Abstract

Primary lateral sclerosis (PLS) is a rare neurodegenerative disorder at the upper motor neurone extreme of the spectrum of motor neurone disease. The diagnosis is clinical and based on the characteristic features of slowly progressive spasticity beginning in the lower limbs, or more rarely with spastic dysarthria, typically presenting around 50 years of age. The absence of lower motor neurone involvement is considered to be a defining feature, but confident distinction of PLS from upper motor neurone-predominant forms of amyotrophic lateral sclerosis may be difficult in the first few years. Corticobulbar involvement in PLS is frequently accompanied by emotionality. While there may be dysphagia, gastrostomy is rarely required to maintain nutrition. Cognitive dysfunction is recognised, though dementia is rarely a prominent management issue. PLS is not necessarily life shortening. Specialised multidisciplinary care is recommended. Increasing international research cooperation is required if the aspiration of dedicated therapeutic trials for PLS is to be achieved.