Whether or not ALS lesions spread contiguously?

Using clinical information, it was investigated whether lesions in sporadic amyotrophic lateral sclerosis (sALS) spread contiguously from an onset site to the another regions in domino-like manner as hypothesized by prion-like propagation of pathogenic proteins. First, the data from medical records of 53 sALS patients with bulbar or lower limb onset showed that the symptom has noncontiguously spread from the bulbar region to the lower limbs or vice versa, skipping the upper limbs, in 18.9% of the patients. Second, in 18 patients with upper limb onset, correlation between the local progression speed of symptom severity in the onset limb and the interval from onset to involvement of the second region (lower limb) was investigated. The symptom severity was assessed by a score on "dressing and hygene", the subscale of the revised ALS functional rating scale. The two parameters should be positively correlated, if the lesion propagates contiguously from an initially affected motoneuron to the neighbouring ones within the same motoneuron pool (local progression) and then propagates to the another motoneuron pools (regional spread). However, the statistically significant correlation was not found, suggesting that there may be the different mechanisms between local progression and regional spread of ALS lesions.