NIMG-74. A CASE OF NON-CLASSICAL PARANEOPLASTIC ENCEPHALITIS SUPPORTED BY CHANGES ON MRI AND FDG-PET

Abstract

Here we present a case of definite non-classical paraneoplastic encephalitis with clinical and radiographic (MRI, PET) response after systemic chemotherapy. Our patient was a 67-year-old female with a 50-year history of smoking developing progressive dementia. Her first symptom was memory impairment for which her initial neurologic evaluation was negative, but her MMSE score of 28 yielded the diagnosis of pseudodementia. She was started on citalopram to no avail and subsequently developed hallucinations with paranoid ideation and violent outbursts. She was hospitalized for respiratory distress at a non-affiliated hospital, where her encephalopathy workup revealed absent routine serum paraneoplastic antibody titers, mild CSF pleocytosis with lymphocytic predominance. There was no electrographic evidence of seizures. MRI brain showed serpiginous and nodular cortical T2/FLAIR hyperintense lesions affecting the temporal poles, the right insular and frontal cortex. None of these lesions exhibited contrast-enhancement or restricted diffusion. Three weeks later, she was referred to our institution where repeat MRI revealed new left insular T2/FLAIR involvement yet no new enhancement or diffusion restriction. Brain FDG-PET showed generalized cortical hypometabolism with hypermetabolic areas corresponding to T2/FLAIR lesions. Whole-body PET revealed a hypermetabolic lung mass proven to be SCLC on biopsy. As the brain-imaging pattern was atypical for metastatic disease, paraneoplastic encephalitis was favored and brain irradiation was postponed to evaluate response to systemic treatment. After two cycles of etoposide/cisplatin, agents with poor CNS penetration in the absence of blood-brain barrier breakdown, the patient exhibited modest but significant clinical improvement. Her repeat imaging showed near-complete resolution of insular involvement and marked reduction in the extent of T2/FLAIR cortical hyperintensities without any signs of necrosis. At the same time FDG-PET exhibited reduced number of hypermetabolic lesions and improved generalized cortical metabolism. Our findings perhaps represent imaging evidence of network-wise recovery in the setting of paraneoplastic syndrome treated with systemic chemotherapy.