An advanced molecular imaging technique may help detect and monitor neuroinflammation in patients with anti-vimentin antibody-associated autoimmune encephalitis when conventional magnetic resonance imaging (MRI) lacks characteristic abnormalities.
Researchers described a male patient in his late 40s who developed diplopia and gait instability about 6 weeks following COVID-19 vaccination, followed by progressive limb numbness and intermittent swallowing difficulties. Initial cranial and cervical MRI were unremarkable. Following subsequent neurologic deterioration, electrophysiological testing identified sensory axonal injury and brachial plexopathy. Cerebrospinal fluid (CSF) testing detected anti-vimentin immunoglobulin G (IgG) antibodies despite negative serum results. The researchers used fluorine (F)-18–DPA714 positron emission tomography (PET)/MRIto assess neuroinflammatory activity.
Functional assessments included the modified Rankin Scale (mRS), Clinical Assessment Scale for Autoimmune Encephalitis (CASE), and Montreal Cognitive Assessment (MoCA). The patient received intravenous Ig (IVIG)at 0.4 g/kg/day for 5 days, followed by monthly subcutaneous ofatumumab maintenance therapy. Clinical evaluations, antibody testing, and PET/MRI were repeated at 3 months.
At baseline, conventional MRI demonstrated bilateral white matter lesions without the characteristic corticospinal tract abnormalities previously associated with anti-vimentinIgG-associated autoimmune encephalitis. In contrast, F-18–DPA714 PET/MRI revealed elevated tracer uptake in the mesial temporal lobe, frontal lobe, and brainstem. Uptake in the left mesial temporal lobe was 25% above the normal reference,brainstem uptake was 9% above reference values, and left and right frontal lobe uptake was elevated by 14% and 11%, respectively.
At the 3-month follow-up, tracer uptake decreased across the evaluated brain regions. The standardized uptake value ratio in the left mesial temporal lobe declined from 1.61 to 1.11,brainstem uptake decreased from 1.69 to 1.33, and left and right frontal lobe uptake declined by 15% and 13%, respectively. Follow-up conventional MRI revealed no new or active lesions.
These imaging changes accompanied improvements in neurologic function following IVIG induction and ofatumumab maintenance therapy. The patient's gait instability improved, and limb numbness partially resolved. His mRS score decreased from 2 to 1, while his MoCA score increased from 29 to 30. The CASE score remained unchanged at 1. Slight numbness of the right fingertip persisted, but no relapse or significant treatment-related adverse reactions were reported during the 3-month follow-up.
Additional diagnostic findings supported the presence of an autoimmune neurologic process. CSF testing demonstrated anti-vimentinIgG positivity at a titer of 1:10 and type III oligoclonal bands, indicating intrathecal Ig production. Serum testing remained negative for anti-vimentinIgG, while repeat CSF testing at 3 months continued to show antibody positivity at the same titer despite clinical improvement.
The patient's peripheral neurologic abnormalities expanded the previously described clinical presentation of the disorder. Electromyography provided objective evidence of peripheral nervous system involvement. Earlier reports had predominantly characterized anti-vimentinIgG-associated autoimmune encephalitis through central nervous system manifestations, including cerebellar ataxia, cranial nerve abnormalities, and pyramidal tract signs. The current report documented peripheral neuropathy in a middle-aged patient, extending the reported demographic and clinical spectrum.
However, the mechanism underlying peripheral nerve involvement remains uncertain. Although extensive antibody screening reduced the likelihood of a separate antibody-mediated disorder, available testing could not definitively exclude all potential peripheral nerve-directed autoantibodies. Whether anti-vimentinIgG directly contributes to peripheral nerve injury or whether these manifestations occur indirectly through central nervous system inflammation remains unresolved.
The report described short-term improvement following ofatumumab maintenance therapy. The researchers selected the anti-CD20 monoclonal antibody based on the antibody-mediated nature of the disorder and emerging evidence supporting B-cell depletion in autoimmune encephalitis. However, no established maintenance treatment strategy currently exists for anti-vimentinIgG-associated autoimmune encephalitis. The findings did not establish the independent effectiveness of ofatumumab.
The findings are limited by the single-patient design and 3-month follow-up, which prevented conclusions regarding broader diagnostic performance, long-term treatment outcomes, or relapse prevention. Because IVIG induction preceded ofatumumab maintenance therapy, the relative contribution of each treatment to clinical improvement could not be determined. Further investigation is needed to establish whether changes in F-18–DPA714 tracer uptake reliably reflect disease activity and treatment response across patients with this rare disorder.
The imaging technique “exhibits great potential as a sensitive tool for diagnosis and treatment monitoring,” wrote lead study author Siqi Tu, of the Department of Neurology and Institute of Neurology at Shanghai Jiao Tong University Medical School Affiliated Ruijin Hospital, and colleagues.
The study authors reported no conflicts of interest.
Source: BMJ Neurology Open
