A 59-year-old man presented with a 12-month history of progressive gait disturbance. A neurological examination showed a rigidity and hyperreflexia affecting his left leg, an ideomotor apraxia of his left foot, a speech disturbance, and mild deficits in executive functions, collectively indicating a corticobasal degeneration (CBD). Findings from laboratory screening and electrophysiological examination showed no abnormalities, and the results of a cerebrospinal fluid analysis (including tau protein and β-amyloid concentrations) were normal. T1-weighted high-resolution magnetic resonance (MR) imaging revealed an atrophy of the right parietofrontal cortex, and in particular of the right precentral and postcentral gyri (Figure 1). Additionally, tractography based on diffusion tensor MR imaging data was used to analyze the fibers of the corticospinal tract (a 1.5-T neuro-optimized GE tomograph [GE Medical Systems, Milwaukee, Wis], echoplanar sequence). Three-dimensional fiber tractography was computed using a home-built Monte Carlo simulation algorithm with seed points at the level of the medulla oblongata and 5000 starts per seed point (Figure 2). Each tract in Figure 2 represents the mean of more than 10 single paths. Clustering was performed on the basis of distance criteria. We observed a conspicuous reduction in the number of corticospinal projections to the right hemisphere at the level of the cerebral peduncle, the posterior limb of the internal capsule, and the centrum semiovale.
Boelmans K, Kaufmann J, Bodammer N, Heinze H, Niehaus L. Corticospinal Tract Atrophy in Corticobasal Degeneration. Arch Neurol. 2006;63(3):462-463. doi:10.1001/archneur.63.3.462