Abstract:

Background:

Myelitis is a debilitating neurological condition characterized by inflammation and demyelination of the spinal cord. It leaves two-thirds of patients with moderate to severe residual disability. Generally occurring independently, often as a complication of infection, it can also be a component of neuro-inflammatory spectrum disorders like multiple sclerosis, neuromyelitis Optica spectrum disorder (NMOSD), acute disseminated encephalomyelitis, and MOG antibody disease. NMOSD is distinct by the presence of aquaporin-4 IgG antibodies (AQP4-IgG) and has an estimated global prevalence of 1 in a million, predominantly affecting females.

Case presentation:

A 59-year-old female with a questionable history of Brown-Séquard syndrome in 2004, for which she avoided surgery due to concerns about losing mobility, presented with acute neck pain following a bug bite on the back of her neck, with pain and tingling sensation in both the hands. An MRI of the neck revealed T2-weighted hyperintense signals from the cervico medullary junction to the upper border of T1, indicating spinal cord edema(Figure 1). Blood work for paraneoplastic syndrome(s) was negative but the presence of AQP-4 antibodies confirmed the diagnosis of NMOSD. She was treated with a 5-day course of high-dose intravenous methylprednisolone and plasma-exchange, leading to significant symptom improvement. She was placed on rituximab monotherapy (1000 mg once every 6 months) for chronic treatment. case.png

Discussion:

NMOSD is definitively diagnosed based on AQP-4 antibodies in serum and CSF with signs of area postrema syndrome and acute myelitis (2015 diagnostic criteria). Moreover, this patient's symptoms improved following immunotherapy, but not anti-infective medication. Intravenous methylprednisolone is typically used to treat acute NMOSD episodes. If unresponsive, plasma exchange can be added. Acute attack outcomes have improved in single case series by experimental therapies like IVIG, anti-CD20, and anti-complement therapy.

Relapses have reduced with immunosuppressive maintenance therapy using rituximab, azathioprine, mycophenolate mofetil, and oral prednisone. Shi Z et al., with 281 Chinese NMOSD patients, showed azathioprine and mycophenolate mofetil lowered disability and relapse rates. Yaguchi H et al. found cyclophosphamide (monotherapy or in combination with methylprednisolone) effective in both acute and chronic phases. Approved immunotherapies, inebilizumab, eculizumab, and Satralizumab, reduce the relapses and the cumulative impairment. Newer biologics (theravulizumab, ublituximab, aquaporumab, and sedelestat) are undergoing review for use in NMOSD.

Conclusion: For atypical presentation of NMOSD, a high index of suspicion is needed for early treatment and better patient outcomes. Although novel treatment modalities provide a hope for more effective treatment, more trials are required to estimate their safety and efficacy.