Initial report received from literature on 11 October 2014. Objective: Rare disease. Background: There are several categories of primary inflammatory demyelinating disorders, which compromise clinically similar neurologic sequelae. Of interest, clinically isolated syndrome (CIS) and acute disseminated encephalomyelitis (ADEM) are 2 demyelinating conditions of the central nervous system (CNS), whose clinical similarity pose a significant challenge to definitive diagnosis. Yet, both remain important clinical considerations in patients with neurologic signs and symptoms in the context of recent vaccination. Case Report: We report a case of a 50-year-old male with a course of progressive, focal, neurologic deficits with-in 24 h after receiving the influenza vaccine. Subsequent work-up revealed the possibility of an acute central nervous system (CNS) demyelinating episode secondary to the influenza vaccine, best described as either CIS or ADEM. Conclusions: Case reports of CNS demyelination following vaccinations have been previously noted, most often occurring in the context of recent influenza vaccination. This report serves to document a case of CNS demyelination occurring 24 h after influenza vaccination in a middle-aged patient, and will describe some salient features regarding the differential diagnosis of CIS and ADEM, as well as their potential management. A 50-year-old male patient, had received a dose of INFLUENZA VACCINE (batch number, dose, dose in series, route and site of administration was not reported) on an unspecified date. The patient had a medical history significant for hypothyroidism, hyperlipidemia, gastroesophageal reflux disease, psoriasis, attention deficit hyperactivity disorder, depression, and a right-sided supraclavicular phrenic nerve lipoma, which was removed in 2007. Patient's surgical history included hernia repair, appendectomy, knee arthroscopy, tonsillectomy, and excision of the aforementioned lipoma. Patient's family history revealed hypertension and heart disease within the maternal lineage, and a sister with anemia. The patient was a former smoker of 1 pack per day for 3 years, successfully quitting in 1983. The patient also reported occasional alcohol intake and no recreational drug use. An allergy to penicillin was noted. The patient concomitant medications include levothyroxine, dexlansoprazole, clotrimazole/betamethasone cream, methylphenidate, and alprazolam. On an unspecified date one day after vaccination, the patient experienced acute central nervous system (CNS) demyelinating episode secondary to the influenza vaccine/either CIS or ADEM, progressive, focal, neurologic deficits, left-sided weakness/left arm weakness, left arm numbness, full left arm paresthesia, blurred vision in the left eye, "itchy" sensation over the entire left face and acute central nervous system (CNS) demyelinating episode secondary to the influenza vaccine/either CIS or ADEM. It was reported that the   [Due to memory limitations, the remainder of this text could not be compared.]  neurologic examination also revealed slight facial asymmetry on tests for cranial nerves 5 and 7. The remaining cranial nerves were grossly normal. Motor testing showed arm and leg weakness at 3/5 and left-sided drift. Tone was increased on the left, and coordination was slightly diminished on the left compared to the right with rapidly alternating movement. No tremor or ataxia was noted. Sensation to pain, temperature, and vibration was intact. Reflexes were 3+ on the left, and 2+ on the right, with down-going toes bilaterally. On an unspecified date the patient was hospitalized. Laboratory investigations include - Results of a comprehensive metabolic panel, coagulation studies, and complete blood count were all within normal limits. LDL (Low-density lipoprotein) and triglycerides were elevated at 106 mg/dL and 193 mg/dL, respectively. The full evaluative course of this patient was extensive and initially focused on a working diagnosis of acute stroke. A chest x-ray, performed on admission, was unremarkable. Computed tomography (CT) of the head without contrast did not reveal any space-occupying lesion, no intracranial hemorrhage, hydrocephalus, or shifting of the ventricles. Evidence of cerebral infarction or edema was non-existent. Similarly, CT angiography of the head and neck was unremarkable. Bilateral carotid duplex studies demonstrated carotid stenosis less than 40% on the right and the left. On the second day of hospitalization, magnetic resonance imaging (MRI) of the brain and full spinal cord with- and without-contrast were obtained during further work-up. MRI of the brain showed no distinct intra-axial hemorrhage, mass, mass effect, or enhancing lesion, or evidence of acute stroke. Scattered foci of bright T2 FLAIR signal changes were seen in the peri- and non-periventricular region, deep hemispheric centrum, peritrigonal, and cortical/subcortical regions, indicative of a demyelinating disease. MRI of the cervical spine proved benign, and MRI of lumbar and thoracic spine were unremarkable and without evidence of herniated disc pulpous or spinal stenosis. A cerebrospinal fluid (CSF) sample was obtained by lumbar puncture, which proved to be completely normal by laboratory evaluation, and gram stain was negative with no growth on culture after 7 days. Additionally, cytological analysis of the spinal fluid showed no evidence of malignancy. Testing for oli-goclonal bands within the CSF was also negative. Cardiology work-up was also performed. This included an EKG, which showed normal sinus rhythm, an echocardiogram revealed mild left atrial dilation and a left ventricular ejection fraction of 60%. Corrective treatments include: Medically, with a proposed diagnosis of post-vaccination NCS demyelination secondary to influenza vaccination, a 5-day course of twice-daily intravenous methylprednisolone (500 mg) was prescribed, followed by a 12-day tapered course of once-daily oral prednisone (20 mg). Additionally, the patient was referred for comprehensive in-patient rehabilitation. Upon presentation to the in-patient rehabilitation unit (IPR), the patient was alert and oriented to person, place, and time. He exhibited no cranial nerve abnormalities. He had significant left hemiparesis, with both upper and lower extremity strength graded as 1/5. Our patient demonstrated mild balance deficits in the seated position and severe balance deficits in the standing position. Sensation was diminished to light touch, pain, and proprioception in the left arm and leg. He required maximal physical assistance with all activities of daily living (ADL) and mobility, including bed mobility, transfers, and ambulation up to 40 feet. Severe knee coordination deficits in the left arm and leg were demonstrated. His admission functional independence measure (FIM) score was 74. Rehabilitation treatment consisted of intense ADL, gait, and transfer training, as well as strengthening exercises. Body-weight supported gait training was implemented using treadmill and over-ground tracking systems. Upper extremity exercises were facilitated using different devices. His IPR stay lasted 12 days. He was given 3 hours of daily therapy, combined physical and occupational therapy, during his 12-day stay, with 1 day of rest. After a successful rehabilitation program, he was discharged home. He was able to perform all ADLs at either an independent or standby-assist level, with the exception of tub transfers, which required minimal physical assist. Our patient was able to walk 150 feet, transfer, and climb a flight of stairs with modified independence. His discharge FIM score was 106. At the time of this report the outcome of event was unknown. Documents held by sender: yes (MRI images).