Can ALS be diagnosed using an EMG?

An EMG examination is a supplementary diagnostic test used to support clinical diagnosis. The EMG does not provide findings that are specific enough to ALS to allow a diagnosis to be made based on the EMG alone. The diagnosis of ALS is based on physical (neurological) findings of muscle weakness (paresis), muscle wasting (myopathy), or muscle stiffness (spasticity), which are present in specific combinations. The EMG supports and “objectifies” the clinical findings.

EMG diagnostics can be used in the early stages of ALS to detect the spread of the disease from a region showing external signs (with obvious symptoms) to another region (still without outward signs, but already showing EMG changes) (EMG-assisted diagnosis of ALS). A diagnosis of ALS based “solely” on an EMG is not possible, even according to international diagnostic criteria. In any case, the presence of neurological symptoms is required for a diagnosis of ALS. In certain forms of ALS, particularly primary lateral sclerosis (PLS), EMG abnormalities may be completely absent.