Successive affection of bilateral temporomesial structures in a case of non-paraneoplastic limbic encephalitis demonstrated by serial MRI and FDG-PET

Abstract

Sirs,Non-paraneoplastic limbic encephalitis (NPLE) often results in an unfavorable clinical course with progressive neuropsychological deficits and epileptic seizures despite treatment [1][2][3]. Magnetic resonance imaging (MRI), fluorodeoxyglucose positron emission tomography (FDG-PET) and antibodies against voltage-gated potassium channels (VGKC-Ab) are helpful in monitoring the course of the disease [3][4][5]. We present a follow-up of a NPLE patient over a 3-year period with successive affection of bilateral temporomesial structures.A 67-year-old man with no relevant medical history presented with recurrent episodes of visual hallucinations, memory impairment, disorientation and myoclonic jerks. Neurological examination was unremarkable; however neuropsychological testing revealed severe verbal (shortterm) memory, speech fluency and visual recognition deficits. EEG showed an intermittent theta-focus as well as intermittent right temporal ictal rhythmic activity. On MRI hyperintensity and diffuse swelling of the right hippocampus on T2-and diffusion-weighted (DWI) images was found. FDG-PET revealed right temporomesial hypermetabolism and bilateral hypometabolism in the temporal lobes (Fig. 2a). There were no signs of tumor in the wholebody PET examination. CSF (including virological analysis) was normal except for elevated VGKC-Ab levels ([9085 pM, controls \100 pM). Thyroid function and autoantibodies tests were negative. The diagnosis of NPLE was made and methylprednisolone (MP; 4000 mg i.v. over 5 days) as well as gabapentin treatment was initiated. Figure 1 shows the course of the disease, examination results and therapeutic management.Three months later, the patient presented with a deterioration of symptoms. MRI showed an atrophy of the right hippocampus, with mild residual T2-hyperintensity. FDG-PET showed left temporal hypermetabolism and a right temporomesial ''cold'' lesion (Fig. 2b). VGKC-Ab were still elevated ([8067 pM). Treatment with MP (5000 mg i.v. over 5 days) was started again. Six months later he was re-admitted with progressive memory impairment, confirmed by neuropsychological examination. Now on MRI, left hippocampal edema was found and FDG-PET demonstrated severe hypometabolism in both temporomesial regions. After 2 months of stable condition, there was once again neuropsychological deterioration. There were no significant changes on MRI compared to the previous examinations and the FDG-PET showed left temporomesial hypometabolism. IV immunoglobulin therapy (150 g over 3 days) was applied. Two and 4 months later MRI and FDG-PET findings remained unchanged. VGCK-Ab levels were almost normal. Memory impairment had temporarily deteriorated before improving again, this time under immunosuppressive treatment with azathioprine (100 mg/ d). At the last two visits (after 2 and 3.5 years) the patient was seizure-free under gabapentin and showed an improvement of his cognitive functions under azathioprine treatment. MRI showed left hippocampal atrophy and FDG-PET hypometabolism in both temporomes...

MRI Findings in Autoimmune Voltage-Gated Potassium Channel Complex Encephalitis with Seizures: One Potential Etiology for Mesial Temporal Sclerosis

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Striatal hypermetabolism in limbic encephalitis

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Persistent anterograde amnesia following limbic encephalitis associated with antibodies to the voltage-gated potassium channel complex

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