The ulnar nerve runs to the pinky side of the hand where it is responsible for both muscle actions and sensations. Because the nerve must travel through a small canal at the wrist, the nerve can become entrapped resulting in pinky and or ring finger numbness as well as difficulty pulling your thumb in towards your hand and using your pinky, depending on which portion of the nerve is compressed.
Ulnar nerve compression can be caused by numerous factors. Soft tissue tumors can impinge on the nerve in the narrow space it has to travel into the palm. Long-term trauma can also cause nerve damage, like vibrations (jackhammer use), prolonged pressure on the wrist (i.e. weight lifting and bike riding), which is often conservatively treated by rest and occupational adjustments. Acute trauma, like wrist bone fractures can also impinge on the ulnar nerve. Arthritis and metabolic conditions, such as alcoholism, hypothyroidism or diabetes can also play a role.
When diagnosing patients with ulnar nerve entrapment, doctors must consider multiple sites higher in the arm that could potentially be causing the problems at the hand and take a careful history including occupational use and length and duration of the hand numbness or muscle weakness. Examination should also include strength tests, sensation testing, ulnar nerve testing along its path through the arm, and a vascular examination. All results should be compared to the uninvolved side. MRI, x-rays, and nerve conduction tests can also help determine exactly why and where the nerve is being compressed.
Ulnar nerve compression is first treated by nonsurgical management, such as rest or physical therapy. If symptoms do not resolve within two to four months surgery is recommended. Surgery involves either removal of the compressive tissue, wrist fracture repair, or open up the canal through which the ulnar nerve runs. Evidence is sparse regarding surgical outcomes, however the existing studies show good results with surgery.