Optic neuritis and
myelitis are manifestations in both
multiple sclerosis (MS) and
neuromyelitis optica (NMO). But unlike MS, NMO is characterized by severe
optic neuritis, longitudinally extensive and
transverse myelitis, and the presence of aquaporin-4 antibody. Since patients with
optic neuritis and
myelitis have often been diagnosed with "
optic-spinal MS (OSMS)" in Asia, it was obscure whether "OSMS" is synonymous with NMO or includes both NMO and MS.
Interferon β (IFNβ)-1a and -1b are used as the first-line disease-modifying
therapy for MS. However, some neurologists have been reluctant to use IFNβ to treat patients with optic-spinal symptoms, because IFNβ
therapy is not efficacious in NMO. To evaluate the
therapeutic effect of IFNβ in patients with "genuine" OSMS, we retrospectively evaluated Japanese MS patients who fulfilled the following six criteria: 1) Relapsing-remitting MS with optic-spinal presentation alone (no brain symptoms), 2) With or without asymptomatic brain MRI lesions, 3)
Oligoclonal IgG band-positive, 4)
aquaporin-4 antibody seronegativity, 5) No
myelitis extending longitudinally over ≥ 3 vertebral segments, and 6) Duration of IFNβ-1b
therapy ≥ 2 years. Among 157 patients with MS, six (four women and two men, age 43.8 ± 8.5 years old) met all the criteria. Their Expanded Disability Status Scale scores were lowered (4.1 ± 2.4 → 3.1 ± 2.8) (P = 0.033) and annualized relapse rate was decreased (0.59 ± 0.34 → 0.13 ± 0.15) (P = 0.027) after IFNβ-1b
therapy. These results suggest that IFNβ is therapeutically effective in inhibiting functional worsening and reducing relapse rate in "genuine" OSMS.