Cause
The optic nerve comprises axons that emerge from the retina of the eye and carry visual information to the primary visual nuclei, most of which is relayed to the occipital cortex of the brain to be processed into vision. Inflammation of the optic nerve causes loss of vision, usually because of the swelling and destruction of the myelin sheath covering the optic nerve. The most common cause is multiple sclerosis or ischemic optic neuropathy due to thrombosis or embolism of the vessel that supplies the optic nerve. Up to 50% of patients with MS will develop an episode of optic neuritis, and 20-30% of the time optic neuritis is the presenting sign of MS. The presence of demyelinating white matter lesions on brain MRI at the time of presentation of optic neuritis is the strongest predictor for developing clinically definite MS. Almost half of the patients with optic neuritis have white matter lesions consistent with multiple sclerosis. Some other common causes of optic neuritis include infection (e.g. a tooth abscess in the upper jaw, syphilis, Lyme disease, herpes zoster), autoimmune disorders (e.g. lupus, neurosarcoidosis, neuromyelitis optica), methanol poisoning, Vitamin B12 deficiency, beriberi, dysautonomia (i.e. autonomic nervous system dysfunction), and diabetes, or an injury to the eye. In neuromyelitis optica higher AQP4 autoantibody levels are associated with the occurrence of optic neuritis.Less common causes are: papilledema, brain tumor or abscess in the occipital region, cerebral trauma or hemorrhage, meningitis, arachnoidal adhesions, sinus thrombosis, liver dysfunction, or late stage kidney disease.
Surgery
Surgical interventions are used for both symptomatic relief of the SVT as well as for preventing the development of more serious complications (e.g. pulmonary embolism). Surgical interventions include ligation of the saphenofemoral junction, ligation and stripping of the affected veins, and local thrombectomy. Because of the risk of symptomatic pulmonary embolism with surgery itself, surgical interventions are not recommended for the treatment of lower limb SVTs by the 2012 American College of Chest Physicians guidelines and the 2012 British Committee for Standards in Haematology guidelines. The use of surgery for the treatment of SVT is controversial. Prognosis
SVT is often a mild, self-resolving medical condition. The inflammatory reaction may last up to 2–3 weeks, with possible recanalization of the thrombosed vein occurring in 6–8 weeks. The superficial vein may continue to be hyperpigmented for several months following the initial event. Epidemiology
In a French population, SVT occurred in 0.64 per 1000 persons per year. History
SVTs have been historically considered to be benign diseases, for which treatment was limited to conservative measures. However, an increased awareness of the potential risks of SVTs developing into more serious complications has prompted more research into the diagnosis, classification, and treatment of SVTs. Research
A Cochrane review recommends that future research investigate the utility of oral, topical, and surgical treatments for preventing the progression of SVTs and the development of thromboembolic complications. Footnotes


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