Is NMO different than a form of MS? No, but..

The following is based on presentations at a conference including Elliott Frohmann, Brian Weinshenker, Stephen Galetta and others. Officially, it is not yet established as a different disease, but is different based on demographic, clinical, MRI, pathological, immunologic, prognostic, and therapeutic criteria.

Clinical differences between NMO and MS abound. The spinal cord lesions in the two diseases are different. In NMO, the lesions are in the central gray, extend over many segments, and may be necrotic. Eosinophils and neutrophils are abundant. The inflammation is extensive in perivascular areas especially in the micro-vessels. In MS, spinal cord lesions are non-necrotic, smaller, macrophages predominate, and inflammation occurs at the edge of the plaque and along myelin sheaths, not nearly as much along the perivascular edges. Unlike NMO, rosettes do not form.

In NMO, oligoclonal banding is absent, unlike MS. Clonal expansion is not important in NMO, suggesting that the blood brain barrier is not integral to the process. NMO IgG is present in 70 % of cases, v. < 10 % in MS. Systemic autoimmune disease suchas Sjogren's and lupus are abundant, whereas there is only a slight increase in autoimmunity in MS. Many cases of myelitis in patients with SLE or Sjogren's previously thought to be vasculitis are NMO positive, suggesting a different diagnosis. Recurrent transverse myelitis is often NMO positive, suggesting a subset of patients with that condition have that diagnosis. In MRI, brain lesions are "uncommon" in NMO but can occur. They usually are located around the hypothalamus, thalamus and third ventricle, and around the periphery of the cerebellum. However, 8% or so are atypical and can mimic the lesions in multiple sclerosis, with hemispheric lesions. Brain lesions, like cord lesions, can present as long linear lesions in the medulla especially in area postrema and the solitary tract. In one series, 17 %of patients presented with hiccups, correalting with the above pathology. Similarly, optic nerve lesions may be long and centrally located in NMO and extend all the way back to the chiasm. CSF often has a pleocytosis. Asian demyelinating variants may in some cases represent NMO.

Unlike MS, in NMO a secondary progressive course is rare and damage is done during the attacks themselves. If the attacks can be controlled, so can the disease. Plasmapheresis works extremely well in this condition.Rituxan works well as a chronic treatment to control attacks. Beta interferon does not work well.