Frequency of Type-1 Berrettini's Connection in a Neurophysiology Laboratory.

 This study aims to estimate the frequency of Berrettini's ulnar-median nerves communication in a neurophysiology laboratory.  A total of 358 hands belonging to patients, both sexes, median age of 58 years, was studied. Antidromic sensory nerve conduction studies of the ulnar nerves, registered in digits III and IV were performed in search of the ulnar-median communication. A Berrettini's percentage was calculated in each communication: [(amplitude SAP digit III/amplitude SAP digit IV) × 100].  Ulnar-median nerves communication (Berrettini's branch) was found in 37 hands (10.95%), with a female gender predominance. Bilaterality percentage was low (1.78%). Most communications encountered had a Berretini's percentage between 11 and 50%. Some of them exceeded 100%.  Electromyographers should routinely search for this nerve communication, especially in those patients undergoing carpal tunnel syndrome or Dupuytren's contracture surgeries.