Risk of developing multiple sclerosis (MS) after single episode of optic neuritis

• a clinical diagnosis of multiple sclerosis is only made when neurological events are separated in space and time
  • therefore one episode of optic neuritis does not mean that a patient fits the clinical criteria for a diagnosis of multiple sclerosis
  • the risk of developing multiple sclerosis depends on a number of factors such as age and gender (1)
    • for example, a young man with a first episode of optic neuritis has about a 50% risk of having a further episode of optic neuritis or other demyelinating phenomena in the next 15 years (and therefore satisfying the clinical diagnosis of multiple sclerosis) (1)
    • an Italian study examined the cumulative risk of developing multiple sclerosis and states (2):
      • probability of multiple sclerosis was 13% after 2 years, 30% after 4 years, 38% after 6 years, and 49% after 8 and 10 years
      • multiple sclerosis occurred in 42 (59%) of 71 patients with brain lesions detected with magnetic resonance imaging (MRI)
      • no patient with normal MRI exam developed the disease
        • patients with 3 or more MRI-detected lesions presented a shorter first interattack interval and a higher relapse rate compared to subjects with only 1 or 2 lesions
      • predictive value of CSF examination and of evoked potentials was poor
  • many neurologists and ophthalmologists will order an MRI scan if a patient has a first episode of optic neuritis - this is for prognostic reasons and will allow a clinician to gain information about the number of active and inactive lesions as well as the clinical picture

Reference:

1. Pulse (2004); 64 (24): 80.
2. Ghezzi A et al. The prognosis of idiopathic optic neuritis. Neurol Sci. 2000;21(4 Suppl 2):S865-9.