A distinct MR imaging phenotype in amyotrophic lateral sclerosis: correlation between T1 magnetization transfer contrast hyperintensity along the corticospinal tract and diffusion tensor imaging analysis

Abstract

Background and purpose: In the search for a diagnostic marker in ALS, we focused our attention on the hyperintense signal intensity in T1 MTC MR images along the CST, detected in some patients and not found in other patients with ALS and in control subjects. The aim of this study was to investigate the relationship between the hyperintense signal intensity in T1 MTC images and white matter damage. To this purpose, we studied potential heterogeneities in DTI values within our patients by using TBSS without a priori anatomic information.

Materials and methods: In 43 patients with ALS and 43 healthy control subjects, the presence or absence of T1 MTC hyperintense signal intensity was evaluated. With a DTI analysis with a TBSS approach, differences in FA distribution between the 2 groups (patients with T1 MTC hyperintense signal intensity and patients without it) compared with each other and with control subjects were investigated.

Results: We found regional differences in white matter FA between patients with T1 MTC hyperintense signal intensity (37.2%) and patients without it. Patients with T1 MTC abnormal signal intensity showed lower FA strictly limited to the motor network and the posterior aspect of the body of the CC without extramotor FA reductions, whereas patients without this sign showed FA reductions in several confluent regions within and outside the CST and in the whole CC.

Conclusions: T1 MTC hyperintense signal intensity in the CST and posterior CC, when present, is specific for ALS and represents, among patients with ALS, a possible distinct phenotype of presentation of the disease with prominent UMN involvement.

Fig 1.

T1 MTC MR sagittal (A and B) and axial (C) images show a hyperintense signal intensity along the CST and in the posterior aspect of the CC (B).

Fig 2.

Blue voxels show the regions within and outside the CST, where the FA is significantly reduced in patients with ALS with T1 MTC hyperintense signal intensity compared with patients with ALS without T1 MTC hyperintense signal intensity (all P values < .05, corrected at the cluster level). Red voxels show the regions where the FA is significantly increased in patients with ALS with T1 MTC hyperintense signal intensity compared with patients with ALS without T1 MTC hyperintense signal intensity (all P values < .05, corrected at cluster level). In the CC, patients with T1 MTC hyperintense signal intensity compared with patients without T1 MTC hyperintensity show a significantly lower FA only in the posterior aspect of the body of the CC, whereas they show higher FA in the entire CC, in the splenium, in the genu, and in the anterior body.