Neuromyelitis optica (NMO) is an inflammatory disorder of the central nervous system characterized by immune-mediated demyelination and axonal damage that targets the optic nerves and spinal cord. NMO was initially thought to be a variant of multiple sclerosis (MS) due to the overlap of symptoms; however, it is now known that an NMO-specific immunoglobulin G (IgG) autoantibody, anti-aquaporin 4 (AQP4), plays a role in NMO pathogenesis. The AQP4 antigen is a water channel protein that is highly concentrated in spinal cord gray matter and the astrocytic foot processes in the blood-brain barrier. The laboratory finding of anti-AQP4 antibodies is diagnostic for NMO and helps to distinguish NMO patients from those with MS, with higher serum levels correlating severity of disease activity.
The typical clinical features of NMO/NMOSD (NMO Spectrum Disorders) are acute and include varying degrees of vision loss (optic neuritis) and features of transverse myelitis, which can include limb weakness, sensory loss, and bladder dysfunction. Hypothalamic and brainstem involvement occurs in a minority of patients, which can manifest as hiccups, intractable nausea, and respiratory failure. NMO/NMOSD typically has a recurring, relapsing course.
The treatment for acute and chronic episodes of NMO/NMOSD includes glucocorticosteroids and therapeutic plasma exchange (TPE). TPE has been shown to be beneficial in the management of acute and chronic episodes of NMO/NMOSD, likely through the removal of the anti-AQP4 antibody and other inflammatory substances from the blood. Although observational studies show TPE is beneficial in NMO/NMOSD, limited specific information is known regarding these apheresis procedures, patients' degree of response to these procedures, and the characteristics of patients who benefited. As part of the neurologic diseases subcommittee of the ASFA research committee, a multi-institutional retrospective study was conducted to help answer these questions with the purpose of gaining an understanding of specific TPE procedural information, response of acute NMO/NMOSD symptoms to TPE, and patient characteristics associated with TPE response. The study also determined the safety and efficacy of TPE in the treatment of NMO/NMOSD.
The multicenter retrospective study was conducted at 13 US hospitals performing apheresis procedures, of which two were pediatric and 11 were adult or adult/pediatric combined. Subjects studied were diagnosed with NMO/NMOSD who received TPE during a presentation of acute disease. A total of 114 patients were enrolled in the study. Patients were more likely to be female and Caucasian, with an average age at diagnosis of 43 years. The most common clinical findings in patients before plasma exchange was begun were: paraparesis, bilateral sensory loss, blindness, and sphincter dysfunction.
On average, five procedures were performed during each treatment series. The most frequently performed plasma exchange volume was 1.0 to 1.25, using 5% albumin for the replacement fluid. Most patients (52%) did not require an additional course of TPE and noted “mild” to “moderate” clinical status improvement. Maximal symptom improvement appeared by the fourth or fifth TPE treatment. A minority of procedures were associated with an adverse event (9.9%, 75/759), the most common being citrate toxicity (3.6%, 27/759).
TPE improved the clinical status of both adult and pediatric patients. Adults responded more favorably than children. Procedural characteristics, including number of TPEs, plasma volume exchanged, and replacement fluid used, were similar between institutions. TPE was well-tolerated and had a low severe adverse event profile.
Shanna Morgan, MD
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