What is the treatment for pseudointernuclear ophthalmoplegia?

Treatment of Pseudointernuclear Ophthalmoplegia

The treatment for pseudointernuclear ophthalmoplegia should target the underlying cause, which is most commonly myasthenia gravis, with acetylcholinesterase inhibitors, immunosuppressive therapy, and intravenous immunoglobulin being the primary treatment options. 1, 2

Understanding Pseudointernuclear Ophthalmoplegia

Pseudointernuclear ophthalmoplegia (pseudo-INO) is a clinical condition that mimics true internuclear ophthalmoplegia but has a different underlying pathophysiology:

• True internuclear ophthalmoplegia results from lesions in the medial longitudinal fasciculus (MLF) in the brainstem, commonly caused by multiple sclerosis, stroke, or trauma 3
• Pseudo-INO presents with similar clinical features (adduction deficit on lateral gaze with dissociated nystagmus of the abducting eye) but is caused by neuromuscular junction disorders rather than brainstem lesions 1
• The most common cause of pseudo-INO is myasthenia gravis, an antibody-mediated autoimmune disease affecting neuromuscular junctions 2

Diagnostic Approach

Before initiating treatment, proper diagnosis is essential:

• MRI of the brain and brainstem to rule out true INO caused by MLF lesions 1, 2
• Blood tests for anti-acetylcholine receptor antibodies (anti-AChR) and other myasthenia-related antibodies 1
• Tensilon (edrophonium) test to confirm myasthenia gravis 4
• Repetitive nerve stimulation test showing decrementing response 2

Treatment Protocol

First-Line Treatment

• Acetylcholinesterase inhibitors:
  • Pyridostigmine (Mestinon) is the mainstay of symptomatic treatment 2
  • Typically started at 30-60mg three to four times daily, with dose adjustments based on clinical response 1
  • Neostigmine may be used as an alternative or for diagnostic purposes 2

Second-Line Treatment

• Immunomodulatory therapy:
  • Corticosteroids (prednisone/prednisolone) starting at moderate doses (20-40mg daily) with gradual dose adjustments 2
  • Steroid-sparing agents such as methotrexate or azathioprine for long-term management 2

Acute Exacerbation Management

• Intravenous immunoglobulin (IVIG) at 2g/kg divided over 2-5 days for rapid improvement in severe cases 2
• Plasma exchange as an alternative to IVIG in patients who don't respond to or cannot tolerate IVIG 1

Thymectomy Consideration

• Evaluation for thymic abnormalities with chest CT or MRI 1
• Thymectomy should be considered, especially in patients with thymoma or in younger patients with generalized myasthenia gravis 2

Monitoring and Follow-up

• Regular assessment of ocular motility and other myasthenic symptoms 1
• Monitoring for side effects of medications, particularly with long-term immunosuppressive therapy 2
• Adjustment of treatment based on clinical response and disease progression 2

Special Considerations

• Pseudo-INO may be accompanied by other neurological manifestations, including pyramidal tract damage, which typically resolves with appropriate treatment of the underlying myasthenia gravis 2
• Some patients may present with additional findings such as downshoot in the adducting eye, which should not be confused with other neurological disorders 4
• Unlike true INO caused by traumatic brain injury, which may be irreversible, pseudo-INO typically responds well to appropriate treatment of myasthenia gravis 5, 2

Pitfalls to Avoid

• Misdiagnosis as true INO leading to inappropriate treatment or delayed diagnosis of myasthenia gravis 1
• Failure to recognize pseudo-INO as a presentation of myasthenia gravis, especially when it occurs without classic symptoms like ptosis 1
• Inadequate treatment of underlying myasthenia gravis, which can lead to progression of disease and additional neurological manifestations 2