Snapshot A 36-year-old man presents to his primary care physician due to hand weakness. He reports that his symptoms are accompanied by "tingling" of the 4th and 5th digits. He says that his symptoms worsen when placing the phone to his ear for a long period of time or resting on his elbow. He does not recall any trauma to the wrist or elbow but reports elbow pain. His social history is significant for working as a construction worker. On physical exam, the patient has decreased grip strength on the right arm, as well as a decreased sensation on the 4th and 5th digit. Introduction Anatomy the ulnar nerve arises from the C8 and T1 anterior rami of the brachial plexus above the elbow the ulnar nerve courses medially at the elbow the ulnar nerve courses posteriorly of the medial epicondyle before entering the forearm at the forearm the ulnar nerve branches to provide motor innervation to the flexor carpi ulnaris flexor digitorum profundus sensory information after branching in the forearm to the palmar ulnar aspect of the hand (by the palmar cutaneous branch) dorsal ulnar aspect of the hand (by the dorsal cutaneous branch) at the wrist the ulnar nerve enters Guyon canal, which travels along the ulnar artery components of Guyon canal floor of the canal tranverse carpal ligament pisohamate ligament roof of the canal palmar fascia palmaris brevis muscle in the hand the ulnar nerve branches into superficial and deep branches Ulnar Neuropathies Ulnar NeuropathiesLocationEtiologyPresentationElbowInjury to the medial epicondyleCompression in the cubital tunnelcubital tunnel syndromeParalysis of theflexor carpi ulnarisflexor digitorum profundus (medial half)interosseiimpaired abduction and adductionlumbricals (medial two)weakened movement of the 4th and 5th digitSensory impairment in all regions supplied by the ulnar nerveUnable to grip paper when placed between the fingersWristLaceration of the wristParalysis of theinterosseiimpaired abduction and adductionlumbricals (medial two)weakened movement of the 4th and 5th digitUnable to grip paper when placed between the fingersUlnar clawSensoryimpairment of thepalmar and superficial branchespalmar side of the medial one and half fingers (5th and 1/2 of 4th digit)preservation of thedorsal branch