Stroke-Like Lesion in an m.3243A>G Carrier Presenting as Hyperperfusion and Hypometabolism

Abstract

Carriers of the m.3243A>G variant typically manifest with stroke-like episodes (SLEs), of which the morphological correlate on imaging is the stroke-like lesion (SLL). The pathophysiology of SLLs is poorly understood but acute and chronic stages are delineated. Here we present the case of an m.3243A>G carrier who presented with hypometabolism during his second SLL. The patient was a 56-year-old male who was diagnosed with MELAS (mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes) at the age of 50 upon a third SLE, muscle biopsy, and the detection of the m.3243A>G variant in the muscle. A fluorodeoxyglucose-positron emission tomography (FDG-PET) during the second SLE revealed hypometabolism in the occipital lobes bilaterally. The patient was misdiagnosed for years and was repeatedly exposed to mitochondrion-toxic drugs (metformin, steroids, valproic acid, oxcarbazepine, zolpidem). The previous data and the present findings indicate that the hypometabolism on FDG-PET together with reduced oxygen-extraction fraction (OEF) on OEF-MRI and hyperperfusion on perfusion-weighted imaging (PWI) characterise best the acute stage of an SLL. In conclusion, an acute SLE in m.3243A>G carriers typically manifests with a mismatch between hyperperfusion on PWI or single-photon emission computed tomography (SPECT) and hypometabolism on FDG-PET and hypointensity on OEF-MRI. Since SLEs are not vascular events, they should be managed by a multispecialist approach and not by general or stroke neurologists.