Accuracy of crescent sign on ocular ultrasound in diagnosing papilledema

The crescent sign on ocular ultrasound and correlation with elevated intracranial pressure: A prospective cohort study

OBJECTIVES

While lumbar puncture (LP) remains gold standard for assessing intracranial pressure (ICP), LP can be difficult to perform and lead to complications. Noninvasive correlations for elevated ICP via ocular ultrasound (OUS) have shown mixed results. The primary objective of this study is to identify the frequency and test characteristics of the crescent sign on OUS for elevated ICP. Secondary objectives include comparison of test characteristics to optic nerve sheath diameter (ONSD) and optic disc elevation (ODE).

DESIGN

Single center, prospective, observational cohort study enrolling adults (age ≥ 18 years) who presented to an outpatient Neurology LP clinic. An OUS protocol was performed prior to scheduled LP, with measurement of the opening pressure (OP) by manometry. Patients were excluded if LP was unable to be completed (for any reason) or if completed in the sitting position. Elevated OP was defined as ≥25cmH2O.

RESULTS

In total, 68 patients were enrolled; seven were excluded due to no OP measured, leaving 61 patients for analysis. Forty-six patients had normal OP, while 15 had elevated OP. The crescent sign was observed in 19 patients (31 %). Overall sensitivity, specificity, and accuracy of the crescent sign was 67 %, 80 %, and 74 %, respectively. Comparison of accuracy between the six other OUS findings demonstrated no significant differences between test characteristics (p > 0.10 for each).

CONCLUSIONS

The crescent sign was observed in 31 % of patients, with moderate sensitivity, specificity, and accuracy for elevated ICP. This study has several limitations and evaluations in the acute care setting are needed.

Ultrasound detected increase in optic disk height to identify elevated intracranial pressure: a systematic review

BACKGROUND

Elevated intracranial pressure (eICP) is a serious medical emergency that requires prompt identification and monitoring. The current gold standards of eICP detection require patient transportation, radiation, and can be invasive. Ocular ultrasound has emerged as a rapid, non-invasive, bedside tool to measure correlates of eICP. This systematic review seeks to explore the utility of ultrasound detected optic disc elevation (ODE) as an ultrasonographic finding of eICP and to study its sensitivity and specificity as a marker of eICP.

METHODS

This systematic review followed the preferred reporting items for systematic reviews and meta-analyses guidelines. We systematically searched PubMed, EMBASE, and Cochrane Central for English articles published before April 2023; yielding 1,919 total citations. After eliminating duplicates, and screening the records, we identified 29 articles that addressed ultrasonographically detected ODE.

RESULTS

The 29 articles included a total of 1249 adult and pediatric participants. In patients with papilledema, the mean ODE ranged between 0.6 mm and 1.2 mm. Proposed cutoff values for ODE ranged between 0.3 mm and 1 mm. The majority of studies reported a sensitivity between 70 and 90%, and specificity ranged from 69 to 100%, with a majority of studies reporting a specificity of 100%.

CONCLUSIONS

ODE and ultrasonographic characteristics of the optic disc may aid in differentiating papilledema from other conditions. Further research on ODE elevation and its correlation with other ultrasonographic signs is warranted as a means to increase the diagnostic accuracy of ultrasound in the setting of eICP.

Diagnostic Accuracy of Ocular Ultrasonography in Identifying Raised Intracranial Pressure among Pediatric Population

INTRODUCTION

Role of CT scan, MRI, ophthalmoscopy, direct monitoring by a transducer probe in identifying raised intracranial pressure (ICP) in emergency department is limited. There are few studies correlating elevated optic nerve sheath diameter (ONSD) measured by point of care ultrasound (POCUS) with raised ICP in pediatrics emergencies. We studied the diagnostic accuracy of ONSD, crescent sign, and optic disc elevation in identifying increased ICP in pediatrics.

METHODS

Prospective observational study was done between April 2018 and August 2019 after ethics approval. Out of 125 subjects, 40 patients without clinical features of raised ICP were recruited as external controls and 85 with clinical features of raised ICP as study subjects. Their demographic profile, clinical examination, and ocular ultrasound findings were noted. This was followed by CT scan. Out of 85 patients, 43 had raised ICP (cases) and 42 had normal ICP (disease controls). Diagnostic accuracy of ONSD in identifying raised ICP was evaluated using STATA.

RESULTS

The mean ONSD in case group was 5.5 ± 0.6 mm, 4.9 ± 0.5 mm in disease control group and external control group was 4.8 ± 0.3 mm. Cut-off of ONSD for raised ICP at ≥4.5 mm had a sensitivity and specificity of 97.67% and 10.98%, while ≥5.0 mm showed a sensitivity and specificity of 86.05% and 71.95%. Crescent sign and optic disc elevation had good correlation with increased ICP.

CONCLUSION

ONSD ≥5 mm by POCUS identified raised ICP in pediatric population. Crescent sign and optic disc elevation may function as additional POCUS signs in identifying raised ICP.

Utility of Ultrasound and Optical Coherence Tomography in Differentiating Between Papilledema and Pseudopapilledema in Children

BACKGROUND

Differentiating between papilledema and pseudopapilledema in children presenting with mild-to-moderate optic nerve head elevation is challenging. This study sought to determine which B-scan ultrasonography (BSUS) and optical coherence tomography (OCT) features, individually or in combination, are best able to differentiate between papilledema and pseudopapilledema in children.

METHODS

Children presenting with optic nerve head elevation of unknown etiology were eligible if they underwent BSUS and OCT performed by the same investigator. The absolute optic nerve sheath diameter (in millimeter) along with the presence/absence of a hyperreflective nodule(s) at the optic nerve head (indicative of druse) from BSUS was determined. The average circumpapillary retinal nerve fiber layer (cpRNFL), diameter of Bruch membrane opening, maximum papillary height, and the presence/absence of hyper-/hyporeflective lesions at the optic nerve head were calculated. Sensitivity and specificity were calculated to evaluate which BSUS and OCT imaging features, individually and in combination, accurately classified children as having papilledema vs pseudopapilledema.

RESULTS

One hundred eighty-one eyes from 94 children (mean age, 11.0 years; range, 3.2-17.9) were included; 36 eyes with papilledema and 145 eyes with pseudopapilledema. Among BSUS features, optic nerve sheath widening (>4.5 mm) demonstrated the best sensitivity (86%; 95% confidence interval [CI], 64%-96%) and specificity (88%; 95% CI, 79%-94%) for papilledema. Among OCT measures, cpRNFL thickness of ≥140 µm demonstrated the best sensitivity (83%; 95% CI, 66%-93%) and specificity (76%; 95% CI, 66%-84%) to identify papilledema. The presence of both optic nerve sheath widening (>4.5 mm) and cpRNFL thickness of ≥140 µm reduced the sensitivity (72%; 95% CI, 52%-86%) but increased specificity (95%; 95% CI, 88%-98%).

CONCLUSION

BSUS (optic nerve sheath widening [>4.5 mm]) and OCT (cpRNFL thickness ≥140 µm), individually and collectively, have good diagnostic accuracy for differentiating between papilledema and pseudopapilledema. The presence of druse does not exclude the diagnosis of papilledema.

Papilledema: A review of etiology, pathophysiology, diagnosis, and management

Papilledema is optic nerve head edema secondary to raised intracranial pressure (ICP). It is distinct from other causes of optic disk edema in that visual function is usually normal in the acute phase. Papilledema is caused by transmission of elevated ICP to the subarachnoid space surrounding the optic nerve that hinders axoplasmic transport within ganglion cell axons. There is ongoing controversy as to whether axoplasmic flow stasis is produced by physical compression of axons or microvascular ischemia. The most common cause of papilledema, especially in patients under the age of 50, is idiopathic intracranial hypertension (IIH); however, conditions that decrease cerebrospinal fluid (CSF) outflow by either causing CSF derangements or mechanically blocking CSF outflow channels, and rarely conditions that increase CSF production, can be the culprit. When papilledema is suspected clinically, blood pressure should be measured, and pseudopapilledema should be ruled out. Magnetic resonance imaging of the brain and orbits with venography sequences is the preferred neuroimaging modality that should be performed next to look for indirect imaging signs of increased ICP and to rule out nonidiopathic causes. Lumbar puncture with measurement of opening pressure and evaluation of CSF composition should then be performed. In patients not in a typical demographic group for IIH, further investigations should be conducted to assess for underlying causes of increased ICP. Magnetic resonance imaging of the neck and spine, magnetic resonance angiography of the brain, computed tomography of the chest, complete blood count, and creatinine testing should be able to identify most secondary causes of intracranial hypertension. Treatment for patients with papilledema should be targeted toward the underlying etiology. Most patients with IIH respond to weight loss and oral acetazolamide. For patients with decreased central acuity and constricted visual fields at presentation, as well as patients who do not respond to treatment with acetazolamide, surgical treatments should be considered, with ventriculoperitoneal shunting being the typical procedure of choice.

Role of Ocular Ultrasonography to Distinguish Papilledema From Pseudopapilledema

BACKGROUND

We prospectively evaluated the sensitivity and specificity of ocular ultrasonography (OUS) to distinguish papilledema from pseudopapilledema.

METHODS

Forty-nine study participants, with optic disc elevation, underwent neuro-ophthalmic evaluation, OUS, fundus photography, and optical coherence tomography (OCT) of the optic nerve head at the initial and follow-up visits (≤6 months apart). Participants were classified as having papilledema if there was a change in optic nerve appearance on fundus photographs, as determined by a masked observer, between initial and follow-up visits ≤6 months apart. OUS was considered positive when the optic nerve sheath width was >3.3 mm and the 30° test was positive. Ocular ultrasonographic findings were correlated in patients who had papilledema vs patients who had pseudopapilledema. In a subanalysis, OUS findings were also correlated with change in peripapillary retinal nerve fiber layer thickness on OCT of the optic nerve head between initial and follow-up visits.

RESULTS

OUS was 68% (17/25) sensitive for papilledema and 54% (13/24) specific for pseudopapilledema. When using OCT parameters to define papilledema, the sensitivity of OUS to diagnose papilledema decreased to 62%. Positive OUS correlated with elevated opening pressure on lumbar puncture and with signs of increased intracranial pressure on MRI.

CONCLUSION

OUS alone was less sensitive in diagnosing papilledema than previously thought. Therefore, OUS may not be helpful in distinguishing between papilledema and pseudopapilledema.

Role of ultrasonographic optic nerve sheath diameter in the diagnosis and follow-up of papilledema and its correlation with Frisén's severity grading

Purpose:

The aim of this study was to compare the ultrasonographic optic nerve sheath diameter (ONSD) in different grades of papilledema and in controls and to evaluate ONSD in atrophic papilledema/optic atrophy when raised ICP was suspected.

Methods:

Prospective cross-sectional case–control study. Following an ocular examination, papilledema was graded clinically using modified Frisén's grading. An ultrasonographic cross section of the retrobulbar optic nerve was obtained with a posterior transverse scan. Independent t-test and analysis of variance were the statistical tools used in the study.

Results:

The study included 55 cases and 55 age- and gender-matched controls; mean (± standard deviation) age was 37.17 (±11.25) years and male: female ratio was 49:61. There was a statistically significant difference in the mean ultrasonographic ONSD between cases [4.89 (±0.65) mm] and controls [3.12 (±0.22) mm] (P < 0.001). There was a significant difference in the mean ONSD across Frisén's grades of papilledema (P < 0.001). The mean ONSD in atrophic papilledema was 6.2 (±0.75) mm.

Conclusion:

In the presence of symptoms, ultrasonographic ONSD >4 mm is diagnostic of papilledema. Ultrasonographic ONSD correlates well with the severity of papilledema and can be used to follow-up patients with chronically elevated ICP. It is useful in detecting raised ICP in the presence of optic atrophy and to distinguish true papilledema from pseudopapilledema.

Role of Orbital Ultrasound in the Assessment of Clinically Detected Papilledema

BACKGROUND

Increased intracranial pressure (ICP) is frequently seen, and it is considered a serious problem that needs a careful assessment and management, especially by easy and least invasive modalities.

OBJECTIVE

The objective of the study is to assess the optic nerve sheath diameter (ONSD) using transorbital ultrasound (US) as a marker and indicator for diagnosing raised intracranial pressure.

PATIENTS AND METHODS

It is a prospective study that was carried out in Neurology and/or Ophthalmology Clinics, Baghdad Teaching Hospital in the Medical City Complex during the period from June 2016 to May 2017; in this study, 40 patients seeking medical help for other causes were considered to be a control group and the other 40 patients who were complaining of raised ICP symptoms and suggested of having optic disc swelling by ophthalmoscopy examination. All the patients and the control group were examined by transorbital US to measure the ONSD, and then, only the patients with symptoms of raised intracranial underwent a lumbar puncture (LP).

RESULTS

Pearson's correlation test was used, demonstrating a very significant correlation between the ultrasonographic ONSD and the measurements of LP (R > 0.9) and (P < 0.001). Transorbital US yielded high sensitivity (91.6%) with modest specificity (75%) and high accuracy (90.0%) of ONSD was considered the normal the cutoff value of (5 mm) obtained from the control group. The US also showed the crescent sign and the optic disc bulging with lower sensitivity than the ONSD (61.1% and 41.6%, respectively) but with very high specificity (100%) for both.

CONCLUSION

ONSD by transorbital ultrasonography is highly accurate, easily performed, and noninvasive procedure for the detection of raised ICP. Routine daily monitoring of ONSD could be of help in intensive care units when invasive ICP monitoring is not available or contraindicated; it also has a good role in early recognition of intracranial hypertension.