Transorbital sonography in idiopathic intracranial hypertension: Single-center study, systematic review and meta-analysis.

BACKGROUND AND PURPOSE: Transorbital sonography (TOS) provides a noninvasive tool to detect intracranial pressure by assessing optic nerve sheath diameter (ONSD) and optic disc elevation (ODE). The utility of TOS in the diagnosis of idiopathic intracranial hypertension (IIH) has been increasingly recognized. METHODS: A single-center case-control study sought to compare TOS-acquired ONSD and ODE among IIH-cases versus patients with other neurological diseases (controls). Furthermore, a systematic review and meta-analysis was conducted to present pooled mean differences and diagnostic measures of ONSD and ODE between IIH-cases and controls. RESULTS: In the single-center study, consisting of 31 IIH-cases and 34 sex- and age-matched controls, ONSD values were higher among IIH-cases than controls (p<.001), while ODE was more prevalent in cases (65% vs. 15%; p<.001). The receiver-operating characteristic (ROC)-curve analysis revealed that the optimal cutoff value of ONSD for predicting IIH was 5.15 mm, with an area under the curve (AUC) of 0.914 (95% confidence interval [CI]: 0.861-0.967) and sensitivity and specificity values of 85% and 90%, respectively. In a meta-analysis of 14 included studies with 415 IIH-cases, ONSD and ODE values were higher in IIH-cases than controls (mean difference in ONSD 1.20 mm; 95% CI: 0.96-1.44 mm and in ODE 0.3 mm; 95% CI: 0.33-0.67 mm). With regard to ONSD, pooled sensitivity, specificity, and diagnostic odds ratio were calculated at 85.5% (95% CI: 77.9-90.8%), 90.7% (95% CI: 84.6-94.5%), and 57.394 (95% CI: 24.597-133.924), respectively. The AUC in summary ROC-curve analysis was 0.878 (95% CI: 0.858-0.899) with an optimal cutoff point of 5.0 mm. CONCLUSIONS: TOS has a high diagnostic utility for the noninvasive diagnosis of IIH and may deserve wider implementation in everyday clinical practice.

B-mode transorbital ultrasonography for the diagnosis of idiopathic intracranial hypertension: an updated systematic review and meta-analysis.

OBJECTIVES: This systematic review and meta-analysis aimed to evaluate the role of B-mode transorbital ultrasonography (TOS) for the diagnosis of idiopathic intracranial hypertension (IIH) in adults. METHODS: MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials (CENTRAL) (1966-May 2022) were searched to identify studies reporting ultrasonographic data about the optic nerve sheath diameter (ONSD) and optic disc elevation (ODE) in adults with IIH compared to subjects without IIH. The quality of the included studies was evaluated by the Newcastle-Ottawa Quality. RESULTS: Fifteen studies were included (total of 439 patients). The values of ODE ranged from 0.6 to 1.3 mm in patients with IIH. The values of ONSD ranged from 4.7 to 6.8 mm in IIH patients and from 3.9 to 5.7 mm in controls. In IIH patients, the ONSD was significantly higher compared to controls (standardized mean difference: 2.5 mm, 95% confidence interval (CI): 1.6-3.4 mm). Nine studies provided data about the presence of papilledema and the pooled prevalence was 95% (95% CI, 92-97%). CONCLUSIONS: In adults, the thickness of ONSD and the entity of ODE were significantly associated with IIH. B-mode TOS enables to noninvasively detect increased ICP and should be performed, potentially routinely, in any patient with suspected IIH.

Transorbital sonography and MRI reliability to assess optic nerve sheath diameter in idiopathic intracranial hypertension.

BACKGROUND AND PURPOSE: The purpose of this study was to evaluate the performance of magnetic resonance imaging (MRI) in measuring the optic nerve sheath diameter (ONSD) compared to the established method transorbital sonography (TOS) in patients with idiopathic intracranial hypertension (IIH). METHODS: Twenty-three patients with IIH were prospectively included applying IIH diagnostic criteria. All patients received a lumbar puncture with assessment of the cerebrospinal fluid (CSF) opening pressure to assure the IIH diagnosis. Measurement of ONSD was performed 3 mm posterior to inner sclera surface in B-TOS by an expert examiner, while three independent neuroradiologists took measurements in axial T-weighted MRI examinations. The sella turcica with the pituitary gland (and potential presence of an empty sella) and the trigeminal cavity were also assessed on sagittal and transversal T1-weighted MRI images by one independent neuroradiologist. RESULTS: The means of ONSD between ultrasound and MRI measurements were 6.3 mm (standard deviation [SD] = 0.6 mm) and 6.2 mm (SD = 0.8 mm). The interrater reliability between three neuroradiologists showed a high interclass correlation coefficient (ICC) (confidence interval: .573 < ICC < .8; p < .001). In patients with an empty sella, the ONSD evaluated by MRI was 6.6 mm, while measuring 6.1 mm in patients without empty sella. No correlation between CSF opening pressure and ONSD was found. CONCLUSIONS: MRI can reliably measure ONSD and yields similar results compared to TOS in patients with IIH. Moreover, patients with empty sella showed significantly larger ONSD than patients without empty sella.

Intracranial pressure and veins.

This review summarizes the relationship between intracranial pressure and the venous system as far as ultrasound methods are concerned. Although the pressure in cortical veins is tightly and linearly coupled to the intracranial pressure, venous flow velocities in the basal veins are not. However, venous flow velocities reflect better the local cerebral blood flow than measurements in arteries. Therefore, they correlate better with clinical outcome in head trauma and subarachnoid hemorrhage. Transorbital sonography with measurement of the optic nerve sheath diameter and optic disk elevation has evolved to a valuable point of care diagnostic tool in idiopathic intracranial hypertension. In cerebral vein and sinus thrombosis ultrasound is at best a supplementary diagnostic tool, which may have a value in patient follow-up.

Sonographic and ophthalmic assessment of optic nerve in patients with idiopathic intracranial hypertension: A longitudinal study.

BACKGROUND: To assess the validity of neurosonological parameters (transorbital sonography (TOS)) for detection and monitoring of patients with idiopathic intracranial hypertension (IIH). METHODS: Prospective, single-center, case-controlled study in 25 patients with IIH and 19 controls. Visual parameters of papilledema, visual acuity, computerized static threshold perimetry, fundus examination, and neurosonological parameters of papilledema/optic disc elevation (ODE), optic nerve sheath diameter (ONSD) and optic nerve diameter (OND) were recorded at baseline and only for patients with IIH again within 6 months. RESULTS: ONSD was significantly enlarged among individuals with IIH (6.2 ± 0.73 mm) compared to controls (4.99 ± 0.54 mm; p < 0.001). Bilateral ODE was found in 36/50 eyes in patients at their initial visit and in none of the controls. Re-evaluation 6 months later showed a significant reduction of ONSD (6.0 ± 0.7 mm; p = 0.024) and ODE (0.2 (0-1) mm; p ≤0.001). Best corrected visual acuity (BCVA) and square root of lost variance (sLV) remained stable. Headache intensity (Numeric rating scale, NRS) improved significantly p < 0.001. When compared to patients with first diagnosed IIH (n = 18), the subset of patients with preexisting IIH with acute relapse (n = 7) showed persistent but reduced levels of ICP increase. They also presented significant decrease of BVCA (p = 0.01) and mean defect (MD) (p = 0.012). Re-evaluation 6 months later showed significant change in ODE in both groups. CONCLUSIONS: Our study confirmed that TOS and ophthalmological parameters are a valuable and non-invasive method to detect and monitor elevated ICP in IIH.

Sonography of optic nerve sheath diameter identifies patients with middle cerebral artery infarction at risk of a malignant course: a pilot prospective observational study.

INTRODUCTION: To assess the value of optic nerve sheath diameter (ONSD) measurements at different time points to predict the malignant evolution in middle cerebral artery (MCA) infarction and to investigate the relationship between ONSD and infarct volume on follow-up computed tomography (CT). METHODS: In a single-center prospective observational study, we recruited patients with MCA infarction and age- and sex-matched controls. Clinical characteristics including NationaI Institutes of Health Stroke Scale (NIHSS) and ONSD measurement were assessed during the first five days after symptom onset. Volumetric analysis of the infarction was performed by a neuroradiologist, who was blinded to results of ONSD measurement and clinical examinations, based on  CT scans. RESULTS: We enrolled 29 patients with MCA infarction, including 10 with malignant MCA (mMCA) infarction and 14 controls. Mean ONSD on admission was already larger in patients who had developed an mMCA (5.99 ± 0.32 mm) compared to patients with MCA infarction (4.98 ± 0.53 mm; P = 0.003), and to control patients (4.57 ± 0.29 mm; P < 0.001). Correlation was observed between the ONSD mean value bilateral measures per individual and volumetric evaluation of cerebral infarction in the CT scan after one day (r = 0.623; P = 0.002). An ONSD value of 5.6 mm predicted an mMCA with a sensitivity of 100% and specificity of 90% yielding a positive predictive value of 83% and negative predictive value of 100%. CONCLUSIONS: ONSD measurement might be accurate for the noninvasive detection of increased ICP and for the recognition of patients being likely to develop mMCA.

Quantification of Optic Nerve and Sheath Diameter by Transorbital Sonography: A Systematic Review and Metanalysis.

BACKGROUND AND PURPOSE: To date, normal values for optic nerve diameter (OND) and optic nerve sheath diameter (ONSD) for transorbital sonography (TOS) have only been reported by individual small-scale studies, exposing a great variability in the measurement of the OND and ONSD. METHODS: We performed a systematic review and metanalysis of available to date studies on TOS evaluation of adults without elevated intracranial pressure to provide an overview of the published literature, measuring methods and further specify normal values for OND and ONSD. RESULTS: In total, we included 39 studies with 2,927 healthy volunteers (mean age 36.1 years, 44.4% female), so that a total of 5,854 eyes were examined. All pooled analyses were based on random effect models. Mean values for OND were provided in 13 studies. Calculated mean pooled OND value was 3.08 mm (95% confidence interval [CI], 2.9-3.25), with low heterogeneity across studies (I2 = 12.7%). Thirty-four studies provided mean values for ONSD measurement. The pool of mean ONSD measurements was 4.78 mm (95% CI, 4.63-4.94), with evidence of substantial heterogeneity between estimates ONSD (I2 = 50.6%). There were no significant differences (P = .139) in the subsequent subgroup analysis for the different geographic continents. Also, no significant differences could be recorded for the effect of age (P = .824) or gender (P = .093). CONCLUSIONS: TOS is a frequently described and widely used method. We provide reference values of OND and ONSD that are based on metanalytical analysis. Different measuring methods of ONSD result in higher heterogeneity. Subgroup analysis revealed no significant correlation between ONSD and age, gender, or geographic origin.

Sonographic assessment of the optic nerve and the central retinal artery in idiopathic intracranial hypertension.

PURPOSE: Transorbital sonography easily detects papilledema and enlarged optic nerve sheath diameters (ONSD) in IIH (idiopathic intracranial hypertension) patients. As the central retinal artery is located within the optic nerve, its hemodynamic properties might be affected by the increased pressure. In this study we assessed the diagnostic usefulness of transorbital sonography in IIH with a special focus on color Doppler imaging of the central retinal artery. IIH patients presented papilledema and enlarged ONSD. ONSD accurately predicted an increased intracranial pressure in IIH (cut-off: 5.8 mm, 81% sensitivity, 80% specificity). 24 h following therapeutic lumbar puncture ONSD diminished significantly, whereas papilledema was not changed. PSV (peak systolic velocity) and Vmean (mean flow velocity) of the central retinal artery were increased in IIH patients compared to controls. PSV accurately predicted an increase of intracranial pressure (cut-off: 11.0 cm/s, 70% sensitivity, 69% specificity). PI (pulsatility index), PSV and Vmean decreased following lumbar puncture. PSV and Vmean decreases were statistically significant for right eyes only in which the values changed to normal. In summary, besides ONSD enlargement and papilledema transbulbar sonography demonstrated an alteration of central retinal artery blood flow in IIH patients. Especially PSV might serve as valuable surrogate marker for intracranial pressure in IIH. Furthermore, the change of intra-individual central retinal arteries PI might be a valuable parameter to demonstrate response to lumbar puncture in IIH patients.

Optic nerve sheath diameter asymmetry in healthy subjects and patients with intracranial hypertension.

BACKGROUND: Ultrasonography of the optic nerve sheath diameter (ONSD) is used for the non-invasive assessment of increased intracranial pressure (ICP). ONSD values are usually obtained by averaging the measurements of the two eyes, but asymmetric ONSD dilation is possible, leading to potentially inaccurate ICP estimation when using binocular averaging. In addition, few data are available about the asymmetry of the ONSD and the use of the maximum ONSD value between eyes for raised ICP detection. The aim of the study was to evaluate the interocular ONSD asymmetry in healthy subjects and patients with intracranial hypertension (IH) by ultrasonography and to investigate whether the maximum ONSD could be as useful as the binocular assessment. METHODS: Forty healthy subjects and 40 patients with IH (20 with idiopathic intracranial hypertension and 20 with intracerebral hemorrhage) who underwent transorbital sonography were retrospectively enrolled. The prevalence and degree of ONSD asymmetry were compared among groups; ONSD median binocular and maximum values were compared. RESULTS: Forty-two out of 80 subjects (52.5%) showed significant ONSD asymmetry, without significant differences in prevalence among groups (p = 0.28). The median asymmetry was higher in patients than in healthy subjects (0.45 mm vs 0.23 mm; p = 0.007), without significant differences between the two pathologies (p = 0.58). Both binocular and maximum ONSD measurements were significantly higher in patients with IH than in controls (p < 0.001). CONCLUSIONS: Interocular ONSD asymmetry occurs both in healthy subjects and, more consistently, in patients with IH. Both binocular and maximum ONSD may be useful markers for increased ICP detection.

Functional and structural changes in the visual pathway in multiple sclerosis.

INTRODUCTION: Multiple sclerosis (MS) is a heterogeneous disease with an unpredictable course. Visual pathway is a target of the disease and may reflect mechanisms that lead to disability. Structural and functional changes in the visual pathway may be studied by noninvasive techniques such as optical coherence tomography (OCT), visual evoked potentials (VEP), or B-mode transorbital sonography (TOS). OBJECTIVES: The aim is to assess changes in the visual pathway in eyes of MS patients with and without a history of optic neuritis over a 3-year period and to explore their relationship with disability. MATERIALS AND METHODS: In total, 112 eyes from 56 patients with relapsing MS were recruited: 29 with, and 83 without a history of ON (hON and nhON, respectively). Several parameters were measured by OCT, VEP, and TOS. Baseline measurements were also compared to 29 healthy controls. At 36 months, measurements were repeated in all eyes. RESULTS: At baseline, all tests showed significant differences in optic nerve structure and function in both patient cohorts in all the parameters studied, suggestive of more impairment of the visual pathway among the hON cohort. OCT showed significant differences between healthy controls and the nhON cohort. At 36 months, the nhON cohort showed significant changes by OCT, VEP, and TOS suggestive of further visual pathway impairment. OCT measurements also correlated with baseline EDSS among the nhON cohort. CONCLUSIONS: OCT is the most suitable technique and outperforms VEP and TOS to detect subclinical damage in the visual pathway. It discriminated MS patients from healthy controls and showed a progressive decline in optic nerve thickness over time among these patients.

Evaluating optic nerve diameter as a possible biomarker for disability in patients with multiple sclerosis.

BACKGROUND AND PURPOSE: The development of new biomarkers for multiple sclerosis (MS) is of paramount importance to improve our ability to predict disease progression and disability. The aim of this study was to evaluate the potential role of the optic nerve diameter (OND) measured by ultrasonography as a biomarker of early disability in patients with relapsing-remitting multiple sclerosis (RRMS). METHODS: Forty-nine RRMS patients, 23 with a history of optic neuritis (MS-ON) and 26 without a history of optic neuritis (MS N-ON), and 50 age- and sex-matched healthy control subjects were included in the study. The OND and optic nerve sheath diameter (ONSD) were measured by transorbital sonography (TOS), and the retinal nerve fibre layer (RNFL) and ganglion cell complex (GCC) thicknesses were measured by optical coherence tomography (OCT) using the Optovue RTVue™ system (Optovue, Inc., Fremont, CA, USA). RESULTS: There was no significant difference between the patient (whether ON or N-ON eyes) and control groups in either the OND (p=0.979) or the ONSD (p=0.911). However, patients with an expanded disability status scale (EDSS) score >2 had a significantly lower OND and RNFL thicknesses (p=0.014, p=0.010 respectively) than patients with an EDSS score ≤2. Statistical logistic regression revealed that OND was an independent predictor of EDSS>2 (p=0.044, OR =0.000, 95% CI=0.000-0.589). CONCLUSION: The OND, as measured by ultrasonography, could be potentially used as a biomarker for the detection of early disability in RRMS patients.

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.

Sonographic assessment of optic nerve and ophthalmic vessels in patients with idiopathic intracranial hypertension.

BACKGROUND: Early diagnosis and proper monitoring of intracranial pressure (ICP) in idiopathic intracranial hypertension (IIH) could reduce morbidity. OBJECTIVES: The objective was to explore and monitor reflection of raised ICP in IIH on optic nerve sheath diameter (ONSD), papillary height and ophthalmic vessels hemodynamics, using transorbital sonography (TOS). METHODS: The study included 24 IIH patients and 30 controls. Patients were compared to controls (phase I) then reassessed twice; 1 week and 4 weeks later (phase II). Both groups underwent clinical evaluation and TOS to measure ONSD, papillary elevation, and color Doppler indices of the ophthalmic vessels. Patients underwent lumbar puncture (LP) to measure cerebrospinal fluid (CSF) pressure. RESULTS: ONSD was significantly higher in patients compared to controls (p < 0.001). The cut-off value was 6.2 mm. Papillary elevation (p = 0.006) and ONSD (p = 0.006) were significantly reduced 4 weeks following LP. Baseline color Doppler indices of the ophthalmic vessels were comparable between both groups and the changes observed during the follow-up visits in the patients were insignificant. CONCLUSION: Reflected ICP changes on ONSD and papilla, measured by TOS, could be a valuable noninvasive additional tool to diagnose and monitor IIH patients. IIH insignificantly influences ophthalmic vessels hemodynamics. Abbreviation BMI: Body mass index. CSF: Cerebrospinal fluid. EDV: End diastolic velocity. ICP: Intracranial pressure. IH:intracranial hypertension. IIH: Idiopathic intracranial hypertension. LP: Lumbar puncture. MI: Mechanical index. MRI: Magnetic resonance imaging. MRV: Magnetic resonance venography. OA: Ophthalmic artery OND: Optic nerve diameter. ONSD: Optic nerve sheath diameter. OV: Ophthalmic vein. PIs: Pulsatility indices. PSV: Peak systolic velocity. ROC: Receiver operator characteristic. TOS: Trans-orbital sonography.

Ocular ultrasound for monitoring pseudotumor cerebri syndrome.

The aim of this study was to evaluate the feasibility of ocular ultrasound in the follow-up of pseudotumor cerebri syndrome and to correlate ultrasound with clinical parameters. In a cohort study of 22 consecutive adult patients, ocular ultrasound was performed measuring optic nerve sheath diameter, optic nerve diameter, and optic disc elevation compared with symptoms referred by the patients. The patients showed increased optic nerve sheath diameter [median, 6.51 mm (interquartile range 6.13-7.10)], optic nerve diameter [3.02 mm (2.86-3.27)], and optic disc elevation [0.90 mm (0.64-1.36)] at the time of admission and had ophthalmologically confirmed the presence of papilledema in all 22 patients. After 6 months all parameters decreased significantly for optic nerve sheath diameter [6.08 mm (5.59-6.73), P = 0.002], optic nerve diameter [2.87 mm (2.70-3.15), P = 0.007], and optic disc elevation [0.48 mm (0.30-0.70), P < 0.001]. In addition, a discrete negative correlation between optic nerve sheath diameter and headache change after 6 months was observed with ρ = - 0.477 and P = 0.02. No correlation was found between optic disc elevation and headache. In conclusion, longitudinal follow-up with ocular ultrasound combined with clinical information may provide support for treatment of this condition.

A Case of Hypertensive Encephalopathy with Enlarged Optic Nerve Sheath Measured by Transorbital Sonography.

This case report describes our experience in using transorbital sonography to evaluate pathological changes in the central nervous system in hypertensive encephalopathy. A 49-year-old man with nausea, headache, and mild confusion was diagnosed with hypertensive encephalopathy by brain magnetic resonance imaging (MRI), which revealed vasogenic edema in the bilateral thalamus and the brain stem. Lumbar puncture showed no severe intracranial hypertension. Transorbital sonography showed an increase in the optic nerve sheath diameter (ONSD). Repeated examination revealed a return of the ONSD to an almost normal range after a reduction in blood pressure and a resolution of symptoms. An improvement in cerebral vasogenic edema was confirmed by brain MRI. ONSD might be related to the severity of cerebral vasogenic edema. Repeated measurement of ONSD by transorbital sonography may be useful to assess the pathological course and the effect of treatment in hypertensive encephalopathy.

Transorbital Sonography and Visual Outcome for the Diagnosis and Monitoring of Optic Neuritis.

BACKGROUND AND PURPOSE: Transorbital sonography (TOS) is a promising tool to support the clinical diagnosis of optic neuritis (ON) by showing thickening of optic nerve. In this study, we aimed to define its specific role in follow-up of ON patients. METHODS: We measured ultrasonography parameters and visual acuity (VA) at presentation and after 1 year in 45 patients with newly diagnosed ON. Two vascular sonographers used B-mode TOS to evaluate mean optic nerve diameter (OND) and optic nerve sheath diameter (ONSD). RESULTS: Median ONSD values were significantly thicker in patients with ON in the affected eye (6.4 mm, interquartile range [IQR]: 6.0-6.9) at presentation compared with the nonaffected side (5.7 mm; IQR: 5.2-6.1) (P < .001). The median OND was not significantly thicker at presentation in the affected eye (3.0 mm; IQR: 2.9-3.4) compared with the fellow eye (2.9 mm; IQR: 2.8-3.2) (P = .09). Logarithmic VA was significantly compromised at presentation in the affected eye (.16; IQR: .00-.55) compared with fellow eye (.00; IQR: .00-.00) (P < .001). After 1 year, no significant difference (P ≥ .05) was found between ONSD or OND of the affected side compared with the nonaffected side. VA improved in most of the patients but remained significantly impaired in affected eye after 1 year. CONCLUSIONS: TOS is a useful tool to support diagnosis of ON. This technique seems to have less value to evaluate atrophy of the optic nerve after 12 months.

Intra- and interobserver reliability of transorbital sonographic assessment of the optic nerve sheath diameter and optic nerve diameter in healthy adults.

PURPOSE: Transorbital optic nerve sonography (TOS) can measure the optic nerve inclusive the sheath diameter (ONSD) and the optic nerve diameter (OND), which are useful parameters in the diagnosis of several neurological disorders. Data on the reproducibility of TOS are, however, required to use B-mode sonography for clinical purposes. The aim of this study was to assess intra- and interobserver reliability of ultrasound-based evaluations of both OND and ONSD in healthy subjects. METHODS: Using a 4-11-MHz linear array transducer, the OND and ONSD of 20 healthy subjects were independently measured by two expert investigators. RESULTS: Depicting the optic nerve and its sheath was possible in all subjects. The intra- and interobserver reliability was high for both ONSD and OND measurements. Intraobserver agreement, analyzed with Cronbach´s Alpha, was higher for ONSD (range: 0.69-0.72) than for OND measurements (range: 0.55-0.65). No differences in interobserver reliability between ONSD and OND measurements were found (p = 0.83 for right and 0.47 for left eye). CONCLUSIONS: Transorbital B-mode sonography is a feasible method to assess both ONSD and OND with a high intra- and interobserver reliability. Technical difficulties in differentiating the optic nerve from its sheaths may explain the lower intraobserver agreement for OND than that for ONSD measurements.

Enlarged Optic Nerve Sheath in Aneurysmal Subarachnoid Hemorrhage despite Normal Intracranial Pressure.

INTRODUCTION: This study investigates the diagnostic value of optic nerve sheath diameter (ONSD) assessed by transorbital sonography for estimation of intracranial pressure (ICP) in patients with aneurysmal subarachnoid hemorrhage (SAH). METHODS: Simultaneous measurements of the ONSD and ICP in 27 patients suffering from SAH and acute hydrocephalus after placement of an extraventricular drain. RESULTS: Despite normal mean ICP values ONSD was significantly higher in patients with SAH compared with healthy volunteers and no relevant decline of ONSD over time could be identified. In addition, no correlation between ONSD and ICP was observed. CONCLUSIONS: In patients with SAH and acute hydrocephalus after aneurysm rupture, the ONSD remains expanded after normalization of ICP. This is most likely due to an impaired retraction capability of the optic nerve sheath. This finding should be considered when using transorbital sonography in the neuromonitoring of aneurysmal SAH.

B-mode transorbital ultrasononography for the diagnosis of acute optic neuritis. A systematic review.

OBJECTIVE: In patients with acute optic neuritis (AON) transorbital sonography may reveal a thickening of the retrobulbar portion of the optic nerve. Our aim was to systematically review the diagnostic accuracy of ultrasonography of optic nerve diameter (OND) for assessment of AON. METHODS: MEDLINE, EMBASE (1966-October 2014) was searched to identify studies reporting data on patients with AON (with/without multiple sclerosis) assessed by B-mode transorbital ultrasonography. Thereafter, the studies retrieved were screened based on predefined inclusion and exclusion criteria. Data were extracted and the quality of the included studies was evaluated. RESULTS: Seven studies (162 patients) were included. The OND was significantly thicker in the affected eye compared with its unaffected fellow or controls. An increased OND was found in 78-100% of patients. Four studies determined papilledema in 6-43% of patients. CONCLUSIONS: Transorbital sonography is a sensitive, highly accessible and user-friendly technique for the detection of significant optic nerve thickening on the side affected by AON and represents an adjunctive tool for the diagnosis of AON. Compared to visual evoked potentials, TOS may provide different, though complementary, information on the pathophysiology of AON. SIGNIFICANCE: B-mode transorbital ultrasonography provides promising support for the clinical diagnosis of AON.