You probably remember my recent post regarding my plateau of progression and that I wrote to Kings Hospital for a response to 3 questions. Here is the reply
Many apologies for the long delay in my replying.
To respond to your questions:
1. A pattern of plateau is rare. I would say fewer than 5% experience this, and probably fewer than 1%.
2. The diagnosis of ALS is based on the pattern of weakness and its distribution. This would not change since the condition does not reverse, so you would still have ALS. The condition has stopped progressing for some reason.
3. It would be ideal to study people who plateau, but the problem is how. Most research needs large numbers of people to obtain statistically meaningful results, and because this event is so rare and is in a rare disease, we would need a considerable length of time to recruit enough people. Most funding agencies will not consider this.
We have studied prolonged survival, which is a similar but not identical issue, in two studies. The first was of the clinical characteristics of people with long survival. We found that the pattern of ALS did not help in predicting who would plateau or progress very slowly. The PLS pattern showed very slow progression, but half the people who lived a very long time had the typical ALS pattern with no obvious pointers to a slowing of the disease (Prolonged survival in motor neuron disease: a descriptive study of the King's database 1990-2002. Turner MR, et al, Al-Chalabi A. J Neurol Neurosurg Psychiatry. 2003). The second study was a genetic analysis of everyone from several centres, to see whether any gene variants were associated with a longer survival. We found that variants of the KIFAP3 gene were associated with better survival (Reduced expression of the Kinesin-Associated Protein 3 (KIFAP3) gene increases survival in sporadic amyotrophic lateral sclerosis. Landers JE, et al, Al-Chalabi A, Brown RH Jr. Proc Natl Acad Sci U S A. 2009). This has not been replicated by others. In a related study, we collaborated with colleagues from Holland who found that the UNC13A gene could affect survival (Genome-wide association study identifies 19p13.3 (UNC13A) and 9p21.2 as susceptibility loci for sporadic amyotrophic lateral sclerosis. van Es MA, et al. Nat Genet. 2009), and colleagues from Belgium who found that variation in the EPHA4 gene could EPHA4 is a disease modifier of amyotrophic lateral sclerosis in animal models and in humans. Van Hoecke A, et al. Nat Med. 2012). We are in the process of performing full genome sequencing of 50 people, half with very long survival and half with very aggressive disease, to see if there are any genetic differences that might be relevant.
I hope that helps.
With very best wishes,