Abstract
Neuromyelitis optica is an inflammatory disease characterized by neuritis and myelitis of the optic nerve. Its physiopathology is connected with the aquaporin-4 water channel, since antibodies against aquaporin-4 have been found in the cerebrospinal fluid and blood of neuromyelitis optica patients. The seropositivity for aquaporin-4 antibodies is used for the diagnosis of neuromyelitis optica or neuromyelitis optica spectrum disease. On the other hand, aquaporin-4 is expressed in astrocyte feet in the brain-blood barrier and subventricular zones of the brain ventricles. Aquaporin-4 expression is high in cerebrospinal fluid in hydrocephalus. Furthermore, neuroepithelial denudation precedes noncommunicating hydrocephalus and this neuroepithelial disruption could allow aquaporin-4 to reach anomalous brain areas where it is unrecognized and induce the generation of aquaporin-4 antibodies which could cause the neuromyelitis optica and certain types of hydrocephalus.
Highlights
Neuromyelitis optica (NMO) or Devic’s disease is an autoimmune disorder affecting the optic nerve and spinal cord, where the aquaporin-4 water channel (AQP4) plays an important role
There is about a 5% overlap with other autoimmune diseases [2]. These findings support the suggestion that any patient with an autoimmune optic neuropathy which is seropositive for AQP4 autoantibodies should be given a diagnosis of NMO or NMO spectrum disease (NMOSD) [3, 4]
AQP4 presence in the cerebrospinal fluid (CSF) has been proposed as a diagnostic biomarker of hydrocephalus type [5]; the sites and mechanisms of CSF reabsorption are relevant to the pathophysiology of hydrocephalus [6]
Summary
Neuromyelitis optica (NMO) or Devic’s disease is an autoimmune disorder affecting the optic nerve and spinal cord, where the aquaporin-4 water channel (AQP4) plays an important role. Antibodies against AQP4 are detectable in the cerebrospinal fluid (CSF) of most patients with neuromyelitis optica (NMO) spectrum disease, mainly when it is worsening. Seropositivity for AQP4-Ab is the only validated diagnostic biomarker for autoimmune optic neuropathies [1] since the diagnostic specificity of this test is almost 99%. There is about a 5% overlap with other autoimmune diseases [2] These findings support the suggestion that any patient with an autoimmune optic neuropathy which is seropositive for AQP4 autoantibodies should be given a diagnosis of NMO or NMO spectrum disease (NMOSD) [3, 4]. Studies [7, 8] indicate the existence of a brain-wide pathway facilitating the exchange of CSF and interstitial fluid via para-arterial CSF influx, paravenous interstitial clearance, and a transparenchymal pathway dependent on water transport through astrocytic AQP4 channels
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