CASE 14863 Published on 17.07.2017

The value of conventional and diffusion magnetic resonance imaging in a rare mitochondrial disorder: Leigh syndrome - a case report

Section

Neuroradiology

Case Type

Clinical Cases

Authors

Anastasia Zikou1, Christina Naka1, Meropi Tzoufi2, Vaseilios Xydis1, Maria I. Argyropoulou1.

1. Department of Clinical Radiology
2. Department of Child Health
Medical School of Ioannina, Greece.
Email: anzikou@cc.uoi.gr
Patient

9 months, female

Categories
Area of Interest Neuroradiology brain ; Imaging Technique MR, MR-Diffusion/Perfusion
Clinical History
A 9-month-old girl presented to our hospital with intense irritability, motor and achieved milestones regression, hypotonia and chaotic nystagmoid optic movements in oblique axon, after meningococcal vaccination. Arterial blood gas and cerebrospinal fluid examination showed elevated lactic acid. Fundoscopy, electroencephalogram and electrocardiogram were normal. MRI of the brain followed.
Imaging Findings
Brain MRI of the infant showed bilateral, symmetrical swelling in the putamen and the substantia nigra with hyperintensity on T2-weighted images (Fig. 1) and hypointensity on plain T1-weighted images (Fig. 2) without enhancement after gadolinium administration. On DW images, the same regions revealed severely restricted diffusion and low signal on apparent diffusion coefficient (ADC) maps (Fig. 3). Follow-up brain MRI six months later showed that the previous affected regions had mild hyperintensity on T2-weighted images (Fig. 4) and slightly free diffusion on DW images and on ADC maps (Fig. 5). Based on MRI findings, the clinical signs and the increased lactic acid the presence of Leigh Syndrome (LS) was the most likely diagnosis. Therapy for the suspected mitochondrial disorder was started. The infant showed neurological improvement but biochemical analysis showed permanent elevation of lactic acid. The child died at the age of eight and the parents denied brain biopsy.
Discussion
LS, also referred to as subacute necrotising encephalopathy, is a rare neurodegenerative disease caused by mitochondrial dysfunction from a hereditary genetic defect. The minimum birth prevalence of LS is ~ 1 in 5000 births. The onset of symptoms is typically seen between 3 and 12 months of age, but there is a wide range of disease onset. Clinical presentation in LS may be varied. The disease expresses with psychomotor delay or regression, muscular hypotonia, progressive brainstem signs (especially strabismus, nystagmus and swallowing difficulties), ataxia, pyramidal signs and respiratory insufficiency. The onset of symptoms is usually following common infections [1-5]. Mitochondrial dysfunction leads to respiratory chain deficiency and systemic elevation of lactic acid in the blood, urine or cerebral spinal fluid (CSF) while muscle biopsy pathology is often normal in up to 50% of LS patients [6]. Over the last few decades, several sets of diagnostic criteria were developed to assist recognition and diagnosis of mitochondrial disorders, based on the combination of 1) the clinical presentation 2) the cerebrospinal fluid, and 3) the brain MRI findings. Bilateral, symmetric focal hyperintensities on T2-weighted images in the basal ganglia, the thalamus, the substantia nigra, the brainstem nuclei, the spinal cord, and the optic nerves are the most characteristic MR imaging findings. DWI can differentiate the acute lesions from chronic lesions in LS and might be useful to include in the MRI diagnostic protocol. In the acute phase of injury, when mitochondrial function is acutely impaired, the Na+, K+-ATPase production is reduced causing cytotoxic oedema; this is seen as a hyperintense signal on diffusion weighted image acquisition, or low signal on apparent diffusion coefficient (ADC) maps [7-9]. If no permanent damage ensues, T2-weighted and diffusion images may return to normal tissue intensity. However, if spongiform degenerations, necrosis, and gliosis appears in late stages, the affected regions display hyperintense on T2-weighted images with increased diffusion on ADC maps [7, 10]. Most of the symptoms seen on physical examination in a case of possible LS can be localised to regions of the brain and brainstem that correspond to MRI changes with conventional T2-weighted sequences. Also DWI can differentiate the acute lesions from chronic lesions very well in LS and might be useful in MRI diagnostic protocol.
Differential Diagnosis List
Leigh syndrome
Other mitochondrial disorders
Acute necrotising encephalitis of childhood
Final Diagnosis
Leigh syndrome
Case information
URL: https://www.eurorad.org/case/14863
DOI: 10.1594/EURORAD/CASE.14863
ISSN: 1563-4086
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