Management After IVMP and IVIG in Anti-LGI1 Encephalitis
If there is no clinical, radiological, or electrophysiological improvement 2-4 weeks after completing combined first-line therapy (IVMP + IVIG), initiate second-line immunotherapy with rituximab, as anti-LGI1 encephalitis is an antibody-mediated autoimmunity. 1
Immediate Assessment
Before proceeding, evaluate for:
- Clinical response: Assess cognitive function (especially memory), seizure control (including faciobrachial dystonic seizures), and overall functional status using standardized scales (CASE score, mRS)
- Radiological changes: Repeat brain MRI to look for resolution or persistence of medial temporal lobe hyperintensities
- Electrophysiological improvement: Follow-up EEG if initially abnormal
Treatment Algorithm Based on Response
If Patient Shows Improvement After IVMP + IVIG
Start bridging/maintenance therapy immediately 1:
- Oral prednisone taper: Begin with gradual taper over 3-6 months
- Alternative: Monthly IVIG or IVMP infusions during the taper period
If No Improvement After 2-4 Weeks of Combined Therapy
Proceed directly to second-line immunotherapy 1:
Rituximab is the preferred second-line agent because:
- Anti-LGI1 encephalitis is antibody-mediated (surface antigen)
- Rituximab targets B-cell mediated autoimmunity effectively
- Multiple case reports demonstrate dramatic improvement with rituximab when first-line therapy fails 3
Do NOT use cyclophosphamide - this is reserved for cell-mediated autoimmunity (classical paraneoplastic syndromes with intracellular antigens) 1
Alternative Second-Line Options
If rituximab fails or is contraindicated:
- Plasma exchange (PLEX): 5-10 sessions every other day 1
- Particularly effective in refractory cases
- Consider first if patient has severe hyponatremia or high thromboembolic risk
- Avoid in agitated patients or those with bleeding disorders
Novel/Experimental Therapies
If conventional second-line therapies show no clear improvement 1:
- Efgartigimod (FcRn antagonist): Emerging evidence shows rapid efficacy in reducing anti-LGI1 antibody titers when combined with methylprednisolone 4
- Tocilizumab (IL-6 inhibitor)
- Bortezomib
Note: These have minimal supporting evidence and should only be considered after exhausting conventional options
Critical Considerations
Anti-LGI1 Encephalitis is Highly Steroid-Responsive
- This condition is specifically noted as steroid-responsive, particularly for faciobrachial dystonic seizures 1
- If initial IVMP was inadequate, consider whether the dose or duration was sufficient before escalating
Tumor Screening is Essential
- Anti-LGI1 can be paraneoplastic (though less commonly than other antibodies)
- Ensure CT chest/abdomen/pelvis has been completed
- Consider whole-body FDG-PET if initial screening negative 1
Common Pitfalls to Avoid
Waiting too long to escalate: The 2-4 week window is critical - don't delay second-line therapy if there's no response 1
Using cyclophosphamide instead of rituximab: This is a common error - cyclophosphamide is for intracellular antigen syndromes, not surface antibody conditions like anti-LGI1 1
Inadequate maintenance therapy: Even with good initial response, patients need bridging therapy to prevent relapse 1
Ignoring persistent cognitive impairment: This remains a major disability contributor even after immunotherapy and requires sustained management 5
Overlooking hyponatremia: Severe hyponatremia is common in anti-LGI1 encephalitis and may influence choice of second-line therapy (favor PLEX over IVIG) 1
Monitoring During Treatment
- Serial antibody titers: Track serum anti-LGI1 levels to assess treatment response 4
- Functional assessments: Regular CASE scores, mRS, and cognitive testing (MMSE)
- Adverse events: Particularly with prolonged steroid use - monitor for diabetes, hypertension, infections 5
- Relapse surveillance: Long-term follow-up essential as relapses can occur 2, 6