Background: Motor neuron diseases can affect the upper motor neuron and/or the lower motor neuron. Both amyotrophic lateral sclerosis (ALS) and primary lateral sclerosis (PLS) are motor neuron diseases, and there is much debate as to whether these are 2 separate disorders or simply 2 points on a continuum.
Objective: To determine which clinical features at onset and during follow-up could help differentiate between PLS and ALS.
Design: Retrospective study comparing patients with a diagnosis of PLS or ALS for differences in symptoms or signs at disease onset and during follow-up.
Setting: Tertiary referral center. Patients Six hundred sixty-one patients with ALS and 43 patients with PLS were included in the study.
Results: At presentation, stiffness was the only symptom that was significantly different between patients with PLS and patients with ALS (observed in 47% and 4% of patients, respectively; P<.001). During follow-up, limb wasting was rare in patients with PLS (2%, compared with 100% in patients with ALS; P<.001). Disease duration was significantly longer in patients with PLS compared with patients with ALS (mean +/- SD, 11.2 +/- 6.1 vs 3.8 +/- 4.2 years, respectively; P<.001). During the 16 years of follow-up, the mortality rate was significantly lower in patients with PLS compared with patients with ALS (only 33% vs 89%, respectively; P<.001).
Conclusion: Our findings suggest that a patient presenting with spasticity who does not develop wasting within 3 years most likely has PLS.