Metabolic stroke or stroke-like lesion: Peculiarities of a phenomenon

Objectives: One of the most frequent cerebral lesions in mitochondrial disorders(MIDs) on imaging is the stroke-like lesion(SLL) clinically manifesting as stroke-like episode (SLE, metabolic stroke). This review aims at discussing recent advances concerning the presentation, diagnosis, and treatment of SLLs.

Methods: Systematic literature review using appropriate search terms.

Results: SLLs are the hallmark of MELAS but occasionally occur in other MIDs. SLLs are best identified on multimodal, cerebral MRI. SLLs may present as uni-/multilocular, symmetric/asymmetric, cortical/subcortical, supra-/infratentorial condition, initially resembling a cytotoxic edema and later a vasogenic edema, or a variable mix between them. SLLs run through an acute and a chronic stage. The acute stage is characterised by a progressively expanding lesion over days, weeks, or months, showing up as increasing hyperintensity on T2/FLAIR, DWI, and PWI and by hyperperfusion, that does not conform to a vascular territory. ADC maps are initially hypointens to become hyperintens during the course. More rarely, a variable mixture of hyper- and hypointensities may be found. The chronic stage is characterised by hypoperfusion, gadolinium enhancement, and regression of hyperintensities to various endpoints. SLLs originate from an initial cortical lesion due to focal metabolic breakdown, which either remains stable or expands within the cortex or to subcortical areas. Some SLLs show spontaneous reversibility (fleeing cortical lesions) suggesting that neuronal/glial damage does not reach the threshold of irreversible cell death.

Conclusions: SLLs are a unique feature of various MIDs in particular MELAS. SLLs are dynamic and change their appearance over time. SLLs are accessible to treatment.