west nile virus ( wnv ) is an arthropod borne neurotropic single stranded rna flavivirus . the virus is introduced into the host by the vector ( culex mosquito ) during its blood meal . wnv originated in the middle east and africa but in recent years has reached the united states . from 1999 to 2011 , a total of 31,414 cases of wnv were reported in the united states . the 2012 incidence of wnv neuroinvasive disease was 0.3 per 100,000 in the united states . approximately 45% of wnv cases were reported in texas , usa . seasonal outbreaks occur annually but are often quite focal and unpredictable in size and location . the majority of those infected with wnv are asymptomatic and only 20 - 30% will present with flu like symptoms . less than 1% of individuals will eventually develop neurological deficits . immunocompromised and elderly patients are more prone to developing wnv meningitis or encephalitis compared to the general population . wnv and other arboviral infections should be considered in the differential diagnosis of aseptic meningitis or encephalitis , especially if the geographical area is prone to wnv infection . the definitive diagnosis of wnv meningoencephalitis is a combination of clinical suspicion and csf serology . we are presenting a very rare case of a immunocompromised patient that developed opsoclonus myoclonus syndrome following wnv encephalitis . forty - eight year old caucasian female presented with a sudden onset of altered mental status after being found unresponsive . she was confused with intermittent bouts of alertness / lethargy and unintelligible responses to questioning . her medical problems included endometrial cancer that was treated with a total abdominal hysterectomy with bilateral salpingectomy and postoperative chemotherapy . the endometrial adenocarcinoma was a stage 2 according to the international federation of gynecology and obstetrics ( figo ) staging : 8 cm tumor , grade 2 , no lymph node involvement , and < 50% invasion of the myometrium and cervical stroma . the patient was currently in remission after receiving chemotherapy ( paclitaxel and carboplatin ) and dexamethasone . initial vital signs on admission included a rectal temperature was 41.1 degrees celsius , tachycardia ( heart rate of 108 ) , stage 1 hypertension ( blood pressure of 140/61 ) and tachypnea ( respiratory rate of 34 ) . pertinent physical examination findings revealed a morbidly obese female that was alert but not oriented to person , place or time and only able to answer yes or no to questioning . her pupils were 3 mm bilaterally , equal round and reactive to light with intact extraocular movements and no nystagmus noted . no motor or sensory deficits to light , touch , pain , position sense or vibration noted . initial laboratory work - up ( table 1 ) was unremarkable except hyponatremia and thrombocytopenia . brain computed tomography ( ct ) on admission was negative for any acute pathological abnormalities . the patient was started on ceftriaxone 2 g iv daily , vancomycin 2 g iv twice daily , and acyclovir 1.5 g iv every 8 hours due to our high suspicion of encephalitis . a lumbar puncture with cerebrospinal fluid ( csf ) analysis and csf serology ( table 2 ) was consistent with aseptic meningitis . magnetic resonance imaging ( mri ) of the brain was unremarkable for any acute intracranial abnormalities . vancomycin and acyclovir were discontinued and fluconazole 400 mg po daily was added to the management on the sixth hospital and ceftriaxone was continued until the tenth hospital day . by the seventh hospital day , we noted involuntary random movements of her eyes ( see video 1 ) and generalized jerking movements ( myoclonus ) , mostly in lower extremities . an electroencephalography ( eeg ) showed a severe and diffuse slowness , consistent with encephalopathy . she was placed on fosphenytoin 100 mg iv every 8 hours without any improvement . on the eighth hospital day , her gcs decreased to 3 and was subsequently intubated . the platelet count continued to decrease during the hospitalization and eventually reached its lowest count of 2110/ul by the tenth hospital day . the west nile virus ( wnv ) antibody igm and igg were noted to be positive on the twelfth hospital day . after determining that the encephalitis was due to the wnv we continued supportive care and discontinued the fluconazole . they diagnosed her to have opsoclonus myoclonus syndrome ( oms ) induced by the wnv meningoencephalitis . paraneoplastic antibodies anti - yo , anti - hu , anti - ri and anti - nmdar were negative . a percutaneous endoscopic gastrostomy tube ( peg ) and tracheostomy were performed on hospital day 26 . the patient continued to have improvement in her neurological status and was subsequently discharge to a long term acute care ( ltac ) facility for further rehabilitation . she underwent rehabilitation for six months and eventually had complete resolution of her neurological deficits on follow visit . opsoclonus - myoclonus syndrome ( oms ) is a rare neurological disorder associated with chaotic multidirectional eye movements , myoclonus and less frequently cerebellar ataxia . the eye movements are characterized by multidirectional , high amplitude , arrhythmic and conjugate ocular saccadic intrusions without intersaccadic latency causing oscillopsia . it should not be confused with nystagmus which is usually unidirectional and has a slow component . myoclonus may affect any part of the body and may be evoked by action , intention , auditory and visual stimuli . the pathogenesis of opsoclonus is unknown but , one hypothesis suggests that opsoclonus is due to damage of the omnipause cells in the nucleus raphe interpositus of the pons . this prevents unwanted saccades by inhibiting burst neurons in the paramedian pontine reticular formation and rostral interstitial nucleus of cajal . another explanation suggests that opsoclonus may be generated by disinhibition of the oculomotor region of the fastigial nucleus by a process that interferes with the inhibitory projections of the purkinje cells of the deep cerebellar nuclei to the fastigial nuclei . the pathogenesis is not fully understood , however , an autoimmune pathophysiology has been proposed . autoimmune dysfunction of purkinje cells in the dorsal vermis and subsequent disinhibition of oculomotor fastigial region seems to be the most probable mechanism . however , other common causes of opsoclonus include paraneoplastic , viral brainstem encephalitis and drugs . the onconeuronal antibodies associated with oms are anti - ri antibodies ( gynecologic cancers ) and , less frequently , anti - hu , anti - yo , and anti - ma-2 antibodies . paraneoplastic diseases associated with oms include small - cell lung , ovarian and breast cancer . most infectious disease causes involve the central nervous system or a post infection immune mediated process . the post infectious mechanism has been described as a dysfunction of the cell mediated and humoral immune response . this immune mediated process was postulated because the presence of autoantibodies and the response of oms to immunosuppressive therapy . the specific microorganism is rarely identified however oms has been reported to occur after infection with enterovirus , borrelia burgdorferi , streptococcus , coxsackie virus , epstein - barr virus , mumps or west nile virus . opsoclonus myoclonus syndrome can result in significant long term neurological sequelae if either untreated or undertreated . therapy options have been directed towards the suppression of antibody formation and the removal of the autoantibodies . several therapeutic attempts can be utilized to remove the autoantibodies in patients with oms , such as ivig , plasmapheresis , and immunoadsorption . however there is no available data from clinical trials that suggest a definitive treatment strategy . because the opsoclonus - myoclonus syndrome is so rare , there are no randomized controlled trials to provide guidelines for either symptomatic or disease modifying treatments . according to current medical literature , only two other case reports have reported opsoclonus myoclonus syndrome induced by west nile virus encephalitis .