Type:
Educational Exhibit
Keywords:
Neuroradiology brain, MR, CT, Diagnostic procedure, Ischaemia / Infarction
Authors:
T. Hill, Y. Perchyonok, G. Fitt; Melbourne/AU
DOI:
10.1594/ranzcr2015/R-0108
Imaging findings OR Procedure details
Part A – Stroke mimics
1.
TOXIC METABOLIC PATHOLOGIES
Multiple toxic and metabolic abnormalities may mimic stroke including MELAS,
abnormal glucose levels,
Wernicke’s encephalopathy and hepatic encephalopathy.
1.
Mitochondrial Encephalomyopathy with Lactic Acidosis and Stroke Like Episodes (MELAS)
Mitochondrial encephalomyopathy with lactic acidosis and stroke like episodes is a disorder cause by mutations in mitochondrial DNA.
Clinical Presentation:
Manifestations of the disease occur in childhood or early adulthood.
Hallmarks are lactic acidosis and stroke like episodes with hemiparesis and/or cortical blindness.
Other clinical features include tonic clonic seizures,
recurrent migraine,
myopathy and sensorineural hearing loss.
5
Pathology:
A particular mitochondrial defect involving a transfer RNA gene accounts for the vast majority of cases.5 Lactic acidaemia due to impaired energy production and increased mitochondria seen within smooth muscle cells of arteries and arterioles,
leads to luminal narrowing and impaired vessel autoregulation.5-7
Imaging:
Key imaging feature:
High DWI signal crossing vascular territories and predominantly occurring in a posterior location.
Fluctuating low attenuation and T2/FLAIR hyperintensity on CT and MRI respectively corresponds to areas of oedema.
Abnormal density and signal is evident mainly within the grey matter with gyral expansion,
although the subcortical white matter may be involved. Occipital and parietal lobes are characteristically involved.
Basal ganglia changes may also seen.
T2/FLAIR hyperintensity may have associated areas of:
- diffusion restriction corresponding to cytotoxic oedema/infarct; or
- increased DWI and ADC signal corresponding to vasogenic oedema and this can be seen in regions where there is resolution or persistence of signal abnormality on conventional MRI.
Gyral enhancement may be seen on post contrast T1 weighted images.
Signal abnormalities may resolve completely or evolve into regions of encephalomalacia.8-11
See Figures 1 and 2.