Evidence suggests that basic CSF parameters, such as elevated protein and white blood cell counts, are some of the most sensitive and specific tests for autoimmune encephalitis.2 Thus, if the patient is amenable and logistical factors are in place, it may be reasonable to pursue LP earlier in some cases without waiting for serum antibody assays to return (these results can take several weeks). CSF inflammatory changes without neuronal antibodies should lead to other diagnostic considerations (eg, systemic inflammatory disease, psychosis attributed to systemic lupus erythematosus).7 While nonspecific, serum laboratory values that may increase suspicion of anti-NMDA receptor encephalitis include hyponatremia6 and an elevated neutrophil-to-lymphocyte ratio (NLR).28 An NLR >4 in conjunction with CSF albumin-to- serum albumin ratio >7 is associated with impaired blood brain barrier integrity and a worse prognosis for those with anti-NMDA receptor encephalitis.28
Additional clinical features that may sway decisions in favor of obtaining LP despite negative findings on EEG, MRI, and serum antibodies include increased adverse reactions to antipsychotics (eg, neuroleptic malignant syndrome), prodromal infectious symptoms, known tumor, or new-onset neurologic symptoms after initial evaluation.2,8
Table 2 summarizes key features of laboratory and diagnostic findings in anti-NMDA receptor encephalitis.
When should you pursue a more extensive workup?
There are some practical tools and rating scales to help clinicians conceptualize risk for autoimmune encephalitis. For psychiatric purposes, however, many of these scales assume that LP, MRI, and EEG have already been completed, and thus it is challenging to incorporate them into psychiatric practice. One such tool is the Antibody Prevalence in Epilepsy and Encephalopathy scale; a score ≥4 is 98% sensitive and 78% to 84% specific for predicting antineural autoantibody positivity.10 Table 3 describes warning signs that may be useful in helping clinicians decide how urgently to pursue a more extensive workup in the possibility of autoimmune encephalitis.
The importance of catching anti-NMDA receptor encephalitis is underscored by the fact that appropriate treatment is very different than for primary psychosis, and outcomes worsen with delay to appropriate treatment.20 Without treatment, severe cases may progress to autonomic instability, altered consciousness, and respiratory compromise warranting admission to an intensive care unit. While the details are beyond the scope of this review, the recommended treatment for confirmed cases of anti-NMDA receptor encephalitis includes tumor removal (if indicated), reducing inflammation (steroids), removing antibodies via IV immunoglobulins, or plasma exchange.8,29 Progression of the disease may warrant consideration of rituximab or cyclophosphamide. In nonresponsive cases, third-line treatments include proteasome inhibitors or interleukin-6 receptor antagonists.8 For patients with severe catatonia, some studies have investigated the utility of electroconvulsive therapy.30 Conceptually, clinicians may consider the utility of antipsychotics as similar to recommendations for hyperactive delirium for the management of psychotic symptoms, agitation, or insomnia. However, given the risk for antipsychotic intolerance, using the lowest effective dose and vigilant screening for the emergence of extrapyramidal symptoms, fever, and autonomic instability is recommended.
Finally, something objective
Ms. L receives haloperidol 2 mg and undergoes an MRI without contrast. Findings are unremarkable. A spot EEG notes diffuse background slowing in the theta range, prompting lumbar puncture. Findings note 0.40 g/L, 0.2 g/L, and 3.5 for the total protein, albumin, and albumin/CSF-serum quotient (QAlb), respectively; all values are within normal limits. A mild lymphocytic pleocytosis is present as evidenced by a cell count of 35 cells/µL. The CSF is sent for qualitative examination of immunoglobulin G and electrophoresis of proteins in the CSF and serum, of which an increased concentration of restricted bands (oligoclonal bands) in the CSF but not the serum would indicate findings of oligoclonal bands. CSF is sent for detection of anti-NMDA receptor antibodies by indirect immunofluorescence, with a plan to involve an interdisciplinary team for treatment if the antibodies return positive and to manage the case symptomatically in the interim.
A small subpopulation of patients who present with apparent first-episode psychosis will have symptoms caused by autoimmune encephalitis (specifically, anti-NMDA receptor encephalitis). We provide 4 screening questions to determine when to pursue a workup for an autoimmune encephalitis, and describe relevant clinical symptoms and warning signs to help differentiate the 2 conditions.
- Askandaryan AS, Naqvi A, Varughese A, et al. Anti-N-methyl-D-aspartate receptor encephalitis: neuropsychiatric and multidisciplinary approach to a patient not responding to first-line treatment. Cureus. 2022;14(6):e25751.
- Kayser MS, Titulaer MJ, Gresa-Arribas N, et al. Frequency and characteristics of isolated psychiatric episodes in anti-NMDA receptor encephalitis. JAMA Neurol. 2013;70(9):1133-1139.
Drug Brand Names
Clozapine • Clozaril
Haloperidol • Haldol
Olanzapine • Zyprexa
Quetiapine • Seroquel
Rituximab • Rituxan