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Carpal Tunnel Syndrome

We have a 35-year-old female who presents to your office with an eight week history of right hand pain carpal tunnel syndrome, carpel tunnel syndrome. The pain is associated with numbness and paresthesias in the right thumb and index finger. Symptoms are intermittent and wake her up at night. She shakes her wrist out, when she is awakened by the symptoms and this gives her some relief. Patients will shake their wrist out, you can ask them if they are doing this.

Now her work up is an electrodiagnostic study and the impression is abnormal, slowing across the carpal tunnel of the median sensory and median motor nerve without loss of amplitude and it is consistent with an early carpal tunnel syndrome. There is no evidence of a cervical radiculopathy.

As you can see here, this is the median nerve coming down and basically the distal most aspect of the median nerve is what is affected in a carpal tunnel syndrome. There is a delineation between the palmar aspect of the sensory and the finger sensory portion on the palmar aspect of the hand. The reason that this is delineated is that this part of the median nerve sensory jumps.

Now the prevalence of carpal tunnel is 55 to 125 cases per 100,000. Although sometimes in my practice I think it is a little higher than that. It is the most common nerve entrapment. Females are more at risk. It is a 3 to 1 ratio, females having carpal tunnel as opposed to males. Repetitive activity involving the wrist is a very high risk and also, recently the squareness of the wrist.

There is a classification for carpal tunnel syndrome, and we start out with early and its numbness, parasthesia, pain in the median nerve distribution. Symptoms are intermittent and worse at night, shaking the wrist out in the middle of the night is common. Intermediate is continuously diminished sensation in the median nerve distribution. There is reduced ability to manipulate fine objects.

The advantage of surgical decompression of the transverse carpal ligament is promoted, but here is where some of the controversy comes in with carpal tunnel syndrome. The problem comes in when something called dying back. Now if you remember I talked about wallerian degeneration, that is when the nerve itself dies distal to the injury.

Nerves are injured mechanically, metabolically through infection and through inflammation. Now mechanically it’s 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.

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.

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.

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 to the injury.

Our last classification is neurotmeses. Neurotmeses is basically severance of the entire nerve. You lose the axon the myelin and the connective tissues, the worse to have. Functionally, it is the same as axonmesis so you have loss of nerve conduction at the injury site and distal to the injury site.