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Quantitative MRI criteria for optic pathway enlargement in neurofibromatosis type 1
Robert A Avery1, Awais Mansoor2, Rabia Idrees2
1From the Center for Neuroscience and Behavior (R.A.A., R.J.P.), The Gilbert Family Neurofibromatosis Institute (R.A.A., R.J.P.), the Sheikh Zayed Institute for Pediatric Surgical Innovation (A.M., E.B., M.A.A., M.G.L.), and The Brain Tumor Institute (R.J.P.), Children's National Health System; The George Washington University (R.I.); and The George Washington University School of Medicine and Health Sciences (M.G.L.), Washington, DC. averyr@email.chop.edu.
Insights
This study establishes quantitative MRI thresholds for enlarged optic pathways in children with neurofibromatosis type 1 (NF1). These reference values help identify optic pathway gliomas (OPGs) more accurately in NF1 patients.
Area of Science:
- Neuroimaging
- Pediatric Neurology
- Genetics
Background:
- Neurofibromatosis type 1 (NF1) is a genetic disorder associated with an increased risk of optic pathway gliomas (OPGs).
- Accurate and objective diagnostic criteria for OPGs in NF1 patients are crucial for timely intervention.
Purpose of the Study:
- To establish quantitative size thresholds for the optic nerve, chiasm, and tract in children with NF1.
- To differentiate between normal and enlarged anterior visual pathway (AVP) structures in NF1 patients.
Main Methods:
- High-resolution T1-weighted MRI scans were analyzed in 186 children (0.5-18.6 years) with and without NF1.
- Quantitative measurements (diameter, volume) of AVP structures were calculated.
- The 95th percentile of measurements from a control group defined thresholds for abnormal enlargement.
Main Results:
- Children with NF1 showed significantly larger optic nerve diameter and volume, optic chiasm volume, and total brain volume compared to controls.
- Total brain volume was a predictor of optic nerve and chiasm volume in controls.
- Applying the 95th percentile thresholds to NF1 participants yielded high specificity (>80%) for detecting enlarged AVP measures.
Conclusions:
- Quantitative reference values for AVP enlargement in NF1 patients have been determined.
- These objective criteria can aid in the development of improved diagnostic standards for OPGs in NF1.
- Enhanced diagnostic accuracy can lead to better management of NF1-associated OPGs.
Objective:
To determine quantitative size thresholds for enlargement of the optic nerve, chiasm, and tract in children with neurofibromatosis type 1 (NF1).
Methods:
Children 0.5-18.6 years of age who underwent high-resolution T1-weighted MRI were eligible for inclusion. This consisted of children with NF1 with or without optic pathway gliomas (OPGs) and a control group who did not have other acquired, systemic, or genetic conditions that could alter their anterior visual pathway (AVP). Maximum and average diameter and volume of AVP structures were calculated from reconstructed MRI images. Values above the 95th percentile from the controls were considered the threshold for defining an abnormally large AVP measure.
Results:
A total of 186 children (controls = 82; NF1noOPG = 54; NF1+OPG = 50) met inclusion criteria. NF1noOPG and NF1+OPG participants demonstrated greater maximum optic nerve diameter and volume, optic chiasm volume, and total brain volume compared to controls (p < 0.05, all comparisons). Total brain volume, rather than age, predicted optic nerve and chiasm volume in controls (p < 0.05). Applying the 95th percentile threshold to all NF1 participants, the maximum optic nerve diameter (3.9 mm) and AVP volumes resulted in few false-positive errors (specificity >80%, all comparisons).
Conclusions:
Quantitative reference values for AVP enlargement will enhance the development of objective diagnostic criteria for OPGs secondary to NF1.
