Use of A-scan Ultrasound and Optical Coherence Tomography to Differentiate Papilledema From Pseudopapilledema

Exploring the utility of retinal optical coherence tomography as a biomarker for idiopathic intracranial hypertension: a systematic review

This study aimed to examine the existing literature that investigated the effectiveness of optical coherence tomography (OCT) and optical coherence tomography angiography (OCT-A) as a biomarker for idiopathic intracranial hypertension (IIH). Our search was conducted on January 17th, 2024, and included the databases, Medline, Scopus, Embase, Cochrane, Latin American and Caribbean Health Sciences Literature (LILACS), International Standard Randomized Controlled Trial Number (ISRCTN) registry, and the International Clinical Trials Registry Platform (ICTRP). Our final review included 84 articles. In 74 studies, OCT was utilized as the primary ocular imaging method, while OCT-A was employed in two studies including eight studies that utilized both modalities. Overall, the results indicated that IIH patients exhibited significant increases in retinal nerve fiber layer (RNFL) thickness, total retinal and macular thickness, optic nerve head volume, and height, optic disc diameter and area, rim area, and thickness compared to controls. A significant correlation was observed between cerebrospinal fluid (CSF) pressure and OCT parameters including RNFL thickness, total retinal thickness, macular thickness, optic nerve head volume, and optic nerve head height. Interventions aimed at lowering CSF pressure were associated with a substantial improvement in these parameters. Nevertheless, studies comparing peripapillary vessel density using OCT-A between IIH patients and controls yielded conflicting results. Our systematic review supports OCT as a powerful tool to accurately monitor retinal axonal and optic nerve head changes in patients with IIH. Future research is required to determine the utility of OCT-A in IIH.

Diagnostic dilemma of papilledema and pseudopapilledema

BACKGROUND

Papilledema is the optic disc swelling caused by increased intracranial pressure (ICP) that can damage the optic nerve and cause subsequent vision loss. Pseudopapilledema refers to optic disc elevation without peripapillary fluid that can arise from several optic disc disorders, with optic disc drusen (ODD) being the most frequent cause. Occasionally, pseudopapilledema patients are mistakenly diagnosed as papilledema, leading to the possibility of unneeded procedures. We aim to thoroughly examine the most current evidence on papilledema and pseudopapilledema causes and several methods for distinguishing between both conditions.

METHODS

An extensive literature search was conducted on electronic databases including PubMed and google scholar using keywords that were relevant to the assessed pathologies. Data were collected and then summarized in comprehensive form.

RESULTS

Various techniques are employed to distinguish between papilledema and pseudopapilledema. These techniques include Fundus fluorescein angiography, optical coherence tomography, ultrasonography, and magnetic resonance imaging. Lumbar puncture and other invasive procedures may be needed if results are suspicious.

CONCLUSION

Papilledema is a sight-threatening condition that may lead to visual affection. Many disc conditions may mimic papilledema. Accordingly, differentiation between papilledema and pseudopailledema is crucial and can be conducted through many modalities.

Optic Nerve Sheath Diameter Point-of-Care Ultrasonography Quality Criteria Checklist: An International Consensus Statement on Optic Nerve Sheath Diameter Imaging and Measurement

OBJECTIVES

To standardize optic nerve sheath diameter (ONSD) point-of-care ultrasonography (POCUS) and improve its research and clinical utility by developing the ONSD POCUS Quality Criteria Checklist (ONSD POCUS QCC).

DESIGN

Three rounds of modified Delphi consensus process and three rounds of asynchronous discussions.

SETTING

Online surveys and anonymous asynchronous discussion.

SUBJECTS

Expert panelists were identified according to their expertise in ONSD research, publication records, education, and clinical use. A total of 52 panelists participated in the Delphi process.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Three Delphi rounds and three asynchronous discussion rounds generated consensus on quality criteria (QC). This started with 29 QC in addition to other QC proposed by expert panelists. The QC items were categorized into probe selection, safety, body position, imaging, measurement, and research considerations. At the conclusion of the study, 28 QC reached consensus to include in the final ONSD POCUS QCC. These QC were then reorganized, edited, and consolidated into 23 QC that were reviewed and approved by the panelists.

CONCLUSIONS

ONSD POCUS QCC standardizes ONSD ultrasound imaging and measurement based on international consensus. This can establish ONSD ultrasound in clinical research and improve its utility in clinical practice.

The Vienna idiopathic intracranial hypertension database-An Austrian registry

BACKGROUND

Idiopathic intracranial hypertension (IIH) is becoming increasingly more prevalent bearing the risk of visual impairment and affecting the quality of life. Clinical presentation and outcome are heterogeneous. Large, well-characterized cohorts are scarce.

OBJECTIVE

To characterize the clinical spectrum, diagnostic findings, therapeutic management, and outcome of IIH.

METHODS

We identified patients with IIH according to modified Friedman criteria treated at our center between 2014 and 2021. The Vienna IIH database is described in detail.

RESULTS

Of 113 patients 89% were female (mean age 32.3 years). Median body mass index (BMI) was 31.8, with 85% overweight (BMI > 25) and 5% were classified as IIH without papilledema. Headache was present in 84% and showed migraine features in 43%. Median opening pressure in lumbar puncture was 31 cmH2O. Pharmacotherapy (predominantly acetazolamide) was established in 99%, 56% required at least 1 therapeutic lumbar puncture and 13% a surgical intervention. After a median 3.7 years follow-up, 57% had achieved significant weight loss, papilledema was present in 59% and headache in 76% (58% improved). Comparing initial presentation to follow-up, perimetry was abnormal in 67% vs. 50% (8% worsened, 24% improved) and transorbital sonography in 87% vs. 65% with a median optic nerve sheath diameter of 5.4 mm vs. 4.9 mm. Median peripapillary retinal nerve fiber layer thickness decreased from 199 µm to 99 µm and ganglion cell layer volume from 1.13 mm3 to 1.05 mm3.

CONCLUSION

The large representative Vienna IIH cohort characterizes IIH-related symptoms, diagnostic findings, treatment, and outcome emphasizing substantial long-term sequelae of IIH. Future analyses will aim to refine phenotyping and identify factors predicting outcome.

Effects of head-down tilt on optic nerve sheath diameter in healthy subjects

PURPOSE

Intracranial pressure increases in head-down tilt (HDT) body posture. This study evaluated the effect of HDT on the optic nerve sheath diameter (ONSD) in normal subjects.

METHODS

Twenty six healthy adults (age 28 [4.7] years) participated in seated and 6° HDT visits. For each visit, subjects presented at 11:00 h for baseline seated scans and then maintained a seated or 6° HDT posture from 12:00 to 15:00 h. Three horizontal axial and three vertical axial scans were obtained at 11:00, 12:00 and 15:00 h with a 10 MHz ultrasonography probe on the same eye, randomly chosen per subject. At each time point, horizontal and vertical ONSD (mm) were quantified by averaging three measures taken 3 mm behind the globe.

RESULTS

In the seated visit, ONSDs were similar across time (p > 0.05), with an overall mean (standard deviation) of 4.71 (0.48) horizontally and 5.08 (0.44) vertically. ONSD was larger vertically than horizontally at each time point (p < 0.001). In the HDT visit, ONSD was significantly enlarged from baseline at 12:00 and 15:00 h (p < 0.001 horizontal and p < 0.05 vertical). Mean (standard error) horizontal ONSD change from baseline was 0.37 (0.07) HDT versus 0.10 (0.05) seated at 12:00 h (p = 0.002) and 0.41 (0.09) HDT versus 0.12 (0.06) seated at 15:00 h (p = 0.002); mean vertical ONSD change was 0.14 (0.07) HDT versus -0.07 (0.04) seated at 12:00 h (p = 0.02) and 0.19 (0.06) HDT versus -0.03 (0.04) seated at 15:00 h (p = 0.01). ONSD change in HDT was similar between 12:00 and 15:00 h (p ≥ 0.30). Changes at 12:00 h correlated with those at 15:00 h for horizontal (r = 0.78, p < 0.001) and vertical ONSD (r = 0.73, p < 0.001).

CONCLUSION

The ONSD increased when body posture transitioned from seated to HDT position without any further change at the end of the 3 h in HDT.

Clinical approach for suspected optic disc swelling in children: recommendations based on a six-year review

CLINICAL RELEVANCE

Suspected optic disc swelling is a common presentation in children. The delineation between true optic disc swelling and pseudopapilloedema, its common masquerade, requires careful evaluation. A streamlined pathway is required to avoid unnecessary investigations.

BACKGROUND

Papilloedema requires urgent neuroimaging, however, perceived optic disc swelling is not always true papilloedema. This study aims to investigate the outcome of referrals for optic disc swelling and formulate features that may assist in investigation and diagnosis.

METHODS

A retrospective review of referrals for optic disc swelling to the Queensland Children's Hospital, Australia, between January 2014 and June 2020 was undertaken.

RESULTS

Four hundred and ten children were referred for optic disc swelling. Sixty-six patients were confirmed with optic disc swelling, and 344 patients had pseudopapilloedema. The average age was 10.10 ± 3.57 and 9.90 ± 3.50 years, respectively. The most common aetiology of optic disc swelling was idiopathic intracranial hypertension (n = 25). Optic disc drusen constituted the majority of pseudopapilloedema (n = 239) and the remainder were crowded/tilted discs (n = 105). True optic disc swelling patients were more likely to experience headache (OR = 8.68, p < 0.01) and visual disturbance (OR = 2.14, p = 0.03). B-scan was the most sensitive for the detection of optic disc drusen (100%), followed by optical coherence tomography (70.38%) and fundus autofluorescence (44.86%). The retinal nerve fibre layer thickness was significantly thicker in true optic disc swelling compared to pseudopapilloedema (p < 0.01). Twenty-two (33.33%) true optic disc swelling patients and 33 (9.59%) pseudopapilloedema patients underwent neuroimaging prior to ophthalmology review.

CONCLUSIONS

Suspected optic disc swelling in children is most likely pseudopapilloedema. Referrals should include neurological assessment, visual acuity, fundus photography, and optical coherence tomography to assist in the triage for ophthalmic review. Neuroimaging prior to ophthalmic review should be discouraged for children without neurological symptoms.

Optic nerve sheath diameter and axial length in patients with optic disc drusen: a cross-sectional study

AIM

Measuring the optic nerve sheath diameter (ONSD) and the anteroposterior axial length of the eye in patients with optic disc drusen (ODD).

METHODS

A total of 43 healthy volunteers and 41 patients with ODD were included in the study. The ONSD and axial length were measured in the posterior position using an ultrasound device (E-Z Scan AB5500 +) probe with a 10 MHz frequency. The ONSD was measured 3 mm behind the globe wall. Receiver operating characteristic (ROC) curve analysis was performed to determine patients with ODD using ONSD. Any p-value of < 0.05 was accepted to demonstrate significance.

RESULTS

The ONSD was significantly higher (5.2 mm and 4.8 mm, p = 0.006, respectively), and the axial length was shorter (21.82 ± 2.15 mm and 23.27 ± 1.96 mm, p = 0.002, respectively) in the ODD group. The spherical equivalent was more commonly seen as hypermetropic in the ODD group (1.00 [- 0.85 to 1.75]). In the ROC analysis to determine the ONSD value in ODD diagnosis, the area under the curve was 0.6754 (95% confidence interval 0.559-0.788, p = 0.006). ONSD cutoff of 5.70 mm had a sensitivity of 0.366 and a specificity of 0.907 to diagnose ODD.

CONCLUSION

In this study, the ONSD was significantly higher in the ODD group. The axial length was shorter in the ODD group. This study is the first in the literature to evaluate the ONSD in patients with optic disc drusen. Further studies are needed in this regard.

Detection of increased intracranial pressure in trans-oral robotic thyroidectomy using optic nerve sheath diameter measurement

BACKGROUND

During transoral robot-assisted thyroidectomy, there is a risk of increasing intracranial pressure because the site of CO₂ insufflation is narrow and close to the brain.

METHODS

We analyzed the pre- to post-CO₂ neck insufflation change in the optic nerve sheath diameter during transoral robot-assisted thyroidectomy. Changes in vital-signs, airway pressure, and arterial carbon dioxide pressure were analyzed along with postoperative complications.

RESULTS

Among the 30 participants, the post-CO₂ inflation mean optic nerve sheath diameter (5.64 ± 0.54 mm) was higher than the pre-induction diameter (4.81 ± 0.37 mm) with a mean difference of 0.83 (95% CI, 0.69-0.97; p < 0.001), but returned to baseline after CO₂ deflation in most cases. One participant had sustained increased optic nerve sheath diameter (6.35 mm) associated with severe new-onset postoperative headache.

CONCLUSION

Transient elevation in the intracranial pressure during low-pressure CO₂ neck insufflation in the transoral robot-assisted thyroidectomy did not appear to adversely affect patients.

Ultrasound Detection of Intracranial Hypertension in Brain Injuries

In recent years, the measurement of optic nerve sheath diameter with ultrasound to detect the presence of increased intracranial pressure has widely spread. It can be qualitatively and effectively used to identify intracranial hypertension. Intracranial pressure can rise due to acute injury, cerebral bleeding, hydrocephalus, brain tumors and other space-occupying abnormalities, and it is linked to a high death rate. The purpose of this review is to give a general overview of the most relevant scientific publications on ultrasonographic evaluation of the optic nerve in case of brain injuries published in the last 30 years, as well as to analyze the limits of the most extensively used B-scan approach. Fifty-two papers chosen from the PubMed medical database were analyzed in this review. Our findings revealed that ocular ultrasound is an useful diagnostic tool in the management of intracranial hypertension when it exceeds a certain value or after head trauma. As a result, an ultrasound of the optic nerve can be extremely helpful in guiding diagnosis and treatment. The blooming effect is one of the most critical restrictions to consider when using B-scan ultrasonography. Since amplitude-scan ultrasound, also known as A-scan, does not have this limit, these two diagnostic techniques should always be used together for a more full, accurate, and trustworthy ultrasound examination, ensuring more data objectivity.

Optic Nerve Drusen Evaluation: A Comparison between Ultrasound and OCT

This observational study compared optic coherence tomography (OCT) and B-scan in the detection of optic disc drusen. In total, 86 eyes of 50 patients with optic disc drusen (ODD) (36 bilateral) with a mean age of 34.68 ± 23.81 years, and 54 eyes of 27 patients with papilledema, with a mean age of 35.42 years ± 17.47, were examined. Patients with ODD, diagnosed with ultrasound, underwent spectral-domain OCT evaluation. With US, 28 ODD cases were classified as large (4 buried and 24 superficial), 58 were classified as point-like (6 buried, 49 superficial and 3 mixed). Then, all patients underwent OCT. OCT was able to detect the presence of ODD and/or peripapillary hyperreflective ovoid mass structure (PHOMS) in 69 eyes (p < 0.001). In particular, 7 eyes (8.14%) showed the presence of ODD alone, 25 eyes (29.07%) showed only PHOMS and 37 eyes (43.02%) showed ODD and PHOMS. In 17 eyes (19.77%) no ODD or PHOMS were detected. In the papilledema group, no ODD were observed with both US and OCT. OCT showed the presence of drusen or similar lesions in only 80.23% of the cases highlighted by the US scan, so it does not allow for certain ODD diagnoses, especially in the case of buried ODD.

Variability Within Optic Nerve Optical Coherence Tomography Measurements Distinguishes Papilledema From Pseudopapilledema

BACKGROUND

To report a linear risk score obtained using clock-hour optical coherence tomography (OCT) data from papilledema and pseudopapilledema nerves that differentiates between the 2 diagnoses with high sensitivity and specificity.

METHODS

Patients presenting to a single neuro-ophthalmologist with papilledema or pseudopapilledema were included for a retrospective review. The absolute consecutive difference in OCT retinal nerve fiber layer (RNFL) thickness between adjacent clock hours and the mean magnitude of thickness for clock hours 1-12 were compared between the 2 groups using mixed-effect models adjusting for age and clock hour with a random intercept for subjects and eyes (nested within subject). The area under the curve (AUC) for the receiver operating characteristics curve and a separate calibration curve was used to evaluate potential clinical usage.

RESULTS

Forty-four eyes with papilledema and 72 eyes with pseudopapilledema, 36 of whom had optic nerve drusen met criteria. The papilledema group had a higher mean RNFL thickness (papilledema = 163 ± 68 µm, pseudopapilledema = 82 ± 22 µm, P < 0.001). The papilledema groups also had more variability between consecutive clock hours (papilledema = 57 ± 20 µm, pseudopapilledema = 26 ± 11 µm, P < 0.001). A linear combination of each patient's averaged values separated the 2 groups with an AUC of 98.4% (95% CI 95.5%-100%) with an optimized sensitivity of 88.9% and specificity of 95.5% as well as good calibration (mean absolute error = 0.015).

CONCLUSIONS

Patients with papilledema have higher intrinsic variability and magnitude within their OCT, and this finding reliably distinguishes them from those with pseudopapilledema.

Custom Optical Coherence Tomography Parameters for Distinguishing Papilledema from Pseudopapilledema

SIGNIFICANCE

Causes of papilledema can be life-threatening; however, distinguishing papilledema from pseudopapilledema is often challenging. The conventional optical coherence tomography (OCT) scan for assessing the optic nerve often fails to detect mild papilledema. Our study suggests that parameters derived from volumetric OCT scans can provide additional useful information for detecting papilledema.

PURPOSE

Optical coherence tomography analysis of the optic nerve commonly measures retinal nerve fiber layer thickness (RNFLT) along a 1.73-mm-radius scan path. This conventional scan, however, often fails to detect mild papilledema. The purpose of this study was to evaluate additional OCT-derived measures of the optic nerve head (ONH) and peripapillary retina for differentiating papilledema (all grades and mild) from pseudopapilledema.

METHODS

Cirrus OCT ONH volume scans were acquired from 21 papilledema (15 mild papilledema), 27 pseudopapilledema, and 42 control subjects. Raw scan data were exported, and total retinal thickness within Bruch's membrane opening (BMO) plus RNFLT and total retinal thickness at the following eccentricities were calculated using custom algorithms: BMO to 250, 250 to 500, 500 to 1000, and 1000 to 1500 μm. Minimum rim width was calculated, and BMO height was measured from a 4-mm Bruch's membrane reference plane centered on the BMO.

RESULTS

Retinal nerve fiber layer thickness from BMO to 250 μm, minimum rim width, and BMO height had significantly greater areas under the receiver operating characteristic curve than did conventional RNFLT for differentiating mild papilledema from pseudopapilledema (P < .0001) and greater sensitivities at 95% specificity. Using cutoff values at 95% specificity, custom parameters detected 10 mild papilledema patients, and conventional RNFLT detected only 1. Bruch's membrane opening heights above the reference plane were observed in papilledema only, although many papilledema cases had a neutral or negative BMO height.

CONCLUSIONS

Using OCT volumetric data, additional parameters describing peripapillary tissue thickness, neuroretinal rim thickness, and ONH position can be calculated and provide valuable measures for differentiating mild papilledema from pseudopapilledema.

Accuracy of machine learning for differentiation between optic neuropathies and pseudopapilledema

Background

This study is to evaluate the accuracy of machine learning for differentiation between optic neuropathies, pseudopapilledema (PPE) and normals.

Methods

Two hundred and ninety-five images of optic neuropathies, 295 images of PPE, and 779 control images were used. Pseudopapilledema was defined as follows: cases with elevated optic nerve head and blurred disc margin, with normal visual acuity (> 0.8 Snellen visual acuity), visual field, color vision, and pupillary reflex. The optic neuropathy group included cases of ischemic optic neuropathy (177), optic neuritis (48), diabetic optic neuropathy (17), papilledema (22), and retinal disorders (31). We compared four machine learning classifiers (our model, GoogleNet Inception v3, 19-layer Very Deep Convolution Network from Visual Geometry group (VGG), and 50-layer Deep Residual Learning (ResNet)). Accuracy and area under receiver operating characteristic curve (AUROC) were analyzed.

Results

The accuracy of machine learning classifiers ranged from 95.89 to 98.63% (our model: 95.89%, Inception V3: 96.45%, ResNet: 98.63%, and VGG: 96.80%). A high AUROC score was noted in both ResNet and VGG (0.999).

Conclusions

Machine learning techniques can be combined with fundus photography as an effective approach to distinguish between PPE and elevated optic disc associated with optic neuropathies.