Optic neuritis and multiple sclerosis

Optic neuritis is inflammation of the optic nerve and it is a frequent manifestation of multiple sclerosis, an demyelinating-inflammatory disease of the central nervous system. 

Multiple sclerosis is a chronic and discapacitating neurological disease that mainly affects young adults. It is characterised by inflammation and demyelination of the nervous fibres as well as axonal degeneration. 

Although the exact cause of the disease is unknown, we do know that it is an autoimmune disease. This means that the cells of the immune system form an attack on the organism's own structures, on myelin in this case. 

Optic neuritis may be the first manifestation or flare-up of the disease in 20-30% of patients and up to 50% of patients with multiple sclerosis will suffer from it during the course of the disease.

There may be multiple signs and symptoms of multiple sclerosis and they will mainly depend on the areas of the central nervous systems where demyelination occurs. In the case of optic neuritis, inflammation and demyelination of the optic nerve will occur.  

The typical signs of optic neuritis are predominantly central "blurred vision" and alteration of chromatic vision (particularly intense in the colour red) which sets in sub-acutely in 7-10 days. Up to 90% of patients will present with associated retroocular pain, which triggers or worsens eye movements. 

The diagnosis of optic neuritis is fundamentally clinical. An ophthalmological exploration will show an afferent pupil defect in the affected eye, reduced visual acuity and a central scotoma in the campimetry test. 

Inflammation in the head of the optic nerve or papillitis may be observed, but frequently (in up to 2/3 of patients) we not find any alteration, due to the fact that the inflammation occurs retrobulbarically (behind the head of the optic nerve). 

An episode of optic neurtitis, just like any other flare-up of multiple sclerosis, may be treated with endovenous corticosteroids that will shorten the duration of the symptoms and acclerate visual recovery.

Corticosteroid treatment will not impact the prognosis or long-term functional recovery nor will it affect the risk of developing multiple sclerosis in the future. 

In relation to this risk, different clinical trials have demonstrated that the initiation of immunomodulatory therapy after an initial suggestive episode of multiple sclerosis delays the onset of a second flare-up of the disease. 

These diseases cannot be prevented, but a consultation with ophthalmologists and neurologists specialising in these pathologies may help to understand the risk specific to each patient and therefore evaluate which therapy is most suitable at each stage. The prognosis for optic neuritis is usually good, although in some cases small visual issues may remain. 

A brain MRI has to be performed on each patient with suspected optic neuritis and the detection of oligoclonal bands in the cerebrospinal fluid can also help to determine the risk of developing multiple sclerosis.