A case of neuromyelitis optica developing into myelitis 25 years after optic neuritis

Variation in Evolving Optic Neuritis

BACKGROUND

The typical natural history of optic neuritis is subjected to important exceptions. Recognition of these exceptions has led to valuable insights regarding specific etiologies of optic neuritis. Exceptions to the natural history of recovering optic neuritis are well-defined (e.g., chronic relapsing inflammatory optic neuropathy), but exceptions to the natural history of evolving optic neuritis are less so.

METHODS

Medical records of patients illustrating an atypical course of evolving optic neuritis were reviewed in a retrospective manner. Each patient was treated by at least one of the authors.

RESULTS

Four patients were identified who illustrated an atypical natural history of incipient optic neuritis. Diagnoses included idiopathic optic neuritis, seropositive neuromyelitis optica spectrum disease, anti-myelin oligodendrocyte glycoprotein antibody disease, and multiple sclerosis in 1 patient each. Features of interest included an atypical temporal relationship between development of pain and onset of clinical optic neuropathy, an unusually protracted duration of pain, and an unusually long duration of worsening optic neuropathy before stabilization.

CONCLUSIONS

This case series illustrates the substantial clinical heterogeneity which may be observed in the evolution of optic neuritis. The temporal relationship between development of pain and onset of clinical optic neuropathy, the duration of pain, and duration of worsening optic neuropathy before stabilization are all subjected to significant variability. Although most patients with optic neuritis present with painful vision loss which progresses over 1 week or less, careful attention to the exceptions described herein may facilitate earlier recognition of diagnostically challenging cases.

Eleven episodes of recurrent optic neuritis of the same eye for 22 years eventually diagnosed as neuromyelitis optica spectrum disorder

It is difficult to predict whether a particular attack of neuromyelitis optica spectrum disorder (NMOSD) will affect the optic nerve [optic neuritis (ON): unilateral or bilateral], spinal cord (myelitis), brain or brainstem, or a combination of the above. We report an interesting case of recurrent ON of the same eye for a total of 11 episodes in a Chinese woman. Over a period of 22 years, the attacks only involved the left eye, and never the right eye and also no myelitis. For a prolonged duration, she was diagnosed as recurrent idiopathic ON. Only until she was tested positive for aquaporin 4 antibody that her diagnosis was revised to NMOSD. Optical coherence tomography revealed thinning of the retinal nerve fibre layer (RNFL) for the affected left eye, while the RNFL thickness was within normal range for the unaffected right eye. The disability accrual in NMOSD is generally considered to be attack-related - without a clinical attack of ON, there shall be no visual impairment, and no significant subclinical thinning of RNFL. Our case is in agreement with this notion. This is in contrast to multiple sclerosis where subclinical RNFL thinning does occur. This case highlights the importance of revisiting and questioning a diagnosis of recurrent idiopathic ON particularly when new diagnostic tools are available.