Management of Post-Viral Encephalitis with Normal CSF
This patient with abnormal movements, drowsiness, and recent viral infection with normal CSF findings most likely has autoimmune encephalitis (specifically NMDA receptor or VGKC-complex antibody-associated encephalitis), and should be treated immediately with high-dose corticosteroids (0.5 mg/kg/day oral prednisolone) combined with either intravenous immunoglobulin (0.4 g/kg/day) or plasma exchange. 1
Clinical Recognition and Diagnosis
This presentation is classic for autoimmune encephalitis following viral infection:
Abnormal movements (choreoathetosis, orofacial dyskinesia) with altered consciousness after a viral prodrome strongly suggests NMDA receptor antibody-associated encephalitis, which characteristically presents in two phases: initial confusion/seizures followed by movement disorders and autonomic dysfunction 1
Normal CSF does NOT exclude encephalitis—approximately 90% of NMDA receptor encephalitis cases have normal MRI initially, and CSF can be normal or show only mild lymphocytosis 1
The lymphocytic predominance you describe is consistent with viral or autoimmune encephalitis, though CSF may be completely normal in up to 10% of proven viral encephalitis cases, especially early in illness 1
Immediate Management Algorithm
Step 1: Neuroimaging and Further Investigations
Obtain MRI brain with gadolinium immediately (preferred over CT) to look for hippocampal or white matter signal changes, though normal imaging does not exclude diagnosis 1
Send serum and CSF for autoimmune antibody panels including NMDA receptor antibodies, VGKC-complex antibodies, and other neuronal antibodies 1
Screen for underlying malignancy, particularly ovarian teratoma in females (20-50% of female patients with NMDA receptor encephalitis have teratomas) 1
Step 2: Initiate Immunotherapy Without Delay
Do not wait for antibody results to start treatment—the clinical presentation warrants immediate immunosuppression:
Start oral corticosteroids at 0.5 mg/kg/day prednisolone 1
Add either IVIg (0.4 g/kg/day for 5 days) OR plasma exchange as combination therapy is superior to monotherapy 1
If no response within 2 weeks, escalate to second-line agents: rituximab or cyclophosphamide 1
Step 3: Supportive Care and Monitoring
Admit to monitored setting given drowsiness and risk of autonomic instability, hypoventilation, and seizures 1
Seizure prophylaxis may be needed as seizures occur in the first phase of NMDA receptor encephalitis 1
Arrange multidisciplinary rehabilitation including neuropsychology, neuropsychiatry, speech therapy, physiotherapy, and occupational therapy 1
Critical Pitfalls to Avoid
Do not discharge this patient without a definitive or suspected diagnosis and follow-up plan—96% of encephalitis patients report ongoing complications, yet 33% are discharged without outpatient follow-up 1
Do not assume viral encephalitis and stop at supportive care—the movement disorder component strongly suggests autoimmune etiology requiring immunosuppression 1
Do not delay treatment waiting for antibody confirmation—antibodies may take weeks to return, and early immunotherapy improves outcomes 1
Normal CSF should not reassure you—encephalitis can present with normal CSF, especially in immunocompromised patients or early in disease 1
Expected Clinical Course
With appropriate immunotherapy, confusion and seizures typically improve rapidly, but memory recovery may take months to years 1
Median hospital stay is 160 days for NMDA receptor encephalitis, with many requiring ICU admission 1
Approximately 30% of patients relapse despite treatment, necessitating long-term immunosuppression with agents like azathioprine 1
Antibody levels normalize within 3-6 months with treatment, and steroids can be tapered over 12 months once antibodies are undetectable 1
Long-term Follow-up
Schedule outpatient neurology follow-up before discharge with clear rehabilitation plans 1
Annual tumor screening for several years, particularly if treatment response is poor or relapses occur 1
Monitor for neuropsychiatric sequelae including anxiety, depression, and obsessive behaviors, which often emerge after discharge 1