Yukari Imon

Serial diffusion-weighted imaging in MELAS

Abstract Clinical features of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) resemble those of cerebral infarcts, but the pathogenesis of infarct-like lesions is not fully understood. To characterise these infarct-like lesions, we studied two patients with MELAS using diffusion-weighted (DWI) MRI before and after stroke-like episodes and measured the apparent diffusion coefficient (ADC) in the new infarct-like lesions. These gave high signal on DWI and had much higher ADC than normal-appearing regions. The ADC remained high even 30 days after a stroke-like episode then decreased in lesions, with or without abnormality as shown by conventional MRI. We speculate that early elevation of ADC in the acute or subacute phase reflects vasogenic rather than cytotoxic edema. The ADC of the lesions, which disappeared almost completely with clinical improvement, returned to normal levels, which may reflect tissue recovery without severe damage. To our knowledge, this is the first study of DWI in MELAS.

Abnormal signals on proton density-weighted MRI of the superior cerebellar peduncle in progressive supranuclear palsy

Objective– To assess MRI signal abnormalities of the superior cerebellar peduncle (SCP) in progressive supranuclear palsy (PSP) patients. Material and methods– Signal changes were examined on proton density‐weighted images (PDWI) and on T2‐weighted images (T2WI) of SCP in 9 PSP patients, and findings were compared to those in 20 Parkinsons disease patients and 20 age‐matched control subjects. Results– We observed effacement or lack of clarity of the low signal on PDWI in SCP in 4 of 9 PSP patients, but not in any of the Parkinsons disease patients or control subjects. These signal changes were not observed on T2WI. Conclusions– The signal changes on PDWI may be a specific finding reflecting demyelination and gliosis of SCP in PSP. Our findings suggest that evaluation of SCP on PDWI may be helpful in the diagnosis of PSP patients.

Low intensity areas observed on T2-weighted magnetic resonance imaging of the cerebral cortex in various neurological diseases

The cerebral cortex of patients with Alzheimers disease (AD) or amyotrophic lateral sclerosis (ALS) may show low signal intensity on T2-weighted magnetic resonance images (MRI). Since these low intensity areas (LIA) are also often observed in aged patients with other diseases, we suspected that they might be a non-specific finding. We conducted a retrospective study of LIA in 139 patients with various diseases of the central and peripheral nervous systems, and evaluated their relationship to age and other MRI findings. Brain atrophy, ventricular dilatation, white matter lesions, and LIA were visually evaluated on axial images of the spin echo sequences obtained with a 1.5 tesla (T) system. We found that LIA appeared after age 50 and became more common with advancing age. Their presence correlated with brain atrophy and white matter lesions. They were most frequent in the motor cortex, followed by the occipital and sensory cortices. Their incidence in the motor cortex was significantly higher in patients with central nervous system diseases than in those with peripheral neuropathy. We conclude that LIA are common in old patients with various neurological diseases and suggest that the deposition of iron in the cerebral cortices causes their development.

A decrease in cerebral cortex intensity on T2-weighted with ageing images of normal subjects

Abstract To determine the change in intensity in the cerebral cortex on T2-weighted MRI with ageing, we reviewed the T2-weighted images of 83 normal subjects and measured the signal intensity in the cerebral cortex in 30 subjects randomly selected from them. Low-intensity areas were more common in the cerebral cortex of the aged. The intensity of different cortical regions varied, and the intensity in the temporal and parietal to be decreased with ageing. Presumably, this change of the intensity reflects senile changes, although low intensity is not evident in the temporal cortex because of its high basal intensity level.

Magnetization transfer measurements of cerebral white matter in patients with myotonic dystrophy

To determine whether patients with myotonic dystrophy (MyD) have structural changes in the cerebral white matter, we performed magnetization transfer (MT) imaging of the cerebral white matter in 14 MyD patients and 11 age-matched normal controls. We calculated MT ratios in both the white matter lesions (WMLs) and the normal-appearing white matter (NAWM) of MyD patients using region of interest (ROI) analysis. MT ratios in WMLs were markedly decreased, and all ROIs in NAWM also showed significantly lower MT ratios in MyD patients than in normal controls. The average MT ratio of all ROIs in WMLs and NAWM in each patient showed a significant negative correlation with duration of illness, but not with the patients age or age at onset. The results of the present study indicate not only the presence of pathological changes in WMLs but also the widespread involvement of NAWM in MyD patients. The results also suggest that structural changes in the white matter may be progressive during the clinical course of MyD.

Magnetization Transfer Measurements of Brain Structures in Patients with Multiple System Atrophy

To determine whether magnetization transfer imaging (MTI) demonstrates abnormalities in the brain structures of patients with multiple system atrophy (MSA), we examined 12 patients with clinically probable MSA and 11 control subjects. We calculated magnetization transfer ratios (MTRs) using region of interest analysis from MTI and assessed abnormal signal changes on T2-weighted images. MTRs of the base of the pons, middle cerebellar peduncle, putamen, and white matter of the precentral gyrus were significantly lower in the MSA patients than in the controls. Abnormal signal changes on T2-weighted images were observed in the base of the pons (n = 6), middle cerebellar peduncle (n = 7), and putamen (n = 7). MTRs of regions with abnormal signals were significantly lower than those of regions without abnormal signals and those in the controls. Even the MTRs of the regions without abnormal signals were lower than those in the controls. MTRs of the pyramidal tract, including white matter of the precentral gyrus, posterior limb of the internal capsule, cerebral peduncle, and base of the pons, were significantly lower in patients with pyramidal tract sign (n = 7) than in the controls. Patients with asymmetrical parkinsonism (n = 5) showed significantly lower MTRs in the putamen contralateral to the predominant side of parkinsonian symptoms than the ipsilateral side, although asymmetry of abnormal signal changes on T2-weighted images was not evident in more than half of those patients. This study showed that MTI demonstrates abnormalities in the brains of patients with MSA that seem to reflect underlying pathological changes and that the pathological changes detected by MTI seem to give rise to clinical symptoms. This study also showed that the abnormalities are detected more sensitively and over a larger area by MTI than by conventional magnetic resonance imaging.

Apparent diffusion coefficient measurements in progressive supranuclear palsy.

Abstract We measured the apparent diffusion coefficient (ADC), using diffusion-weighted imaging (DWI) and signal intensity on T2-weighted MRI in the cerebral white matter of patients with progressive supranuclear palsy (PSP) and age-matched normal subjects. In PSP, ADC in the prefrontal and precentral white matter was significantly higher than in controls. There was no significant difference in signal intensity on T2-weighted images. The ADC did correlate with signal intensity. The distribution of the elevation of ADC may be the consequence of underlying pathological changes, such as neurofibrillary tangles or glial fibrillary tangles in the cortex. Our findings suggest that ADC measurement might be useful for demonstrating subtle neuropathological changes.

A necropsied case of Machado-Joseph disease with a hyperintense signal of transverse pontine fibres on long TR sequences of magnetic resonance images

Machado-Joseph disease refers to autosomal dominant spinocerebellar degeneration, and the gene responsible for the disease exhibits an expanded trinucleotide CAG repeat in chromosome 14q32.1.1 Machado-Joseph disease has a wide range of clinical manifestations in addition to the cerebellar ataxia. The diverse disorders are characterised neuropathologically by the involvement of the pallidoluysian, dentatorubral, pontocerebellar, cochleocerebellar, and spinocerebellar systems, lower motor neurons, and dorsal root ganglia. Previous MRI studies disclosed only mild cerebellar and brain stem atrophy in Machado-Joseph disease.2 Our MRI examinations in 31 cases disclosed atrophy of the pons, middle, and superior cerebellar peduncles, and frontal and temporal lobes, together with fourth ventricular dilatation.3 A third of the cases displayed a hyperintense signal of the transverse pontine fibres, which had been found previously in patients with olivopontocerebellar atrophy.4Here, we report on a patient with Machado-Joseph disease with an abnormal pontine signal on MRI, nine months before death, and pathological findings of the necropsied brain. A 46 year old man had been in good health until the age of 23 when he began to stagger and slur his speech. He showed progressive difficulty in walking and was bedridden at the age of 37. Eight years later, he was admitted to hospital because of dysphagia and dysarthria. His father had had Machado-Joseph disease and …