Histological-MRI correlation in the primary motor cortex of patients with amyotrophic lateral sclerosis
To establish the relationship between ALS histopathology and quantitative MRI metrics. ALS patients (N = 8) in advanced stages of the disease were enrolled and, immediately after death, the brain of each patient was removed. Freshly excised ALS tissue was imaged at 3.0 Tesla with T1 and T2 mapping protocols and subsequently stained with astrocyte, myelin, and neuronal markers. Measures of ALS histological stains were compared with the internal control (primary visual cortex) and longitudinal parametric maps. Post-mortem T1 -weighted images demonstrate diminished contrast between gray and white matter and alterations in T1 relaxation within the primary motor cortex. An increase in astrocyte number and reactivity as well as evident neuronal loss, a decrease in axonal density, and unraveling of the myelin sheaths in subcortical white matter were found in the ALS primary motor cortex exhibiting significant T1 relaxation and contrast changes. This study provides a histopathological basis for differences in MR T1 contrast and relaxation seen in the ALS brain.