Session 4: State-of-the-Art: Optic nerve sheath meningioma

Dr Braithwaite’s presentation provides a brief overview of the pathology, morphology, epidemiology, natural history and visual prognosis of optic nerve sheath meningiomas. Case-based reviews from Moorfields Eye Hospital and The National Hospital for Neurology and Neurosurgery illustrate the different ways in which optic nerve sheath meningiomas may present, and these are used to support a focused discussion of the differential diagnosis, and how this may be advanced. The emerging role for optical coherence tomography as a biomarker for monitoring and assessing visual prognosis in compressive optic neuropathies is highlighted, with particular focus on the value of segmenting the macular volume scan to examine the retinal ganglion cell layer volume for evidence of irreversible axonal loss.

Optic nerve-sheath meningiomas (ONSMs) constitute a diagnostic and management challenge. Neuroradiology is integral in the diagnosis and management of these tumours. Neuroradiology is most effective when clinical assessment raises the possibility of ONSMs such that specialised imaging modalities, such as MRI and Gallium Dotatate scans, and imaging specific protocols can then be used to effectively detect and monitor these tumours.There are specific imaging features which strongly suggest the diagnosis of ONSMs however, it is the role of an experienced neuroradiologist to exclude other pathologies such as schwannomas and cavernous haemangiomas which can mimic these appearances. This precludes the undesirable consequences of a biopsy of ONSMs.Advanced neuroimaging holds some promise as a surrogate marker for treatment response given that there is a poor correlation between visual acuity recover and size/morphology of ONSMs.Future initiatives should be directed towards curating a national and/or international database of cases thereby facilitating larger scale series, informing us of the natural history, facilitating effective biomarkers of prognosis and treatment response and for artificial intelligence intiatives for detection of these lesions.

The management of perioptic meningioma has moved from first line surgery to radiotherapy over the past 30 years. Radiotherapy can be expected to stabilise or improve vision in most cases when disease is confined to the orbit. Modern stereotactic fractionated delivery systems reduce the risk of radiation injury to the eye and adjacent structures. The threshold for treatment intervention is determined by the demonstration of progressive loss of function without delaying until irreversible advanced loss has occurred.  There remains a role for surgery to decompress the optic canal in selected cases, and the management of patients with significant middle cranial fossa involvement remains primarily surgical.