Neuromyelitis optica spectrum disorder (NMOSD) is a severe neuroinflammatory disorder primarily affecting the optic nerves and spinal cord. It is associated with a variety of clinical phenotypes and radiological features that can make diagnosis challenging.
We present an atypical and diagnostically challenging case of NMOSD with severe tetraparesis and conus involvement.
This is a case report detailing the complex clinical presentation, workup, and treatment of a patient who was ultimately diagnosed with NMOSD.
A previously healthy 46-year-old woman presented to the emergency room with 2 weeks of unidentifiable nausea/vomiting after a recent ear infection. Shortly after discharge, she returned to the hospital with complaints of worsened generalized weakness and no longer being able to walk. Over the next few days, she became flaccid with 0/5 strength in all 4 extremities. Magnetic resonance imaging (MRI) of the brain showed several nonenhancing lesions in the hypothalamic, anterior medial thalamic, right posterior pontine, and right middle cerebellar peduncular regions. MRI spine showed extensive enhancing lesions in the upper cervical cord and conus medullaris with leptomeningeal enhancement. Cerebrospinal fluid (CSF) studies were notable for lymphocytic-predominant pleocytosis with negative oligoclonal bands and negative cytology. Serum and CSF autoimmune panels were negative. Infectious and malignancy workup was negative. Cell-based assay testing for myelin oligodendrocyte glycoprotein (MOG-Abs) and aquaporin-4 (AQP4-Abs) antibodies were negative. Workup was negative for systemic signs of sarcoidosis or malignancy. She was treated with 5 days of intravenous steroids followed by intravenous immunoglobulin (IVIG) without improvement. She then underwent plasma exchange for 5 sessions. Within a week after completion, her strength gradually improved such that she was antigravity with 4/5 strength in all extremities by discharge to rehab. Because it was unclear if this was a monophasic event, a tentative diagnosis of atypical acute disseminated encephalomyelitis (ADEM) was made. Three months later, she developed muscle spasms in her right arm and was found to have a new enhancing lesion in the right spinal cord at C2. Repeat testing was sent and her AQP4-Ab test returned positive, leading to a final diagnosis of NMO.
This is a complex case with multiple differential diagnoses, including NMO, atypical ADEM, neurosarcoidosis, or lymphoma. Conus involvement is unusual for NMO and tend to be associated more with MOG-Abs compared to AQP4-Abs. Though cell-based assays have high sensitivities (90-94%), testing should be repeated on negative values if clinical suspicion is high.