Giant intracranial meningioma without hemianopic visual field loss

The visual pathway is long and complex, making it vulnerable to intracranial masses after it leaves the orbit. The nature of any loss of vision is a function of anatomy and can contribute to tumour detection and to some extent, tumour localisation.' The classical visual field defect of an intracranial lesion is some form of hemianopia.'** Bitemporal hemianopia results from lesions in or near the sella or chiasm, most commonly pituitary tumours. Post-chiasmal lesions cause homonymous hemianopia, a more common outcome as most of the visual pathway lies posterior to the chiasm. However, a small intracranial portion of the optic nerve lies between the optic foramen and the chiasm, where a lesion might not result in either form of hemianopia. This case report details a patient who presented with visual symptoms caused by a previously undetected giant meningioma of the frontal lobe. These symptoms were vague and associated with minimal visual acuity disruption. There were no other neurological symptoms. Initial perimetric results were inconclusive and did not suggest the size of the tumour or the threat to life it represented. It demonstrates the caution needed when vague symptoms caused by major lesions can easily be attributed to less significant causes.