Fluorodeoxyglucose positron emission tomography findings in NMDA receptor antibody encephalitis

Abstract

A 28-year-old woman presented with a seven day history of insomnia, and changes in mental status. She was agitated, confused with visual hallucinations and combative behaviour. On day 4, she developed partial complex seizure with impairment of awareness and automatisms of lip smacking. During the first 2 weeks, she had become increasingly drowsy and confused, her level of conciousness was severely impaired, with no response to painful stimuli, and orofacial-limb dyskinesias appeared. These symptoms and central hypoventilation led to her being sedated on mechanical ventilation for 4 weeks. On day 31 after admission, a cardiac arrhythmia, characterized by alternating repeated episodes of tachycardia and bradycardia was observed.The serum did not contain anti-nuclear, doublestrand DNA, SS-A or thyroid antibodies. Tumor markers were normal. Lumbar pucture on day 8 after the onset of symptoms showed lymphocytic pleocytosis (22/mm 3 ) with normal protein and glucose concentrations. Cerebrospinal fluid cytology was negative for malignant cells. Anti-voltage-gated potassium channel complex antibodies were not detected.Computed tomography of the chest, abdomen and pelvis was negative. Brain MRI with gadolinium-enhanced T1-weighted, T2-weighted, perfusion, diffusion and FLAIR images on days 2, 12, 31 and 63 were normal.Intravenous immunoglobulin (IVIG) was given at a dose of 400 mg/kg/day for five days (days 31-36). By day 38 she had improved significantly, was awake and alert, and following commands without dyskinesias. On day 42, FDG-PET of the body was normal, but in the brain (Figure) showed increased metabolism in right hemisphere apparently in the territory of the middle cerebral artery and in the left cerebellum compatible with cerebellar diaschisis. NMDA receptor antibodies were positive.NMDA receptor antibody encephalitis is a highly characteristic syndrome evolving in 5 stages, namely, the prodromal phase, psychotic phase, unresponsive phase, hyperkinetic phase, and gradual recovery phase, but only two clear stages have been supported with experimental data . This disorder has often a relapsing course, therefore once patients overcome the hyperkinetic phase, gradual improvement happens in months and full recovery in 3 or more years.Good clinical outcomes, as defined by reductions in modified Rankin scores, correlates with decreased NMDA receptor antibody levels and were associated with early (<40 days) administration of immunotherapies in non-paraneoplastic patients.NMDA receptor antibodies in serum and CSF are considered to be highly specific for this condition 2 . Recent studies show that this disorder can occur even in the absence of teratoma in up to 40% of patients, and even boys and adult men has been affected 1 . In the 45% of patients the brain MRI is normal 2 . In our patient, brain FDG-PET managed to detect the abnormality, whereas MRI appeared normal on several occasions. Different patterns has been reported in NMDA receptor encephalitis, with hypermetabolism unilateral affectation of temporal lobe, b...

Anti-N-methyl-D-aspartate Encephalitis Concomitantly with Tall-cell Variant Papillary Thyroid Carcinoma

“…Recommendations for the treatment of NMDA encephalitis suggest first-line immunosuppression using any combination of intravenous steroids, intravenous immunoglobulin, and/or plasmapheresis [1,10]. Screening also is necessary given the association with tumors [5,6]. If a tumor is identified, removal is recommended.…”

“…If a tumor is identified, removal is recommended. If a tumor is not found, screening has been recommended every six months for approximately four years [1,5-6]. Second-line therapy for NMDA encephalitis includes B and T cell-mediated immunotherapy with rituximab and/or cyclophosphamide [10].…”

“…Management includes immunosuppression and screening with removal of malignancy, if present [1, 5]. Fluorodeoxyglucose positron emission tomography (FDG-PET) can increase the yield of detecting occult malignancy if other imaging studies are unremarkable [6-7]. Immunosuppression is required in all cases [1].…”