Visual-evoked potentials in the assessment of optic gliomas

Predicting pediatric optic pathway glioma progression using advanced magnetic resonance image analysis and machine learning

BACKGROUND

Optic pathway gliomas (OPGs) are low-grade tumors of the white matter of the visual system with a highly variable clinical course. The aim of the study was to generate a magnetic resonance imaging (MRI)-based predictive model of OPG tumor progression using advanced image analysis and machine learning techniques.

METHODS

We performed a retrospective case-control study of OPG patients managed between 2009 and 2015 at an academic children's hospital. Progression was defined as radiographic tumor growth or vision decline. To generate the model, optic nerves were manually highlighted and optic radiations (ORs) were segmented using diffusion tractography tools. For each patient, intensity distributions were obtained from within the segmented regions on all imaging sequences, including derivatives of diffusion tensor imaging (DTI). A machine learning algorithm determined the combination of features most predictive of progression.

RESULTS

Nineteen OPG patients with progression were matched to 19 OPG patients without progression. The mean time between most recent follow-up and most recently analyzed MRI was 3.5 ± 1.7 years. Eighty-three MRI studies and 532 extracted features were included. The predictive model achieved an accuracy of 86%, sensitivity of 89%, and specificity of 81%. Fractional anisotropy of the ORs was among the most predictive features (area under the curve 0.83, P < 0.05).

CONCLUSIONS

Our findings show that image analysis and machine learning can be applied to OPGs to generate a MRI-based predictive model with high accuracy. As OPGs grow along the visual pathway, the most predictive features relate to white matter changes as detected by DTI, especially within ORs.

Visual function assessed by visually evoked potentials in optic pathway low-grade gliomas with and without neurofibromatosis type 1

PURPOSE

To investigate the contribution of full-field transient pattern-reversal visually evoked potentials (PRVEP) on cross-sectional evaluations of visual function in patients with and without neurofibromatosis type 1 (NF1) affected by optic pathway low-grade gliomas (OPLGG).

METHODS

Participants were children and adolescents referred for visual function evaluation and receiving treatment for OPLGG, linked (NF1-OPLGG) or not to NF1 (Non-NF1-OPLGG). An age-adjusted control group was included for comparison. Monocular full-field PRVEPs were recorded from each eye in accordance with ISCEV standards. Parameters of peak-to-peak P100 amplitude (µV) and P100 peak time (ms) were measured. Cutoff normative values obtained from controls for 15' and 60' check sizes were ≥ 9.0 µV for N75-P100 amplitude and ≤ 103.0 ms for P100 peak time. The association of age, gender, tumor resection and NF1 with P100 amplitude reduction and P100 peak time delay was explored by Firth logistic regression modeling.

RESULTS

Participants were 30 patients (15 males, 60% Non-NF1) with ages from 3.6 to 19.9 years (mean ± SD = 9.2 ± 3.8 years; median = 8.4 years) and 19 controls (12 males) with ages from 3.7 to 19.9 years (mean ± SD = 10.4 ± 4.9 years; median = 9.5 years). Overall, 68% of tested eyes presented reduced P100 amplitudes for both check sizes (46% in the NF-1 and 83% in the Non-NF1) and delayed P100 for both check sizes (38% in NF1 and 89% in Non-NF1). Absence of NF1 adjusted for age, gender and tumor resection was significantly associated with marginally reduced P100 amplitude for 15' checks [odds ratio (OR): 6.26; 95% confidence interval (CI) = 0.96-40.94; p = 0.055].

CONCLUSIONS

Full-field PRVEP on cross-sectional evaluations contributed to detect visual dysfunction in two-thirds of patients with OPLGG by highlighting subclinical evidence of visual loss. Abnormalities were more frequent and more severe in OPLGG not linked to NF1 than in NF1-OPLGG; however, there was a difference in surgical management between these groups. PRVEP parameters may provide reliable evidence of visual pathway involvement in OPLGG, helping to hasten treatment before optic atrophy is detected.

Monitoring of optic nerve function in Neurofibromatosis 2 children with optic nerve sheath meningiomas using multifocal visual evoked potentials

Monitoring optic nerve sheath meningiomas (ONSM) in Neurofibromatosis type 2 (NF2) patients remains difficult. Other ocular manifestations of NF2 may obscure ophthalmic assessment of optic nerve function in these patients. Serial magnetic resonance imaging (MRI) used to assess the optic nerve is not without limitations, being expensive and often requiring general anaesthetic in children, with associated risks. This study was undertaken to describe the use of multifocal visual evoked potentials (multifocal VEP, mfVEP) in the regular monitoring of NF2 patients with ONSM. This study involved three NF2 patients with ONSM who undertook mfVEP testing at an academic ophthalmic centre. Same day mfVEP and routine ophthalmic testing were undertaken. Topographical function of the optic nerve was assessed, utilising tools such as asymmetry deviation and accumap severity index. Results were assessed alongside MRI and visual acuity (VA). From the three patients, five eyes had ONSMs, of which two caused unilateral blindness. The remaining three affected eyes had initial VAs 6/6, 6/24, and 6/18. Over follow up, ranging from 5 to 12 years, all tumours progressed, and VA declined for all patients. Multifocal VEP detected optic nerve functional loss corresponding with visual decline. This case series suggests mfVEP is effective in the objective topographic monitoring of optic nerve function in NF2 patients with ONSM. Due also to its safety in a paediatric population, the test may be considered in the routine monitoring of these patients, to be used to assist regular ophthalmic review and MRI scans.

Ophthalmic manifestations in neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is a relatively common multisystemic inherited disease and has been extensively studied by multiple disciplines. Although genetic testing and confirmation are available, NF1 remains a clinical diagnosis. Many manifestations of NF1 involve the eye and orbit, and the ophthalmologist, therefore, plays a significant role in the diagnosis and treatment of NF1 patients. Improvements in diagnostic and imaging instruments have provided new insight to study the ophthalmic manifestations of the disease. We provide a comprehensive and up-to-date overview of the ocular and orbital manifestations of NF1.

Optic Pathway Gliomas in Neurofibromatosis Type 1: An Update: Surveillance, Treatment Indications, and Biomarkers of Vision

Optic pathway gliomas (OPGs) occur in 15%-20% of children with neurofibromatosis type 1 (NF1), leading to visual deficits in fewer than half of these individuals. The goal of chemotherapy is to preserve vision, but vision loss in NF1-associated OPG can be unpredictable. Determining which child would benefit from chemotherapy and, equally important, which child is better observed without treatment can be difficult. Unfortunately, despite frequent imaging and ophthalmologic evaluations, some children experience progressive vision loss before treatment. Indications for chemotherapy usually are based on a comprehensive, quantitative assessment of vision, but reliable vision evaluation can be challenging in young children with NF1-OPG. The ability to identify and predict impending vision loss could potentially improve management decisions and visual outcomes. To address this challenge, ophthalmologic, electrophysiologic, and imaging biomarkers of vision in NF1-OPG have been proposed. We review current recommendations for the surveillance of children at risk for NF1-OPG, outline guidelines for initiating therapy, and describe the utility of proposed biomarkers for vision.

Functional outcome measures for NF1-associated optic pathway glioma clinical trials

OBJECTIVE

The goal of the Response Evaluation in Neurofibromatosis and Schwannomatosis Visual Outcomes Committee is to define the best functional outcome measures for future neurofibromatosis type 1 (NF1)-associated optic pathway glioma (OPG) clinical trials.

METHODS

The committee considered the components of vision, other ophthalmologic parameters affected by OPG, potential biomarkers of visual function, and quality of life measures to arrive at consensus-based, evidence-driven recommendations for objective and measurable functional endpoints for OPG trials.

RESULTS

Visual acuity (VA) assessments using consistent quantitative testing methods are recommended as the main functional outcome measure for NF1-OPG clinical trials. Teller acuity cards are recommended for use as the primary VA endpoint, and HOTV as a secondary endpoint once subjects are old enough to complete it. The optic disc should be assessed for pallor, as this appears to be a contributory variable that may affect the interpretation of VA change over time. Given the importance of capturing patient-reported outcomes in clinical trials, evaluating visual quality of life using the Children's Visual Function Questionnaire as a secondary endpoint is also proposed.

CONCLUSIONS

The use of these key functional endpoints will be essential for evaluating the efficacy of future OPG clinical trials.

Detection of tumor progression in optic pathway glioma with and without neurofibromatosis type 1

BACKGROUND

We wanted to determine the sensitivity and specificity of serial changes in visual acuity and visual evoked potentials (VEPs) to detect radiological progression of tumor volume in children with optic pathway gliomas.

METHODS

From a retrospective review of a cohort of 69 patients, 54 patients met inclusion criteria (31 with primary chemotherapy, 4 with primary radiotherapy, and 19 with stable tumor volume and no treatment). Age at presentation ranged from 0.3 to 13 years. Patients were serially followed by MRI, age-corrected visual acuity in log minimum angle of resolution (logMAR), and pattern VEP. Longitudinal data averaged 7.9 years (range 0.5-16 y). Visual assessments were aligned with MRI data within 6-month intervals. Tumor progression was defined by 25% or greater increase in volume.

RESULTS

Visual acuity in the better eye had poor sensitivity and specificity for detecting tumor volume progression (0.5 and 0.5, respectively). Visual acuity in the worse eye showed worse sensitivity and specificity because false positives (visual decline without tumor progression) were more frequent than true positives (visual decline with tumor progression). VEPs showed slightly better sensitivity and specificity (0.69 and 0.58, respectively). In patients with stable tumors, visual acuity fluctuated ±0.55 logMAR (SD = 0.15) between examinations. VEP amplitude fluctuated -0.74 to 0.48 log units (SD = 0.19) between examinations.

CONCLUSIONS

Serial changes in visual function do not reliably detect tumor progression. Conversely, tumor progression does not reliably indicate decreased visual function. Objective visual function and serial MRIs are complementary in management of optic pathway gliomas.

Role of visual evoked potentials in the assessment and management of optic pathway gliomas in children

OBJECTIVE

The aim of this study is to investigate the role of pattern reversal visual evoked potentials (pVEPs) in the screening and monitoring of optic pathway gliomas (OPGs) in children with and without neurofibromatosis type 1.

METHODS

A review of the English literature published between 1980 and 2012 was performed, with comparison of results of retro- and prospective studies.

RESULTS

Pattern reversal VEPs have a high sensitivity (85.7-100 %) for the diagnosis of OPGs, moreover they are safe and cost-effective. Conversely, they have a low specificity (43-83 %) and are not widely available. Besides, pattern reversal VEP results can be unreliable in young children, because of the need for a good cooperation. The studies that were analyzed have drawbacks, including the small sample size, the retrospective design, the differences in gold standard for diagnosis, the different interpretation of small changes in VEP results and the lack of control groups.

CONCLUSION

There is still debate about the gold standard for the screening and follow-up of OPGs. The added value of pVEPs to the ophthalmic examination is controversial. Randomized controlled trials or prospective multicentre studies are necessary to assess with sufficient accuracy the sensitivity and specificity of pattern reversal VEPs in the screening for OPGs and its follow-up.

Fractional anisotropy of the optic radiations is associated with visual acuity loss in optic pathway gliomas of neurofibromatosis type 1

BACKGROUND

No more than half of patients with neurofibromatosis type 1 (NF1)-associated optic pathway gliomas (OPGs) develop vision loss. Prospectively identifying those who will require therapy remains challenging, because no reliable factors have yet been identified that predict future vision loss. To determine whether brain tissue microstructure is associated with visual acuity loss, we examined diffusion tensor imaging (DTI) and ophthalmologic evaluations in children with NF1-associated OPG.

METHODS

We retrospectively reviewed ophthalmology records and concurrent DTI measurements of the optic nerves, tracts, and radiations from 50 children with NF1-associated OPGs. Multivariate linear regression measured the association between fiber trajectory quantity and white matter integrity on visual acuity measured by the logarithm of the minimal angle of resolution (logMAR).

RESULTS

In multivariate analysis, fractional anisotropy (FA) of the optic radiations was associated with visual acuity loss (adjusted coefficient = -6.081 logMAR/FA; P = .006) after adjusting for age, extent of tumor, DTI acquisition type, prior chemotherapy, and fundus examination findings. The association remained after eliminating tumors involving the optic radiations. In an evaluation of 15 subjects with paired ophthalmologic examination and DTI a year apart, initial FA of the optic radiation was associated with a trend toward change in visual acuity a year later (coefficient = -2.652 logMAR/FA; P = .069).

CONCLUSIONS

A decrease in FA of the optic radiations is associated with abnormal visual acuity in NF1-associated OPGs and may be predictive of visual acuity loss during the following year.

Longitudinal assessment of childhood optic gliomas: relationship between flicker visual evoked potentials and magnetic resonance imaging findings

The aim of this study was to evaluate longitudinally functional and neuro-radiologic findings in childhood optic gliomas (OG), by comparing flicker visual evoked potentials (F-VEPs) with brain magnetic resonance imaging (MRI) changes. Fourteen children (age range: 1-13 years) with OGs underwent serial F-VEP, MRI and neuro-ophthalmic examinations over a 38 month (median, range: 6-76) follow-up. F-VEPs were elicited by 8 Hz sine-wave flicker stimuli presented in a mini-Ganzfeld. Contrast-enhanced MRI examinations were performed. Results of both tests were blindly assessed by independent evaluators. F-VEPs were judged to be improved, stable or worsened if changes in the amplitude and/or phase angle of the response exceeded the limits of test-retest variability (+/-90th percentile) established for the same patients. MRI results were judged to show regression, stabilization or progression of OG based on its changes in size (+/-20%) or extension. Two to seven pairs of F-VEP/MRI examinations per patient (median: 4) were collected. Based on a total of 38 pairs of F-VEP/MRI examinations, both tests agreed in showing worsening (progression), stabilization and improvement (regression) in 5, 15 and 10 cases, respectively. In 3 cases, F-VEPs showed a worsening and MRI a stabilization, while in 5 cases F-VEPs showed an improvement and MRI a stabilization. Agreement between F-VEP and MRI changes was 78.9% (95% CI: +/- 37%, K statistics = 0.67, P < 0.001). The results indicate that longitudinal F-VEP changes can predict changes in MRI-assessed OG size and extension, providing a non-invasive functional assay, complementary to neuro-imaging, for OG follow-up.

Optic pathway gliomas: a review

✓Optic pathway gliomas represent approximately 3–5% of childhood intracranial tumors. They usually occur in children during the first decade of life and are seen in 11–30% of patients with neurofibromatosis Type 1 (NF1). Although these tumors are typically low-grade gliomas, the clinical course and natural history are highly variable, making treatment paradigms difficult. Overall, however, they are often indolent tumors that can be observed over time for progression without initial treatment, especially in patients with NF1. Chemotherapy is the first-line treatment for progressive tumors, and radiation therapy is reserved for patients with progressive disease who are older than 5–7 years. Surgery is reserved for large tumors causing mass effect or hydrocephalus and tumors confined to the orbit or unilateral optic nerve.

Optic pathway gliomas in neurofibromatosis-1: controversies and recommendations

Optic pathway glioma (OPG), seen in 15% to 20% of individuals with neurofibromatosis type 1 (NF1), account for significant morbidity in young children with NF1. Overwhelmingly a tumor of children younger than 7 years, OPG may present in individuals with NF1 at any age. Although many OPG may remain indolent and never cause signs or symptoms, others lead to vision loss, proptosis, or precocious puberty. Because the natural history and treatment of NF1-associated OPG is different from that of sporadic OPG in individuals without NF1, a task force composed of basic scientists and clinical researchers was assembled in 1997 to propose a set of guidelines for the diagnosis and management of NF1-associated OPG. This new review highlights advances in our understanding of the pathophysiology and clinical behavior of these tumors made over the last 10 years. Controversies in both the diagnosis and management of these tumors are examined. Finally, specific evidence-based recommendations are proposed for clinicians caring for children with NF1.

Can screening for optic nerve gliomas in patients with neurofibromatosis type I be performed with visual-evoked potential testing?

BACKGROUND

Screening for optic nerve gliomas (ONGs) in children with neurofibromatosis type 1 (NF1) is problematic. Visual acuity (VA) can be unreliable in children. Magnetic resonance imaging is the most sensitive test for ONG, but it is expensive. This study was designed to determine whether visual-evoked potential testing (VEP) is a sensitive and cost-effective screening test for ONG in NF1 in children.

METHODS

We undertook a retrospective review of patients with NF1 at a tertiary care eye center that were born between 1983 and 2003. VA was considered abnormal if 20/40 or worse or more than 2 lines difference between eyes. VEP was abnormal if the P100 was >108 ms (ms) or the interocular difference was greater than 5.0 ms.

RESULTS

Of 297 patients found with NF1, 144 were children and 30 had VEP and MRI. Of those, 14 had ONG and 16 did not. The average P100 of the VEP was 110.5 ms in patients with ONG compared with 103.1 ms (p = 0.004) in those without ONG. VEP was 86% sensitive and 75% specific in detecting ONG. VA was 50% sensitive and 50% specific. Six patients with ONG had normal vision and abnormal VEP. Two subjects had initial abnormal VEP but normal MRI and showed ONG on follow-up imaging. One subject with ONG had a normal VEP initially but subsequent VEP was abnormal.

CONCLUSION

Using serial VEPs, the sensitivity is 93%. Cost of VEP and MRI is $150 and $1750, respectively. VEP is a sensitive and cost-effective screening test for ONG in NF1. VEP may assist in earlier diagnoses of ONG, especially in children with equivocal or difficult ophthalmic examinations.

Comparison of pattern visual-evoked potentials to perimetry in the detection of visual loss in children with optic pathway gliomas

PURPOSE

We sought to compare visual evoked potentials (VEPs) with standard visual field testing in children with visual pathway gliomas.

METHODS

Fifteen of 40 children with visual pathway gliomas verified on magnetic resonance imaging scan who cooperated with Goldmann visual field (GVF) and 3-channel VEPs were studied. GVFs were obtained in 25 eyes with adequate vision. VEP amplitudes, latencies, and signal-to-noise ratios (SNRs) were compared with control subjects. Four of the patients (5 eyes) also had Humphrey visual field testing.

RESULTS

Twenty-two of 25 eyes had a field defect, 15 eyes showed a relative or absolute hemianopia, 7 eyes showed a central or generalized depression, and 3 eyes were normal. In hemianopic eyes, 87% showed a depression (GVF) or reduced sensitivity (Humphrey field) in the opposite hemifield. VEP amplitudes and SNRs, normally largest at the midline electrode, were significantly reduced in all eyes with visual field loss. By comparison, lateral electrodes showed significantly lower amplitudes and SNRs in patients and controls. Interhemispheric VEP asymmetry (>2:1 ratio) was seen in 67% of patients with hemianopia and 53% of controls.

CONCLUSIONS

Reduction of amplitude and SNR at the midline VEP electrode was a sensitive indicator of visual field loss. Interhemispheric VEP asymmetry was not reliable in detection of a hemianopic field defect. VEPs can be a reliable and objective alternative for the detection of visual loss due to optic pathway glioma in children who are intolerant to visual field testing. We recommend the test protocol include pattern-onset and check reversal stimuli of at least one high and one low spatial frequency.

Utility of multimodal evoked potentials study in neurofibromatosis type 1 of childhood

A group of 21 children affected by neurofibromatosis type 1 has been investigated with the aim of studying multimodal (visual, brainstem auditory, and somatosensory) evoked potentials and their correlations with neurologic, electroencephalographic, and cranial magnetic resonance imaging. In the present series, cranial magnetic resonance imaging and evoked potentials were the most frequently abnormal instrumental tests. In approximately two thirds of the cases at least one of the evoked potentials (particularly visual and auditory evoked potentials) was compromised, always without clinical signs of related sensory (visual, auditory, and somatosensory) pathway pathology and sometimes in the absence of magnetic resonance imaging signs of central nervous system involvement. This study indicates that in patients with neurofibromatosis type 1, multimodal evoked potentials are useful and should be part of the diagnostic protocol of encephalic lesions together with magnetic resonance imaging. The use of both methods could aid in early detection of central nervous system dysfunction in both the initial evaluation of disease and its follow-up.

[Optic pathway gliomas in neurofibromatosis type I. Longitudinal study of 30 cases in two multidisciplinary practices]

The aim of this study was to analyse the outcome of optic pathway gliomas in 30 children with neurofibromatosis type 1, the indications of treatment, and the follow-up and screening protocol.

PATIENTS AND METHODS

All patients with a minimal two years follow-up (median six years, range two to 19 years), in two multidisciplinary consultations of Saint-Vincent-de-Paul (Paris) and Purpan (Toulouse) hospitals, were included in the study. In our series, we practiced systematic screening MRI in children under six years' of age or with neuropsychological deficiency that may imply an unreliable ophthalmological examination.

RESULTS

Thirty-seven percent (11 patients) had progressive ophthalmological signs and were treated, and 63% (19 patients) were not progressive. Our study confirmed that most of optic pathway gliomas were stable during evolution, but rare cases may have bad prognosis.

CONCLUSION

Our study supported the importance of close ophthalmological follow-up during childhood for which screening methods are discussed. There is a consensus to limit treatment for patients with progressive ophthalmological symptoms.