From the Guidelines
Internuclear ophthalmoplegia (INO) and optic atrophy should be diagnosed with a high suspicion of multiple sclerosis (MS), particularly in young adults, and evaluated with MRI of the brain and orbits with contrast, lumbar puncture for cerebrospinal fluid analysis, and visual evoked potentials, as recommended by the most recent guidelines 1. The diagnosis of INO and optic atrophy involves a comprehensive evaluation of the patient's symptoms, medical history, and diagnostic test results. INO is characterized by impaired adduction of the affected eye during horizontal gaze, with nystagmus in the abducting eye, resulting from damage to the medial longitudinal fasciculus (MLF) in the brainstem. Optic atrophy refers to degeneration of the optic nerve, causing vision loss and pale appearance of the optic disc on examination.
Key Diagnostic Considerations
- A thorough ophthalmic examination, including sensorimotor evaluation and completion of the three-step test, to assess for other neuro-ophthalmic signs and symptoms, such as Horner's syndrome, cranial nerve palsy, and nystagmus 1.
- MRI of the brain and orbits with contrast to evaluate for lesions in the MLF, optic nerve, and other brainstem structures, as well as to rule out other potential causes, such as stroke, trauma, infections, or tumors 1.
- Lumbar puncture for cerebrospinal fluid analysis to assess for oligoclonal bands and other markers of MS, as well as to rule out other inflammatory or infectious conditions 1.
- Visual evoked potentials to assess for optic nerve dysfunction and to monitor treatment response.
Treatment and Management
- High-dose corticosteroids (methylprednisolone 1000mg IV daily for 3-5 days) for acute MS relapses, followed by oral prednisone taper, as recommended by the most recent guidelines 1.
- Disease-modifying therapies for MS should be initiated if confirmed, to reduce the frequency and severity of relapses and slow disease progression.
- Symptomatic management may include prism glasses for diplopia and visual aids for vision loss, as well as referral to neurology and neuro-ophthalmology for comprehensive management.
Important Considerations
- Patients with INO and optic atrophy should be referred to both neurology and neuro-ophthalmology for comprehensive management, as these conditions often indicate serious underlying neurological disease requiring prompt diagnosis and treatment.
- A multidisciplinary approach, including ophthalmology, neurology, and radiology, is essential for accurate diagnosis and effective management of INO and optic atrophy.
From the Research
Diagnosis of Internuclear Ophthalmoplegia (INO)
- The diagnosis of INO is based on clinical characteristics, including total or partial failure to adduct one eye in lateral gaze and a monocular nystagmus of the abducting eye 2.
- Magnetic resonance imaging is the method of choice for diagnostic imaging of MLF lesion in patients with INO 2, 3.
- The versional dysconjugacy index (VDI) can be used to quantify prosaccades in patients with MS and diagnose INO 4.
- A saccade test can also be used to diagnose INO, especially in cases where restriction of adduction and dissociated nystagmus are lacking 5.
Causes of INO
- The most common causes of INO are multiple sclerosis and brainstem infarction 2, 6.
- Other causes of INO include head trauma, brainstem and fourth ventricular tumors, Arnold-Chiari malformation, infection, hydrocephalus, and lupus erythematosus 2, 6.
- Unusual causes of INO, such as trauma, tentorial herniation, and iatrogenic injury, can also occur 6.