MR imaging of papilledema and visual pathways: effects of increased intracranial pressure and pathophysiologic mechanisms

Characteristics of the cerebrospinal fluid pressure waveform and craniospinal compliance in idiopathic intracranial hypertension subjects

BACKGROUND

Idiopathic intracranial hypertension (IIH) is a condition of abnormally high intracranial pressure with an unknown etiology. The objective of this study is to characterize craniospinal compliance and measure the cerebrospinal fluid (CSF) pressure waveform as CSF is passively drained during a diagnostic and therapeutic lumbar puncture (LP) in IIH.

METHODS

Eighteen subjects who met the Modified Dandy Criteria, including papilledema and visual field loss, received an ultrasound guided LP where CSF pressure (CSFP) was recorded at each increment of CSF removal. Joinpoint regression models were used to calculate compliance from CSF pressure and the corresponding volume removed at each increment for each subject. Twelve subjects had their CSFP waveform recorded with an electronic transducer. Body mass index, mean CSFP, and cerebral perfusion pressure (CPP) were also calculated. T-tests were used to compare measurements, and correlations were performed between parameters.

RESULTS

Cerebrospinal fluid pressure, CSFP pulse amplitude (CPA), and CPP were found to be significantly different (p < 0.05) before and after the LP. CSFP and CPA decreased after the LP, while CPP increased. The craniospinal compliance significantly increased (p < 0.05) post-LP. CPA and CSFP were significantly positively correlated.

CONCLUSIONS

Both low craniospinal compliance (at high CSFP) and high craniospinal compliance (at low CSFP) regions were determined. The CSFP waveform morphology in IIH was characterized and CPA was found to be positively correlated to the magnitude of CSFP. Future studies will investigate how craniospinal compliance may correlate to symptoms and/or response to therapy in IIH subjects.

Visual outcome after endoscopic third ventriculostomy for hydrocephalus

PURPOSE

Hydrocephalus-related symptoms are mostly improved after successful endoscopic third ventriculostomy (ETV). However, visual symptoms can be different. This study was focused on visual symptoms. We analyzed the magnetic resonance images (MRI) of the orbit and visual outcomes.

METHODS

From August 2006 to November 2016, 50 patients with hydrocephalus underwent ETV. The male-to-female ratio was 33:17, and the median age was 61 years (range, 5-74 years). There were 18 pediatric and 32 adult patients. Abnormal orbital MRI findings included prominent subarachnoid space around the optic nerves and vertical tortuosity of the optic nerves. We retrospectively analyzed clinical symptoms, causes of hydrocephalus, ETV success score (ETVSS), ETV success rate, ETV complications, orbital MRI findings, and visual impairment score (VIS).

RESULTS

The median duration of follow-up was 59 months (range, 3-113 months). The most common symptoms were headache, vomiting, and gait disturbance. Visual symptoms were found in 6 patients (12%). The most common causes of hydrocephalus were posterior fossa tumor in 13 patients, pineal tumor in 12, aqueductal stenosis in 8, thalamic malignant glioma in 7, and tectal glioma in 4. ETVSS was 70 in 3 patients, 80 in 34 patients, and 90 in 13 patients. ETV success rate was 80%. ETVSS 70 showed the trend in short-term survival compared to ETVSS 90 and 80. ETV complications included epidural hematoma requiring operation in one patient, transient hemiparesis in two patients, and infection in two patients. Preoperative abnormal orbital MRI findings were found in 18 patients and postoperative findings in 7 patients. Four of six patients with visual symptoms had abnormal MR findings. Three patients did not show VIS improvement, including two with severe visual symptoms.

CONCLUSIONS

Patients with severe visual impairment were found to have bad outcomes. The visual symptoms related with increased intracranial pressure should be carefully monitored and controlled to improve outcomes.

The efficacy of orbital ultrasonography and magnetic resonance imaging findings with direct measurement of intracranial pressure in distinguishing papilledema from pseudopapilledema

INTRODUCTION

The goal of this study was to evaluate the utility of orbital ultrasonography and magnetic resonance imaging in the diagnosis of idiopathic intracranial hypertension (IIH).

METHOD

We reviewed the medical records of patients referred to our department for suspected IIH.

RESULTS

Seven children were diagnosed with IIH. Nine children revealed pseudopapilledema by optic coherence tomography and/or orbital ultrasonography. When the axial sequences were reexamined, patients with papilledema had optic nerve sheath (ONS) enlargement (6.62 ± 0.70 mm); patients with pseudopapilledema had ONS diameter as 4.62 ± 0.64 mm. There was a significant correlation between the CSF opening pressure and ONS diameter (p < 0.005, r = 0.661). In the papilledema group, the presence of proposed subtle markers as increased tortuosity in the optic nerve was found in six patients. Five of seven patients had a target sign, intraocular protrusion of the optic nerve, and posterior globe flattening.

DISCUSSION

Ophthalmological review is important to avoid unnecessary procedures for detection of true papilledema. ONS diameter is a reliable neuroimaging marker as other subtle markers.

Elevated intracranial pressure and reversible eye-tracking changes detected while viewing a film clip

OBJECTIVE The precise threshold differentiating normal and elevated intracranial pressure (ICP) is variable among individuals. In the context of several pathophysiological conditions, elevated ICP leads to abnormalities in global cerebral functioning and impacts the function of cranial nerves (CNs), either or both of which may contribute to ocular dysmotility. The purpose of this study was to assess the impact of elevated ICP on eye-tracking performed while patients were watching a short film clip. METHODS Awake patients requiring placement of an ICP monitor for clinical purposes underwent eye tracking while watching a 220-second continuously playing video moving around the perimeter of a viewing monitor. Pupil position was recorded at 500 Hz and metrics associated with each eye individually and both eyes together were calculated. Linear regression with generalized estimating equations was performed to test the association of eye-tracking metrics with changes in ICP. RESULTS Eye tracking was performed at ICP levels ranging from -3 to 30 mm Hg in 23 patients (12 women, 11 men, mean age 46.8 years) on 55 separate occasions. Eye-tracking measures correlating with CN function linearly decreased with increasing ICP (p < 0.001). Measures for CN VI were most prominently affected. The area under the curve (AUC) for eye-tracking metrics to discriminate between ICP < 12 and ≥ 12 mm Hg was 0.798. To discriminate an ICP < 15 from ≥ 15 mm Hg the AUC was 0.833, and to discriminate ICP < 20 from ≥ 20 mm Hg the AUC was 0.889. CONCLUSIONS Increasingly elevated ICP was associated with increasingly abnormal eye tracking detected while patients were watching a short film clip. These results suggest that eye tracking may be used as a noninvasive, automatable means to quantitate the physiological impact of elevated ICP, which has clinical application for assessment of shunt malfunction, pseudotumor cerebri, concussion, and prevention of second-impact syndrome.

Diagnostic value of neuro-ophthalmological signs in cases of Chiari I malformation

INTRODUCTION

Our purpose was to evaluate the diagnostic value of measuring diameters of optic nerve sheath (ONSD), presence/absence of papilledema, tortuosity of the optic nerve, flattening of the posterior sclera, and intraocular protrusion of the prelaminar optic nerve for intracranial pressure assessment in cases of Chiari I malformation.

METHODS

In a retrospective study, MRI data of 37 consecutive pediatric patients with Chiari malformation and data of 400 patients without intracranial pathology were compared and analyzed. ONSDs were measured at the point where the ophthalmic artery crosses the optic nerve (anatomical landmark). The correlation analysis was performed with clinical findings, gender, age, papilledema, and other neuro-ophthalmological findings.

RESULTS

ONSD was enlarged in 38 % of cases of Chiari malformation. The enlargement was bilateral, no correlation with age or gender was found (p = 0.67 and p = 0.76, respectively). The presence of papilledema was detected in 19 % of cases presenting less valuable diagnostic sign if compared with ONSD. The tortuosity of the optic nerve was found in 22 % of cases, but in three patients, it was unilateral. All patients with enlarged ONSD and other neuro-ophthalmological signs present were treated surgically, while most of the patients without these signs (20/23) were treated conservatively.

CONCLUSION

In majority of pediatric cases of Chiari malformation, the ONSD is not enlarged and other neuro-ophthalmological signs are not present. Detecting the enlarged ONSD and other neuro-ophthalmological signs in cases of Chiari malformation may indicate the elevated intracranial pressure and necessity for urgent surgical intervention.

The best marker for guiding the clinical management of patients with raised intracranial pressure-the RAP index or the mean pulse amplitude?

Raised intracranial pressure is a common problem in a variety of neurosurgical conditions including traumatic brain injury, hydrocephalus and intracranial haemorrhage. The clinical management of these patients is guided by a variety of haemodynamic, biochemical and clinical factors. However to date there is no single parameter that is used to guide clinical management of patients with raised intracranial pressure (ICP). However, the role of ICP indices, specifically the mean pulse amplitude (AMP) and RAP index [correlation coefficient (R) between AMP amplitude (A) and mean ICP pressure (P); index of compensatory reserve], as an indicator of true ICP has been investigated. Whilst the RAP index has been used both as a descriptor of neurological deterioration in TBI patients and as a way of characterising the compensatory reserve in hydrocephalus, more recent studies have highlighted the limitation of the RAP index due to the influence that baseline effect errors have on the mean ICP, which is used in the calculation of the RAP index. These studies have suggested that the ICP mean pulse amplitude may be a more accurate marker of true intracranial pressure due to the fact that it is uninfluenced by the mean ICP and, therefore, the AMP may be a more reliable marker than the RAP index for guiding the clinical management of patients with raised ICP. Although further investigation needs to be undertaken in order to fully assess the role of ICP indices in guiding the clinical management of patients with raised ICP, the studies undertaken to date provide an insight into the potential role of ICP indices to treat raised ICP proactively rather than reactively and therefore help prevent or minimise secondary brain injury.

Noninvasive assessment of the intracranial pressure in non-traumatic intracranial hemorrhage

The article describes the modified technique of measuring the diameters of the optic nerve sheath (ONSD) for assessment of the intracranial pressure (ICP) in patients with intracerebral or subarachnoid hemorrhage (SAH). The CT scans of 443 patients were analyzed retrospectively. The ONSDs were measured at 3mm behind the globe and at the point where the ophthalmic artery crosses the optic nerve. The ONSD/eyeball transverse diameter (ETD) ratio was calculated. The correlation analysis was performed with the Glasgow Coma Scale score, Hemispheric Stroke Scale score, Glasgow Outcome Score, and invasive ICP readings. ONSD was enlarged in 95% of patients with intracerebral hemorrhage or SAH. Pathological ONSDs were 6.6±0.8mm (cut-off value >5.5mm; p<0.05). ONSD/ETD ratio was 0.29±0.05 against normative 0.19±0.02 (p<0.01) with no correlation with initial Glasgow Coma Scale score or Hemispheric Stroke Scale score. There was an inverse correlation between ONSD/ETD ratio and Glasgow Outcome Score (r=-0.7) and direct correlation with invasive ICP readings. This study provides further evidence that in patients with intracranial hemorrhage and SAH, the presence of ONSD greater than a threshold of 5.5mm is significantly predictive of invasively measured elevated ICP. The prediction of raised ICP can be further refined by measuring ONSD at the point where the optic nerve and the ophthalmic artery cross, and by determining the ratio between the ONSD and ETD.

Papilledema as a Diagnostic Sign of Cerebral Edema on Postmortem Magnetic Resonance Imaging

The purpose of this study was to investigate papilledema (PA) as a diagnostic criterion for the presence of antemortem or agonal cerebral edema despite normal postmortem brain swelling on postmortem magnetic resonance imaging (PMMR) in comparison with conventional autopsy.One hundred subjects with head PMMR and autopsy were included in this study. The sensitivities, spec icities, positive predictive values (PPVs), negative predictive values (NPVs), and accuracies were calculated in terms of the PA, PMMR, and cerebral edema on autopsy. Spearman r tests were used to analyze the linear correlations of PA and the radiological and autoptic determination of cerebral edema.In autopsy, the sensitivity regarding the presence of PA and cerebral edema was 66.2% (PPV, 70.5%), and specificity was 48.6% (NPV, 28.3%), with an overall accuracy of 60%. On PMMR, the sensitivity was 86.6% (PPV, 95%). The specificity was 90.9% (NPV, 34%), with an overall accuracy of 88%. The Spearman correlation revealed a statistically significant result (P < 0.001), which indicated a strong linear correlation of the presence of PA and cerebral edema with the autopsy results and the PMMR results.The presence of PA may aid in the diagnoses of cerebral edema despite normal postmortem brain swelling based on PMMR.

Visual impairment

This chapter can guide the use of imaging in the evaluation of common visual syndromes: transient visual disturbance, including migraine and amaurosis fugax; acute optic neuropathy complicating multiple sclerosis, neuromyelitis optica spectrum disorder, Leber hereditary optic neuropathy, and Susac syndrome; papilledema and pseudotumor cerebri syndrome; cerebral disturbances of vision, including posterior cerebral arterial occlusion, posterior reversible encephalopathy, hemianopia after anterior temporal lobe resection, posterior cortical atrophy, and conversion blindness. Finally, practical efforts in visual rehabilitation by sensory substitution for blind patients can improve their lives and disclose new information about the brain.

Imaging of Pediatric Orbital Diseases

This article reviews a variety of congenital and developmental disorders of the pediatric orbit with particular emphasis on ocular lesions, followed by a description of developmental and neoplastic orbital and ocular masses. The relationship of these diseases to various syndromes and/or known genetic mutations is also highlighted.

Idiopathic intracranial hypertension: ongoing clinical challenges and future prospects

Idiopathic intracranial hypertension (IIH) is an uncommon disorder characterized by increased intracranial pressure without radiological or laboratory evidence of intracranial pathology except empty sella turcica, optic nerve sheath with filled out cerebrospinal fluid spaces, and smooth-walled nonflow-related venous sinus stenosis or collapse. This condition typically affects obese women. The incidence of IIH is increasing with the rising prevalence of obesity. Persistent headache is the most common symptom. Visual impairment is a serious complication that may not be recognized by the patients. This paper reviews clinical manifestations, diagnostic challenges, and current treatments of IIH in adults. Various imaging modalities have been studied on their validity for detection of IIH and papilledema. This review also includes new studies on medical, surgical, and interventional management of this condition. Acetazolamide and topiramate are the only two medications that have been studied in randomized controlled trials about their efficacy in treatment of IIH. In patients who have severe visual impairment or progressive visual deterioration despite medical management, surgical or interventional treatment may be considered. The efficacy and complications of cerebrospinal fluid diversion, optic nerve sheath fenestration, and endovascular venous stenting reported in the last 3 decades have been summarized in this review. Finally, the prospective aspects of biomarkers and treatments are proposed for future research.

Imaging and interventions in idiopathic intracranial hypertension: A pictorial essay

Intracranial hypertension is a syndrome of elevated intracranial pressure that can be primary or secondary. The primary form, now termed idiopathic intracranial hypertension (IIH), was in the past a disease of exclusion and imaging played a limited role of excluding organic causes of raised intracranial pressure. However imaging markers have been described with patients with IIH at the orbit, sella and cerebral venous system. We wish to reiterate the characteristic imaging features of this poorly understood disease and also emphasise that stenting of the transverse sinus in select cases of IIH is an efficacious option.

Lyme disease-related intracranial hypertension in children: clinical and imaging findings

Lyme disease (LD) is a tick-borne infection that is endemic to multiple areas of the United States. Patients with LD may present with sign and symptoms of intracranial hypertension (IH). The objective of this study is to evaluate the history, clinical findings, CSF analysis, and brain imaging results in pediatric patients with increased intracranial pressure secondary to LD. A retrospective database search was performed using the International Classification of Diseases (ICD) 9/10 codes to identify patients diagnosed with LD and IH between 2004 and 2014 at a tertiary referral pediatric hospital. Clinical, laboratory and neuroimaging data for each patient were reviewed. Seven patients met inclusion criteria; mean age was 9.6 years (standard deviation 4.0 years); 4/7 patients were male. Average body mass index was 18.8 kg/m(2) (standard deviation 3.0 kg/m(2)). Fever was present in four patients. Four had a history of LD related erythema migrans. All had elevated CSF opening pressure with leukocytosis and lymphocytic predominance. MRI obtained in six patients showed contrast enhancement of various cranial nerves. Tentorial enhancement was noted in all patients. In addition, patients had widening of the optic nerve sheath (ONS), optic nerve protrusion, and flattening of the posterior globe consistent with increased intracranial pressure. All patients had resolution of their symptoms after initiation of antibiotic therapy. In endemic areas, LD should be included in the differential of IH. MRI can help distinguish IH due to LD from its idiopathic form due to the presence of tentorial and cranial nerve enhancement in the former in addition to abnormal CSF showing leukocytosis with lymphocyte predominance.

Monitoring of Intracranial Pressure by CT-Defined Optic Nerve Sheath Diameter

BACKGROUND AND PURPOSE

Intracranial pressure (ICP) can be monitored by the optic nerve sheath diameter (ONSD) technique. We hypothesized that diameter of the optic canal (OC) can be a limiting factor for this technique.

METHODS

In the prospective cohort study, we analyzed CT scans of 600 OCs of healthy adults and 54 canals of patients with ICP monitoring. The diameters were measured through its length and the narrowest one was chosen for further analysis. ONSD was measured at 3 and 10 mm from the anterior opening of the canal. The correlation analysis was performed between invasive and ONSD methods of ICP monitoring and OC diameters in pathological cases.

RESULTS

The narrowest cross-sectional area of the normal OC was 13.85±2.89 mm² and varied from 25.5 to 6.6 mm². Apparently 9.17% OCs were narrow (˂10.9 mm²). Correlations exist between the optic nerve sheath area at the 3-mm distance from the anterior opening of the canal and the area of the anterior opening itself (P = .012), and the sheath area 10 mm from the anterior opening and the narrowest part of the canal (P = .015). Cases with narrow canals provided false-negative readings via ONSD method if compared with invasive monitoring.

CONCLUSION

In its narrowest part, the average OC is 11 to 16.75 mm² wide. We suggest measuring this area simultaneously with the ONSD during ICP monitoring. If the area of the narrowest lumen of the canal is less than 10 mm², ONSD technique for ICP monitoring should not be used.

Optic nerve sheath diameters in healthy adults measured by computer tomography

AIM

To measure optic nerve sheath diameters (ONSD) in different locations by computer tomography (CT) and to recommend the best location for cases when ONSD is used for intracranial pressure monitoring.

METHODS

In a prospective cohort study, CT data of 300 healthy adults were analyzed (600 eyes). In all cases, the CT investigation was performed at the Emergency Department because of the various conditions that proved not to be connected with ophthalmological or neurological pathology. The ONSD were measured at 3 mm and 8 mm distance from the globe, and 3 mm from the anterior opening of the optic canal. The correlation analysis was performed with gender, age, and ethnic background.

RESULTS

The right/left ONSD are 4.94±1.51/5.17±1.34 mm at 3 mm, 4.35±0.76/4.45±0.62 mm at 8 mm from the globe, and 3.55±0.82/3.65±0.7 mm at 3 mm from the optic canal. No significant differences correlated with gender of the patients, their age, and ethnic background were found.

CONCLUSION

In healthy persons, the ONSD varies from 5.17±1.34 mm to 3.55±0.82 mm in different locations within the intraorbital space. The most stable results with lesser standard deviation can be obtained if it is measured 8-10 mm from the globe.

MRI in the Evaluation of Acute Visual Syndromes

Acute visual symptom emergencies occur commonly and present a challenge to both clinical and radiologic facets. Although most patients with visual complaints routinely require clinical evaluation with direct ophthalmologic evaluation, imaging is rarely necessary. However, there are highly morbid conditions where the prompt recognition and management of an acute visual syndrome (AVS) requires an astute physician to probe further. Suspicious symptomatology including abrupt visual loss, diplopia, ophthalmoplegia, and proptosis/exophthalmos require further investigation with advanced imaging modalities such as magnetic resonance imaging and magnetic resonance angiography. This review will discuss a variety of AVSs including orbital apex syndrome, cavernous sinus thrombosis, cavernous carotid fistula, acute hypertensive encephalopathy (posterior reversible encephalopathy syndrome), optic neuritis, pituitary apoplexy including hemorrhage into an existing adenoma, and idiopathic intracranial hypertension. A discussion of each entity will focus on the clinical presentation, management and prognosis when necessary and finally, neuroimaging with emphasis on magnetic resonance imaging. The primary purpose of this review is to provide an organized approach to the differential diagnosis and typical imaging patterns for AVSs. We have provided a template for radiologists and specialists to assist in early intervention in order to decrease morbidity and provide value-based patient care through imaging.

Novel Magnetic Resonance Imaging Findings in Children With Intracranial Hypertension

BACKGROUND

Increased intracranial hypertension is defined as elevated intracranial pressure with absence of hydrocephalus, vascular or structural abnormalities, and normal cerebrospinal fluid content. Magnetic resonance imaging abnormalities of the optic nerve and sheath that have been described in adults include increased nerve tortuosity, flattening in posterior aspect of globe, intraocular protrusion of the optic nerve, and enlarged optic nerve sheath.

PURPOSE

We evaluated accuracy of those proposed markers on magnetic resonance imaging in children with increased intracranial hypertension that are described in adults.

MATERIALS AND METHODS

Eleven patients between 3 and 15 years of age with intracranial hypertension were selected for re-evaluation of magnetic resonance imaging that had been previously described as normal to determine the presence of: (1) increased tortuosity and elongation of the optic nerve; (2) enlargement of the optic nerve sheath on axial and coronal T2 so called by us "target sign" and postcontrast T1 sequences; (3) flattening in posterior aspect of the globe; and (4) intraocular protrusion of the optic nerve head.

RESULTS

Of the 11 patients, tortuosity of the optic nerve (10/11, 90.9%) and enlarged optic nerve sheath--target sign (7/11, 63.6%)--were the most common findings. Flattening in the posterior aspect of globe (5/11, 45.5%) and intraocular protrusion (3/11, 27.3%) were also detected as a novel magnetic resonance imaging findings.

CONCLUSION

Magnetic resonance imaging findings of the optic nerve and sheath include valuable signs of intracranial hypertension not only in adults but also in children. This is the first detailed analysis of the magnetic resonance imaging findings in children with increased intracranial hypertension.

MR-derived cerebral spinal fluid hydrodynamics as a marker and a risk factor for intracranial hypertension in astronauts exposed to microgravity

PURPOSE

To quantify the change in cerebral spinal fluid (CSF) production rate and maximum systolic velocity in astronauts before and after exposure to microgravity and identify any physiologic trend and/or risk factor related to intracranial hypertension.

MATERIALS AND METHODS

Following Institutional Review Board (IRB) approval, with waiver of informed consent, a retrospective review of 27 astronauts imaged at 3T was done. Qualitative analysis was performed on T2 -weighted axial images through the orbits for degree of flattening of the posterior globe according to the following grades: 0 = none, 1 = mild, 2 = moderate, and 3 = severe. One grade level change postflight was considered significant for exposure to intracranial hypertension. CSF production rate and maximum systolic velocity was calculated from cine phase-contrast magnetic resonance imaging and compared to seven healthy controls.

RESULTS

Fourteen astronauts were studied. The preflight CSF production rate in astronauts was similar to controls (P = 0.83). Six astronauts with significant posterior globe flattening demonstrated a 70% increase in CSF production rate postflight compared to baseline (P = 0.01). There was a significant increase in CSF maximum systolic velocity in the subgroup without posterior globe flattening (P = 0.01).

CONCLUSION

The increased postflight CSF production rate in astronauts with positive flattening is compatible with the hypothesis of microgravity-induced intracranial hypertension inferring downregulation in CSF production in microgravity that is upregulated upon return to normal gravity. Increased postflight CSF maximum systolic velocity in astronauts with negative flattening suggests increased craniospinal compliance and a potential negative risk factor to microgravity-induced intracranial hypertension.

The usefulness of multimodal imaging for differentiating pseudopapilloedema and true swelling of the optic nerve head: a review and case series

Ophthalmic practitioners have to make a critical differential diagnosis in cases of an elevated optic nerve head. They have to discriminate between pseudopapilloedema (benign elevation of the optic nerve head) and true swelling of the optic nerve head. This decision has significant implications for appropriate patient management. Assessment of the optic disc prior to the advanced imaging techniques that are available today (particularly spectral domain optical coherence tomography and fundus autofluorescence), has mainly used diagnostic tools, such as funduscopy and retinal photography. As these traditional methods rely on the subjective assessment by the clinician, evaluation of the elevated optic nerve head to differentiate pseudopapilloedema from true swelling of the optic nerve head can be a challenge in clinical practice with patients typically referred for further neuroimaging investigation when the diagnosis is uncertain. The use of multimodal ocular imaging tools such as spectral domain optical coherence tomography, short wavelength fundus autofluorescence and ultrasonography, can potentially aid in the differentiation of pseudopapilloedema from true swelling of the optic nerve head, in conjunction with other clinical findings. By doing so, unnecessary patient costs and anxiety in the case of pseudopapilloedema can be reduced, and appropriate urgent referral and management in the case of true swelling of the optic nerve head can be initiated.

Perspectives of an innovative ophthalmological technology: optical coherence tomography (OCT)--what should be of interest to the neurologist?

Ocular coherence tomography has revolutionised the prospects of measuring the loss of retinal ganglion cells secondary to degenerative diseases and monitoring time-dependent changes of optic disc morphology, since the resolution has been improved considerably and the time required has been reduced. Although the non-invasive technique promises a high inter-session reproducibility, the limitations of retinal imaging and the problems of segmenting of the retinal layers have to be taken into account. While the first studies were limited to single sessions in small groups, further trials will elucidate how the retinal nerve fibre layer (RNFL) is altered in the course of different episodic forms of multiple sclerosis. This review points out that the examination technique already provides comprehensive information, valuable in the daily care of neurological patients.

Idiopathic intracranial hypertension

Background

Idiopathic intracranial hypertension or pseudotumour cerebri is primarily a disorder of young obese women characterised by symptoms and signs associated with raised intracranial pressure in the absence of a space-occupying lesion or other identifiable cause.

Summary

The overall incidence of idiopathic intracranial hypertension is approximately two per 100,000, but is considerably higher among obese individuals and, given the global obesity epidemic, is likely to rise further. The pathophysiology of this condition is poorly understood, but most theories focus on the presence of intracranial venous hypertension and/or increased cerebrospinal fluid outflow resistance and how this relates to obesity. A lack of randomised clinical trials has resulted in unsatisfactory treatment guidelines and although weight loss is important, especially when used in conjunction with drugs that reduce cerebrospinal fluid production, resistant cases remain difficult to manage and patients invariably undergo neurosurgical shunting procedures. The use of transverse cerebral sinus stenting remains contentious and long-term benefits are yet to be determined.

Conclusion

An understanding of the clinical features, diagnostic work-up and therapeutic options available for patients with idiopathic intracranial hypertension is important both for neurologists and ophthalmologists as visual loss maybe permanent if untreated.

Automated quantitation of the posterior scleral flattening and optic nerve protrusion by MRI in idiopathic intracranial hypertension

BACKGROUND AND PURPOSE

Subjective determination of the posterior sclera flattening and optic nerve protrusion in MRI is challenging because of the 3D nature of the globe morphology. This study aims to develop and compare quantitative measures of globe flattening and optic nerve protrusion with subjective rating, and assess relationships with papilledema grade and intraocular and CSF pressures.

MATERIALS AND METHODS

Data of 34 globes from 7 overweight female patients with idiopathic intracranial hypertension and 6 age- and weight-matched healthy female control subjects were assessed, as well as a subcohort of 4 of the patients with idiopathic intracranial hypertension who underwent follow-up MR imaging 2 weeks after lumbar puncture and initiation of treatment with acetazolamide. MR imaging examination included a 3D CISS sequence on 1.5T and 3T scanners with 0.6-mm isotropic resolution. Subjective ratings of globe flattening were obtained by experienced and inexperienced readers. Quantitative measures of globe flattening, nerve protrusion, and maximal deformation were derived by use of a 2D map of the distances from the globe center to the posterior wall.

RESULTS

Contingency coefficients for globe flattening agreements with subjective rating by the experienced and inexperienced readers were 0.72 and 0.56, respectively. Mean values of the 3 deformation measures were significantly poorer in the idiopathic intracranial hypertension group, with nerve protrusion demonstrating the strongest difference (P = .0002). Nerve protrusion was most strongly associated with papilledema grade with a contingency coefficient of 0.74 (P = .01), whereas globe flattening was negatively correlated with intraocular pressure (R = -0.75, P < .0001). Maximal deformation was negatively associated with CSF opening pressure (R = -0.86, P = .0001). After treatment, only the changes in nerve protrusion and maximal deformation were significant.

CONCLUSIONS

Automated measures of globe deformation improve reliability over subjective rating. Of the 2 globe deformation measures, nerve protrusion had the strongest predictive value for papilledema grade and had the highest sensitivity for assessment of treatment efficacy in idiopathic intracranial hypertension.

Hyperintense optic nerve heads on diffusion-weighted imaging: a potential imaging sign of papilledema

BACKGROUND AND PURPOSE

Changes at the optic nerve head on DWI in the presence of papilledema have not been systematically studied. The purpose of this study was to evaluate if hyperintensity of ON heads on DWI is associated with papilledema.

MATERIALS AND METHODS

In this retrospective study, 19 patients (4 men, 15 women; median age, 32 years) with papilledema and 20 control participants (7 men, 13 women; median age, 48 years) who had undergone prior MR imaging of the brain were identified. Two neuroradiologists blinded to the diagnosis independently reviewed the DWI for the presence of hyperintense signal at the ON head of each eye. If present, they graded the signal as mild or prominent. Groups with and without papilledema were compared for the prevalence of ON head hyperintensity by using the Fisher exact test, with analyses performed both for groups of patients and for individual eyes. Presence of ON head hyperintensity was also studied as a function of Frisen papilledema grade on fundoscopy, when available.

RESULTS

Hyperintensity of the ON heads on DWI was significantly associated with papilledema (P = .001). For the 2 readers, hyperintensity at both ON heads was 26.3% and 42.1% sensitive and 100% specific in the detection of papilledema. The presence of unilateral ON head hyperintensity was not specific for papilledema and was invariably graded as mild when seen in the control group. Patients with higher papilledema grades had a higher prevalence of hyperintensity at the ON heads.

CONCLUSIONS

Hyperintensity of the ON heads on DWI can serve as a useful imaging marker for papilledema, especially if bilateral. Its absence, however, does not exclude papilledema.