Does a clean emg mean no als?

Criteria for ALS: An entirely normal EMG is a strong vote against the diagnosis of ALS. Although an EMG does not diagnose ALS, it would be abnormal if ALS was present.

ALS on EMG: The diagnosis of Amyotrophic Lateral Sclerosis is a difficult one. Electromyography (EMG) can help by demonstrating subclinical evidence for the disease, with fasciculation potentials, fibrillation potentials and positive sharp waves supporting the diagnosis-especially when seen in the glossus (tongue) muscles and the thoracic paraspinals. It would be unusual for the EMG in ALS to be normal.

For the most part: There are some unusual variations of ALS involving mainly bulbar or facial musculature, and in some cases of primary lateral sclerosis, the basic EMG may be non-diagnostic, but in most cases, of ALS, EMG is quite abnormal.