It was reported in a published article, title as stated above that a 16-year-old previously healthy girl presented 10 the emergency room with an acute onset of visual loss over 48 hours. Initially, there was visual loss noted in the right eye accompanied by a left side headache. These symptoms worsened over the next 24 hours to include visual loss involving the left eye with a more diffuse headache. When evaluated in the emergency room at 48 hours after onset, her vital signs were blood pressure 116/65, pulse 68/minute, respirations 14/minute, and temperature 98 degrees F, with a completely normal general physical examination and no signs of systemic illness. Her examination disclosed a visual acuity of only counting fingers bilaterally with mild left side weakness accompanied by sensory loss to pinprick in the left arm. There was a left afferent pupillary defect and normal fundoscopic examination. Her visual ability deteriorated further to inconsistently identifying light and movement from the left eye only. She complained of no other symptoms and denied antecedent trauma or prodromal illness. She had, however, received her second vaccination against human papilloma virus 10 days prior to her presentation. There was no family history of demyelinating disease, collagen-vascular disease, or rheumatological disorders. Magnetic resonance imaging (MRI) of the brain showed swollen enhancement within the chiasm extending into both retrobulbar optic nerves and a right occipitoparietal lobe mass (later disclosed as tumefactive demyelination) with a large zone of surrounding vasogenic edema. Complete spine MRI was normal. Biopsy of the hemispheric mass was performed and histology revealed demyelination. Subsequent cultures for aerobic and anaerobic bacteria, fungus, acid fast bacilli, and examination for parasites were negative as were serum immunoglobulin G and immunoglobulin M titers for Toxoplasma gondii. The erythrocyte sedimentation rate was 16 and the white blood cell count was 6900 with 89% granulocytes and 9% lymphocytes. The patient received a 5-day course of high-dose intravenous steroids (1g methylprednisolone/divided each 6 hours), followed by 5 double-volume plasma exchanges with no visual improvement. Other diagnostic testing included neuromyelitis optics (neuromyelitis optica-immunoglobulin G), antinuclear antigen, Sjorgren syndrome (SS-A, 88-8), rheumatoid factor, angiotensin-converting enzyme, which were all normal or negative. Three months after the onset, the patient still had not regained any visual function, her weakness and sensory deficit recovered completely however. A repeat MRI of the brain revealed resolution of the hemispheric and chiasmal lesions. At 6 months her funduscopic examination disclosed bilateral optic disc pallor. A repeat MRI at this time demonstrated no new lesions and continued resolution of the previously identified chiasmal enhancement and tumefactive lesion. Again complete spine MRI was normal. Cerebrospinal fluid was obtained 6 months after initial symptom onset. Cerebrospinal fluid cytology was negative for malignancy; additional studies revealed B clear and colorless fluid with 3 white blood cells and 0 red blood cells per microliter, glucose 61 mg/dL and simultaneous serum glucose of 91 mg/dL, protein 30 mg/dL, lactate 1.5 mmol/L, and negative oligoclonal immunoglobulin G hands. At 18 months after the onset of her symptoms, her examination remained stable with no further neurological complaints, persistent profound visual impairment) inconsistently identifying light and movement from the left eye only. An MRI of the brain was performed and was unchanged compared with the previous one done at 6 months. There were no further demyelinating events within the next 18 months. In the context of prior vaccination in a 16-year-old girl, acute demyelinating encephalomyelitis is likely to explain the multifocal deficits. This demyelinating event could also represent the index attack of neuromyelitis optics known to cause severe bilateral visual loss due to optic neuritis with poor recovery. The monophasic course of our patient's demyelinating event and the lack of "dissemination in time", make a diagnosis of clinically definite multiple sclerosis unlikely. At this time, a divergence of opinion is notable from authors of various case series attempting to identify predictive factors of clinically definite multiple sclerosis in children who present with a first central nervous system demyelinating event or initial bilateral optic neuritis. The brain biopsy in this case showed a primary inflammatory demyelinating process without axonal loss. Lymphocytes and macrophages were present within the plaque and in the perivenular spaces. These findings do not distinguish between multiple sclerosis, acute demyelinating encephalomyelitis, and their variants; a more subtle distinction may lie in the fact that in multiple sclerosis, inflammatory cells are generally present throughout the plaque rather than restricted only to the perivenular cuff, a feature that is more characteristic of acute demyelinating encephalomyelitis. It is possible that human papilloma virus was the precipitant for the demyelinating event in the patient presented here. It is tempting to speculate whether there may be a specific immune mechanism initiated with human papilloma virus not yet identified, which resulted in not only acute demyelinating encephalomyelitis but also in an unusual clinical course that resulted in persistent visual loss. Upon internal review visual loss in the right eye accompanied by a left side headache was determined to be an other important medical event. No further information is available.