Hyperintensity of the corticospinal tract on FLAIR: A simple and sensitive objective upper motor neuron degeneration marker in clinically verified amyotrophic lateral sclerosis

Objective: The involvement of upper motor neuron (UMN) degeneration is crucial to the diagnosis of amyotrophic lateral sclerosis (ALS). However, it is difficult to detect in the early stages, and particularly with predominantly lower motor neuron (LMN) dysfunction. Thus, objective and sensitive UMN degeneration markers are needed for an accurate and early diagnosis. Several studies have investigated the abnormal signal changes in brain MRI for patients with ALS, so we hope to develop a neuroimaging diagnosis method in brain MRI that can evaluate UMN degeneration.

Materials and methods: We investigated corticospinal tract (CST) hyperintensity on MRI-fluid attenuated inversion recovery (FLAIR) images for 82 clinically verified ALS patients and 38 age-and gender-matched control subjects. Visual evaluation of the FLAIR images was analyzed independently by 3 observers. The clinical examination was implemented by an experienced neurological physician.

Results: The three observers' views were identical regarding CST hyperintensity on FLAIR images in subcortical precentral gyrus, centrum emiovale, internal capsule, and cerebral peduncles levels (p>0.05). The frequency of CST hyperintensity is significantly higher for the ALS group than the control group in subcortical precentral gyrus, centrum semiovale, posterior limbs of internal capsule and cerebral peduncles levels. (p<0.01). The mean areas under the receiver operating characteristic curves (AUC) values were not different among clinical examinations, CST hyperintensity and mixed-examination (CST hyperintensity and clinical examination groups) in subcortical precentral gyrus, centrum semiovale, internal capsule, and cerebral peduncles levels (p>0.05), although AUC values of CST hyperintensity was slightly higher than clinical examination in centrum semiovale level. There was no statistically significant correlation between CST hyperintensity and age of onset, gender, disease duration, region of onset, and clinical UMN manifestation. (p>0.05).

Conclusion: CST hyperintensity was found more frequently in patients with ALS compared to the matched control group. It can be used to evaluate UMN degeneration effectively in subcortical precentral gyrus, centrum semiovale and cerebral peduncles levels. Combining CST hyperintensity and clinical examination can improve the sensitivity of diagnostic performance for UMN degeneration in ALS.