Tuberculous meningitis (TBM) is a challenging entity to diagnose and treat, carrying a high mortality. TBM has a strong predilection for the basal parts of the brain. Optochiasmatic arachnoiditis (OCA) is a rare complication of TBM which involves the arachnoid mater of the optic nerve and the chiasmatic cisterns. This entity is infrequently encountered as a paradoxical reaction when the patient is on Anti-TB medication. It is hypothesized that with treatment, a massive release of mycobacterial proteins occur, which provokes an intense delayed-type hypersensitivity reaction, leading to the development of the characteristic lesions of OCA.

A 24-year-old patient presented with a 2-week history of fever, neck stiffness and vomiting along with a prodrome of frequent headaches and constitutional symptoms. CSF studies showed a neutrophilic picture with high proteins and a severe sugar drop (21% of venous blood sugar). A clinical diagnosis of TB meningitis was made, and treatment with standard Anti TB chemotherapy and IV dexamethasone was commenced.

Two months later, the patient complained a persistent headache with deteriorating visual acuity in his right eye and a temporal field defect in his left eye. MR imaging of the brain showed a large cluster of ring enhancing lesions in the supra-sellar region compressing the optic chiasm. This was compatible with the diagnosis of OCA. Due to the suspicion of a paradoxical reaction, his immunosuppression was intensified with the addition of Thalidomide. Despite the above measures and the continuation Anti TB treatment for over 14 months, the clinical manifestations and imaging abnormalities of OCA persist. Multidisciplinary team discussions are currently underway to consider a second line ATT regimen and surgical decompression of the above lesions.

This case aims to highlight OCA as a complication of TBM and the therapeutic challenges associated with it.