Case Presentation: A 38 yr. old female presented with personality and behavior changes for the last 4 months which were described as episodes of impulsivity and outbursts of anger. Patient endorsed frequent episodes of headache and confusion caused by strong odors such as spices and garlic. She had progressive short-term memory deficit, often asking same questions repeatedly. Neurology consultation included extensive workup, which resulted in a normal MRI (per radiology read) and EEG. Her Lumbar puncture, TSH, thiamine, ammonia, drug screen, ethanol tox screen, ceruloplasmin, folate, heavy metals, and Lyme disease antibodies were normal. She was discharged with neurology follow-up alongside pending CSF autoimmune analysis. One week later, she had a tonic-clonic seizure while sleeping. She was started on Keppra, however her LTVM continued to show left and right subclinical focal seizures requiring the addition of Vimpat, phenytoin, and Onfi for incomplete control. Repeat lumbar puncture revealed negative 14-3-3 but mild leukocytosis. A detailed review of her initial MRI uncovered bifrontal sulcal and juxta-cortical FLAIR changes. She was discharged on four epileptics as noted above. Ten days later, her CSF autoimmune analysis resulted positive for VGKC- LGI1 antibodies. She was hospitalized for IV steroids resulting in resolution of difficult to control epileptiform discharges and discontinuation of phenytoin, Onfi and phenytoin. She was discharged on Vimpat and steroid taper. Unfortunately, she was readmitted ten days later, due to a breakthrough seizure with a sodium of 121 mg/dl on presentation. Her labs were consistent with SIADH. EEG showed no seizure-like activity. She continues to follow with neurology as an outpatient with plans to initiate immunomodulation with rituximab and has been seizure free since her last hospitalization.

Discussion: Voltage-gated potassium channels (VGKC) are thought to be the target of antibodies against LGI1, CASPR2, and Contactin-2.13.1 (1) . Leucine-Rich Glioma-Inactivated-Protein-1 (LGI1) autoimmune encephalitis (AE), an uncommon (0.7/100,000 patients) neurological disorder, largely affecting elderly males (median age 60) with progressive memory loss, Facio brachial dystonia seizures (FBDS) and behavior changes (2). Typical MRI brain shows bilateral T2 weighted and FLAIR changes in the medial temporal lobes. CSF analysis is usually normal with occasional leukocytic pleocytosis (3) . Approximately 60% of cases have hyponatremia due to SIADH. (1,4). Paraneoplastic associations are rare (5). Treatment includes corticosteroids, IVIG, or plasma exchange. Immunomodulation with rituximab is considered second-line for refractory or recurrent disease (6). Our patient differed from a typical presentation of LGI1 autoimmune encephalitis by following distinguishing features. The patient’s demographics are middle-aged female, whereas the median age and sex are classically elderly males. Her tonic-clonic seizures followed cognitive deficit rather than well-documented FBDS preceding the memory changes. Lastly, the MRI changes were noted in bifrontal-juxtacortical regions rather than temporal areas.

Conclusions: This is a report of a case of autoimmune encephalitis in a middle-aged woman. Features including behavior changes, chronic-progressive cognitive decline, atypical MRI changes, late-onset hyponatremia, and absence of FBDS make this case particularly unique to the LGI1 encephalitis.