Primary Lateral Sclerosis

Excerpt

Primary lateral sclerosis (PLS) is a selective upper motor neuron disorder characterized by insidious onset of symptoms in the absence of lower motor neuron involvement. This condition is a diagnosis of exclusion. Therefore, other causes of upper motor neuron dysfunction, including hereditary spastic paraplegia, must be ruled out. The clinical course of PLS is typically more prolonged and benign than that of amyotrophic lateral sclerosis (ALS). PLS classically involves the lower limbs in a symmetric distribution, although heterogeneity exists with some patients presenting with bulbar onset of symptoms.

Clinical symptoms include stiffness, bulbar symptoms (eg, difficulty speaking and swallowing), labile affect (ie, pseudobulbar affect), mild weakness, and balance and coordination difficulties. PLS is diagnosed after a detailed clinical history, physical exam, and diagnostic testing have excluded other causes. Electromyography (EMG) is often normal but can aid in differentiating PLS from ALS when lower motor neuron dysfunction is observed. Brain magnetic resonance imaging (MRI) may be normal but can show changes in the precentral gyrus or corticospinal tracts, although these findings are not specific to PLS. No cure or disease-modifying treatment has been established for PLS, and treatment is supportive with the primary goal of improving functional mobility.