Abstracts

Rationale: Rapidly progressive dementia (RPD) is defined by subacute or acute development of cognitive impairment, of which sporadic Creutzfeldt-Jakob disease (sCJD) is a rare but devastating disorder. The differential diagnosis of sCJD include treatable conditions, one of which is autoimmune encephalitis (AE). AE and sCJD often share similar clinical features, EEG patterns, and occasionally DWI-MRI findings. Expeditious diagnostic workup is necessary when either disease is suspected, and in turn to guide prompt treatment and prognostication. The aim of this observational study is to compare the clinical, EEG, and neuroimaging features between AE and sCJD, among which better characterization of EEG data may be revealing. Methods: We reviewed clinical notes, lab results, brain MRI findings, and the EEG data of 4 sCJD and 7 AE patients. AE were confirmed with autoantibodies in CSF or serum. sCJD were confirmed based on the updated sCJD clinical diagnostic criteria. Results: All 4 sCJD patients presented with subacute onset and rapidly progressive dementia, associated with symptoms such as gait instability/ataxia, apraxia, hallucination and aphasia. One patient was noted with clinical seizures that evolved into non-convulsive status epilepticus. One patient had myoclonus jerks. Ribboning hyperintensity on diffusion-weighted MRI (DWI-MRI) was seen in all 4 patients. Of the EEG features: 2 had periodic sharp-wave complexes (PSWC) , 1 had irregular periodic discharges, and the last had non-specific EEG findings. The patient presented with aphasia and clinical seizures were aggressively treated with anti-convulsants and sedation due to the concern for refractory status. Clinical suspicion of sCJD was raised after serial EEG and brain imaging were performed. CSF study confirmed the diagnosis with elevated Tau protein. Two of the 4 patients deceased within 6 months, and 2 others elected hospice care. Among 7 AE patients, 2 had anti-NMDAR antibody (Ab), 3 had anti-GABAbR Ab, 1 had anti-LGI-1 Ab, and 1 was diagnosed clinically without confirmed antibody. All patients, except the one with anti-LGI-1 ab, presented with prodromal infectious symptoms prior to the onset of personality changes and behavioral neuropsychiatric symptoms (agitation, behavioral outbursts, cognitive deficits). Most patients were also noted with dysautonomia and orofacial dyskinesia. AE with anti-NMDAR had a more uniform course with sequential multi-stage manifestations. Seizures were the main manifestation in patients with anti-GABAbR and anti-LGI-1. Brain imaging of AE patients were non-specific. Pseudo-cortical ribbon sign or focal cortical DWI signals were seen in the context of status epilepticus. Such ictal or post-ictal brain imaging changes were often transient and resolved after seizure suppression and immunotherapy. Periodic discharges, mostly lateralized were seen in AE patients with clinical seizures. Otherwise, the EEG of other AE patients showed non-specific delta slowing or normal findings. After immunotherapy, patients with AE survived, except for one patient who elected comfort care with comorbid small cell lung cancer. Conclusions: Differentiating between sCJD and AE remains challenging and is of utmost importance given the different prognosis and treatment. Due to overlap in early clinical presentations between sCJD and AE, high clinical suspicion for sCJD is needed if certain brain imaging findings (cortical ribbon sign) and PSWC EEG features are present. Specifically, serial EEG and brain imaging along with CSF analysis can assist in the diagnosis of sCJD, and should be promptly considered when there is a lack of response to immunotherapies. Funding: No funding