Classification of optic neuritis

Optic neuritis literally means the inflammation of optic nerve.

Optic neuritis can be classified by location and causes.

According to location,

1. anterior part of optic nerve induces optic disc swelling 
2. posterior part inflammation does not result in disc swelling.

Causes of inflammation were divided into two categories.

1. Pure inflammation such as multiple sclerosis (MS), neuromyelitis optica (NMO) or autoimmune disorders. 
2. Infection related inflammation.

In my opinion, although I try to detect any abnormal findings in blood test. almost optic neuritis is idiopathic.

When it comes to proven causes of the optic neuritis

1. Anti-Aquaporin 4 (AQP-4) antibody positive finding
2. Multiple sclerosis related.
3. Syphilis
4. Anti nuclear antibody (ANA). 

In Korea, optic neuritis related with MS is very rare, however, AQP-4 positive ON is not uncommon. Thus, I always do AQP-4 Ab. test in optic neuritis.

Sometimes, there have been detected ANA in the optic neuritis. Actually I don't know the relationship between optic neuritis and ANA. It may not be cause but coincidence. 

In conclusion,
I do AQP-4 test and Syphilis blood test in the optic neuritis. MRI can be performed depend on case, however, we should consider cost-effectiveness of MRI.