Differentiating Slowly Progressive Subtype of Lower Limb Onset ALS From Typical ALS Depends on the Time of Disease Progression and Phenotype.

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What's in a name? Is Flail leg syndrome a variant of ALS or another disease? There are many anomalies in medicine, for example cancer sufferers in Western Europe could have a much different life expectancy when moving abroad, even when the new country is very similar to the country of origin.

It's a bit similar in ALS, it looks like ALS is not exactly the same disease in US, EU or Asia. Sometimes there is a understandable reason for example the statistical frequency of SOD1 mutations is different in Asia from US. Sometimes it is simply a matter of different semantics, some neurologists tell ALS is both upper and lower motor neurons, others have different opinions.

"Flail leg syndrome" is a Asian variant of amyotrophic lateral sclerosis with the characteristics of slow progression and the symptoms confined to the lumbosacral region for extended periods. In US it would have probably been called "Progressive Muscular Atrophy".

Yet there is no genetic background behind Flail leg syndrome, so why is it a regional appellation? In this new publication the scientists astonishingly decided that a slow progressing disease must be called "Flail leg syndrome".

The objective of a new study was to determine a cutoff time of disease progression that could differentiate Flail leg syndrome from the typical lower limb onset Amyotrophic Lateral Sclerosis.

A cutoff point analysis was performed with maximally selected log-rank statistics in patients with lower limb onset Amyotrophic Lateral Sclerosis registered from 2009 to 2013.

Based on the cutoff duration from the lower limb onset to second region (14 months), all patients were divided into the slowly progressive subtype of lower limb onset Amyotrophic Lateral Sclerosis group and the typical lower limb-onset Amyotrophic Lateral Sclerosis group.

Unsurprisingly the FLS was characterized by slower progression, less and later respiratory dysfunction, and a more benign prognosis than the typical lower limb onset Amyotrophic Lateral Sclerosis.

Patients with FLS exhibited a median diagnostic delay of 25 months, a median duration of 24 months from lower limb onset to second region, a forced vital capacity abnormity rate of 12.5% at the first visit to authors' department, and a median survival time of 80 months, which were significantly different from those of patients with typical lower limb onset Amyotrophic Lateral Sclerosis. The 5-year survival rate of the FLS group was much higher than that of the other group.

Now what all this mean? That if you select patients with a slow progression, you find they have a slow progression, is it high quality science?

Read the original article on Pubmed

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