Abnormal peripheral nervous system physiology Phrenic neuropathy 2025-08-10T11:09:56Z A functional deficit of the phrenic nerve. Phrenic neuropathy (PhN) is a debilitating condition characterized by impairment of the diaphragm muscle, the primary inspiratory muscle. Diaphragm muscle ultrasound is a noninvasive tool that appears to offer both high sensitivity and specificity for diagnosis. Alternatively, electrodiagnostic studies can assess phrenic nerve health. PhN is commonly diagnosed via diaphragm muscle US or fluoroscopy (sniff test) with paradoxical or significantly decreased diaphragm muscle movement. Phrenic nerve neuropathy