Cubital Tunnel Syndrome

Ulnar neuropathy at the elbow — The clinical features of ulnar neuropathy at the elbow (UNE) are understood based upon knowledge of the motor and sensory distribution of the ulnar nerve and its major branches. Sensory symptoms of numbness or paresthesiae in the ulnar nerve distribution are the most frequent initial complaints . It is the author’s impression that patients usually experience the sensory symptoms over the volar aspect of the fourth and fifth digits and ulnar aspect of the hand. The presence of sensory symptoms in the dorsal ulnar or palmar cutaneous territory is helpful in localizing the lesion proximal to the distal forearm or wrist, but these complaints are not always present. As an example, in one study of 25 patients with UNE, sensory symptoms involved the digital terminal branches, the palmar cutaneous territory, and the dorsal cutaneous territory in 92, 80, and 72 percent of patients, respectively . Some patients with severe and persistent numbness have sensory symptoms that split the ring finger. Medial elbow pain or aching is common and many patients report referred pain along the medial forearm. Sensory symptoms from UNE are often brought on by sustained elbow flexion (eg, when talking on the phone or lying on one's side with the elbow flexed). Symptoms can also be provoked by leaning on the elbow or when performing activity that requires sustained or repetitive grip, or repeated forearm pronation and supination. Motor symptoms in UNE are less common than sensory symptoms, but range from mild weakness of intrinsic hand muscles to severe wasting and claw hand deformity (picture 1). Some patients will report only mild weakness and clumsiness of the hand during activities requiring dexterity and fine control such as buttoning or typing. Loss of dexterity due to ulnar neuropathy is usually indicative of weakness of the intrinsic hand muscles (ie, the lumbricals and interossei), in contrast to mild median nerve injury, where loss of dexterity is most often related to sensory loss. More significant involvement of the ulnar-innervated forearm muscles, primarily flexor digitorum profundus to the fourth and fifth digits, leads to complaints of grip weakness and difficulty lifting and carrying. In a report of 25 patients with UNE, weakness of the first dorsal interosseous, abductor digiti minimi, flexor digitorum profundus, and flexor carpi ulnaris was present in 84, 76, 56, and 20 percent of patients, respectively . This distribution is consistent with our clinical experience. Ulnar neuropathy at the wrist — Ulnar neuropathy at the wrist (UNW) typically presents with hand weakness and atrophy, loss of dexterity, and variable sensory involvement. The extent of clawing of digits four and five can be worse with lesions at the wrist than at the elbow as a result of sparing of the flexor digitorum profundus and weakness of the third and fourth lumbricals, resulting in greater muscle imbalance. Injury to the terminal branches of the ulnar nerve at the wrist is often divided into four sites and their associated clinical scenarios: ●1) Injury to the main trunk of the nerve proximal to or within Guyon's canal. These lesions will produce sensory symptoms in the distribution of the superficial terminal branches, and motor involvement of all ulnar innervated intrinsic hand muscles (hypothenar muscles, interossei, lumbricals three and four, and the adductor pollicis). ●2) Injury to the deep terminal motor branch of the ulnar nerve proximal to the branches supplying the hypothenar muscles. This will again produce motor symptoms in all of the ulnar-innervated intrinsic hand muscles but no sensory symptoms. ●3) Injury to the deep motor branch distal to the hypothenar muscles will spare the hypothenar muscles and result in no sensory symptoms, but the remainder of the ulnar-innervated intrinsic hand muscles will be affected. ●4) Injury to the superficial terminal branch supplying the superficial sensory branches will result in sensory involvement of the digital branches but no motor involvement. Clinically detectable dysfunction of the palmaris brevis muscle innervated by this branch is unlikely. While this classification makes sense anatomically, the actual anatomic site of the lesion does not reliably correlate with the clinical features of UNW. As an example, a lesion within Guyon's canal can spare the hypothenar branch or deep motor branch. This is a result of the fascicular arrangement of the nerve and the typically incomplete involvement of all fascicles with injury or compression a given level, especially with lesions of the main trunk of the nerve within Guyon's canal. Nevertheless, this approach provides a framework for clinical assessment prior to further investigation.