Objective:

To report a case of mGlur1 encephalitis presenting with hyperfamiliarity of faces (HFF) and musical seizures.

Background:

mGluR1 antibody-related encephalitis (mGluR1-ARE) is a rare autoimmune disease affecting the cerebellum. There is limited data describing its presentation. Despite ataxia and dysarthria being common in mGluR1-ARE, musical hallucinations and HFF are very rare.

Design/Methods:

A 65-year-old Caucasian woman presented to the hospital with a week of musical hallucinations, HFF, gait imbalance and hearing loss. Physical exam revealed dysarthria and bilateral appendicular and axial ataxia. CTA Head/Neck, MRI brain, metabolic, infectious, paraneoplastic, and vitamin testing were normal. Serology revealed elevated anti-thyroglobulin antibodies (anti-TG), but normal anti-thyroperoxidase antibodies. TSH was low; free T4 was normal. EEG revealed no seizures but rare frontotemporal sharp waves with risk of focal seizures from the frontotemporal region. Levetiracetam controlled the musical hallucinations and HFF. Treatment with methylprednisolone and IVIG demonstrated substantial improvement in ataxia over several weeks. Patient was discharged to rehabilitation with neuro-immunology follow-up. Autoimmune panel revealed positive mGluR1 antibodies, leading to a diagnosis of mGluR1-ARE.

Results:

While musicogenic seizures are common, musical hallucinations due to seizures are rarely documented, with two cases being autoimmune (mGluR1 and IgLON5). Our patient presentation is unique and emphasizes the importance of evaluating for autoimmune processes when there are unusual cognitive perceptions including musical hallucinations and HFF. In this case, anti-TG was misleading and unrelated. In contrast to the reported mGluR1-ARE with musical seizures, our patient experienced ataxia, which is consistent with mGluR1-ARE having predilection to the cerebellum and the temporal lobe. To our knowledge, our case is the first auto-immune encephalitis case with HFF. The only other reported case was seronegative although mGLuR1 was not tested.

Conclusions:

Our case emphasizes the importance of evaluating for mGluR1-ARE in patients with unclear diagnosis presenting with atypical musical hallucinations, HFF and ataxia despite anti-TG positivity.