We read with interest the article by Dr Keane on internuclear ophthalmoplegia (INO). There is an area of doubt concerning the exact focus of neurologic damage in the enrolled INO cases about which we would like to learn more from the author.
Medial rectus limitation or slowing, dissociated nystagmus and preserved convergence are deemed as the essential components of INO due to medial longitudinal fasciculus damage.1 However, the adduction palsies seen in INO are not unique and can be mimicked by adduction defect due to infranuclear ophthalmoplegia.2 The only clinical checkpoint that can distinguish these 2 is the recognition of an impaired vertical vestibulo-ocular reflex.2 Perhaps Dr Keane can enlighten us further with respect to this query.
Liu DTL, Li C, Lee VYW. Internuclear Ophthalmoplegia. Arch Neurol. 2006;63(4):626. doi:10.1001/archneur.63.4.626-a