If you find a technical term in the text which you do not understand and which is not referenced to the glossary here please email me and I will add it. You can of course look these terms up easily online but I have tried to tailor the explanations here to the subject of CTS. If you are struggling with the interpretation of medical language in general then the Medical Librarians Association publishes a handy layman's guide to 'Medspeak'
Lesion - A difficult term much beloved of the medical profession. It is a convenient mental shorthand name which allows you to refer to a problem without knowing exactly what kind of thing it is. Linguistically the word literally means an injury but it is used for all kinds of disease states in constructions which are usually ways of saying in which body part or system a problem lies. Thus one may say that, in a patient with carpal tunnel syndrome ‘the lesion lies in the median nerve at the wrist’ because that is where the nerve is injured but in a patient with a kidney tumour one could equally well say that the lesion lies in the left kidney when talking about a completely different kind of disease process.
Syndrome - A collection of observations about a patient, which may include symptoms, signs or laboratory or imaging results which together make a recognisable pattern which is worth identifying with a name so that it can be discussed easily. A syndrome can have multiple different causes - it does not need to be a single disease but it is usually the case that a syndrome is believed to have a ‘common pathway’ thus in carpal tunnel syndrome the linking feature is generally believed to be raised pressure in the carpal tunnel - whatever the cause.
False positive - In the context of a diagnostic test, an abnormal test result indicating the presence of disease ‘x’ in a patient who does not actually have disease ‘x’. Every diagnostic test produces some false positive results, some more than others.
False Negative - In the context of a diagnostic test, a normal result for a test intended to detect disease ‘x’ in a patient who DOES in fact have disease ‘x’. Every diagnostic test has some false negative results too and again the proportion of these varies. All tests for CTS have significant false negative rates over 5%, some of them much higher.
Sensitivity - The ability of a test to detect a disease. Technically the proportion of individuals with disease ‘x’ in whom the test in question produces an abnormal result indicating the presence of disease ‘x’.
Specificity - Technically the proportion of individuals without disease ‘x’ in whom a test for disease ‘x’ produces a normal result. A perfect medical test would be abnormal in every patient with the disease in question and normal in everyone else but no medical test in use today achieves this ideal.
Idiopathic - derived from Greek and literally meaning ‘a disease of its own kind’ this term refers to disease for which no obvious cause can be established. Thus one can have carpal tunnel syndrome secondary to a wrist fracture or secondary to amyloid deposits in the carpal tunnel and in both of those cases we have a plausible cause for the problem. In most cases of CTS however no such cause can be identified and these cases are termed ‘idiopathic’. (See the entire section devoted to causes of idiopathic CTS though!)
The ‘Parachute argument’ - The more extreme apostles of evidence based medicine are fond of discounting all evidence regarding the effectiveness of medical interventions which is not derived from double blind, prospective, randomised clinical trials. For some interventions however the therapeutic effect is so obvious that there is no need for such trials - the effectiveness of the parachute in preventing death in persons falling out of aircraft at high altitude does not need a formal trial to demonstrate it. Some things about carpal tunnel syndrome fall into this category, such as the question of whether surgery is effective or not, but concentration on questions which did not really need answering has sometimes diverted attention and effort away from more difficult questions for which we do need answers.
Thenar eminence - the group of muscles at the base of the thumb. These are mostly innervated by branches of the median nerve and thus can become weak and wasted in advanced CTS (illustration needed)
Hypothenar eminence - the muscular bulge on the side of the palm opposite the thenar eminence (the little finger side). These muscles are innervated by the ulnar nerve and wasting of these muscles is NOT a feature of CTS.
Revision date - 3rd June 2011