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Figures
- Fig 1.
Axial MR imaging shows temporal evolution of an acute cortical lesion in a patient with MELAS presenting with an acute stroke-like episode with left upper limb sensory loss. A, DWI (b = 1000) image from the day after symptom onset shows hyperintense intracortical signal in the middle-third of the right postcentral gyrus (hand/arm region of the primary somatosensory cortex). B, ADC image shows corresponding hypointense intracortical signal in keeping with diffusion restriction (white and black arrows). C, T2-weighted spin-echo image shows T2 hyperintensity in the deeper cortical layers and juxtacortical white matter (black arrow), with sparing of the superficial cortex (white arrow). D, Progress T2-weighted spin-echo image obtained 3 weeks later shows focal intracortical hypointense signal (black arrow) and mild volume loss, in keeping with pseudolaminar necrosis (black toenail sign).
- Fig 2.
Axial MR imaging shows 4 examples of symmetric cortical involvement by acute lesions in patients with MELAS. A, T2-weighted spin-echo image shows symmetric hyperintense signal in the deep cortex and juxtacortical white matter of the bilateral medial frontal gyri, with sparing of the superficial cortex (typical for pseudolaminar involvement). B, T2-weighted spin-echo image shows symmetric hyperintense intracortical signal in the middle-thirds (black arrows) of the bilateral precentral gyri (hand regions of the primary motor cortex), with sparing of the superficial cortex. C, T2-FLAIR image shows symmetric cortical and subcortical hyperintense signal in the pericalcarine cortex of the bilateral medial occipital lobes (primary visual cortex). D, T2-FLAIR image shows symmetric cortical and subcortical hyperintense signal in the posterior halves of the bilateral superior temporal gyri (primary auditory cortex).
Tables
Patient No. Sex Agea (yr) No. of MR Imaging Studies Available Genetic Testing Results Clinical Presentation: First Available MR Imaging 1b Female 20 2 MT-TL1 m.3243A>G Stroke-like episode
Right facial numbness2b Female 27 1 MT-TL1 m.3243A>G Heteroplasmy 21% Asymptomatic
Screening MRI after sibling diagnosed3 Male 56 1 MT-TL1 m.3243A>G Follow-up study
Childhood diagnosis4 Female 23 10 MT-TL1 m.3243A>G Stroke-like episode
Right hemiparesthesia followed 1 week later by partial status epilepticus5 Female 32 2 MT-TL1 m.3243A>G Follow-up study
Childhood diagnosis6 Female 18 8 MT-TL1 m.3243A>G Seizure
Left upper limb paresthesia with secondary generalization7 Male 26 6 MT-TL1 m.3243A>G Encephalopathy
Confusion and headaches8 Female 40 1 MT-TL1 m.3243A>G Stroke-like episode
Right homonymous hemianopiaSequence Intensity No. of Lesions: Deep No. of Lesions: Cortical Acute (first week) Total: 5 Total: 36 T1 (spin-echo) ↓ 0 24 T2 (spin-echo) ↑ 5 36 T2 sparing of superficial cortex 23 T2 FLAIR ↑ 5 36 DWI (b = 1000) ↑ 0 34 ADC ↓ 0 30 SWI ↓ 0 0 Subacute (second-to-fourth weeks) Prior low ADC 0 30 Follow-up imaging available 0 29 T1 ↑ 12 T2: black toenail sign ↓ 21 SWI ↓ 7 Prior normal/high ADC 5 6 Follow-up imaging available 5 6 T1 ↑ 0 0 T2: black toenail ↓ 0 0 SWI ↓ 0 0 Chronic (>3 mo) Prior low ADC 0 30 Follow-up imaging available 0 19 Volume loss 19 Prior normal/high ADC 5 6 Follow-up imaging available 4 4 Volume loss 2 0 1H-MRS performed Doublet at 1.3 ppm 5 Patients Long TE (288 ms) Elevated 5 Patients Intermediate TE (144 ms) Inverted 5 Patients Affected white matter 5 Patients Nonaffected white matter 3 Patients Note:—↓ indicates hypointense signal; ↑, hyperintense signal.
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