Autoimmune Encephalitis is an inflammatory condition of the brain due to antibodies against onconeuronal proteins. Paraneoplastic Parkinsonism is very rare. We report the first case of AMPA receptor encephalitis presenting with symptoms of parkinsonism, an atypical presentation of a rare entity. 

A 71-year-old female with multiple comorbidities presented in a state of stupor with complaints of insidious onset slowly progressive recent memory impairment, progressive slowness in performing daily activities, inability to communicate, and acute onset urinary incontinence. CNS examination initially showed a GCS of E2V1M4 with Grade 2 rigidity in all extremities. MRI Brain showed subtle T2 FLAIR hyperintensities in the peri-ventricular and subcortical white matter. Serum and CSF studies showed AMPA 1 antibody positivity. The FDG PET showed an avid speculated soft tissue density lesion in the upper inner quadrant of the right breast with active right axillary lymph nodes (Histopathology- Infiltrating duct carcinoma Grade 2 NST T2N2aMx). The patient was managed using IVIg and steroids following which her sensorium improved to a GCS of E4M6V5. UPDRS at this point was 29. She subsequently underwent therapy for her tumor following which there was a significant decrease in parkinsonian symptoms and an improvement in memory without the use of any antiparkinsonian medications (UPDRS score-6).  During the four years of follow-up, she has remained independent and can perform all her activities of daily living. Hence this autoimmune encephalitis case can be classified as a definite paraneoplastic neurological syndrome (PNS Care score-9).

We propose that Parkinsonism, in our case, is probably a paraneoplastic neurological syndrome associated with antibodies against the AMPA receptor, as the symptoms and signs recovered with cancer treatment.