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Carpal tunnel syndrome is a very common peripheral neuropathy; however, its symptoms are such that they are often overlooked by patients or misdiagnosed by their primary care physicians or nurse practitioners, leading to progression of the condition so severe that sometimes even surgical options will be of little benefit. This article reviews current literature on carpal tunnel syndrome and its signs and symptoms, diagnosis and differential diagnosis, and treatment options.
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Carpal tunnel syndrome (CTS) is one of the most common peripheral neuropathies in the world (Andrews & Shpritz, 2004; Atroshi et al., 1999; Greenberg, 2006). Although not a common acute ailment that many neuroscience nurses (surgical or medical) would have to care for, its prevalence within the general population is such that general knowledge of the condition may be useful when considering acute patient care in context of associated comorbidities (with CTS as one of them). The following article reviews current literature on CTS and its related anatomy, signs and symptoms, assessment, diagnosis and differential diagnosis, and treatment options.
Literature Review
Research continues today into CTS in relation to its causes and most appropriate treatments. The risk factors and prevalence continue to be investigated among numerous and varied subgroups within the population considered being a risk. Potential factors that may contribute to CTS can be occupation, age, physical illness, and a number of factors that have been hypothesized (Bahrami, Rayegani, Fereidouni, & Baghbani, 2005; Bongers, Schellevis, van den Bosch, & van der Zee, 2007; Violante et al., 2007). How an appropriate diagnosis is determined (Bland, 2005, 2007; Longstaff, Milner, O'Sullivan, & Fawcett, 2001; Wainner et al., 2005) and its relevant treatment options (Akalin et al., 2002; Baysal et al., 2006; Crawford & Laiou, 2007; Gooch & Mitten, 2005; O'Connor, Marshall, & Massy-Westropp, 2007) also continues to be refined.
Anatomy
The carpal tunnel is a space located posteriorly between the carpal bones of the wrist (moving from fight to left: trapezium, trapezoid, capitate, and hamate), forming the hard "carpal floor," and anteriorly, where the transverse carpal ligament forms a fibrous sheath or the "carpal roof" (see Fig 1). The tunnel itself is filled with the flexor tendons of the hand and the median nerve. The median nerve originates from numerous spinal nerves from C5 to T1. It has both sensory and motor functions of the thumb and first, second, and the lateral aspect of the third digit. Consequently, it is vital for not only grip but also for sensory inputs related to hand function.
Causes
Any decrease in the space of carpal tunnel caused by flexion or extension of the wrist, increase in mass within the tunnel, or external forces compressing this space such as edema or inflammation will exert pressure onto the median nerve and potentially elicit CTS symptoms. This pressure can be caused by
1. repetitive use of the wrist through rotation, flexion (found in the automotive or building industries), or extension, particularly in the dominant hand (found in occupations like secretarial or computer work or musicians);
2. trauma to the wrist or hand area resulting in fracture and/or edema;
3. metabolic, inflammatory, and/or infectious processes which may change the associated and surrounding structures of tendons, nerves synovial spaces, or tissue (usually bilateral as a result of systemic condition); an example of metabolic/hormonal changes that may cause CTS is pregnancy;
4. medications that increase edema such as some hormone replacement therapies (estrogens);
5. congenital malformations associated with an abnormally small carpal tunnel space; and
6. idiopathic causes.
[FIGURE 1 OMITTED]
Carpal Tunnel Syndrome
The prevalence of CTS is approximately 3.8% of the general population; women are 3 to 4 times more likely to develop the condition (Burke, Ellis, McKenna, & Bradley, 2003), and it affects both wrists in 50% of cases (Greenberg, 2006). The syndrome itself is evident in patients' symptoms which are directly associated with the digits the median nerve innervates (see Fig 1). If this compression is prolonged, segmental demyelination of the median nerve will occur (Katz & Simmons, 2002), resulting in possible permanent damage to the nerve with a subsequent loss of sensory and motor function in the affected hand.
Signs and Symptoms
The affected individual usually first experiences sensory changes associated with CTS at night, and, if left untreated, the symptoms eventually become continuous. This altered sensation can be in the form of tingling, numbness, or pain (which can be described as sharp, electric shocks or even a burning sensation) affecting areas innervated by the median nerve and proximally as high as the elbow. Weakness in the affected hand is a late sign and is common for those with moderate to severe CTS. The patient usually complains of inability or frustration when it comes to gripping objects because of the related motor deficit.
Differential Diagnosis
During assessment, the examiner needs to bear in mind that CTS-like signs and symptoms may result from a number of other disorders including but not limited to
1. cervical radiculopathy,
2. thoracic outlet syndrome,
3. pronator syndrome,
4. direct injury of the median nerve,
5. entrapment of the deep palmar branch of ulnar nerve,
6. peripheral neuropathy, and
7. compartment syndrome of the forearm.
Because there are numerous possibilities for similar symptoms, it is best to perform a thorough upper limb assessment on any patient presenting with CTS-like symptoms.
Assessment
Diagnosis of CTS requires thorough assessment of the patient. A detailed record of basic demographic data including a patient's age, gender, and occupation as well as a patient's medical past history is a good starting place. Clinical findings from a focused assessment are used in conjunction with neurodiagnostics to support a diagnosis of CTS. This assessment will also indicate the severity of CTS and the most effective treatment options.
Physical examination of the wrist and hand should include assessment of the presence of localized edema or bruising around the wrist, palm, or forearm. This visual assessment of the affected limb (or limbs) may indicate other pathology such as wrist fracture (and related compartment syndrome), localized infection, or any number of metabolic conditions. Atrophy of the muscles of the wrist and forearm should also be assessed, taking particular note of any thenar eminence atrophy (Burke et al., 2003), which is commonly found in severe causes of CTS along with an associated loss of function.
Sensory Assessment
A description of how the altered sensation is perceived by the patient is critical. When assessing sensation, consider the normal dermatomes associated with the affected hand and arm as well as abnormal findings that may indicate other neurology (see Table 1). CTS should only affect the palmar aspect of the hand but can radiate up the arm as high as the elbow (D'Arcy & McGee, 2000). Ask the patient to describe these altered sensations: Does the patient experience pain, tingling, or numbness? Where is the altered sensation located? Does the altered sensation radiate or move elsewhere such as the shoulders or neck (the latter may indicate cervical cord problems)? What is the time of onset? What factors exacerbate or alleviate the symptoms? One common behavior patients may exhibit with CTS is the shaking of their affected hand in a downward "flick-like motion," which allows some relief of their symptoms; this is commonly referred to as the flick sign. The clinician must decide whether the clinical picture is indicative of CTS or some other neurological, neuromuscular, or vascular disorder.
Assessment of sensory perception of light touch and two-point discrimination in the affected fingertips and palmar aspects of the hand controlled by the median nerve as well as the forearm should be performed. This will not only allow the examiner to determine the severity of CTS but also identify whether it is purely a local condition or symptom that may be initiated more proximally such as cervical radiculopathy. Reproduction or exacerbation of symptoms can be elicited in any number of ways.
Motor Assessment
Compression of the median nerve also affects motor function of the hand. The examiner must evaluate hand motor function, appropriately grade it, and document his or her findings (Table 2). This should be done systematically from shoulder to finger tips (Table 3). First, asking the patient to grip the examiner's hands will assess generalized strength and function of flexion of the hand (C7-T1 nerve roots). The median nerve also serves the abductor pollicis brevis, the opponens pollicis, and the superficial head of the flexor pollicis brevis; involves the muscles to the thumb (Li, Harkness, & Goitz, 2005); and is the most specific motor assessment for CTS. Assessment of thumb strength is performed by instructing the patient to raise his or her thumb perpendicular to the palm as the examiner applies resistance to it; this isolates the strength of the abductor pollicis brevis, which is innervated only by the median (D'Arcy & McGee, 2000). Any decrease in power may be attributed to CTS (Eathorne, 2005).
Reflexes
To complete the clinical neurological assessment of the patient, reflexes should be tested (see Table 4), graded (Table 5), and documented. The significance of reflexes is not to specifically diagnose CTS, but rather it is to rule out other pathology which may present with CTS-like symptoms and complete a thorough upper limb neurological examination.
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