I was recently the on-call Neurologist for The Royal London Hospital, which over the weekend can have an immense catchment area extending as far as Southend Hospital. It was during said on call that I was contacted by the on-call registrar. The story was of a pregnant lady experiencing unilateral eye pain and profound visual loss. Their working diagnosis was retrobulbar neuritis (inflammation of optic nerve behind the globe); as the optic disc appearances were normal. She also complained of swelling of the affected eye and sub-conjunctival haemorrhage.
The treatment of course is steroids to dampen down the inflammation, but in someone who is pregnant you will need to evaluate the risk to the baby of this treatment, as well as the risk associated with performing a contrast enhanced MRI.
So in many cases you fall back on your history and examination to be doubly sure of your diagnosis. Understanding how different eye conditions involving optic nerve inflammation present will stand you in good stead. This is particularly important, as was in this case when the presentation was one of functional visual loss (non-organic disorder). Very few people in the community know that pain on eye movement is more characteristic of optic nerve inflammation.
This review in Frontiers, therefore was very timely. I’ve listed some of the key take home messages from this article.
- The optic nerve itself doesn’t convey pain, the origin of the pain is the meninges covering the optic nerve.
- At the apex of the eye cavity the optic nerve is proximal to the superior and medial rectus (eye muscles). Consequently, upon eye movement the contraction of these muscles irritate the inflamed optic nerve sheath causing pain. Mild periocular pain (around the eye) and headache may also be experienced.
- Lack of pain following eye movement is always related to the lesion being located in the intracranial part of the optic nerve.
- MS- optic neuritis (ON): classical pain with eye movement, unilaterality, and reversible visual impairment.
- NMSOD (Neuromyelitis Optica)-ON: Pain followed by severe and irreversible visual loss as well as bilaterality.
- MOGAD (MOG antibody)-ON: Bilateral severe orbital pain and headache with mild vision loss.
- Pain resolves over a short period (normally less than 1 week) or with steroid treatment.
Pain Symptoms in Optic Neuritis
Signs and symptoms of optic neuritis (ON), an autoimmune disorder of the central nervous system (CNS), differ between patients. Pain, which is commonly reported by ON patients, may be the major reason for some patients to visit the clinic. This article reviews the presence of pain related to ON with respect to underlying disorders, including multiple sclerosis (MS), neuromyelitis optica spectrum disorder (NMOSD), and myelin oligodendrocyte glycoprotein associated disease (MOGAD). The aim of this review is to provide an overview of pain symptoms in accordance with the context of various pathophysiological explanations, assist in differential diagnosis of ON patients, especially at the onset of disease, and make recommendations to aid physicians make decisions for follow up diagnostic examinations.