Presentation
Recent epidural anesthesia. New onset acute urinary retention ?epidural hematoma.
Patient Data
Long segment T2 hyperintensity throughout the cervical and thoracic cord involves more than two thirds of the cross sectional area. From T3 to T7/8 there is patchy enhancement of the involved cord.
There was no epidural hematoma or cord compressive lesion (including MRI lumbar spine , not included here).
T2/FLAIR hyperintensity about the right lateral ventricle trigone, temporal horn and occipital horn, with further signal abnormality involving corpus callosum and periaqueductal grey matter. There are no lesions running perpendicular to the lateral ventricles, and no deep or subcortical white matter lesions.
This distribution of intracranial lesions corresponds to areas of high expression of the aquaporin 4 receptor that is implicated in the immunopathogenesis of NMO. There are no stereotypical 'Dawson's finger' or juxtacortical lesions that are common in multiple sclerosis.
Case Discussion
A longitudinally extensive cord lesion carries a broad differential diagnosis including parainfectious, autoimmune, demyelinating and vascular conditions. Presence of enhancement, or in lieu of enhancement a proven CSF pleocytosis and increased protein, confirm that this is an inflammatory process.
Relevant findings on brain imaging and clinical features (for example concurrent or recent febrile illness, or evidence of an autoimmune or connective tissue disorder) can then be employed to assist in narrowing the imaging differential diagnosis.
In this case, the distribution of brain lesions corresponds to sites of high expression of aquaporin 4 receptor which points toward NMO, a diagnosis later confirmed by positive NMO autoantibody.
Neuromyelitis optica is a relapsing demyelinating condition that affects spinal cord and optic nerves. Compared to multiple sclerosis, NMO affects an older age group (39 years compared with 29 years), with more pronounced female predominance, and with disproportionate representation from the nonwhite population.
Previously grouped with MS, NMO is now recognized as an autoimmune channelopathy, due to autoantibodies against the aquaporin 4 water channel receptor.
Cord involvement is characterized by longitudinally extensive T2 hyperintense lesions rather than the small peripheral lesions that are typical of MS.
Brain lesions, where present, usually involve subependymal regions and hypothalamus where the aquaporin 4 receptorhas high rates of expression.
NMO antibody testing is highly sensitive and specific for the diagnosis.
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