Episode 55: Undifferentiated encephalopathy and autoimmune encephalitis, with Casey Albin

How to evaluate the patient with unexplained encephalopathy, and a practical approach to diagnosing autoimmune encephalitis with an emphasis on anti-NMDA receptor encephalitis—with Dr. Casey Albin (@CaseyAlbin), neurologist and neurointensivist, assistant professor of Neurology and Neurosurgery at Emory, and part of the NeuroEmcrit team. Claim your CME credit here! Find us on Patreon here! Buy your merch here! Takeaway lessons * Common causes of unexplained encephalopathy are: * Metabolic/systemic problems (myxedema, hypercarbia, uremia, vitamin deficiency, etc), which are common, but often found on routine labs. * Toxicologic exposures (drugs, heavy metals like Wilson’s, etc) * Primary neurologic events. These differentiate into acute and subacute processes. * In the altered patient found down with normal CT head and grossly normal labs, consider seizure and tox causes. * Give thiamine indiscriminately and widely to patients with altered mental status; it is harmless and Wernicke-Korsakoff may fool you. * Start with the history and meds. Simple intoxications like baclofen overdose can cause incredibly dense coma. * Inquire as to recent history of behavioral changes, neurologic phenomena, illness, etc. Prolonged or subacute symptoms significantly narrow the differential of a neurologic cause. * Always consider basilar artery stroke in the obtunded patient with a non-focal exam! Get a CTA early to evaluate the posterior circulation, as they may be a candidate for thrombolysis or thrombectomy. * With an unexplained diagnosis suspected to be neurologic in nature, have a low threshold for obtaining MRI (generally with gadolinium), lumbar puncture, and EEG. The urgency and order of these may depend on clinical suspicion, other tests, and availability. A spot EEG to rule out status epilepticus, followed by either LP or MRI (whichever is available first) is often a good sequence. * Have a relatively high threshold to start anti-epileptics for “seizure risk” or for vaguely epileptiform activity on EEG in the absence of true seizure, particularly if continued EEG monitoring (either continuous or frequent spot studies) are readily available. These drugs tend to remain prescribed for a long time, are not often discontinued by downstream providers, and can lead to future polypharmacy and lifestyle impacts. * To unpack autoimmune causes, build a syndrome by considering the timeline and the affected areas (e.g. portions of the brain or spine involved on imaging). * Creutzfeldt-Jakob disease should be suspected from the clinical history, or classic MRI findings such as cortical ribboning and “hockey sticks” in the basal ganglia. Without some specific suspicion, testing is usually not indicated. * A normal brain MRI can occur in some autoimmune encephalitides. For instance, anti-NMDAR encephalitis can have absolutely normal MRIs, which can be a helpful differentiator from limbic encephalitis (the latter tending to have characteristic MRI findings). * The Mayo Clinic and ARUP laboratories have a broad autoimmune encephalitis panel that can be sent for undifferentiated encephalitis; it tests for multiple antibodies and is updat...