Diffusion tensor imaging (DTI) appears to be superior to magnetic resonance imaging (MRI) in the detection of early structural brain abnormalities in patients with Wilson disease, according to a systematic review recently published in Brain Imaging and Behavior

The increased copper levels associated with Wilson disease can cause structural brain damage, particularly in the basal ganglia, thalamus, and brainstem. Most of these changes are detectable through MRI, with T2 hypersensitivity in the putamen and the double panda sign being some of the hallmark findings, Amirali Karimi, of the Tehran University of Medical Sciences in Iran, and colleagues noted.

DTI is an MRI-based technique that measures the rate and direction of the moving water molecules inside myelin sheaths and neuronal membranes, the researchers noted. Fractional anisotropy (FA), 1 of the main indices of the technique, is a sensitive parameter of microstructural abnormalities and is complemented by mean diffusivity (MD), axial diffusivity, and radial diffusivity, which help identify the specific problem, the authors added.

Read more about Wilson disease diagnosis

Although the utility of DTI in other neurologic pathologies has been demonstrated by several studies, there is a lack of information regarding its value in Wilson disease. Therefore, the authors aimed to conduct a systematic review of studies describing DTI findings in Wilson disease. 

The keywords diffusion tensor imaging and Wilson disease were used to search databases such as PubMed and Embase, excluding case reports, nonhuman studies, and studies not in English. The Newcastle–Ottawa scale was used to assess the risk of bias in the included studies. After applying exclusion criteria, 10 studies out of approximately 200 were included in the review.

The selected studies reported DTI anomalies in all brain regions typically affected by Wilson disease and other areas, such as the lobar region. However, FA appeared to be inconsistent across the selected studies. For example, some studies detected FA abnormalities in the putamen, and others reported decreased FA in the putamen. MD was more consistent than FA across the studies and was increased in all studies that measured it.

Three studies reported DTI to be superior to T2-weighted FLAIR MRI in detecting early structural abnormalities in patients with Wilson disease, with DTI detecting abnormalities in patients with normal-appearing MRIs.

In some cases, DTI measurements corresponded with levels of neurologic dysfunction. One study demonstrated that symptoms corresponded with specific fiber volumes.

“Additional studies will be required to validate specific DTI measures for characterizing patients with WD or providing objective and quantifiable markers for longitudinal treatment follow-up,” the authors concluded. 

Reference

Karimi A, Mohammadi S, Salehi M, Dager S. Brain microstructural abnormalities in patients with Wilson’s disease: a systematic review of diffusion tenor imaging studies. Brain Imaging Behav. Published online November 3, 2022. doi:10.1007/s11682-022-00733-7