The pronator quadratus (PQ) muscle is a muscle target in diagnosis of anterior interosseous nerve (AIN) syndrome, and it can be studied by both surface or needle electrode methods. In general, authors preferred surface recording than needle method because of the rather painful procedure to record the compound muscle action potentials (CMAPs) from its belly, and several parameters were measured such as distal motor latency (DML) after stimulation of the median nerve at the elbow and activation of its motor branch at the forearm (i.e. anterior interosseous nerve). Some authors recommended determining tha anterior interosseous nerve latency (AINL) for excluding median nerve neuropathy, especially in patients with normal ulnar and radial motor and sensory conductions but unobtainable median nerve distal conduction from the abductor pollicis brevis (APB) muscle. In this cases, performing AINL gives information about the presence of carpal tunnel syndrome (CTS) or entrapment neuropathy of the median nerve at the forearm, such as the AIN.