The authors present an interesting review article detailing current treatment options for optic neuritis (ON). They discuss the care of typical ON (demyelinating), atypical ON (not associated with MS and requiring continued immunosuppression), and special scenarios (e.g., pediatric ON, acute demyelinating encephalomyelitis, and ON during pregnancy).
They define typical ON as associated with multiple sclerosis, and subcategorize it into steroid-dependent and steroid-refractory cases. The authors cite the landmark Optic Neuritis Treatment Trial, which demonstrated that three days of high-dose IV corticosteroids hastened visual recovery after ON but did not change visual outcome at six months. High-dose IV steroids also were shown to delay the onset of clinically-definite MS and improve contrast sensitivity, visual fields and color vision. Other studies compared high-dose IV dexamethasone to high-dose IV methylprednisolone, revealing similar outcomes. The authors also propose intramuscular or subcutaneous adrenocorticotropic hormone as an option for patients unable to tolerate steroids.
Steroid-refractory demyelinating ON can be treated with a second round of high-dose IV steroids, therapeutic plasma exchange (TPE), or immunoadsorption or IV immunoglobulin. TPE consists of removing the patient's plasma from whole blood and infusing an albumin solution. The mechanism of TPE is unclear, but it is hypothesized that the removal of pathogenic complement and circulating immunoglobulins is therapeutic.
Causes of atypical ON include systemic autoimmune disease, vasculitis, and sarcoidosis. Treatment of atypical ON includes high-dose IV steroids followed by a slow steroid taper, immunosuppressive agents (e.g. azathioprine, cyclosporine), and antimetabolites (e.g. cyclophosphamide, chlorambucil, methotrexate).
Neuromyelitis optica often affects females in their mid- to late 30s, with more than 80 percent exhibiting a relapsing-remitting course with more severe recurrent attacks than those with MS. Treatment of neuromyelitis optica consists of high-dose IV methylprednisolone, TPE and IV immunoglobulin. Azathioprine, at a target dose of 2.5 to 3.0 mg/kg/day, has shown promising results in preventing relapses in neuromyelitis optica. Other therapies for relapse prevention in neuromyelitis optica include rituximab, mycophenolate mofetil therapy, cyclophosphamide and natalizumab.
The authors say treatment of pediatric ON is often of a longer duration than treatment of adult ON. Compared with adult cases, pediatric ON is more likely to show papillitis, be bilateral, and present with severe vision loss. Two-thirds of pediatric cases exhibit a prodromal viral illness. Treatment options include high-dose steroids, IV immunoglobulin and TPE.
The last special scenario the authors describe is ON in pregnancy. While the third trimester is protective against MS attacks, there is an increased risk of relapse postpartum. IV methylprednisolone is a pregnancy category C drug. Other possible treatments during pregnancy include IV immunoglobulin and possibly immunoadsorption.