Hyperintense and hypointense MRI signals of the precentral gyrus and corticospinal tract in ALS: A follow-up examination including FLAIR images

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Abstract

In amyotrophic lateral sclerosis (ALS) patients, hyperintense signals at the subcortical precentral gyrus in brain fluid attenuated inversion recovery (FLAIR) MR images have been found more frequently than in controls. Quantitative analysis has revealed a significant increase of the FLAIR-magnetic resonance imaging (MRI) signal at the subcortical precentral gyrus of ALS patients compared to healthy controls. In addition, hypointense signals at the rim of the precentral gyrus in FLAIR and T2-weighted images have been shown in ALS patients. In 17 ALS patients, we evaluated hyperintense signals in T2-, T1-, proton density-weighted and FLAIR MR images, and hypointense signals in T2-weighted and FLAIR images 15.7±3.0 months after the initial examination by visual scoring. In FLAIR images, a quantitative analysis was added. The visual scores of hyperintense signals along the corticospinal tract did not change significantly in all sequences. However, the quantitative evaluation of FLAIR images revealed a significant increase of the signal intensity at the subcortical precentral gyrus (p<0.005). In addition, the frequency of the visually evaluated hypointense signals at the precentral gyrus increased significantly (p<0.05). The change of MR results did not correlate with the change of clinical parameters. In ALS patients, the increase of the quantified MRI signal at the subcortical precentral gyrus in FLAIR images and the increase of hypointense signals at the rim of the precentral gyrus corroborate the hypothesis that these signals are related to the upper motor neuron degeneration in ALS. Their specificity and clinical relevance have to be clarified further.

Introduction

Magnetic resonance imaging (MRI) of the brain is currently performed in patients with suspected amyotrophic lateral sclerosis (ALS) to exclude conditions resembling ALS. Recently, some reports focused on MRI signal changes in confirmed ALS patients. T2-weighted MR images of the brain have shown hyperintense alterations of the corticospinal tract [1], [2], [3], [4], [5], [6], [7]. In fluid attenuated inversion recovery (FLAIR) images, hyperintense changes in the subcortical white matter of the precentral gyrus were seen even more often than in T2-weighted images [8]. In our recent study in 31 ALS patients, hyperintense alterations along the corticospinal tract were revealed by FLAIR images significantly more often than by T2-, T1- and proton density-weighted images [9]. There is some overlap with findings in healthy controls [8], [9]. However, the quantified FLAIR signal (contrast to noise ratio, CNR) at the subcortical precentral gyrus was significantly higher in the ALS patients than in the healthy controls [9].

In addition to the hyperintense white matter changes, hypointense signals at the margin of the precentral gyrus (“low signal rim”) has been found in some ALS patients in T2-weighted [2], [4], [8], [9], [10], [11] and, recently, also in FLAIR images [8], [9]. To further investigate hyperintense signals of the corticospinal tract and hypointense signals of the precentral gyrus in ALS, we repeated MR imaging of the head at least 1 year after the first examination.

Section snippets

Patients

Seventeen ALS patients were included in the follow-up study (12 men, 5 women, age 29–67 years, mean age 53.29±9.53 years, 6 bulbar, 11 spinal onset). This group was a subgroup of the 31 patients studied previously [9]. The diminished number of reexamined patients compared to the first examination was caused by the death of 4 patients, 6 patients refused the reexamination and 4 patients were lost to follow-up. The time from the onset of the disease to the first examination was 15.35±10.30 months

Visual evaluation

In some patients, there was a slight increase of the hyperintense signals along the corticospinal tract, especially at the subcortical precentral gyrus (Fig. 2A,B) and at the pons (Fig. 2C,D) in FLAIR images. However, the visual evaluation of the total group showed no significant change (p>0.05) at the precentral subcortical gyrus or any other part of the corticospinal tract (Table 1). The sum score of all five evaluated levels changed slightly from 10.12±1.83 (mean±S.D.) to 10.30±2.23 in FLAIR

Discussion

Amyotrophic lateral sclerosis is characterized by the degeneration of lower and upper motor neurons. Affliction of the lower motor neurons is easily determined by electrodiagnostic methods. Assessment of upper motor neuron degeneration is often limited in the clinical as well as in the electrodiagnostic examination. Additional information may be gained by MR imaging of the brain. In few ALS patients, hyperintense alterations of the corticospinal tract have been seen in proton density-weighted

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