Diagnosis of Isaacs Syndrome Clinical evaluation Results of nerve conduction and EMG studies The diagnosis of Isaacs syndrome is based on the above clinical findings and results of nerve conduction and EMG studies, which show characteristic abnormalities; these abnormalities include after-discharges on nerve conduction studies and, on needle EMG studies, fasciculation potentials, myokymic discharges, neuromyotonic discharges, fibrillation potentials, and cramp discharges, most prominent in distal limb muscles.