Differentiating white matter lesions in multiple sclerosis and migraine using monoexponential and biexponential diffusion measurements

Differentiation of hemispheric white matter lesions in migraine and multiple sclerosis with similar radiological features using advanced MRI

Background and aim

White matter hyperintensities (WMHs), presented on T2-weighted or fluid-attenuated inversion recovery magnetic resonance imaging (MRI) sequences, are lesions in the human brain that can be observed in both migraine and multiple sclerosis (MS).

Methods

Seventeen migraine patients and 15 patients with relapsing-remitting multiple sclerosis with WMHs, and 17 healthy subjects age-and sex-matched to the migraine group were prospectively enrolled and underwent conventional and advanced MRI studies with diffusion-and perfusion-weighted imaging and single voxel proton magnetic resonance spectroscopy.

Results

In both disease groups, elevated T2 relaxation time, apparent diffusion coefficient (ADC) values, and decreased N-acetyl-aspartate levels were found in the intralesional white matter compared to the contralateral normal-appearing white matter (NAWM), while there was no difference between the hemispheres of the control subjects. Migraine patients had the lowest intralesional creatine + phosphocreatine and myo-inositol (mI) values among the three groups, while patients with MS showed the highest intralesional T1 and T2 relaxation times, ADC, and mI values. In the contralateral NAWM, the same trend with mI changes was observed in migraineurs and MS patients. No differences in perfusion variables were observed in any groups.

Conclusion

Our multimodal study showed that tissue damage is detectable in both diseases. Despite the differences in various advanced MRI measures, with more severe injury detected in MS lesions, we could not clearly differentiate the two white matter lesion types.

White Matter Lesions in Migraine

Migraine, the third most common disease worldwide, is a well-known independent risk factor for subclinical focal deep white matter lesions (WMLs), even in young and otherwise healthy individuals with no cardiovascular risk factors. These WMLs are more commonly seen in migraine patients with transient neurologic symptoms preceding their headaches, the so-called aura, and those with a high attack frequency. The pathophysiology of migraine-related deep white matter hyperintensities remains poorly understood despite their prevalence. Characteristic differences in their distribution related to chronic small vessel ischemic disease compared with that of common periventricular WMLs in the elderly suggest a different underlying mechanism. Both ischemic and inflammatory mechanisms have been proposed, as there is increased cerebral vulnerability to ischemia in migraineurs, whereas there is also evidence of blood-brain barrier disruption with associated release of proinflammatory substances during migraine attacks. An enhanced susceptibility to spreading depolarization, the electrophysiological event underlying migraine, may be the mechanism that causes repetitive episodes of cerebral hypoperfusion and neuroinflammation during migraine attacks. WMLs can negatively affect both physical and cognitive function, underscoring the public health importance of migraine, and suggesting that migraine is an important contributor to neurologic deficits in the general population.

Chemotherapy response evaluation in a mouse model of gastric cancer using intravoxel incoherent motion diffusion-weighted MRI and histopathology

AIM

To determine the role of intravoxel incoherent motion (IVIM) diffusion-weighted (DW) magnetic resonance imaging (MRI) using a bi-exponential model in chemotherapy response evaluation in a gastric cancer mouse model.

METHODS

Mice bearing MKN-45 human gastric adenocarcinoma xenografts were divided into four treated groups (TG1, 2, 3 and 4, n = 5 in each group) which received Fluorouracil and Calcium Folinate and a control group (CG, n = 7). DW-MRI scans with 14 b-values (0-1500 s/mm²) were performed before and after treatment on days 3, 7, 14 and 21. Fast diffusion component (presumably pseudo-perfusion) parameters including the fast diffusion coefficient (D*) and fraction volume (f_p), slow diffusion coefficient (D) and the conventional apparent diffusion coefficients (ADC) were calculated by fitting the IVIM model to the measured DW signals. The median changes from the baseline to each post-treatment time point for each measurement (ΔADC, ΔD* and Δf_p) were calculated. The differences in the median changes between the two groups were compared using the mixed linear regression model by the restricted maximum likelihood method shown as z values. Histopathological analyses including Ki-67, CD31, TUNEL and H&E were conducted in conjunction with the MRI scans. The median percentage changes were compared with the histopathological analyses between the pre- and post-treatment for each measurement.

RESULTS

Compared with the control group, D* in the treated group decreased significantly (ΔD*_treated% = -30%, -34% and -20%, with z = -5.40, -4.18 and -1.95. P = 0.0001, 0.0001 and 0.0244) and f_p increased significantly (Δf_ptreated% = 93%, 113% and 181%, with z = 4.63, 5.52, and 2.12, P = 0.001, 0.0001 and 0.0336) on day 3, 7 and 14, respectively. Increases in ADC in the treated group were higher than those in the control group on days 3 and 14 (z = 2.44 and 2.40, P = 0.0147 and P = 0.0164).

CONCLUSION

Fast diffusion measurements derived from the bi-exponential IVIM model may be more sensitive imaging biomarkers than ADC to assess chemotherapy response in gastric adenocarcinoma.

Age at onset and seizure frequency affect white matter diffusion coefficient in patients with mesial temporal lobe epilepsy

In mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS), structural abnormalities are present not only in the hippocampus but also in the white matter with ipsilateral predominance. Although the timing of epilepsy onset is commonly associated with clinical and semiological dissimilarities, limited data exist regarding white matter diffusion changes with respect to age at epilepsy onset. The aim of this study was to investigate diffusion changes in the white matter of patients with unilateral MTLE-HS with respect to clinical parameters and to compare them with an age- and sex-matched healthy control group. Apparent diffusion coefficients (ADCs) were derived using monoexponential approaches from 22 (11 early and 11 late age at onset) patients with unilateral MTLE-HS and 22 age- and sex-matched control subjects after acquiring diffusion-weighted images on a 3T MRI system. Data were analyzed using two-tailed t-tests and multiple linear regression models. In the group with early onset MTLE-HS, ADC was significantly elevated in the ipsilateral hemispheric (p=0.04) and temporal lobe white matter (p=0.01) compared with that in controls. These differences were not detectable in late onset MTLE-HS patients. Apparent diffusion coefficient of the group with early onset MTLE-HS was negatively related to age at epilepsy onset in the ipsilateral hemispheric white matter (p=0.03) and the uncinate fasciculus (p=0.03), while in patients with late onset MTLE-HS, ADC was no longer dependent on age at epilepsy onset itself but rather on the seizure frequency in the ipsilateral uncinate fasciculus (p=0.03). Such diffusivity pattern has been associated with chronic white matter degeneration, reflecting myelin loss and higher extracellular volume which are more pronounced in the frontotemporal regions and also depend on clinical features. In the group with early onset MTLE-HS, the timing of epilepsy seems to be the major cause of white matter abnormalities while in late onset disease, it has a secondary role in provoking diffusion changes.

Increased diffusion in the normal appearing white matter of brain tumor patients: is this just tumor infiltration?

Altered diffusion in the normal appearing white matter (NAWM) of glioma patients has been explained by tumor infiltration. The goal of the present study was to test this explanation indirectly by examining whether these alterations were also present in the contralateral NAWM of non-infiltrative tumors like meningiomas; and to search for other possible reasons for this abnormality. Twenty-seven patients with histologically verified glioma (grade II-IV), 22 meningioma patients and two groups of age- and sex-matched healthy controls underwent diffusion weighted imaging (DWI) on a 3T MR. All patients were examined before treatment. Apparent diffusion coefficient (ADC) values were calculated in the entire NAWM of the hemisphere contralateral to the tumor. ADC values of the NAWM were compared between groups with Mann-Whitney U-test and multiple linear regression. The relations of ADC in NAWM to glioma grade and to tumor volume were also investigated. ADC values of the contralateral NAWM were significantly higher in both glioma and meningioma patients compared to controls (P = 0.0006 and 0.0099, respectively). ADC value was higher in the NAWM of high grade gliomas than in low grade gliomas (P = 0.0181) and in healthy control subjects (P = 0.0003). ADC did not depend on tumor volume in any of the patient groups. Elevated ADC in the NAWM of both glioma and meningioma patients might indicate that the effect of infiltrating tumor cells is not the only reason for the alteration as it has been previously suggested. Although the role of mass effect was not proved, other mechanisms might also contribute to ADC elevation.