Amyotrophic lateral sclerosis

What it is

Amyotrophic lateral sclerosis is a neurodegenerative disease with selective loss of pyramidal neurons in the primary motor cortex and of motor neurons or anterior horn cells in the spinal cord, so that both upper and lower motor neuron signs are present. It is one of the diseases of the anterior horn, with spinal muscular atrophy and polio. The macroscopic picture is thin anterior roots and mild atrophy of the precentral gyrus, the primary motor cortex. The microscopic picture is loss of neurons in the anterior horn, a LMN lesion; degeneration and atrophy of the lateral corticospinal tracts, a UMN lesion; loss of neurons in the motor nuclei of CNs V, IX, X and XII; and denervation atrophy of muscle with small, angular fibers. Mutation of the copper-zinc superoxide dismutase (SOD1) gene may be implicated.

How it presents

The LMN symptoms are muscle atrophy and fasciculation; the UMN symptoms are spasticity, hyperreflexia and pathologic reflexes. Bulbar involvement is present (++), and there are NO sensory deficits. One case is a 40 years old man with 10 months of progressive weakness involving the right arm, similar symptoms in the left arm eight months later, and bilateral shoulder pain without weakness; a few months later he developed a pseudobulbar effect and weakness in his limbs that affected his gait. Examination showed fasciculations in the arms, atrophy of the right arm, brisk reflexes in UL and LL with pathological spread, upgoing plantars bilaterally and a normal sensory examination. Amyotrophic lateral sclerosis is also one of the neurologic causes of oropharyngeal dysphagia.