Marfanoid features and X-linked mental retardation associated with craniofacial abnormalities: the Lujan-Fryns syndrome Aspectos marfanoides e retardo mental ligado ao X associados a anormalidades craniofaciais: síndrome de Lujan-Fryns

Appleton1, in 1911, reported the first description of this anatomical variation based on a forearm dissection. He found only the posterior radial nerve interosseous branch with absent SRN, below the elbow. On the dorsum of the hand, the LACN extended out beyond its usual distribution to supply the SRN territory (Figure). The dorsal branch of the ulnar nerve had greater ramifications than those usually observed by completing the innervation of the dorsal hand. Other authors2-5 have studied the distribution of LACN and SRN in the dorsum of the hand and confirmed the existence of this anatomical variation. In our assessment, the occurrence of an anatomical variation involving LACN and SRN, in which the cutaneous territory of the SRN is wholly or partially supplied by the LACN, can explain the data obtained in the presence of total lesion of the radial nerve in the arm. In cases of proximal radial nerve injury, the occurrence of this variation may lead to diagnostic errors in the EDX study, in which a total axonal damage may erroneously be considered as partial lesion with a conduction block component.