Diagnostic Evaluation in Suspected AIE
In this page, you will find the recommended investigations in suspected AIE based on the Canadian Consensus Guidelines
Continue scrolling below to review the full discussion and list of investigations
Recommended Investigations for All Patients Suspected to Have AIE
MRI brain with / without gadolinium
MRI brain with/without gadolinium should be obtained for all patients with suspected AIE
Neural Antibody Testing
Comprehensive panel-based serum-CSF antibody testing is recommended for all patients. Laboratory methodology is critically important in neural Ab testing because the choice of assay directly impacts diagnostic sensitivity, specificity, and clinical interpretation. Click on the link below for additional information
EEG
EEG can provide evidence of focality when MRI is normal
CSF Examination
CSF examination is recommended for all patients to assess for inflammatory changes, rule out mimics and detect neural antibodies. Scroll down to review recommended testing
Additional Laboratory Testing (Blood)
Additional blood testing is strongly recommended to establish the diagnosis and exclude common mimics including routine, metabolic, systemic autoimmune, infectious and neural antibody testing. Scroll down to review the recommended tests
Malignancy Screening
All subtypes of AIE may be associated with malignancies and a paraneoplastic presentation cannot be ruled out clinically. Therefore, screening is recommended for all patients at initial presentation. Scroll down to review the recommended three-step process for malignancy screening
CSF Examination
Tests in bold are strongly recommended. The remaining tests are recommended if clinically indicated based on the patient history
| Routine | ☐ Cell count and differential ☐ Protein ☐ Glucose ☐ CSF protein electrophoresis to identify CSF-specific oligoclonal bands ☐ CSF IgG and albumin to calculate IgG index ☐ Cytology |
| Infectious | ☐ HSV, VZV, enterovirus PCR ☐ Bacterial culture and sensitivity ☐ Mycobacterial culture, AFB smear ☐ Cryptococcus testing ☐ Syphilis VDRL (if serum testing positive) ☐ CMV, HHV-6 ☐ Fungal cultures ☐ JCV PCR |
| Neural Antibody Testing | ☐ Comprehensive Panel Based (Paired with serum) |
| Malignancy suspected of leptomeningeal involvement | ☐ Flow cytometry |
| ☐ Hold ≥ 3 ml for future testing |
Additional laboratory Test (Blood)
Tests in bold are strongly recommended. The remaining tests are recommended if clinically indicated based on the patient history
| Routine | ☐ Complete blood count ☐ Electrolytes, creatinine ☐ Liver function tests ☐ Glucose ☐ Serum along with CSF protein electrophoresis to identify CSF-specific oligoclonal bands ☐ Serum along with CSF IgG and albumin to calculate IgG index |
| Metabolic | ☐ TSH ☐ Vitamin B12 ☐ Toxicology |
| Systemic Autoimmune | ☐ ANA and ENA panels ☐ CRP ☐ Anti-dsDNA, C3, C4, ANCA panel |
| Infectious | ☐ HIV, Syphilis screening ☐ Hepatitis B (Core Ab, Surface Ab, Surface Ag)/Hepatitis C, TB skin test/Quantiferon TB ☐ Respiratory viral panel ☐ Arbovirus serology, Lyme serology ☐ Fungal, parasitic, helminthic, amoebic tests (Consider infectious disease consultation) |
| Neural Antibody Testing | Comprehensive panel-based antibody testing (Paired with CSF) |
Other Antibody Testing Based on Clinical Phenotype | ☐ MOG antibody ☐ Aquaporin-4 antibody ☐ GQ1b ganglioside antibody |
Malignancy Screening
Is a three-step process including CT body, sex specific malignancy screening and a whole-body PET scan. The process is terminated early if a neoplasm is detected or if three steps are exhausted without a neoplasm detected.
For additional information, review the figure below:
Reference: Hahn C, Budhram A, Alikhani K, et al. Canadian Consensus Guidelines for the Diagnosis and Treatment of Autoimmune Encephalitis in Adults. Can J Neurol Sci. Published online February 5, 2024. doi:10.1017/cjn.2024.16