What is the appropriate work‑up and initial management for a young female with autoimmune encephalitis?

Management of Young Female with Autoimmune Encephalitis

Immediately initiate a systematic diagnostic workup with brain MRI and/or EEG, perform lumbar puncture to rule out infection, send neuronal autoantibodies in both serum and CSF, and once infection is excluded, start high-dose intravenous methylprednisolone without waiting for antibody results. 1

Diagnostic Workup

Immediate Paraclinical Testing

• Brain MRI and/or EEG to identify focal or multifocal brain abnormalities 1
• Lumbar puncture is essential to:
  • Rule out infectious/neoplastic causes
  • Test for oligoclonal bands, IgG index, IgG synthesis rate
  • Send CSF for neuronal autoantibodies 1
• Serum testing for neuronal autoantibodies and other potential causes based on clinical presentation 1

Additional Testing When Initial Studies Are Uninformative

• Brain FDG-PET if high clinical suspicion persists despite negative MRI/EEG 1

Cancer Screening (Critical in Young Females)

Given the association with ovarian teratomas in young women, perform:

• CT chest, abdomen, pelvis with contrast (or MRI if CT contraindicated) 1
• If negative, add mammogram/breast MRI, pelvic ultrasound, and/or whole body FDG-PET based on specific antibody profile and risk factors 1

Acute Immunotherapy

First-Line Treatment

Start treatment empirically once infection is ruled out—do not wait for antibody confirmation 1, 2

• High-dose intravenous methylprednisolone (IVMP) is the preferred initial therapy 1
• Alternative first-line options if steroids contraindicated:
  • IVIG (preferred in agitated patients or bleeding disorders) 1
  • Plasma exchange/PLEX (5-10 sessions every other day; preferred in severe hyponatremia, high thromboembolic risk, or associated demyelination) 1

When to Escalate First-Line Therapy

If no improvement after initial treatment cycle:

• Add IVIG or PLEX to corticosteroids 1
• 62% of experts add a different first-line agent if initial therapy fails 1

For severe presentations from the outset (NMDAR-antibody picture, new-onset refractory status epilepticus, severe dysautonomia):

• Start combination therapy immediately (steroids + IVIG or steroids + PLEX) rather than sequential treatment 1

Second-Line Immunotherapy

If no clinical or radiological improvement 2-4 weeks after combined first-line therapy, escalate to second-line agents 1

Choice of Second-Line Agent

• Rituximab (preferred by 80% of experts):

  • Dosing: 375 mg/m² weekly × 4 weeks OR 1000 mg × 2 doses (2 weeks apart) 1
  • Use for antibody-mediated disease (NMDAR-antibody encephalitis, faciobrachial dystonic seizures) 1
  • Less toxic than cyclophosphamide 1

• Cyclophosphamide (600-1000 mg/m²):

  • Consider for cell-mediated disease (classical paraneoplastic syndromes, patients with known/suspected cancer) 1

Third-Line Options for Refractory Cases

If conventional second-line therapies fail, consider experimental approaches (minimal evidence):

• Tocilizumab (IL-6 inhibition)
• Bortezomib (proteasome inhibitor)
• Low-dose IL-2 1

Bridging/Maintenance Therapy

After acute treatment response, initiate:

• Gradual oral prednisone taper, OR
• Monthly intravenous immunoglobulin, OR
• Monthly intravenous methylprednisolone 1

Critical Pitfalls to Avoid

1. Do not delay treatment waiting for antibody results—antibody testing has long turnaround times and may be negative despite true AE 1, 2
2. Do not miss tumor screening—young females with AE have significant risk of ovarian teratoma; tumor removal is essential for recovery 1, 2
3. Do not use PLEX in agitated patients—IVIG is safer and more practical in this population 1
4. Do not undertreat severe presentations—combination therapy from the start improves outcomes in NMDAR-antibody encephalitis, status epilepticus, or severe dysautonomia 1
5. Recognize that MRI may be normal—AE often causes minimal structural damage, making diagnosis challenging; rely on clinical picture and CSF findings 3