CASE 12858 Published on 28.07.2015

Imaging findings in MELAS syndrome

Section

Neuroradiology

Case Type

Clinical Cases

Authors

Ainhoa Camarero Miguel, José Antonio Pérez Retortillo, Luis Gijón de la Santa, Lidia Nicolás Liza

Hospital Universitario de Guadalajara,
Sescam, Radiology;
Donantes de Sangre Guadalajara,
Spain;
Email:ainhoacm@gmail.com
Patient

41 years, male

Categories
Area of Interest Neuroradiology brain ; Imaging Technique CT, MR, MR-Diffusion/Perfusion, MR-Angiography, MR-Spectroscopy
Clinical History
A 41-year-old male patient with a history of deafness, mitral valve prolapse, arterial hypertension but without toxic habits came to the emergency room with dyschromatopsia and mild dysarthria. Ten days before, he had been diagnosed with ischaemic stroke after having developed a confusional state and fluctuating sensory aphasia that recovered completely.
Imaging Findings
The non-enhanced CT performed at the first visit to the emergency room (Fig. 1) showed cortico-subcortical atrophy, ischaemic lesions in the left parietal and right temporal regions and bilateral basal ganglia calcification.
The first MR (Fig. 2) showed an increased signal in T2-sequences in the deep right temporal region and a more extensive predominantly cortical lesion in the left parietal-occipital lobe. Diffusion-weighted imaging detected enhancement in the left parietal lesion without appreciating this phenomenon in the right temporal one. These findings were related to acute ischaemic injury in the left parietal region and chronic ischaemic lesion in the right deep temporal lobe.
The second MR made two weeks after the previous one (Fig. 3), still showed the cortical hypersignal in the parietal-occipital lobe. There was a new cortical hyperintense image in the left occipital paramedian gyrus with restricted diffusion and increased Apparent Diffusion Coefficient.
The hyperintense area in right temporal region was resolved. MR-spectroscopy showed a peak of lactate in both parasagittal parietal areas.
Discussion
The MELAS syndrome refers to a mitochondrial disease with encephalomyopathy, lactic acidosis and stroke-like episodes [1-6]. It was first described by Pavlakis in 1984 [1] and is included in mitochondrial cytopathies: a set of syndromes characterized by an impairment of mitochondrial function failure of ATP production in the affected cells. The pathogenesis is not clear; there are usually several mutations, the most common in position 3.2343 of the mitochondrial DNA (60-90% of cases).
Clinically, it usually starts before 40 years of age and the classic triad presents with lactic acidosis, seizures and "stroke-like" episodes [4]. We can find other manifestations such as sensorineural hearing loss, muscular weakness, maculopathy or renal dysfunction. Anyway, focal deficits are clinically indistinguishable from stroke.
CT findings are nonspecific [3]: Symmetrical calcifications in the basal ganglia, parietal and occipital focal hypodensities and generalized atrophy with prominent dilated occipital horns.
MR findings are more specific and may show hyperintense fluctuating cortical/subcortical lesions in T2-weighted sequences, predominantly in parietal and occipital lobes than can affect various vascular territories. In the acute and subacute stages, the affected areas show high signal on diffusion-weighted images and an apparent diffusion coefficient (ADC) lower than that in the normal brain. A lactate peak is identified on MR spectroscopy (MRS) with voxels situated at both parasagittal parietal areas [2-6].
The diagnostic of MELAS syndrome is made by muscle biopsy, where ragged red muscle fibres are seen with proliferation of mitochondrial elements and increased intermyofibrillar lipid deposits.

There is no specific treatment, so just symptomatic treatment is applied such as the implantation of a cochlear prothesis for sensorineural hearing loss and antiepileptic drugs for the seizures. Administration of Coenzyme Q 10 and L-carnitine have proved beneficial in selected patients. Administration of L-Arginine in the acute phase of stroke seems to reduce their severity and applied in the interictal period it decreases the frequency of the strokes.
Differential Diagnosis List
MELAS: mitochondrial encephalomyopathy, lactic acidosis, and "stroke-like" episodes.
Stroke
MERRF (Myoclonic Epilepsy with Ragged-Red Fibres)
Leigh syndrome
Kearns-Sayre syndrome
Final Diagnosis
MELAS: mitochondrial encephalomyopathy, lactic acidosis, and "stroke-like" episodes.
Case information
URL: https://www.eurorad.org/case/12858
DOI: 10.1594/EURORAD/CASE.12858
ISSN: 1563-4086
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