Tips on examination technique
Typical findings in early CTS
Typical findings in late CTS
Other findings that indicate a possible alternative diagnosis
Inspection
Look for wasting of thenar eminence and trophic changes to the pulps and skin
Often no abnormal findings
Indentation of thenar eminence due to wasting of abductor pollicis brevis or flattening of whole thenar eminence
Interrosseus wasting may give rise to
Trophic changes of the pulps and skin corresponding to the median nerve territory
Intermetacarpal guttering – ulnar nerve or T1 involvement
Sensation
Changes in light touch are very sensitive. Test at the pulp of the index finger and the pulp of the little finger to see if the patient can detect a difference between the median and ulnar territory.
May not have any changes initially, or may describe index sensation as reduced compared with the little finger
Progresses to complete loss of sensation in median innervated area
Numbness including the little finger – consider ulnar involvement
Two point discrimination is an innervation density test rather than a threshold test, so will not show any detectable change until very late. If an objective measure is required then Semmstein Weiss monofilaments are a threshold test and therefore more sensitive.
Reduced sensation in a glove distribution – consider peripheral neuropathy as may be seen in diabetes
Paesthesia or numbness in a dermatomal distribution, e.g. Thumb and index for C6, middle finger for C7 – consider radiculopathy
Motor power
Test all muscle groups innervated by the median nerve;
Often full strength maintained
Progressive weakness of muscles innervated distal to CT
Weakness of muscles innervated proximal to CT may indicate other pathology or compression more proximally, such as deep to the heads of PT or at the neck
Distal to CT;
Abductor pollicis brevis
Proximal to CT;
Flexor pollicis longus – e.g. use the ‘O’ sign (see Fig. 12.1)
Flexor digitorum superficialis to all digits and flexor digitorum profundus to index and middle
Flexor carpi-radialis
Provocation tests (see text for description)
‘Tinel’s’ sign
Often positive at carpal tunnel
May become negative in very late stages
May be positive in proximal forearm on compression deep to PT
Phalen’s test
Usually positive, but may take 40 s or more to elicit paresthesia
Positive within a few seconds, may go numb rather than experience paraesthesia. In very late cases where numbness is dense and permanent no change in symptoms can be elicited and the test is negative
Pronator provocation
Negative
Negative
May be positive if compression is occurring deep to heads of PT
Inspection, together with an examination of sensation to the digit. Motor power, particularly of the intrinsic, following by provocation tests of all potential compression sites along the nerve.
Provocation Tests
Tinel’s Sign
The term ‘Tinel’s sign’ in this context is actually a misnomer, as Tinel described paraesthesia occurring in the distribution of a nerve when the nerve has been injured and percussion is used distal to the point of injury. This is specifically a sign indicating progression of recovery following a nerve injury, by eliciting symptoms from the immature advancing nerve ends. However, it is very commonly used in the context of carpal tunnel syndrome and other compression syndromes where it is taken to mean paraesthesia provoked by percussion at the site of the compression.
Percussive tapping is used to provoke the symptoms and should be started from the index or middle finger distally to proximal to the elbow following the line of the median nerve. The patient should be asked before the percussion is started to indicate if at any point it causes unpleasant tingling. Symptoms elicited at the CT indicate likely compression, although percussion should continue proximally to check whether they are also elicited at the pronator teres (PT) site.
Phalen’s Test
In 1966 Phalen described his wrist-flexion test in which ‘the patient is asked to hold the forearms vertically and to allow both hands to drop into complete flexion at the wrist for approximately 1 min’ [8]. Figure 12.2 shows the posture the hands should be placed in to perform Phalen’s test. The test is positive if it produces CTS symptoms in less than 1 min.
Fig. 12.1
(a) The O sign for testing FPL Shows a competent O and the strength of FPL can be tested by the examiner linking a finger through the O and attempting to break it against resistance from the patient. (b) When FPL is very weak the patient is unable to make an O as seen here
Fig. 12.2
The position of the hands for eliciting Phalen’s sign
Many variations on this test have been described, some of which are thought to be more sensitive, although this may be at the expense of a higher false positive rate. Also, most of them involve an amount of pressure applied either by the examining doctor or by the patient pressing their hands together. Both of which introduce an element of variability that may make the sign less reliable and comparison between case series’ more difficult.
Pronator Provocation
The space available for the nerve deep to PT is reduced by resisted contraction of the muscle with the elbow extended. If the gap between the two heads of pronator is palpated and light pressure applied, the patient will experience discomfort if compression is present. Rarely, however, actual paraesthesia is elicited.
It can be seen from the table that in the early stages there is little to find on examination, other than possible positive provocation signs. However, if there is a clear history of typical symptoms and one or more positive provocation signs, this is usually enough to make a diagnosis of CTS. In later stages, provocation tests may become negative, but other signs become apparent. If the history or findings are NOT typical then nerve conduction studies (NCS) should be considered in order to confirm or exclude the diagnosis.
Clinical Pearl
If there are any findings indicating possible compression by pronator teres (PT) then nerve conduction studies (NCS) should be used to assess involvement of the nerve at this level.
However, when a referral for NCS is made to confirm the diagnosis of CTS many centres would only carry out a focused examination at the carpal tunnel level. Therefore, if there is suspicion about possible compression at PT level, then these clinical findings must be included in the NCS referral to help guide the appropriate tests – i.e. for the NCS to assess the median nerve at the CT and more proximally in the forearm. Similarly, if symptoms extend into the ulnar nerve territory this should be highlighted.
Treatment Options
Treatment options that have been found to be of benefit include splinting, steroid injection and surgery.
Splinting
A recent Cochrane review concluded that many of the trials for splinting were poorly conducted and provided only weak evidence of beneficial effect. However, where patient’s symptoms are mainly nocturnal, a night splint can be very effective at relieving their symptoms in the short term, with benefit being experienced up to 1 year from the initiation of treatment [10].
Clinical Pearl
The splint needs to be positioned, such that it holds the wrist in neutral, which maximises the cross sectional area within the carpal tunnel. However, many commercially available wrist splints are designed to support a painful wrist in a functional position and they therefore hold the wrist in 20–30° of extension. This is not appropriate for carpal tunnel syndrome, as it increases the traction on the nerve and reduces the space within the tunnel. As a consequence, patients who are using off the shelf splints may experience little benefit, or even be made worse.
Steroids
Treatment of carpal tunnel syndrome with injection of steroids into the carpal tunnel has also been the subject of a recent Cochrane review.
The conclusion was that:
Steroid injection provided clinical improvement 1 month after injection, compared with a placebo,
Compared with oral steroid, an injection of steroids at the carpal tunnel provided greater benefit for up to 3 months,
The improvement seen with steroid injection is not significantly greater than that seen with anti-inflammatory medication and splintage,
Improvement is no greater with 2 injections than 1
Long term benefit has not been demonstrated [11].
Relief of symptoms with steroid injection is both diagnostic and predictive of a beneficial outcome from surgical release. It may, therefore, be useful in those cases where there is doubt over the diagnosis and symptoms are severe enough to warrant an invasive diagnostic procedure that may also give temporary relief. However, the injection requires expertise, so injection into the carpal tunnel by an untrained practitioner should not be used as a substitute for expert clinical review. Long term effects of steroid injection into the carpal tunnel are not known and, in the author’s experience of referrals following injection in the primary care setting, complications of injection can include complex regional pain syndrome and tendon rupture. In conclusion, steroid injection has a limited place, but can be offered to patients with mild symptoms of recent onset, in whom splintage has not sufficiently relieved their symptoms. Follow up, or clear instructions to return if symptoms are not relieved within 4 weeks, should be given so that there is no undue delay to further investigation or treatment. Also, the likelihood of the temporary nature of the relief should be explained to the patient, along with the advice that if symptoms return surgical treatment should be considered.
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