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Disorders of eyeball position and movement

As discussed previously, there is an intimate functional association between the innervation to the extraocular muscles and the vestibular system. The extraocular muscles are innervated by cranial nerve III (oculomotor), cranial nerve IV (trochlear) and cranial nerve VI (abducent) (). Any strabismus due to a lesion in one or more of these cranial nerves must be differentiated from lesions affecting the extraocular muscles (including traumatic rupture and extraocular myositis). • Lesions simultaneously affecting CNs III, IV and VI result in external ophthalmoplegia, and internal ophthalmoplegia if the pupillary constrictor (CN III) is affected. • Lesions with only cranial nerve III involvement may present with a ventrolateral strabismus; more rarely lesions may only affect single muscle groups, resulting in a strabismus opposite to the normal function of the denervated muscle. • Lesions affecting the trochlear nerve in isolation are extremely rare but, where they do occur, will result in loss of function of the ipsilateral dorsal oblique muscle (brainstem lesions may result in loss of function, ipsilateral or contralateral). The dorsal oblique muscle functions to rotate the dorsal portion of the globe nasally Read more […]