This report shows that magnetic resonance diffusion tensor imaging and fiber tracking can identify changes of the corticospinal tract in clinically diagnosed primary lateral sclerosis patients.
A 67-yr-old man presented with quadriparesis and dysarthria. Slowness and clumsiness of the left hand became evident at the age of 62 yrs. Spasticity involved the left arm and soon spread to all four limbs. In addition, spasticity caused spastic dysarthria. At age 65, he showed gait disturbance and occasional falling. He was unable to walk unaided by age 67. He showed respiratory distress and aspiration occasionally.
On examination, there was motor weakness (MRC score of 4–5) of both upper and lower extremities, bilateral ankle clonus, bilateral Barbinski responses, and spasticity, but no atrophy or fasciculations were observed.
Brain magnetic resonance imaging, cerebral spinal fluid examination, and standard laboratory tests, including serum glucose, Hba1c, thyroid hormones, vitamin B12 and folate levels, viral (HIV, hepatitis B), and long-chain fatty acid were normal. Vasculitis markers (ANA, cANCA, pANCA, anti-DNA antibodies) and cerebral spinal fluid oligoclonal band were negative.
Distal latencies, motor conduction velocities, F waves, and sensory nerve conduction were normal. Needle electromyography was performed in the muscles of both upper and lower extremities, tongue, and lower thoracic spine and showed normal resting potential and normal motor unit potential.
Fractional anisotropy (FA) and mean diffusivity of pyramidal tract were evaluated with magnetic resonance diffusion tensor imaging. The FA values were 0.452 and 0.460 at the left and right midbrain, 0.080 and 0.105 at the left and right ventral pons, and 0.074 and 0.110 at the left and right medulla. FA values were reduced in our patient compared with mean values of controls and amyotrophic lateral sclerosis patients.1 Abnormally decreased color of the pyramidal tract at the midpons was revealed on anisotropy map with directional color (Fig. 1). We performed fiber assignment by two-point continuous tracking between the posterior limb of the internal capsule and the cerebral peduncle. Tracking of axonal projection revealed severe depletion of corticospinal and corticobulbar projection fibers with preserved corticopontocerebellar fibers (Fig. 2).
Primary lateral sclerosis is a rare form of motor neuron disease characterized by selective degeneration of corticospinal and corticobulbar tracts. Ulug et al.2 reported decreased diffusion anisotropy on the posterior limb of the internal capsule in seven primary lateral sclerosis patients with quantitative diffusion tensor imaging.
In the present report, we used diffusion tensor imaging and tract tracking to examine one patient who met clinical criteria for primary lateral sclerosis. The quantitative diffusion properties were measured at the level of the brainstem with FA values, and tract tracking was obtained between the posterior limb and the cerebral peduncle. The FA values at the midbrain, pons, and medullar were lower than those of control group and amyotrophic lateral sclerosis group,1 and tract tracking showed severe depletion of the corticospinal and corticobulbar tracts with a relatively preserved corticopontocerebellar tract.
1. Hong YH, Lee KW, Sung JJ, Chang KH, Song IC: Diffusion tensor MRI as a diagnostic tool of upper motor neuron involvement in amyotrophic lateral sclerosis. J Neurol Sci
© 2006 Lippincott Williams & Wilkins, Inc.
2. Ulug AM, Grunewald T, Lin MT, et al: Diffusion tensor imaging in the diagnosis of primary lateral sclerosis. J Magn Reson Imaging