Certified Neuroscience Registered Nurse (CNRN) Practice Exam

The serum NMO IgG antibody is considered the most sensitive marker for neuromyelitis optica (NMO). This antibody, which targets the aquaporin-4 (AQP4) water channel, plays a critical role in the pathophysiology of NMO. The presence of this antibody is a defining feature that differentiates NMO from other demyelinating diseases such as multiple sclerosis.

When testing for NMO, the detection of this antibody is essential because it not only aids in the diagnosis but also has implications for prognosis and treatment. High levels of sensitivity make it a key marker in identifying individuals with this condition, often even before the clinical symptoms manifest or detectable brain MRI changes occur.

In comparison, while CSF oligoclonal bands can indicate neurological inflammation and are useful in diagnosing multiple sclerosis, they are not as specific or sensitive for NMO. Brain MRI abnormalities may present in patients with neuromyelitis optica, but their presence alone is not definitive for diagnosis. Visual evoked potentials are helpful for assessing visual pathway function but do not serve as a direct marker for NMO itself. Thus, the serum NMO IgG antibody stands out as the most reliable and sensitive diagnostic tool for neuromyel