anti - n - methyl - d - aspartate receptor ( anti - nmdar ) encephalitis is an increasingly recognized etiology of previously unexplained encephalopathy and encephalitis , since its original description in 2007 , . the disease has initially been described in women with an ovarian teratoma but can also be seen in seen in women without an ovarian teratoma , men . the syndrome usually develops with a sequential presentation of symptoms including headache and fever followed by behavioral changes , psychosis , catatonia , decreased level of consciousness , dyskinesias , and autonomic instability . extreme delta brush ( edb ) is a novel electroencephalogram ( eeg ) finding seen in 30.4% of patients with anti - nmdar encephalitis . the presence of this pattern is associated with a more prolonged illness , although the specificity of this pattern is unclear . additionally , the frequency and sensitivity of edb in anti - nmdar encephalitis , its implications for outcome , and whether there is a relationship between this pattern and antibody titers in serum and csf have yet to be determined . we report a 27-year - old woman with no significant past medical history who was brought to the emergency department after becoming  odder  at home one week after the funeral of her boyfriend . her family reported that she had not been sleeping or eating for a week , and she had been  rambling wildly  to herself ever since her boyfriend 's funeral . she required chemical sedation in the emergency department as she became violent and hostile towards staff members . she was admitted to the inpatient psychiatry ward for a presumed acute stress reaction with psychosis . she remained uncooperative and was exhibiting delusions that she had to leave because her boyfriend had survived the shooting and was actually waiting for her at home . two days later , she was noted to have sialorrhea and was picking at her clothes and bed sheets . however , she was unresponsive after this seizure and would no longer verbalize or answer questions . the neurology consultant observed that she had minimal responsiveness to voice , had intermittent picking movements at her bed sheets or clothing and was reaching for any instruments used to examine her [ i.e. , stethoscope or reflex hammer ] . she also had a dysconjugate gaze when her eyelids were held open and was hyperreflexic throughout . the initial electroencephalogram ( eeg ) , performed 3  days after presentation , demonstrated frequent electrographic seizures arising independently from the right and left hemispheres . she was given intravenous ( iv ) lorazepam , started on intravenous fosphenytoin , and transferred to the neurological intensive care unit ( icu ) . a lumbar puncture was performed , showing 76  white blood cells / mm with a lymphocytic predominance ( 11  red blood cells / mm , a protein level of 43  mg / dl , and a glucose level of 112  mg / dl ) . the csf was sent for numerous studies including a full paraneoplastic panel , herpes simplex virus pcr , varicella zoster virus pcr , epstein  barr virus pcr , cytomegalovirus pcr , arbovirus panel , anti - nmda receptor antibody titer , cytology , and flow cytometry . brain mri with fluid - attenuated inversion recovery ( flair ) images on 7/6/2013 , 4  days after presentation , revealed abnormal high signal in the right medial temporal lobe . on repeat brain mri imaging done two days later on 7/8/2013 , she had hippocampal hyperintensity bilaterally on flair images and enhancement after gadolinium contrast administration ( fig additionally , her continuous eeg monitoring within the first few days began to demonstrate frontally maximal high - voltage beta activity superimposed on frontally maximal delta waves ( fig .  2 ) . this pattern of  extreme delta brush had been described as highly suggestive of anti - nmdar encephalitis . given suspicion for an autoimmune - mediated process causing her symptoms , 1000  mg of methylprednisolone was started on 7/9/2013 , 7  days after presentation . in addition , she was then started on plasmapheresis once the steroid course was completed . her csf result was positive for anti - nmda receptor antibodies , and her diagnosis was therefore confirmed as anti - nmda receptor encephalitis . numerous studies including ct torso , pelvic and vaginal ultrasound , pelvis mri , and a pet scan either showed no evidence of malignancy or were limited by body habitus . a pelvic ultrasound was repeated given persistent elevated concern for an occult malignancy and revealed a right ovarian mass that was concerning for an underlying tumor . on 8/14/2013 , 43  days after presentation , she underwent laparoscopic right salpingo - oophorectomy . surgical pathology report was consistent with a mature cystic teratoma , which was ultimately believed to be the etiology of her immune - mediated encephalitis . unfortunately , there was no evident response to treatment . despite completing 15 rounds of plasmapheresis , high - dose steroids , cyclophosphamide , rituximab , and ketamine , her oral  facial and limb dyskinesias continued to be pronounced , and she continued to have large fluctuations in temperature , blood pressure , and heart rate . her anti - nmdar antibody remains positive ( last tested on 11/11/2013 , 132  days after presentation ) . additionally , follow - up eeg performed on 10/31/2013 , 121  days after presentation , continued to show pronounced extreme delta brush ( fig .  3 ) . we report a 17.5-week follow - up of a young woman with anti - n - methyl - d - aspartate receptor ( anti - nmdar ) encephalitis associated with an ovarian teratoma . the diagnosis was confirmed by persistence of a positive serum anti - nmdar antibody and the continued presence of extreme delta brush ( edb ) on continuous eeg . extreme delta brush is a novel eeg finding seen in many patients with anti - nmdar encephalitis . in this particular patient , although specificity is uncertain , early diagnostic evaluation for malignancy should be pursued on the basis of clinical findings and edb before the titers return . because edb is associated with a more prolonged illness , whether the persistence of this pattern has further implications for outcome is unclear . whether there is a relationship between this edb pattern and antibody titers in serum and csf has yet to be determined . additionally , whether there is a relationship between persistence of the anti - nmdar antibody and continued edb is also unclear . however , the persistence of the finding has not been adequately correlated with outcomes or prognosis and requires further investigation .