April 16, 2015
Pronator Syndrome – Have you ever heard of it?
Recurrent carpal tunnel syndrome is not common. Perhaps 1:200 to 1:100 patients who undergo carpal tunnel release will get recurrent persistence of carpal tunnel syndrome despite a properly performed carpal tunnel release. In analyzing a person with persistent symptoms after carpal tunnel release or in the person who gets recurrence of symptoms, the differential diagnosis needs to include pronator syndrome. Pronator syndrome is a very unusual scenario wherein the median nerve is being compressed in the upper forearm as it passes through the pronator teres muscle. It is often a clinical diagnosis because we cannot prove the median nerve is entrapped there. Localizing tenderness or Tinel's sign and nerve conduction studies are usually not, but can be sometimes, helpful. Adding to the difficulty of making and confirming a diagnosis is the problem with persistent abnormalities on a person's nerve conduction study. The nerve conduction study abnormality is due to changes in the anatomy of the nerve's response to pressure on the nerve. In nerve entrapment syndrome treated early, these changes usually revert to normal. In almost everyone, they will at least improve. The combination of carpal-tunnel-type symptoms (from compression of the median nerve) are considerably improved with a median nerve conduction study at the level of the wrist with possible abnormality on needle electrode (EMG if performed – though rarely beneficial in this case) and a heightened sense of awareness will lead to the correct diagnosis and appropriate treatment. Use of the pressure-specified sensory device (PSSD) is also useful. Therefore, if you have persistent or recurrent carpal tunnel symptoms and it has been proved that the symptoms are definitely from the median nerve and not from untreated ulnar nerve entrapment at the elbow, consider the potential of pronator syndrome.