients who did not develop rebound high-pressure headaches (n = 82), those with rebound high-pressure headaches were younger, more often female, and more often had an extradural CSF collection on spinal imaging.

CONCLUSIONS

Rebound high-pressure headache occurs in about one-fourth of patients following treatment of SIH and is more common in those with restriction of cerebral venous outflow.

Correlations among brain and spinal MRI findings in spontaneous intracranial hypotension

Objectives

Several brain and spinal magnetic resonance imaging signs have been described in spontaneous intracranial hypotension. Their correlations are not fully studied. This study aimed to explore potential mechanisms underlying cerebral neuroimaging findings and to examine associations among spinal and brain magnetic resonance imaging signs.

Methods

We conducted a retrospective review of magnetic resonance myelography and brain magnetic resonance imaging records of patients with spontaneous intracranial hypotension. Categorical principal component analysis was employed to cluster brain neuroimaging findings. Spearman correlation was employed to analyze associations among different brain neuroimaging findings and between brain and spinal neuroimaging findings.

Results

In patients with spontaneous intracranial hypotension (n = 148), categorical principal component analysis of brain neuroimaging signs revealed two clusters: Cerebral venous dilation and brain descent. Among all brain magnetic resonance imaging signs examined, only midbrain-pons angle associated with anterior epidural cerebrospinal fluid collection length (surrogate spinal cerebrospinal fluid leak severity) (n = 148, Spearman’s ρ = −0.38, p < .001). Subgroup analyses showed that the association between midbrain-pons angle (within brain descent cluster) and spinal cerebrospinal fluid leak severity was presented in patients with convex margins of the transverse sinuses (n = 122, Spearman’s ρ = −0.43, p < .001), but not in patients without convex margins (n = 26, Spearman’s ρ = −0.19, p = .348). The association between severity of transverse sinus distension and spinal cerebrospinal fluid leak severity was only presented in patients without convex margins (n = 26, Spearman’s ρ = 0.52, p = .006).

Conclusion

This study indicates that there are two factors behind the brain neuroimaging findings in spontaneous intracranial hypotension: Cerebral venous dilation and brain descent. Certain brain neuroimaging signs correlate with spinal cerebrospinal fluid leakage severity, depending on different circumstances.

European headache federation guideline on idiopathic intracranial hypertension

Background

Idiopathic Intracranial Hypertension (IIH) is characterized by an elevation of intracranial pressure (ICP no identifiable cause. The aetiology remains largely unknown, however observations made in a number of recent clinical studies are increasing the understanding of the disease and now provide the basis for evidence-based treatment strategies.

Methods

The Embase, CDSR, CENTRAL, DARE and MEDLINE databases were searched up to 1st June 2018. We analyzed randomized controlled trials and systematic reviews that investigate IIH.

Results

Diagnostic uncertainty, headache morbidity and visual loss are among the highest concerns of clinicians and patients in this disease area. Research in this field is infrequent due to the rarity of the disease and the lack of understanding of the underlying pathology.

Conclusions

This European Headache Federation consensus paper provides evidence-based recommendations and practical advice on the investigation and management of IIH.

Electronic supplementary material

The online version of this article (10.1186/s10194-018-0919-2) contains supplementary material, which is available to authorized users.

Sonography of the optic nerve sheath diameter before and after microsurgical closure of a dural CSF fistula in patients with spontaneous intracranial hypotension - a consecutive cohort study

OBJECTIVE

Spontaneous intracranial hypotension is caused by spinal cerebrospinal fluid leakage. Patients with orthostatic headaches and cerebrospinal fluid leakage show a decrease in optic nerve sheath diameter upon movement from supine to upright position. We hypothesized that the decrease in optic nerve sheath diameter upon gravitational challenge would cease after closure of the leak.

METHODS

We included 29 patients with spontaneous intracranial hypotension and refractory symptoms admitted from 2013 to 2016. The systematic workup included: Optic nerve sheath diameter sonography, spinal MRI and dynamic myelography with subsequent CT. Microsurgical sealing of the cerebrospinal fluid leak was the aim in all cases.

RESULTS

Of 29 patients with a proven cerebrospinal fluid leak, one declined surgery. A single patient was lost to follow-up. In 27 cases, the cerebrospinal fluid leak was successfully sealed by microsurgery. The width of the optic nerve sheath diameter in supine position increased from 5.08 ± 0.66 mm before to 5.36 ± 0.53 mm after surgery ( p = 0.03). Comparing the response of the optic nerve sheath diameter to gravitational challenge, there was a significant change from before (-0.36 ± 0.32 mm) to after surgery (0.00 ± 0.19 mm, p < 0.01). In parallel, spontaneous intracranial hypotension-related symptoms resolved in 26, decreased in one and persisted in a single patient despite recovery of gait.

CONCLUSIONS

The sonographic assessment of the optic nerve sheath diameter with gravitational challenge can distinguish open from closed spinal cerebrospinal fluid fistulas in spontaneous intracranial hypotension patients. A response to the gravitational challenge, that is, no more collapse of the optic nerve sheath while standing up, can be seen after successful treatment and correlates with the resolution of clinical symptoms. Sonography of the optic nerve sheath diameter may be utilized for non-invasive follow-up in spontaneous intracranial hypotension.

Cotransporter-mediated water transport underlying cerebrospinal fluid formation

Cerebrospinal fluid (CSF) production occurs at a rate of 500 ml per day in the adult human. Conventional osmotic forces do not suffice to support such production rate and the molecular mechanisms underlying this fluid production remain elusive. Using ex vivo choroid plexus live imaging and isotope flux in combination with in vivo CSF production determination in mice, we identify a key component in the CSF production machinery. The Na⁺/K⁺/2Cl⁻ cotransporter (NKCC1) expressed in the luminal membrane of choroid plexus contributes approximately half of the CSF production, via its unusual outward transport direction and its unique ability to directly couple water transport to ion translocation. We thereby establish the concept of cotransport of water as a missing link in the search for molecular pathways sustaining CSF production and redefine the current model of this pivotal physiological process. Our results provide a rational pharmacological target for pathologies involving disturbed brain fluid dynamics.

Osmotic forces do not suffice to explain the rate of cerebrospinal fluid (CSF) production. Here, the authors show that the Na⁺/K⁺/2Cl⁻ cotransporter in the choroid plexus contributes substantially to CSF production via its inherent ability to cotransport water.

Clinical symptoms and results of autonomic function testing overlap in spontaneous intracranial hypotension and postural tachycardia syndrome

Background and purpose:

Orthostatic headache is a hallmark of patients with spontaneous intracranial hypotension (SIH) but may also occur in patients with postural tachycardia syndrome (POTS). Our aim was to compare the clinical symptoms and findings of autonomic function testing in patients with SIH and POTS.

Methods:

This was a retrospective analysis of the clinical symptoms and findings of autonomic function testing, including sympathetic vasoconstrictor and parasympathetic cardiac function as well as head-up tilt in patients with SIH and POTS.

Results:

Nine patients with confirmed SIH and 48 with POTS (neuropathic N = 35, hyperadrenergic N = 5, deconditioned N = 8) were included. SIH patients experienced on average a shorter disease duration than patients with POTS. Orthostatic headache was present in all patients with SIH and 27% of patients with POTS. There was a broad overlap of other clinical symptoms of orthostatic intolerance. Screening autonomic function testing revealed normal sympathetic and parasympathetic function in all patients. All patients with SIH showed an excessive clinically symptomatic heart rate increase during standing, fulfilling the diagnostic criteria for POTS.

Conclusion:

Clinical symptoms and results of autonomic function testing overlap in SIH and POTS. Hence, patients with prominent orthostatic headache fulfilling the diagnostic criteria for POTS should also be evaluated for further testing of a spinal cerebrospinal fluid leak, in the absence of a history of lumbar puncture.

Behavioral Variant Frontotemporal Dementia as a Serious Complication of Spontaneous Intracranial Hypotension

BACKGROUND

Behavioral variant frontotemporal dementia (bvFTD) is a devastating early onset dementia. Symptoms of bvFTD may be caused by spontaneous intracranial hypotension (SIH), a treatable disorder, but no comprehensive study of such patients has been reported.

OBJECTIVE

To describe detailed characteristics of a large cohort of patients with SIH and symptoms of bvFTD.

METHODS

We identified patients with SIH who met clinical criteria for bvFTD. Patients were compared to a cohort of SIH patients without bvFTD.

RESULTS

The mean age for the 21 men and 8 women was 52.9 yr (range, 37–65 yr). All 29 patients with bvFTD symptoms had hypersomnolence. Magnetic resonance imaging showed brain sagging in all patients, cerebrospinal fluid (CSF) opening pressure low in about half of patients, but a spinal CSF leak could not be detected in any patient. All patients underwent epidural blood patching, but 26 patients eventually underwent 1 or more surgical procedures. Overall, a good outcome was obtained in 21 patients (72%); 20 (91%) of 22 patients who had not undergone prior Chiari surgery compared to 1 (14%) of 7 patients who did undergo Chiari surgery (P &lt; .003). Compared to SIH patients without symptoms of bvFTD (n = 547), those with bvFTD symptoms were older, more often male, less often demonstrated CSF leak on spinal imaging, and more often underwent surgery (P &lt; .02).

CONCLUSION

bvFTD in SIH is rare and associated with brain sagging and hypersomnolence. Spinal CSF leaks are rarely detected. bvFTD symptoms are often refractory to the usual percutaneous procedures but most patients can be cured.

Impaired cerebrospinal fluid pressure

Abnormalities of cerebrospinal fluid (CSF) pressure are relatively common and may lead to a variety of symptoms, with headache usually being the most prominent one. The clinical presentation of alterations in CSF pressure may vary significantly and show a striking similitude to several primary headache syndromes. While an increase in CSF pressure may be of primary or secondary origin, a pathologic decrease of CSF pressure is usually the result of a meningeal rupture with a resulting leakage of CSF. The pathophysiologic mechanisms of idiopathic intracranial hypertension (IIH) remain largely unknown. However recent evidence indicates that an abnormality in CSF outflow and absorption is likely to play a significant role. Treatment usually consists of a combination of weight loss and a pharmacologic approach using carbonic anhydrase inhibitors. Recent results of the first randomized, double-blind, placebo-controlled trial (RCT) with acetazolamide proved its efficacy in reducing headache and visual disturbances. Clinical evidence suggests efficacy for topiramate and furosemide but no RCT has been conducted to date to confirm these results. In contrast to IIH, spontaneous intracranial hypotension frequently remits spontaneously without specific treatment. If necessary, treatment options range from conservative methods to epidural blood or fibrin sealant patches and surgical interventions.

How and when to refer patients diagnosed with secondary headache and other craniofacial pain in the Emergency Department and Primary Care: Recommendations of the Spanish Society of Neurology's Headache Study Group

INTRODUCTION

When secondary headache is suspected and the patient is referred to the emergency department or to the outpatient neurology clinic, it is important to know which are the appropriate complementary examinations to perform and the suitable referral pathway for patients to follow. In order to establish recommendations on this matter, the Spanish Society of Neurology's Headache Study Group (GECSEN) has decided to issue a series of agreed recommendations constituting a referral protocol for patients with headache and/or craniofacial neuralgias.

DEVELOPMENT

Young neurologists with an interest and experience in headache were invited to draft a series of practical guidelines in collaboration with GECSEN's Executive Committee. For practical reasons, the document was divided into 2 articles: the first focuses on primary headaches and craniofacial neuralgias and this second article on secondary headaches and other craniofacial pain. In order for the recommendations to be helpful for daily practice, they follow a practical approach, with tables summarising referral criteria, examinations to be performed, and referral to other specialists.

CONCLUSIONS

We hope to offer a guide and tools to improve decision-making regarding patients with headache, identifying complementary tests to prioritise and referral pathways to be followed, in order to avoid duplicated consultations and delayed diagnosis and treatment.

Cerebrospinal fluid outflow resistance as a diagnostic marker of spontaneous cerebrospinal fluid leakage

OBJECTIVE Spinal CSF leakage causes spontaneous intracranial hypotension (SIH). The aim of this study was to characterize CSF dynamics via lumbar infusion testing in patients with and without proven spinal CSF leakage in order to explore possible discriminators for the presence of an open CSF leak. METHODS This analysis included all patients with suspected SIH who were treated at the authors' institution between January 2012 and February 2015. The gold standard for "proven" CSF leakage is considered to be extrathecal contrast accumulation after intrathecal contrast injection. To characterize CSF dynamics, the authors performed computerized lumbar infusion testing to measure lumbar pressure at baseline (opening pressure) and at plateau, as well as pulse amplitude, CSF outflow resistance (R_CSF), craniospinal elastance, and pressure-volume index. RESULTS Thirty-one patients underwent clinical imaging and lumbar infusion testing and were included in the final analysis. A comparison of the 14 patients with proven CSF leakage with the 17 patients without leakage showed a statistically significantly lower lumbar opening pressure (p < 0.001), plateau pressure (p < 0.001), and R_CSF (p < 0.001) in the group with leakage. Sensitivity, specificity, and positive and negative predictive values for an R_CSF cutoff of ≤ 5 mm Hg/(ml/min) were 0.86, 1.0, 1.0, and 0.89 (area under the curve of 0.96), respectively. The median pressure-volume index was higher (p = 0.003), and baseline (p = 0.017) and plateau (p < 0.001) pulse amplitudes were lower in patients with a proven leak. CONCLUSIONS Lumbar infusion testing captures a distinct pattern of CSF dynamics associated with spinal CSF leakage. R_CSF assessed by computerized lumbar infusion testing has an excellent diagnostic accuracy and is more accurate than evaluating the lumbar opening pressure. The authors suggest inclusion of R_CSF in the diagnostic criteria for SIH.

Diagnosis and clinical features of common optic neuropathies

Disorders of the optic nerves (optic neuropathies) are some of the most common causes of visual loss, and can present in isolation or with associated neurological or systemic symptoms and signs. Several optic neuropathies-especially inflammatory optic neuropathies-are associated with neurological disorders and thus are often diagnosed and treated by neurologists. The mechanisms underlying optic neuropathies are diverse and typically manifest with decreased visual acuity, altered colour vision, and abnormal visual field in the affected eye. Diagnosis is made on the basis of clinical history and clinical examination, of which several aspects are particularly important, including the mode of onset of visual loss, the presence of pain with eye movements, the visual acuity, and the retention of colour vision. Advances in optic nerve imaging-particularly retinal digital photography, optical coherence tomography, and MRI techniques-have revolutionised the diagnosis and follow-up of patients with an optic neuropathy. Furthermore, improvement and generalisation of some ancillary tests, such as diagnostic antibodies for neuromyelitis optica, allows better phenotyping of the heterogeneous inflammatory optic neuropathies.

Effect of gravity and microgravity on intracranial pressure

KEY POINTS

Astronauts have recently been discovered to have impaired vision, with a presentation that resembles syndromes of elevated intracranial pressure on Earth. Gravity has a profound effect on fluid distribution and pressure within the human circulation. In contrast to prevailing theory, we observed that microgravity reduces central venous and intracranial pressure. This being said, intracranial pressure is not reduced to the levels observed in the 90 deg seated upright posture on Earth. Thus, over 24 h in zero gravity, pressure in the brain is slightly above that observed on Earth, which may explain remodelling of the eye in astronauts.

ABSTRACT

Astronauts have recently been discovered to have impaired vision, with a presentation that resembles syndromes of elevated intracranial pressure (ICP). This syndrome is considered the most mission-critical medical problem identified in the past decade of manned spaceflight. We recruited five men and three women who had an Ommaya reservoir inserted for the delivery of prophylactic CNS chemotherapy, but were free of their malignant disease for at least 1 year. ICP was assessed by placing a fluid-filled 25 gauge butterfly needle into the Ommaya reservoir. Subjects were studied in the upright and supine position, during acute zero gravity (parabolic flight) and prolonged simulated microgravity (6 deg head-down tilt bedrest). ICP was lower when seated in the 90 deg upright posture compared to lying supine (seated, 4 ± 1 vs. supine, 15 ± 2 mmHg). Whilst lying in the supine posture, central venous pressure (supine, 7 ± 3 vs. microgravity, 4 ± 2 mmHg) and ICP (supine, 17 ± 2 vs. microgravity, 13 ± 2 mmHg) were reduced in acute zero gravity, although not to the levels observed in the 90 deg seated upright posture on Earth. Prolonged periods of simulated microgravity did not cause progressive elevations in ICP (supine, 15 ± 2 vs. 24 h head-down tilt, 15 ± 4 mmHg). Complete removal of gravity does not pathologically elevate ICP but does prevent the normal lowering of ICP when upright. These findings suggest the human brain is protected by the daily circadian cycles in regional ICPs, without which pathology may occur.

Transverse Sinus Stenosis Is the Most Sensitive MR Imaging Correlate of Idiopathic Intracranial Hypertension

BACKGROUND AND PURPOSE

Patients with idiopathic intracranial hypertension have transverse sinus stenosis on gadolinium-bolused MRV, but other MR imaging signs are less consistently seen. Our aim was to demonstrate that transverse sinus stenosis could be identified on conventional MR imaging, and this identification would allow improved diagnostic sensitivity to this condition.

MATERIALS AND METHODS

MR imaging and MRV images from 63 patients with idiopathic intracranial hypertension and 96 controls were reviewed by using 3 independent procedures. MRV images were graded for the presence and degree of stenosis of the transverse sinus. Postgadolinium coronal T1-weighted sequences were evaluated independent of MRV. The dimensions of the proximal and distal transverse sinus were measured from the MRV examinations, and the cross-sectional area of the transverse sinus was calculated. Correlation among the 3 modes of evaluation of the transverse sinus was conducted by using Wilcoxon/Kruskal-Wallis, Pearson, and Spearman ρ nonparametric statistical techniques.

RESULTS

Transverse sinus stenosis was identified bilaterally on MRV in 94% of patients with idiopathic intracranial hypertension and in 3% of controls. On coronal T1 postgadolinium MR images, transverse sinus stenosis was identified in 83% of patients with idiopathic intracranial hypertension and 7% of controls. Previously described MR imaging signs of intracranial hypertension were identified in 8%-61% of patients with idiopathic intracranial hypertension. Correlation among the 3 modes of evaluation was highly significant (P < .0001).

CONCLUSIONS

Even without the assistance of an MRV sequence, neuroradiologists can validly identify bilateral transverse sinus stenosis in patients with intracranial hypertension more reliably than other previously described MR imaging findings in this condition. We conclude that transverse sinus stenosis is the most useful and sensitive imaging indicator of this disease state.

Evolving evidence in adult idiopathic intracranial hypertension: pathophysiology and management

Idiopathic intracranial hypertension (IIH) is a rare but important disease associated with significant morbidity. There is an expected rise in prevalence in line with the escalating global burden of obesity. Modern revisions in the terminology and diagnostic criteria for IIH help guide clinicians in investigations and researchers in standardising recruitment criteria for clinical trials. The pathophysiology of IIH is incompletely characterised; suggested underpinning mechanisms include the role of cerebrospinal fluid regulation as well as metabolic and endocrinological perspectives. Recent treatment trials are providing insights into the management but debate still surrounds key areas in treatment. This review will provide an up-to-date discussion on the potential pathogenic mechanisms and management of IIH.

Imaging Signs in Spontaneous Intracranial Hypotension: Prevalence and Relationship to CSF Pressure

BACKGROUND AND PURPOSE

Patients with spontaneous intracranial hypotension often exhibit low CSF pressure and changes on brain MR imaging and/or evidence of CSF leak on myelography. We investigated whether individual imaging signs of spontaneous intracranial hypotension correlate with measured CSF pressure and how frequently these 2 markers of spontaneous intracranial hypotension were concordant.

MATERIALS AND METHODS

We performed a retrospective, cross-sectional study of 99 subjects with spontaneous intracranial hypotension. Prevalence of brain and myelographic imaging signs of spontaneous intracranial hypotension was recorded. CSF pressure among subjects with or without individual imaging signs was compared by using a 2-tailed t test and ANOVA. Concordance between low CSF pressure (≤6 cm H2O) and imaging was defined as the presence of the sign in a subject with low CSF pressure or absence of the sign when pressure was not low.

RESULTS

Dural enhancement, brain sagging, and venous distension sign were present in 83%, 61%, and 75% of subjects, respectively, and myelographic evidence of CSF leak was seen in 55%. Marginal correlations between CSF pressure and brain sagging (P = .046) and the venous distension sign (P = .047) were found. Dural enhancement and myelographic evidence of leak were not significantly correlated with CSF pressure. Rates of concordance between imaging signs and low CSF pressure were generally low, ranging from 39% to 55%.

CONCLUSIONS

Brain and myelographic signs of spontaneous intracranial hypotension correlate poorly with CSF pressure. These findings reinforce the need to base the diagnosis of spontaneous intracranial hypotension on multiple diagnostic criteria and suggest the presence of patient-specific variables that influence CSF pressure in these individuals.

Spontaneous intracranial hypotension: diagnosis to management

Spontaneous Intracranial Hypotension typically occurs from spontaneous CSF leak. CSF volume depletion rather than decrease in CSF pressure is thought to be the main causative feature for intracranial hypotension. More and more cases of intracranial hypotension are getting diagnosed with the advances in the imaging. The advances in the imaging have also led to the better understanding of the dynamic changes that occur with intracranial hypotension. The old theories of CSF overproduction or CSF underproduction have not been substantially associated with intracranial hypotension. It has also led to the fore different atypical clinical features and presentations. Although, it has been known for a long time, the diagnosis is still challenging and dilemma persists over one diagnostic modality over other and the subsequent management. Spontaneous CSF leaks occur at the spinal level and the skull base and other locations are rare. The anatomy of spontaneous intracranial hypotension is a very complex process with significant overlap in connective tissue disorders, previous dural weakness or meningeal diverticula. To localize the location of the CSF leak-CT myelography is the modality of choice. CSF cysternography may provide additional confirmation in uncertain cases and also MRI spine imaging may be of significant help in some cases. Spontaneous intracranial hypotension continues to be a diagnostic dilemma and our effort was to consolidate available information on the clinical features, diagnostics, and management for a practicing neurologist for a "15-20 min quick update of the topic".

Understanding idiopathic intracranial hypertension: mechanisms, management, and future directions

Idiopathic intracranial hypertension is a disorder characterised by raised intracranial pressure that predominantly affects young, obese women. Pathogenesis has not been fully elucidated, but several causal factors have been proposed. Symptoms can include headaches, visual loss, pulsatile tinnitus, and back and neck pain, but the clinical presentation is highly variable. Although few studies have been done to support evidence-based management, several recent advances have the potential to enhance understanding of the causes of the disease and to guide treatment decisions. Investigators of the Idiopathic Intracranial Hypertension Treatment Trial (IIHTT) reported beneficial effects of acetazolamide in patients with mild visual loss. Studies have also established weight loss as an effective disease-modifying treatment, and further clinical trials to investigate new treatments are underway. The incidence of idiopathic intracranial hypertension is expected to increase as rates of obesity increase; efforts to reduce diagnostic delays and identify new, effective approaches to treatment will be key to meeting the needs of a growing number of patients.

Overdiagnosis of idiopathic intracranial hypertension

OBJECTIVE

To delineate the factors contributing to overdiagnosis of idiopathic intracranial hypertension (IIH) among patients seen in one neuro-ophthalmology service at a tertiary center.

METHODS

We retrospectively reviewed new patients referred with a working diagnosis of IIH over 8 months. The Diagnosis Error Evaluation and Research taxonomy tool was applied to cases referred with a diagnosis of IIH and a discrepant final diagnosis.

RESULTS

Of 1,249 patients, 165 (13.2%) were referred either with a preexisting diagnosis of IIH or to rule out IIH. Of the 86/165 patients (52.1%) with a preexisting diagnosis of IIH, 34/86 (39.5%) did not have IIH. The most common diagnostic error was inaccurate ophthalmoscopic examination in headache patients. Of 34 patients misdiagnosed as having IIH, 27 (27/34 [79.4%]; 27/86 [31.4%]) had at least one lumbar puncture, 29 (29/34 [85.3%]; 29/86 [33.7%]) had a brain MRI, and 8 (8/34 [23.5%]; 8/86 [9.3%]) had a magnetic resonance/CT venogram. Twenty-six had received medical treatment, 1 had a lumbar drain, and 4 were referred for surgery. In 8 patients (8/34 [23.5%]; 8/86 [9.3%]), an alternative diagnosis requiring further evaluation was identified.

CONCLUSIONS

Diagnostic errors resulted in overdiagnosis of IIH in 39.5% of patients referred for presumed IIH, and prompted unnecessary tests, invasive procedures, and missed diagnoses. The most common errors were inaccurate ophthalmoscopic examination in headache patients and thinking biases, reinforcing the need for rapid access to specialists with experience in diagnosing optic nerve disorders. Indeed, the high prevalence of primary benign headaches and obesity in young women often leads to costly and invasive evaluations for presumed IIH.