Primary lateral sclerosis is a rare neuromuscular disease with slowly progressive weakness in voluntary muscle movement. PLS belongs to a group of disorders known as motor neuron diseases. PLS affects the upper motor neurons (also called corticospinal neurons) in the arms, legs, and face. It occurs when nerve cells in the motor regions of the cerebral cortex gradually degenerate, causing movements to be slow and effortful.
Data on the incidence of primary lateral sclerosis (PLS) are uncertain. In contrast, data on ALS are well documented; ALS affects 2-3 individuals per 100,000 population each year. The 8 patients with PLS reported by Pringle et al in 1992 were identified over a period of 10 years among a population of 500 patients with ALS.
Medication to relieve muscle spasms (spasticity), such as baclofen, tizanidine (Zanaflex) or clonazepam (Klonopin). These medications are taken by mouth (orally). If your spasticity isn't controlled with oral medication, doctor may recommend surgically implanting a medication pump to deliver baclofen directly to your spinal fluid (intrathecal baclofen).