RT Journal Article SR Electronic T1 Internuclear ophthalmoplegia JF Practical Neurology JO Pract Neurol FD BMJ Publishing Group Ltd SP 149 OP 153 DO 10.1136/practneurol-2016-001428 VO 17 IS 2 A1 Virgo, Jonathan D A1 Plant, Gordon T YR 2017 UL http://pn.bmj.com/content/17/2/149.abstract AB A brainstem lesion of any type that involves the medial longitudinal fasciculus (MLF) can cause internuclear ophthalmoplegia (INO). This primarily affects conjugate horizontal gaze and classically manifests as impaired adduction ipsilateral to the lesion and abduction nystagmus contralateral to the lesion. Here, we describe the anatomy of the MLF and review the clinical features of INO. We also describe conjugate horizontal gaze palsy and some of the ‘INO-plus’ syndromes.