Optic neuritis

Question 1

What is optic neuritis?

Answer 1

Inflammation of the optic nerve

Question 2

Describe the epidemiology of optic neuritis?

Answer 2

• Most common cause → Multiple Sclerosis (may be presenting manifestation of MS)
• F>M, typical age range 30-50 yrs old

Question 3

What are the presenting symptoms/ signs of optic neuritis?

Answer 3

1. Vision Loss → occurs quite quickly, over hours to days
2. Decrease in visual acuity over days to a couple of weeks with scotoma → described as seeing through cloud or fog
3. Peri-Orbital Pain → exacerbated by eye movements
4. Colour desaturation → colour of objects not as bright as before/ Dyschromatopsia: Patients experience impaired color discrimination, particularly involving the red-green spectrum.
5. RAPD (Relative Afferent Pupillary Defect) → sign observed during the swinging-flashlight test whereupon the patient’s pupils (both) dilate when a bright light is swung from the unaffected eye to the affected eye (afferrent = optic nerve, efferent = occulomotor nerve, afferrent defect in this case).
6. Optic Disc Swelling → papillitis
7. Symptoms of MS

Question 4

What investigations are used to diagnose optic neuritis?

Answer 4

1. Gadolinium-Enhanced MRI of Orbit and Brain → may show enlarged optic nerve and help diagnose MS too.
2. Swinging-flashlight test → for RAPD

Question 5

How is optic neuritis managed?

Answer 5

High-Dose Corticosteroids → prednisolone
1. Intravenous methylprednisolone as the first-line treatment for optic neuritis.
- Although intravenous methylprednisolone is preferred, there is no absolute contra-indication to the use of oral steroids for optic neuritis.

Question 6

What complications may arise following optic neuritis?

Answer 6

development of MS, recurrent optic neuritis, chronically reduced visual acuity

Question 7

Describe the prognosis of optic neuritis

Answer 7

recovers sponteously over several weeks or months.

Question 8

Describe the pathogenesis of optic neuritis

Answer 8

The pathogenesis of optic neuritis is largely based on inflammatory processes triggering activation of T-cells. These activated cells can traverse the blood-brain barrier, leading to a hypersensitivity reaction against neuronal structures.

Question 9

What are some causes of optic neuritis?

Answer 9

1. Demyelinating lesions: Multiple sclerosis (MS) is the most common cause of demyelinating optic neuritis.
2. Autoimmune disorders: Certain autoimmune disorders can also incite the inflammation of the optic nerve.
3. Infectious conditions: Infections, particularly those affecting the central nervous system, may contribute to the development of optic neuritis.
   (optic neuritis is also strongly associated with ethambutol.)