Optic Chiasmal Fungal Granuloma - Rare Cause of Blindness

Abstract

Intracranial fungal infections are rare. Their presentation is mostly subtle, clinically atypical in presentation, and they are usually mistaken for tuberculosis or brain tumour. Aspergillosis is the most common cause of intracranial fungal infections. Fungal infection enters the brain directly from the paranasal sinuses, ear, skull bone, or haematogenous spread from the lungs and gastrointestinal tract, or direct inoculation during surgery or trauma. The pathology depends on the route of spread, host immunity, and type of fungus. Intracranially, fungal infection invades brain matter or blood vessels. [1] The rarity of brain fungal infection, with nonspecific clinical picture, and progression to a fatal outcome provides considerable challenges for both diagnosis and management. Invasive sino-orbital fungal infections are rarely reported in immunocompetent patients in literature.  We could not find anything related to primary fungal granuloma of the optic tract reported in literature. We report a case of primary fungal granuloma of optic chiasm in an immunocompetent patient.[2] 13-year-old female patient presented to us with sudden onset of loss of vision in both eyes. There were no other complaints. On neurological examination, there was no vision in both eyes (no perception of light). On fundoscopy, there was bilateral optic atrophy. Rest of the neurological examination was normal. Patient was investigated for magnetic resonance imaging (MRI) of brain with contrast study. MRI of brain was suggestive of a 2.2 x 1.8 x 1.6 cm mass in suprasellar region with its epicentre in the optic chiasma and extending to both optic nerves and optic tract. The lesion was separate from the underlying pituitary gland. The lesion was iso-intense on T1 weighted images and hyper-intense on T2 weighted images. It showed homogenous post-contrast enhancement. Our primary differential diagnosis was optic nerve glioma. Patient underwent immediate surgery, right peritoneal craniotomy, for excision of lesion. Intra-operatively, a firm yellowish white colored lesion arising from the optic chiasm was seen. Safe subtotal excision was done. Post-operative, there was no improvement in vision.