Factors such as a delay in performing a magnetic resonance imaging (MRI) study, the presence of nonneurological symptoms, and a negative aquaporin 4 (AQP4) IgG test could contribute to a late neuromyelitis optica spectrum disorder (NMOSD) diagnosis detrimental to the health of the patient, according to a recently published study in Multiple Sclerosis and Related Disorders.

Epidemiological data shows that up to 40% of NMOSD cases are initially misdiagnosed, the researchers noted. Because NMOSD shares several clinical characteristics with multiple sclerosis (MS), an important percentage of cases are initially labeled as MS. However, clinicians have several diagnostics tools available to differentiate between the 2, they added.

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The underlying pathophysiology of NMOSD makes an early diagnosis, and a timely beginning of treatment fundamental for the future quality of life of the patient, as the risk of disability accumulation following relapses is high, the study authors said.

Furthermore, evidence suggests that administering disease-modifying therapy for patients with MS to NMOSD leads to a worse prognosis, the research team noted.

Therefore, the authors aimed to assess the factors contributing to NMOSD misdiagnosis through a retrospective study including data from 199 patients with NMOSD with sufficient medical record data. Researchers constructed a timeline for each patient commencing with symptom onset. 

Approximately 35% of the 199 patients were initially misdiagnosed after symptom onset. Although AQP4-IgG was positive in over 85% of patients, 55 seropositive patients were initially misdiagnosed.

The authors noted that patients with nonneurological symptoms such as nausea, vomiting, and hiccups were more likely to be misdiagnosed regardless of AQP4-IgG serostatus. Despite a neurological origin is not usually considered in patients presenting these symptoms, a duration of over 48 hours should be a criterion for neurological assessment as they could be originated through damage in the area postrema.

The frequency of AQP4-IgG was significantly greater in the accurately diagnosed group. Similarly, the period between symptom onset and evaluation by neuroimmunology was greater in the misdiagnosed group, with a median difference of approximately 4 years. The period between symptom onset and the performance of a first MRI was significantly longer in the misdiagnosed group.

‘’Our findings not only define important factors for consideration when establishing a differential diagnosis but emphasize the need for further awareness towards NMOSD,” the authors concluded.


Smith AD, Moog TM, Burgess KW, et al. Factors associated with the misdiagnosis of Neuromyelitis Optica Spectrum disorder. Mult Scler and Relat Disord. Published online January 2, 2023. doi:10.1016/j.msard.2023.104498