Tolosa–Hunt Syndrome and IgG4 Diseases in Neuro-Ophthalmology

Tolosa–Hunt syndrome (THS) remains a challenging diagnosis for many neurologists. Often believed to be a rare presentation, the classical presentation is known to involve cranial nerves and tissues surrounding the cavernous sinus. Traditionally, a diagnosis of THS is considered when all secondary conditions have been ruled out. Yet, newer findings have elaborated a complex pathogenetic process with some overlap from the IgG4 spectrum of disorders, with which it shares many phenotypic similarities. In this narrative review, we present an updated picture of the condition focusing on the latest developments in the pathogenesis, diagnosis, and clinical management of these two conditions and use illustrative examples to highlight the salient features of this rare presentation.