Science News: Natural History of "Pure" Primary Lateral Sclerosis

Submitted by: Hristelina Ilieva, MD, PhD
Edited by: Betul Gondogdu, MD

Hassan A, Mittal SO, Hu WT, Josephs KA, Sorenson EJ, Ahlskog JE. Natural history of “pure” primary lateral sclerosis. Neurology. 2021;96(17):e2231-e2238. doi:10.1212/WNL.0000000000011771

Summary: This retrospective review of pure primary lateral sclerosis (PLS) patients seen at Mayo Clinic-Rochester over a 26 year period (1990-2016), describes clinical characteristics and laboratory findings of 43 patients. Of these, 25 (58%) were female; median onset-age was 50 years (range: 38-78), and median follow-up duration was 9 years (range:4- 36). The ascending paraparesis phenotype (N=30; 70%) was most common, followed by hemiparetic-onset (N=9; 21%) and bulbar-onset (N=4; 9%). Among the 30 paraparetic-onset cases, bladder symptoms (n=18; 60%) and dysarthria (n=15; 50%) were more common than pseudobulbar affect (n=9; 30%); and dysphagia (n=8; 27%).  By last follow-up 17/30 (56%) used a cane; 6 (20%) required a wheelchair. The paraparetic-variant, compared with hemiparetic and bulbar-onset, had youngest onset (48 vs. 56 vs. 60 years, respectively; p=0.02). Five patients died, 1 required a feeding tube, and none required permanent non-invasive ventilation. Two patients developed minor EMG abnormalities. The remainder 39 had persistently normal EMGs. Pure PLS did not convert to ALS after median 9 years disease duration in this population. After years of pure PLS, less than 5% had a more pervasive neurodegenerative disorder.

Comments: This is a comprehensive review of PLS patients in a single center with longitudinal follow up for a median of 9 years and provides useful information for clinicians with regards to diagnostic criteria and prognosis.