Stroke-like episodes in a young patient

Clinical History

A 29-year-old female patient with recurrent episodes of visual loss and progressive deafness.

Imaging Findings

CT scan shows bilateral calcifications on the basal ganglia. On MRI a cortical subcortical hyperintensity on T2 and FLAIR sequences localized on the left temporo-occipital lobules is seen. This lesion doesn't follow a vascular territory. A mild gyral enhancement was seen after contrast administration.

Discussion

A. MELAS is the acronym for mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes [1]. This disease is a mitochondrial disorder that can affect the central nervous system [2]. It is fundamental to note that mitochondrial genetic information is inherited by the mother exclusively [3]. The mutation affects the nucleotide 3243 mtDNA which encodes for transfer RNA (tRNA) for leucine, a substance with an important role in the intracellular energy production [3]. This alteration causes depletion of NAD+ and NADH+, which results in a shift to anaerobic metabolism, for which the brain cortex is especially susceptible [4]. The grade of damage of the mutation is related to the severity of the disease [3].

B. The classical triad for the clinical presentation of MELAS is lactic acidosis, seizures and stroke-like episodes [3]. These episodes consists of hemiparesis, hemianopia and/or cortical blindness [5]. The evolution of the disease is with relapsing-remitting episodes, but some deficits may be permanent [5]. Other important entities that could be related to MELAS are migraine-like headaches, progressive sensorineural hearing loss, diabetes, cardiac disease and short stature [3, 5].

C. The imaging findings are fundamental for the diagnosis [6]. CT studies can show multiple infarctions, restricted or not to a vascular territory [3]. Atrophy and basal ganglia calcification are some other important findings [3]. On MRI acute chronic infarctions are evident as well [3]. They predominantly affect the parieto-occipital region and are accompanied by a lactate peak in the spectroscopy studies [3, 6]. In DWI, lesions are hyperintense, but in the ADC map the signal intensity of these findings is usually not reduced at all or less reduced than on DWI, because they are due to vasogenic oedema rather than cytotoxic oedema [6]. This feature is important to differentiate MELAS from stroke [6]. A mild gyral enhancement could be seen [3].

D. Evaluation of patients with MELAS should be initially performed with the measurement of serum levels of lactate and pyruvate [7]. Muscle biopsy and analysis of the mtDNA mutation in blood and brain imaging studies may be achieved too [8, 9]. Acute decompensations are not rare, and could present as myopathy, encephalopathy, lactic acidosis, or stroke [9]. Treatment has been based on exercise, dietary manipulations and hydration [9]. Vitamins and xenobiotics could be used in selected cases [9]. Genetic counselling is important in the management of patients with MELAS [8].

E. MELAS is a mitochondrial disorder with a relapsing-remitting course and should be considered in young patients with stroke-like episodes, especially if the lesion extends to multiple vascular territories, with predominantly parieto-occipital regions involvement.

Differential Diagnosis List

Final Diagnosis

Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes

URL:	https://eurorad.org/case/14780
DOI:	10.1594/EURORAD/CASE.14780
ISSN:	1563-4086