Primary lateral sclerosis (PLS) is a rare neuromuscular disease characterized by progressive muscle weakness in the voluntary muscles. PLS belongs to a group of disorders known as motor neuron diseases. Motor neuron diseases develop when the nerve cells that control voluntary muscle movement degenerate and die, causing weakness in the muscles they control. PLS only affects upper motor neurons.
Single photon emission computed tomography (SPECT) scan studies in 2 patients showed reduced uptake in the motor cortex, as did positron emission tomography (PET) scan studies in 2 of 3 patients. Magnetic resonance spectroscopy (MRS) showed abnormal N -acetylaspartate/creatine ratios in 12 of 18 patients with PLS.
Treatment for individuals with PLS is symptomatic. Muscle relaxants such as baclofen, tizanidine, and the benzodiazepines may reduce spasticity. Other drugs may relieve pain and antidepressants can help treat depression. Physical therapy, occupational therapy, and rehabilitation may prevent joint immobility and slow muscle weakness and atrophy.