Kathylund, Filmmaker: my understanding is that if the 'only' problem a person has is ALS then a muscle biopsy should reveal the muscle is healthy, although perhaps atrophied (from less than normal use, for example). This can help an M.D. rule out many other possibilities and if ALS is the only one left, that is likely the 'diagnosis' that will develop. In ALS affected tissue, EMG tests can, at least for a while, show giant and/or polyphasic action potentials . . . these signals are 'louder' than the normal ones that should appear. If such giant and/or polyphasic signals appear, then the region of the patient's neuro-muscular system tested is undergoing processes that are trying to heal . . . there are many things that can cause these healing processes to activate, an athletic injury is probably the most common . . . but ALS is another. In most cases these processes will be successful but can require almost a year to complete. If the processes persist for a year or more, then one of the criteria for the ALS 'diagnosis' is usually considered satisfied (persistent lower motor neuron disorder). There are additional requirements for the 'diagnosis.' I do not believe a biopsy will show active denervation, the EMG will show active efforts to REINNERVATE the muscle area and if this persists for too long a period of time, active denervation is IMPLIED. ALS disease processes are widely believed to cause active denervation . . . but the matter remains unproven because the cause(s) of ALS remain unknown. Denervated muscle tissue will indeed atrophy. Technically, neither the muscle biopsy nor the EMG may show active denervation.
