Carpel Tunnel Syndrome Case File

Carpel Tunnel Syndrome Case File

Eugene C. Toy, MD, Andrew J. Rosenbaum, MD, Timothy T. Roberts, MD, Joshua S. Dines, MD

CASE 29

A 47-year-old right-hand dominant female presents to the clinic with a 2-month history of intermittent numbness and tingling in her right hand, specifically the index and middle fingers. She often finds the symptoms worst when using her computer and when driving home. Her symptoms are significantly affecting her career as a journalist. She also complains of pain in the same distribution that wakes her up almost nightly. She denies any history of trauma. Her past medical history is significant only for type 2 diabetes mellitus (DM), which is well controlled with oral agents. She does not smoke and drinks 1 or 2 glasses of wine on occasion, and her body mass index is 32 kg/m2. Physical examination reveals a slightly overweight but otherwise healthy-appearing female. Both of her upper extremities appear normal, with no obvious signs of trauma. On her right hand, there is a palpable 2+ radial pulse and a normal Allen test. Two-point discrimination is measured at 8 mm on both the radial and ulnar borders of the index and middle fingers as well as the radial border of the ring finger. There is normal (< 5 mm) 2-point discrimination on the ulnar border of the ring finger and on both sides of the small finger. Sensation in the palm is normal.

► What is the most likely diagnosis?

► How would you confirm the diagnosis?

► What is the initial treatment for this condition?

ANSWER TO CASE 29:

Carpel Tunnel Syndrome                              

Summary: A 47-year-old woman with a history of well-controlled type 2 DM has complaints of worsening numbness and tingling in her right hand for 2 months. She works as a journalist, spending much of her time on a computer. She has no history of trauma and is otherwise healthy. Vital signs are normal, and physical exam is remarkable for decreased 2-point discrimination on her index and middle fingers, as well as the radial side of her ring finger.

• Most likely diagnosis: Carpal tunnel syndrome (CTS).
• Diagnostic testing: An electromyogram (EMG) and nerve conduction studies may help confirm the diagnosis. EMG studies may show an increase in motor and/or sensory latency across the wrist. Up to 10% of patients with clinical symptomatology, however, have normal EMG studies.
• Initial management: Nonsteroidal anti-inflammatory drugs (NSAIDs), if not contraindicated, and night splinting are the best initial management strategy.

ANALYSIS

Objectives

1. Understand the pathoanatomy responsible for carpal tunnel syndrome.
2. Describe the physical exam findings of carpal tunnel syndrome.
3. Recognize underlying conditions (both physiologic and pathologic) that may predispose one to carpal tunnel syndrome.
4. Distinguish carpal tunnel syndrome from other diseases or conditions that may mimic its presentation.
5. Understand the conservative and surgical treatment options for carpal tunnel syndrome and their indications.

Considerations

For any patient with acute neurologic complaints isolated to an extremity, it is important to first rule out trauma as an underlying cause. This patient denies a history of trauma, is without significant medical comorbidities, and appears reliable, so further imaging is unlikely to aid the diagnosis. In patients with complicated, unclear, or unreliable histories, radiographs may help eliminate several causes of neurologic symptoms such as fractures, deformities, congenital abnormalities, masses, and other lesions.

    There are other conditions that may mimic carpal tunnel syndrome, but can often be distinguished with a thorough physical exam and history. Traumatic conditions such as a distal radius fracture or scaphoid fracture may present with some symptoms that overlap with those of carpal tunnel syndrome, but would likely be discovered with adequate workup. More proximal nerve pathologies such as

cervical radiculopathy or proximal median nerve compression should have additional findings not found in isolated carpal tunnel syndrome, such as paresthesias in the thenar distribution, and would not have positive test findings on provocative tests aimed at eliciting symptoms within the carpal canal (ie, Phalen, Tinel, and Durkan signs). Cubital tunnel syndrome has similar pathology and presentation to carpal tunnel syndrome, but in a different nerve distribution. If the patient fails conservative management, carpal tunnel release surgery is very effective at alleviating symptoms of carpal tunnel syndrome. If performed early, surgical decompression can prevent permanent denervation of the thenar muscles and halt further deterioration of symptoms. In many operative cases, sensation is restored and symptoms resolve. With regard to operative technique, the results from open and endoscopic surgery are comparable.

APPROACH TO:

Carpal Tunnel Syndrome                                 

DEFINITIONS

CARPAL TUNNEL: A narrow canal in the volar (palmar) wrist that typically contains the median nerve, superficial and deep finger flexor tendons, and the long flexor tendon of the thumb.

GUYON CANAL: Also known as the ulnar tunnel, this volar wrist canal is located just ulnar (medial) to the carpal tunnel and contains the ulnar artery and ulnar nerve. Compression within this tunnel can lead to a similar syndrome to carpal tunnel, with symptoms instead found in an ulnar nerve distribution.

MEDIAN NERVE COMPRESSION SYNDROME: A spectrum of compression neuropathies of the median nerve with varying names and symptoms, depending on the location of pathology. When the nerve is compressed proximally, most commonly between the two heads of the pronator teres muscle, it is called pronator teres syndrome, and is characterized by volar hand and forearm numbness as well as potential weaknesses in the thumb flexors and distal flexors of the index and middle fingers. The median nerve can be compressed in several key locations, the most distal of which is in the carpal tunnel.

CLINICAL APPROACH

Relevant Anatomy

The carpal tunnel can be described exactly as it is named—as a tunnel (or canal) passing through the wrist. Understanding the anatomy of the canal, including its borders and its contents, is key to understanding the basis of carpal tunnel syndrome. The carpal canal is formed by the transverse carpal ligament volarly (palmar), the scaphoid and trapezium radially, and the hamate and triquetrum ulnarly. Within the canal passes the median nerve and 9 flexor tendons: 4 tendons of the flexor digitorum profundus (FDP), 4 tendons of the flexor digitorum superficialis (FDS), and the single tendon of the flexor pollicis longus (FPL).

    The median nerve is responsible for sensation to the volar (palmar) surface of the thumb, index finger, long finger, and the radial (lateral) half of the ring finger. The sensation of the palm and thenar eminence is normal in carpal tunnel syndrome because the palmar cutaneous branch of the median nerve arises proximal to the carpal tunnel and crosses the wrist superficial to the transverse carpal ligament to give sensation to the palm. In most instances, the recurrent motor branch of the median nerve comes off the median nerve distal to the nerves coursing within the canal, so that compressive effects on the median nerve may also affect the recurrent motor branch.

    Decreasing the effective size of the canal (ie, prolonged or repetitive wrist flexion/ extension, etc) or increasing the relative size of the canal’s contents (ie, flexor tendon inflammation/swelling) can lead to carpal tunnel syndrome. This explains why many patients with carpal tunnel syndrome complain of worsened symptoms at night, as it is thought that most people sleep with their wrists in a flexed position.

Diagnosis

Carpal tunnel syndrome is a clinical diagnosis, meaning the diagnosis is based primarily on history and physical exam findings, with adjunctive tests such as EMG studies used to confirm—but never make—the diagnosis. Physical exam findings such as decreased sensation and 2-point discrimination in the distribution of the median nerve at the fingers with sparing of sensation of the thenar eminence and palm are pathognomic for carpal tunnel syndrome. Tinel sign involves percussion over the median nerve at the wrist, and Phalen sign involves holding the wrist in flexion for 1 minute. Both tests are positive if they result in reproduction of symptoms. The Durkan test, or carpal tunnel compression test, is performed with the examiner holding pressure over the patient’s carpal tunnel, while distracting the patient. Reproduction of symptoms within 30 seconds of compression is considered positive. Although the patient in this case does not describe weakness or atrophy of the thenar musculature, a decrease in pinch/grip strength may occur in more advanced stages of carpal tunnel syndrome.

    EMG studies may help clarify the diagnosis of CTS. Such studies may demonstrate a latency and/or asymmetry between the affected and nonaffected hands. Many normal physiologic and/or pathologic conditions may promote the onset of carpal tunnel syndrome. These include, but are not limited to, pregnancy, type 2 DM, gout, rheumatoid arthritis, and hypothyroidism. The mechanisms by which these conditions cause carpal tunnel syndrome are not fully understood. However, each condition is thought to promote a state of inflammation and thus elevated pressure within the carpal canal. Patients should be evaluated for potential underlying causes of carpal tunnel syndrome. Underlying etiologies, if present, must be addressed prior to operative treatment.

TREATMENT

When carpal tunnel syndrome is diagnosed, the most conservative mode of treatment is attempted first. Nighttime symptoms are often the result of the naturally-flexed position of the resting wrist. Removable splints that hold the wrist in neutral, the position in which the carpal tunnel is least compressed, are usually effective at reducing symptoms. Additionally, anti-inflammatories (NSAIDs) are an effective treatment option. In patients whose symptoms are not sufficiently relieved by these options, corticosteroid injections directly into the carpal tunnel may be an option. Local steroid therapy may provide transient relief; however, symptoms often return. Note that there is prognostic value to such therapies, as patients who respond well to steroid injections have a greater chance of successful relief from surgery.

    The definitive treatment for carpal tunnel syndrome refractory to conservative management is a carpal tunnel release. This involves releasing the transverse carpal ligament using either a direct open or endoscopic technique. Carpal tunnel release is a relatively fast outpatient procedure with generally low complication rates and excellent outcomes.

COMPREHENSION QUESTIONS

29.1 A 43-year-old health care worker complains of nocturnal wrist pain and has significant pain when pressure is applied to her volar wrist for more than 10 seconds. Which of the following structures is not usually contained within the carpal tunnel?

A. Tendon(s) of FDP

B. Tendon(s) of FPL

C. Palmar cutaneous branch of the median nerve

D. Tendon(s) of FDS

E. Motor fibers of the median nerve

29.2 A 52-year-old retired woman is referred to your clinic with complaints of numbness and tingling in her left (dominant) hand worse at night for the past 3 months. She also complains of significant fatigue and 10-lb weight gain over the same period of time. She denies any medical history and takes no medications. On exam, she is overweight and appears somewhat lethargic, but appears healthy otherwise. On her left hand she has decreased 2-point discrimination on her index and middle fingers. Her grip strength is normal, and she has no thenar atrophy. What is the next best step in management of this patient?

A. Left hand carpal tunnel release

B. EMG/nerve conduction velocity studies of left upper extremity

C. Cervical spine magnetic resonance imaging (MRI)

D. Lab studies including complete blood count, basic metabolic panel, thyroid-stimulating hormone, T3, and free T4

E. Referral for counseling regarding recent changes in her lifestyle

29.3 A 56-year-old postmenopausal woman is seen in the clinic with complaints of mild numbness and tingling in her right hand, most notably in the index and middle fingers. She takes medication for osteoporosis but is otherwise healthy. Her history is unremarkable except for a wrist fracture after a fall onto her right hand 2 years ago that was fixed with open reduction internal fixation. Her postoperative course was uncomplicated. Physical examination in the office reveals a well-healed surgical incision on the volar aspect of her wrist, normal grip strength, and no sensory deficits. X-rays reveal hardware in adequate alignment, with evidence of bony union at a previous distal radius fracture site. What is the next best step in her management?

A. Provision cast immobilization and follow-up x-ray for occult refracture

B. MRI of right wrist

C. Emergency surgical release of transverse carpal ligament

D. NSAID administration with close follow-up

E. Serum erythrocyte sedimentation rate, C-reactive protein, complete blood count, and wrist aspiration, with cytologic analysis, Gram stain, and culture of aspirate

ANSWERS

29.1 C. The palmar cutaneous branch of the median nerve is given off approximately 5 cm proximally to the carpal tunnel in most patients. This explains why patients with carpal tunnel syndrome typically have sparing of sensation of the thenar/palmar aspect of the affected hand. The motor fibers of the median nerve branch off distally to the tunnel, and as a result, patients may exhibit weakness and/or atrophy of the thenar musculature. The 9 flexor tendons of FDP, FDS, and FPL are all contained within the carpal tunnel.

29.2 D. The patient in this question does exhibit symptoms of carpal tunnel syndrome. However, her history and physical exam also point strongly to undiagnosed hypothyroidism. Further workup and treatment of her metabolic condition should be performed before intervention of her carpal tunnel

symptoms.

29.3 D. Distal radius fractures and subsequent fixation are associated with a number of potential complications, including iatrogenic carpal tunnel syndrome of variable severity. In this case, the patient does have postoperative symptoms that are consistent with carpal tunnel syndrome, but they are mild and intermittent. Acute or emergency carpal tunnel release is not indicated. There are no signs of infection or refracture, and cast immobilization may exacerbate her symptoms. MRI of the wrist would not likely provide any new information. The correct choice would be conservative management with close follow-up to monitor for change in symptoms.

    CLINICAL PEARLS    

► The carpal tunnel is an effectively closed space, containing the median nerve, among other structures. Any reduction in volume of this finite space can lead to increased pressure upon, and thus dysfunction of, the median nerve. This results in carpal tunnel syndrome. ► Carpal tunnel syndrome is a clinical diagnosis, made by history and physical exam findings; adjunctive tests such as EMG studies may be used to confirm, but never make, the diagnosis. ► Other neurologic conditions or injuries may be differentiated from carpal tunnel syndrome by thorough history and physical exam, including exact localization of motor and sensory symptoms. ► Conservative management should always be attempted before operative treatment of CTS. If conservative management fails, surgical carpal tunnel release is performed with either open or endoscopic techniques. Both methods are associated with excellent outcomes.

REFERENCES

American Academy of Orthopaedic Surgeons. Clinical guideline on diagnosis of carpal tunnel syndrome. 2007. www.aaos.org/Research/guidelines/CTSdiagnosisguide.asp . 

American Academy of Orthopaedic Surgeons. Clinical practice guideline on the treatment of carpal tunnel syndrome. 2008. www.aaos.org/Research/guidelines/CTStreatmentguide.asp . 

Bednar MS, Light TR. Disorders of the nerves of the hand. In: HB Skinner, ed. Current Diagnosis and Treatment in Orthopedics. 4th ed. New York: McGraw-Hill; 2006:559-567. 

Bienek T, Kusz D, Cielinski L. Peripheral nerve compression neuropathy after fractures of the distal radius. J Hand Surg Br. 2006;31:256-260. 

Fuller DA, Barrett M, Marburger RK, Hirsch R. Carpal canal pressures after volar plating of distal radius fractures. J Hand Surg Br. 2006;31:236-239.

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