Secondary trigeminal autonomic cephalgia with cavernous sinus involvement: a diagnostic challenge.

Chronic, side-locked headache refractory to standard treatment warrants investigation for underlying inflammatory, infectious or infiltrative aetiologies. This case highlights a rare presentation of a patient with a chronic history of hemicranial headache who had presented with recent worsening and unresponsiveness to conventional treatment. IgG4-related disease with hypertrophic pachymeningitis (HPM), primarily affects the cavernous sinus and orbital apex, can lead to multiple cranial nerve palsies and mimics secondary trigeminal autonomic cephalalgia. The diagnostic challenge was compounded by concomitant extrapulmonary tuberculosis, a frequent mimic in endemic regions, obscuring the clinical picture. This case underscores the importance of integrating advanced neuroimaging and serological markers for accurate diagnosis. Given the absence of definitive treatment guidelines and high chances of relapses for IgG4-related HPM, it highlights the need for personalised therapeutic strategies and long-term follow-up. This report adds to the limited literature, emphasising the need for heightened clinical suspicion in atypical headache syndromes.