Idiopathic intracranial hypertension

Orbital and intracranial effects of microgravity: findings at 3-T MR imaging

PURPOSE

To identify intraorbital and intracranial abnormalities in astronauts previously exposed to microgravity by using quantitative and qualitative magnetic resonance (MR) techniques.

MATERIALS AND METHODS

The institutional review board approved this HIPAA-compliant, retrospective review and waived the requirement for informed consent. Twenty-seven astronauts (mean age ± standard deviation, 48 years ± 4.5) underwent 3-T MR imaging with use of thin-section, three-dimensional, axial T2-weighted orbital and conventional brain sequences. Eight astronauts underwent repeat imaging after an additional mission in space. Optic nerve sheath diameter (ONSD) and optic nerve diameter (OND) were quantified in the retrolaminar optic nerve. OND and central optic nerve T2 hyperintensity were quantified at mid orbit. Qualitative analysis of the optic nerve sheath, optic disc, posterior globe, and pituitary gland morphology was performed and correlated for association with intracranial evidence of hydrocephalus, vasogenic edema, central venous thrombosis, and/or mass lesion. Statistical analyses included the paired t test, Mann-Whitney nonparametric test for group comparisons, Cronbach α coefficient for reproducibility, and Pearson correlation coefficient.

RESULTS

All astronauts had previous exposure to microgravity and, thus, control data were not available for comparison. The ONSD and OND ranged from 4.7 to 10.8 mm (mean, 6.2 mm ± 1.1) and from 2.4 to 4.5 mm (mean, 3.0 mm ± 0.5), respectively. Posterior globe flattening was seen in seven of the 27 astronauts (26%), optic nerve protrusion in four (15%), and moderate concavity of the pituitary dome with posterior stalk deviation in three (11%) without additional intracranial abnormalities. Retrolaminar OND increased linearly relative to ONSD (r = 0.797, Pearson correlation). A central area of T2 hyperintensity was identifiable in 26 of the 27 astronauts (96%) and increased in diameter in association with kinking of the optic nerve sheath.

CONCLUSION

Exposure to microgravity can result in a spectrum of intraorbital and intracranial findings similar to those in idiopathic intracranial hypertension.

Dynamics of intracranial venous flow patterns in patients with idiopathic intracranial hypertension

OBJECTIVE

To examine the dynamics of intracranial venous flow patterns in patients with idiopathic intracranial hypertension (IIH).

METHODS

Nonrandomized controlled trial analyzing the difference in cerebral perfusion in 13 IIH patients and 12 healthy controls using contrast-enhanced duplex sonography. In patients, an additional 3D gradient echo magnetic resonance venography (MRV) using a new technique was performed to quantify stenosis of the cerebral sinus. The cerebral perfusion parameters, including cerebral transit time (CTT) and time to peak (TTP), were analyzed.

RESULTS

IIH patients had a higher BMI (29.3 [95% CI 26.4, 32.2] vs. 23.3 [95% CI 20.7, 25.9], p = 0.003) and an increased prevalence of headache, but all other clinical characteristics were comparable. The CTT did not differ significantly. The TTP was significantly longer in IIH patients compared to controls (8.5 [95% CI 7.6, 9.4] vs. 7.3 s [95% CI 6.3, 8.1], p = 0.04). Twelve of 13 (92%) IIH patients showed stenosis of the cerebral sinus.

CONCLUSIONS

Our study is the first to report an altered cerebral venous flow in IIH patients compared to controls using a dynamic ultrasonographic technique. A simplified MRV technique confirms the high prevalence and reliable detection of venous stenosis in IIH patients.

Determination of cranio-spinal canal compliance distribution by MRI: Methodology and early application in idiopathic intracranial hypertension

PURPOSE

To develop a method for derivation of the cranial-spinal compliance distribution, assess its reliability, and apply to obese female patients with a diagnosis of idiopathic intracranial hypertension (IIH).

MATERIALS AND METHODS

Phase contrast-based measurements of blood and cerebrospinal fluid (CSF) flows to, from, and between the cranial and spinal canal compartments were used with lumped-parameter modeling to estimate systolic volume and pressure changes from which cranial and spinal compliance indices are obtained. The proposed MRI indices are analogous to pressure volume indices (PVI) currently being measured invasively with infusion-based techniques. The consistency of the proposed method was assessed using MRI data from seven aged healthy subjects. Measurement reproducibility was assessed using five repeated MR scans from one subject. The method was then applied to compare spinal canal compliance contribution in seven IIH patients and six matched healthy controls.

RESULTS

In the healthy subjects, as expected, spinal canal contribution was consistently larger than the cranial contribution (average value of 69%). Measurement variability was 8%. In IIH, the spinal canal contribution is significantly smaller than normal controls (60 versus 78%, P < 0.03).

CONCLUSION

An MRI-based method for derivation of compliance indices analogous to PVI has been implemented and applied to healthy subjects. The application of the method to obese IIH patients suggests a spinal canal involvement in the pathophysiology of IIH.

The syndrome of pseudotumour cerebri and idiopathic intracranial hypertension

PURPOSE OF REVIEW

Idiopathic intracranial hypertension (IIH) is a condition in which raised intracranial pressure is associated with a high body mass index, and in those societies in which the prevalence of obesity is increasing the disorder is of increasing importance. It is one cause of the syndrome of pseudotumour cerebri but the cause and the link with a rise in body weight are not understood. Furthermore the treatment of the more severe, sight-threatening cases is controversial.

RECENT FINDINGS

A major theme in recent years has been an attempt to identify the underlying mechanism of IIH. Some theories - such as the dural sinus stenosis theory - seem to ignore the relationship with weight gain; others have proposed a direct link between obesity and raised intracranial pressure through a specific fat distribution in the body; others through the production of lipokines; and yet others have suggested a converse causation with raised intracranial pressure giving rise to obesity. Uncontrolled case series continue to demonstrate the success of interventions such as cerebrospinal fluid diversion procedures, venous sinus stenting and bariatric surgery but there are no level 1 clinical trials.

SUMMARY

Interest in IIH is increasing and currently generating numerous studies but there is no consensus view on either cause or management.

Intracranial hypertension as the first manifestation of primary Sjögren’s syndrome

Background: Central nervous system involvement with primary Sjögren’s syndrome (pSS) is rare, and often undiagnosed. Sjögren’s syndrome and concomitant intracranial hypertension is a very rare event.

Case: We describe a patient with pSS who presented with intracranial hypertension as the initial symptom of the disease.

Conclusion: This is the first case report of a patient with pSS that presented with intracranial hypertension only.

The incidence and prevalence of idiopathic intracranial hypertension in Sheffield, UK

BACKGROUND AND PURPOSE

The purpose of this study was to identify the incidence and prevalence of idiopathic intracranial hypertension (IIH) in Sheffield, UK.

METHODS

A retrospective review of case notes was conducted to identify cases of IIH seen between 1 January 2007 and 31 December 2008.

RESULTS

Sixteen (15 women and 1 man) new patients were identified to give an incidence within Sheffield of 1.56/100,000/year and 2.86/100,000/year for women. The incidence of IIH in obese women was 11.9/100,000/year. The prevalence of IIH was calculated as 10.9/100,000, and 85.7/100,000 in obese women.

CONCLUSION

A higher incidence of IIH than previously reported UK data was found, which may be because of increasing obesity within the population, or improved case ascertainment.

New considerations in the cause of spontaneous cerebrospinal fluid otorrhea

OBJECTIVE

To examine the demographic and radiographic features of patients with spontaneous cerebrospinal fluid otorrhea and to determine whether they display similar characteristics to patients with idiopathic intracranial hypertension.

STUDY DESIGN

Retrospective case review.

SETTING

Academic, tertiary referral center.

PATIENTS

All individuals presenting with spontaneous cerebrospinal fluid otorrhea, diagnosed between 2000 and 2009, undergoing primary surgical repair.

INTERVENTIONS

All patients underwent surgical repair via a transmastoid, middle fossa, or combined transmastoid-middle fossa approach.

MAIN OUTCOME MEASURES

Patient demographics such as age, race, sex, height, weight, and body mass index, the presence of a radiographically empty or partially empty sella, and preoperative radiographic and intraoperative surgical findings of the temporal bone.

RESULTS

Twenty-three patients underwent primary surgical repair for spontaneous cerebrospinal fluid otorrhea. Fifteen patients underwent preoperative magnetic resonance imaging of the head with 12 (80%) demonstrating the presence of an empty or partially empty sella. Mean body mass index of those patients with an empty or partially empty sella was 38.0 kg/m2 compared with 28.5 kg/m2 for those without an empty sella.

CONCLUSION

Patients with spontaneous cerebrospinal fluid otorrhea are often middle-aged and obese, with females being affected nearly twice as often as males. Empty or partially empty sella was observed in 80% of patients with spontaneous cerebrospinal fluid otorrhea as demonstrated by preoperative magnetic resonance imaging. Patients with spontaneous cerebrospinal fluid otorrhea who display these demographic and radiographic features should be further evaluated for the presence of idiopathic intracranial hypertension.