Ulnar tunnel syndrome

Ulnar tunnel syndrome, also known as Guyon's canal syndrome or Handlebar palsy, is ulnar neuropathy at the wrist where it passes through the ulnar tunnel (Guyon's canal).^[1] The most common presentation is a palsy of the deep motor branch of the ulnar nerve causing weakness of the interosseous muscles. Ulnar tunnel syndrome is usually caused by a ganglion cyst pressing on the ulnar nerve; other causes include trauma to the wrist and repetitive movements, but often the cause is unknown (idiopathic).^[2] Long-distance bicycle rides are associated with transient alterations in ulnar nerve function.^[3] Sensory loss in the ring and small fingers is usually due to ulnar nerve entrapment at the cubital tunnel near the elbow, which is known as cubital tunnel syndrome. It can uncommonly be due to compression at the wrist.