Differentiation between primary lateral sclerosis and amyotrophic lateral sclerosis: examination of symptoms and signs at disease onset and during follow-up.

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.