Your Patient Presents with the Following NCS and EMG Findings

Your patient presents with the following NCS and EMG findings: Decreased CMAP but normal SNAP amplitudes,normal motor and sensory nerve conduction velocity (NCV) values,repetitive motor nerve stimulation (RMNS) shows decreased response post exercise,no insertional activity,few spontaneous fibrillations,and some decreased amplitude polyphasic waveforms.This is suggestive of which of the following myopathic conditions?

A) Myopathy with denervation or polymyositis
B) Myotonia
C) Presynaptic neuromuscular junction (NMJ) disorder
D) Postsynaptic neuromuscular junction (NMJ) disorder