Simplifying the approach: what can we do?

Although it is desirable to simplify the diagnosis of amyotrophic lateral sclerosis (ALS), it is not obvious how to achieve this. Although a simplified electrophysiologic approach can be easily performed, interpretation of the results in a complex differential diagnosis is far from simple. Genetic screening may potentially be useful but is still in its infancy, even in familial ALS. Spasticity scales are most informative when greater degrees of spasticity are present, but usually these cases can also be identified clinically. It is difficult to envisage simplifying the scales because bedside rating scales are inherently not good at the mild end of the spectrum. Although MRI may prove to be useful in simplifying the diagnostic procedure, at present the numbers of patients studied are too small and the findings not sufficiently specific. Among the major issues that must be decided are whether any of the newer diagnostic techniques are sufficiently reliable, sensitive, and specific to allow any further simplification, and whether paraclinical tests are acceptable surrogates for clinical phenomena. The diagnostic approach of moving a possible diagnosis of ALS into the category of probable ALS earlier by giving more weight to electrophysiologic findings appears to be the only option, together with a more rigorous approach to excluding disorders known to mimic ALS. The problem lies less in the specialist reaching a correct diagnosis than at the level of initial evaluation, where the suspicion of ALS may be raised in only 27-40% of cases.