SSEP and F-wave studies in acute inflammatory demyelinating polyradiculoneuropathy.

Somatosensory evoked potentials (SSEPs) and F-wave responses were compared after tibial (PTN) and median (MN) nerve stimulation in patients with acute inflammatory demyelinating polyradiculoneuropathy (AIDP). Nineteen patients were evaluated within 2 weeks of AIDP onset. Each had F-wave and PTN-SSEP studies; 18 had MN-SSEP studies. Ten patients had absent or prolonged MN-SSEP latencies, whereas 16 had abnormal MN F-wave studies. Seventeen patients had an abnormal PTN-SSEP while 12 had abnormal PTN F waves. Every patient with an abnormal MN-SSEP also had an abnormal PTN-SSEP. The most common PTN-SSEP findings were an absent or prolonged latency of N8 or N22. All patients had either an abnormal MN F wave or PTN-SSEP.