Internuclear Ophthalmoplegia

Internuclear Ophthalmoplegia (INO) is a condition that affects the way the eyes move together. It involves a problem in the brainstem, specifically in the area that controls eye muscle coordination. This condition causes difficulty moving one eye inward toward the nose when trying to look sideways, leading to double vision or blurred vision. The main body system involved is the nervous system, particularly the nerves that control eye movements. People with INO often experience problems with horizontal eye movement and may have a compensatory head turn to help see clearly. The condition can result from various causes, including multiple sclerosis or stroke, which damage the nerve pathways responsible for eye coordination. Overall, INO impacts vision and eye alignment, affecting daily activities that require clear, coordinated sight.

Internuclear Ophthalmoplegia (INO) is a disorder caused by a lesion in the medial longitudinal fasciculus (MLF), a critical brainstem tract that coordinates conjugate horizontal eye movements by connecting the abducens nucleus of one side to the oculomotor nucleus of the opposite side. The hallmark pathology is disruption of this pathway, leading to impaired adduction of the ipsilateral eye during lateral gaze, with preserved abduction but often accompanied by nystagmus of the abducting contralateral eye. The most common causes include multiple sclerosis in younger patients and ischemic stroke in older adults. Clinically, INO is significant because it indicates a lesion in the brainstem and helps localize neurological disease. It may present unilaterally or bilaterally and is often associated with other brainstem signs depending on the extent of the lesion. Recognition of INO is important for diagnosing underlying demyelinating or vascular conditions affecting the central nervous system.