Click here to view next page of this article

 

Ulnar Neuropathy at the Elbow

This is a 46 year old anesthesiologist who has gradually noted mild, but progressive weakness in his right hand and numbness in the ring and little fingers. He comes to see you after his wife commented on the wasting of his right first web space. His numbness is constant and involves both dorsum and palmar aspects of the little finger and the palm, but does not extend proximally. He has no other symptoms in his other limbs and denies neck pain except when working with certain surgeries in the operating room. Physical exam reveals wasting in the hypothenar and first web space. Strength is a 4 out of 5 and finger abduction and adduction and thumb adduction.

Now this is a diagram of the ulnar nerve and at the elbow is where our lesion is. You can see here that we have on the dorsum of the hand, this is called the Dorsal ulnar cutaneous distribution or the DUCT distribution of the hand. The reason I point this out is that we can also have entrapments of the ulnar nerve at Guillainís canal at the wrist.

The ulnar compromise about the elbow is second to the carpal tunnel syndrome in the upper extremity focal neuropathies. Risk factors include repeated elbow flexion or extensions, such as truck drivers and leaning on the elbow such as students when they study, also COPD patients, when they are leaning forward to get breaths so they can take that extra puff.

Category two, is persistent sensory complaints with some degree of intrinsic muscle weakness. Category three, is there marked sensory loss, weakness and muscle atrophy. 

Now treatment conservatively is non-steroidals, rest and splinting of the elbow in extension. Category one, I tell patients go by those soft elbow braces that football players wear and it is obviously not going to prevent so much flexion, but it might remind them to keep the elbow extended while they are sleeping and it can be very helpful, a very minor thing to add to their regimen. Surgery is resection of the ligament medial epicondylectomy, transposition of the ulnar nerve and the decision on which procedure may not be determined until the time of the operation by the surgeon. Here is some other mechanical nerve injuries, tarsal tunnel syndrome is the lower extremities equivalent of a carpal tunnel syndrome. It is the tibial nerve being entrapped.

Resistant tennis elbow, posterior interosseous syndrome is when people have lateral epicondylitis that doesnít get better despite adequate treatment. That brings us to the questions from last yearís takes a picture in time while an electrodiagnostic study evaluates the physiology of the neuromuscular system, 79% of patients had different diagnoses after the electrodiagnostic studies from that of the referring physician.

Next question, how quickly should an EMG be ordered after a patient presents to your office with clinical findings? The highest yield will be attained at 3 to 4 weeks for many different reasons that we do not have time to come into, but that is when you want to get the EMG, that is when the study should be done. What are the indications to do an electrodiagnostic study.

Nerves are injured mechanically, metabolically through infection and through inflammation. Now mechanically itís the space where the nerves travel is too small, very simple. Examples are carpal tunnel syndrome through the transverse carpal ligament and lumbosacral radiculopathies from herniated nucleus pulposus. Metabolically the primary metabolic disease breaks the nerve down at the axon or the myelin level, example as being diabetes, obviously a very common malady and uremia from chronic renal insufficiency.

Our focus today is going to be on the mechanical causes of nerve injuries, and we are going to talk about carpal tunnel syndrome, lumbosacral radiculopathies, peroneal neuropathies at the fibular head, cervical radiculopathies and ulnaropathy at the elbow. Before we do that I am going to talk about three classifications of nerve injuries. We are going to start talking through neuropraxia. Now neuropraxia, you can see it is a local myelin injury and if you remember that slide that looked at the nerve itself, and it had myelin on the outside and the axon on the inside.

Here is an example using a blood pressure cuff as our focus of injury. You have a normal nerve again, the nodes of Ranvier right here, saltatory conduction, inside here is the axon, the outside layer being the myelin. You have your cuff in place, the cuff is inflated it causes a breakdown of the myelin.

The second classification is axonmesis, now this is destruction of the axon itself. What you have is something called wallerian degeneration. That means that distal to the injury, the nerve itself dies all at the same time. The reason behind that we think, is that the nerve distal.