[The diagnosis of amyotrophic lateral sclerosis supported by motor evoked potential and brain MRI studies]

A 57-year-old man developed severe muscle weakness and atrophy of the upper extremities within a five-month period. Neurological examination revealed severe weakness and atrophy in the scapular muscles and proximal and distal muscles of the upper extremities. Fasciculations were also observed in the various muscles of the upper extremities. There was neither muscle weakness, atrophy nor fasciculation in either his face, neck muscles or lower extremities. He had no pseudobulbar or bulbar signs. Tendon reflexes were mildly hyperactive in the jaw and lower extremities, and normal in the upper extremities. There were no pathological reflexes, spasticity or sensory disturbances. The needle EMG study revealed denervation potentials in all muscles of the upper extremities examined. The nerve conduction study revealed no findings of the conduction block. Cervical spine X-rays revealed the narrowing of the spinal foramens at the left C3/C4 and bilateral C4/C5, C5/C6, and C6/C7 intervertebral levels. In addition, magnetic resonance imaging (MRI) revealed compressions of the cervical cord at C4/C5 and C5/C6 intervertebral levels. These clinical and neuroradiological findings resembled those of the cervical spondylotic amyotrophy (CSA). However, the motor evoked potential (MEP) study revealed the pyramidal tract dysfunction above the levels of the pyramidal decussation. Furthermore, brain MRI revealed abnormal foci in both internal capsules which were characterized by hyperintense relative to cortical gray matter on T2-weighted images and still hyperintense to white matter on proton-density-weighted images. In addition, T2-weighted images demonstrated a low signal within the motor cortex and hyperintense lesions in the white matter of the precentral gyri. These MRI findings indicated the degeneration of the pyramidal tract and corresponded to those found in the patients with amyotrophic lateral sclerosis (ALS) which have been recently reported. It has been difficult to distinguish ALS from CSA. However, MEP and brain MRI studies were useful for distinguishing these two diseases in this patient. In addition, this patient showed typical MRI findings suggesting the degeneration of the pyramidal tract, although this patient had a relatively short course of illness and did not show obvious physical findings suggesting pyramidal tract dysfunction.