A 71-year-old female with history of breast cancer in the 1990s, post-mastectomy presented after being found unresponsive. She was later seen to have witnessed seizures.  

Her initial MRI brain was unrevealing. EEGs exhibited left-sided temporal delta slowing with sharp waves. Lumbar puncture showed normal opening pressure with minimally elevated protein (45.1mg/dL). CT chest/abdomen/pelvis unveiled thymic hyperplasia and multiple lung nodules; MRI chest confirmed two peripherally enhancing mediastinal nodes. 

She remained confused and intermittently aphasic for 10 days following the admission, though no further seizures were captured. EEG showed persistent left temporal slowing and sharp waves, and new right frontocentral discharges. Repeat MRI in 10 days showed left greater than right hippocampal and thalamic FLAIR hyperintensity.

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She was started on Levetiracetam 500mg twice daily, a 10-day course of IV Methylprednisolone 1g daily, followed by a 5-day course of IVIG. 

Her mental status improved significantly (specifically her delayed recall improved from 0/5 to 5/5 post-treatment), returning to baseline, but she continued to struggle slightly with simple calculations. EEG showed improvement in left temporal slowing and resolution of left temporal sharp waves.   

Late in the hospital course, her paraneoplastic CSF workup came back positive for anti-Hu antibody, confirming the suspected diagnosis of limbic encephalitis in the setting of possible malignancy. 

She is planned for additional cancer workup, including a PET scan, given the concern for metastatic disease.