AUTHOR AND EDITOR INFORMATION

Section 1 of 8  

• Authors and Editors
• Introduction
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Multimedia
• References

INTRODUCTION

Section 2 of 8  

• Authors and Editors
• Introduction
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Multimedia
• References

Background

Carpal tunnel syndrome is defined as the impairment of motor and/or sensory function of the median nerve as it traverses through the carpal tunnel. It is caused either by intrinsic swelling of the median nerve or by extrinsic compression of the median nerve by one of the many surrounding structures of the wrist.

Pathophysiology

The most common cause of carpal tunnel syndrome (CTS) is chronic repetitive stress upon the carpal tunnel. thus the median nerve within it. This can be caused by abnormal positioning of the wrist as occurs during typing, repeated flexion or extension stress (carpentry, carpet weaving), or rapid jarring of the wrist (ie, operating a jackhammer). Fractures or dislocations of the wrist, soft tissue injuries or abnormalities, infection, infiltrative disease, or intraneural hemorrhage also may cause carpal tunnel syndrome.

Frequency

United States

Recent research has shown that the incidence of carpal tunnel syndrome may be as high as 3.7% in the general population, with a higher incidence in individuals who practice wrist maneuvers known to be associated with carpal tunnel syndrome (eg, typing). As many as 50% of cases are bilateral.

Mortality/Morbidity

• Mortality: The likelihood of significant mortality resulting from carpal tunnel syndrome or complications of conservative treatment is exceedingly low. A small risk of death is associated with attempted surgical relief. Deaths are likely to be associated with the patient's prior health status and complications related to anesthesia. Mortality risk has no doubt decreased with the increasing acceptance of endoscopic techniques for carpal tunnel release and the subsequent decrease in both general anesthesia use and time under anesthesia.
• Morbidity: Morbidity of carpal tunnel syndrome is extremely variable and depends highly on duration and severity at presentation, cause, success of conservative therapy (if any), general preoperative health and attitude of the patient, type of surgical release, and numerous psychosocial factors in the postoperative state. Throughout the medical literature, a large number of articles have shown a correlation between these factors and treatment outcome. Conservative therapy failure rates from 1-50% and surgical failure rates from 2-31% have been reported.

Sex

There is a strong female predominance with a male-to-female ratio of 1:3-5.

Age

Carpal tunnel syndrome is found most often in patients aged 30-60 years but many other factors have an influence on the age of incidence of CTS.

Anatomy

Knowledge of carpal tunnel anatomy is important in understanding the pathophysiology of the syndrome. The carpus (composed of the carpal bones) has a concave bony contour on its flexor surface and is covered by the flexor retinaculum. This structure forms the floor and walls of the carpal tunnel and the rigid flexor retinaculum forms its roof. The flexor retinaculum, or transverse carpal ligament, attaches to the scaphoid tubercle, the ridge of the trapezium, and the ulnar aspect of the hook of the hamate and pisiform.

The proximal fibers of the volar carpal ligament contribute to the roof of the carpal tunnel but this contribution is not as significant as that of the thicker flexor retinaculum. The long flexors of the fingers and thumb all pass through the carpal tunnel. The separate flexor digitorum superficialis tendons are arranged in two rows, with the tendons to the third and fourth digits positioned volar to the tendons of the second and fifth digits. The flexor digitorum profundus tendons are arranged in the same coronal plane and the tendon to the second digit is separated from the 3 adjacent profundus tendons.

All 8 flexor tendons are covered with a common synovial sheath. The flexor pollicis longus tendon, contained in its own synovial sheath, is located on the radial aspect of the flexor tendons within the carpal tunnel. The median nerve resides just under the flexor retinaculum and abuts its inner surface. It is located on the lateral side of the flexor digitorum superficialis between the flexor tendon of the middle finger and the flexor carpi radialis.

The nerve is round or oval at the level of the distal radius; it becomes elliptical at the pisiform and hamate. Its position and morphology both are altered during flexion and extension. With the wrist in a neutral position, the median nerve is seen anterior to the flexor digitorum superficialis tendon of the index finger or posterolaterally between the flexor digitorum tendon of the index finger and flexor pollicis longus tendon.

The nerve is forced against the transverse carpal ligament in dorsiflexion or palmoflexion of the wrist. In wrist extension, the median nerve assumes a more anterior position, deep to the flexor retinaculum and superficial to the flexor digitorum superficialis tendon of the index finger. In wrist flexion, the median nerve can be found anterior to the flexor retinaculum or between the flexor digitorum superficialis tendons of the index finger and thumb or middle and ring fingers. In the flexed position, the elliptical shape of the median nerve flattens.

Alteration of median nerve morphology is less pronounced in wrist extension. As much as 20 mm of excursion of the median nerve can occur and frictional forces between the median nerve, adjacent tendons, and the transverse carpal ligament compound the potential irritation caused by morphologic plasticity during flexion and extension.

Clinical Details

Clinical presentation typically includes pain and numbness, often with increased nocturnal pain and/or burning. The thumb, index finger, middle finger, and radial one half of the ring finger most commonly are affected.

• Sensory findings range from minimal loss of sensation to complete anesthesia.
• Muscular atrophy and function loss are late findings, although the abductor pollicis brevis muscle may show earlier involvement.
• Direct pressure measurement in patients with carpal tunnel syndrome reveals increased pressures in the carpal canal (up to 32 mm Hg, compared to 2.5 mm Hg in asymptomatic patients). Pressure changes also can be recorded in extremes of dorsiflexion and palmoflexion.
• Axial CT studies of patients with carpal tunnel syndrome reveal a decrease in the cross sectional area of the carpal canal. Various processes can cause decreased volume of the carpal tunnel, including infections, tenosynovitis of the flexor tendons, Colles fracture, and fracture-dislocation of the radiocarpal, carpal, and carpometacarpal joints. The processes also may cause posttraumatic scarring, fibrosis, or both. Inflammatory processes causing decreased volume within the carpal tunnel include rheumatoid arthritis, gout, pseudogout, amyloid deposition, and granulomatous infectious processes. All of these may produce a tenosynovitis with hyperplastic synovium.
• Tumors of the median nerve (eg, neuromas, fibromas, hamartomas) and tumors extrinsic to the median nerve (eg, ganglion cysts, lipomas, hemangiomas) can create space-occupying masses within the carpal canal.
• Disorders that enlarge the normal structures within the carpal tunnel include acromegaly, hypothyroidism, pregnancy, diabetes mellitus, and systemic lupus erythematosus.
• For reasons not yet understood, volumetric increases occasionally are seen in women who are postmenopausal.
• Developmental etiologies that can be responsible for increased carpal tunnel pressures include a persistent median artery, hypertrophied lumbricals, anomalous muscles, and a distal positioning of the flexor digitorum superficialis muscle. Thus, carpal tunnel syndrome can be produced by compression or swelling of the median nerve.
• When evaluating the differential diagnosis of carpal tunnel syndrome, excluding median nerve damage at a more proximal level is important. If median nerve damage has occurred, the palmocutaneous branch of the median nerve may be affected, thereby causing weakness of the corresponding flexor muscles of the forearm, including the flexor pollicis longus tendon. This contrasts with carpal tunnel syndrome, in which the terminal phalanx of the thumb demonstrates normal flexion without motor impairment. Although the median nerve is composed of both sensory and motor nerve fibers, sensory fibers predominate at the level of the carpal tunnel, explaining the initial findings of sensory deficit and numbness.
• As the disease progresses, wasting and weakness of the thenar muscles occur, with decreased ability to oppose the thumb and anesthesia of the 3.5 digits on the radial side of the hand. No anesthesia of the thenar eminence occurs because the cutaneous branch of the median nerve supplies this structure.

Preferred Examination

The clinical examination is the most important part of the evaluation for CTS. A positive Tinel sign (tingling in the digits supplied by the median nerve) is an indication of nerve entrapment. The Phalen test, tourniquet compression, and direct compression also are used to detect signs of medial nerve entrapment. EMG and nerve conduction studies are useful for confirming the diagnosis of CTS and are most helpful in localizing the level and determining the severity of the median nerve compression. A prolonged sensory conduction or distal motor latency test provides quantitative information regarding these facts. Electrodiagnostic tests such as electromyelography (EMG) and nerve conduction studies are 85-90% accurate in patients with carpal tunnel syndrome, with a false-negative rate of 10-15%. Therefore, in cases of clinically symptomatic CTS with normal EMG and conduction findings, radiology studies can have a strong complimentary role in the evaluation of CTS.

Of radiologic imaging methods, MRI consistently has shown the greatest sensitivity and specificity in the diagnosis and evaluation of carpal tunnel syndrome.

Plain radiographs are really only useful in the evaluation of CTS for showing the anatomic relationship of the carpal bones and evidence of severe prior trauma or fractures.

Helical CT is more sensitive in revealing subtle bony trauma and misalignments and in measuring the cross sectional area of the carpal tunnel syndrome.

Ultrasound can be useful in the evaluation of soft tissues of the carpal tunnel and the median nerve.

Limitations of Techniques

As noted above, electrodiagnostic tests such as EMG and nerve conduction studies are 85-90% accurate in patients with carpal tunnel syndrome, with a false-negative rate of 10-15%.

Plain radiographs usually do not reveal ligamentous or soft tissue abnormalities but may be useful to exclude frank fractures or chronic degenerative/posttraumatic morphologic abnormalities.

CT does not reveal ligamentous or soft tissue abnormalities to any degree. Axial scanners are even more limited since they are unable to allow adequate multiplanar or 3-dimensional reconstructions.

Ultrasound is operator and equipment dependent but recent studies using high-resolution transducers have begun to better explore the potential of this modality.

MRI is useful for the evaluation of all of the intrinsic structures of the wrist (including carpal bones) but may not be widely available, is technique and equipment dependent, can require up to 45 minutes to complete an examination, and is contraindicated in patients with known contraindications to MRI (eg, cardiac pacemakers, older aneurysm clips, new stents or aortic valves, ferromagnetic ocular fragments).

Patient Education: For excellent patient education resources, visit eMedicine's Hand, Wrist, Elbow, and Shoulder Center and Arthritis Center. Also, see eMedicine's patient education article Carpal Tunnel Syndrome.

RADIOGRAPH

Section 3 of 8  

• Authors and Editors
• Introduction
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Multimedia
• References

Findings

Plain radiographs are useful for evaluating the wrist and carpal bones for trauma and fractures (especially the hook of the hamate and the tubercle of the trapezium), severe osteoarthritis, and other arthropathies.

Degree of Confidence

Plain films are of limited use in diagnosing or evaluating carpal tunnel syndrome. Plain films are not useful for evaluating the small soft tissue structures of the carpal tunnel, many of which can cause the syndrome. Only a very rough idea of the cross sectional area of the carpal tunnel is provided using a carpal tunnel view of the wrist.

CT SCAN

Section 4 of 8  

• Authors and Editors
• Introduction
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Multimedia
• References

Findings

CT is useful for its ability to display and evaluate the cross sectional volume of the carpal tunnel and for detecting subtle calcification in the tendons within the canal. CT also provides an excellent tool for evaluating the carpal bones through multiplanar and 3-dimensional reconstructions.

False Positives/Negatives

CT is limited in its ability to visualize the median nerve and tendons of the carpal tunnel well enough to allow a definitive differential diagnoses to be rendered. Therefore, other methods of visualizing the soft tissues of the carpal tunnel are preferable.

MRI

Section 5 of 8  

• Authors and Editors
• Introduction
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Multimedia
• References

Findings

• In patients with flexor tenosynovitis, axial MRI demonstrates bowing of the flexor retinaculum.
• Inflamed synovium and tendon sheaths demonstrate low signal intensity on T1-weighted images and increased signal intensity on T2-weighted, T2*-weighted, and short tau inversion recovery (STIR) sequences.
• Regardless of the etiology of carpal tunnel syndrome, changes in the median nerve are similar and include the following:
  • Diffuse swelling or segmental enlargement of the median nerve may be demonstrated (usually seen best at the level of the pisiform).
  • The median nerve may flatten (usually demonstrated best at the level of the hamate).
  • Palmar bowing of the flexor retinaculum may be noted (usually demonstrated best at the level of the hamate).
  • Increased T2-weighted signal intensity within the median nerve occurs, which is demonstrated best on axial fast spin-echo (FSE) T2-weighted images. If FSE signal sequences are not available, axial gradient-recalled echo (GRE) or inversion recovery (IR) sequences also are sensitive to the increased edema in the median nerve that accompanies carpal tunnel syndrome.
• MRI also is useful in detecting and characterizing space-occupying lesions, such as neuromas, ganglion cysts, lipomas, and hemangiomas.
• Enlargement or swelling of the median nerve proximal to the carpal tunnel, termed a pseudoneuroma, has been documented using MRI.
• Flow-sensitive sequences or dynamic contrast-enhanced MRI can detect a circulatory disturbance causing carpal tunnel syndrome, which is a cause separate from deformation or compression of the median nerve.
• Two abnormal patterns of median nerve enhancement are demonstrated; usually, either marked enhancement of the nerve (attributed to hypervascular edema) or noticeable lack of enhancement (attributed to nerve ischemia) occurs.
• As with the symptoms of carpal tunnel syndrome, flexion or extension of the wrist can alter the pattern from marked enhancement to complete lack of enhancement, presumably because of mechanical obstruction of blood flow to the median nerve. These actions are associated with exacerbation of clinical symptoms.
• In an attempt to resolve carpal tunnel syndrome, incomplete surgical release of the flexor retinaculum can occur and be detected by a residual increase in T2 signal of the median nerve within the carpal tunnel and by direct visualization of the still-connected fibers of the retinaculum.
• Transverse carpal ligament release from the hook of the hamate can cause the contents of the carpal canal and/or the flexor tendons to demonstrate a volar convexity caused by the loss of the normal roof support of the flexor retinaculum.
• In addition to incomplete release of the flexor retinaculum, postoperative MRI changes in failed carpal tunnel surgery include excessive fat within the carpal tunnel, neuromas, scarring, and persistent neuritis. A normal postoperative finding is widening of the fat stripe posterior to the flexor digitorum profundus tendons.
• MRI studies following carpal tunnel release may demonstrate an increase in carpal tunnel volume of up to 24%, often accompanied by a change in shape from oval to circular, resulting in increased anteroposterior and mediolateral diameters.

Degree of Confidence

Early detection of the subtle changes of carpal tunnel syndrome requires soft tissue discrimination not possible using standard radiographs or CT. The ability to evaluate the cross sectional morphologic and signal characteristics of the medial nerve and adjacent structures makes MRI invaluable in characterizing both normal anatomy and abnormal pathology in the carpal tunnel.

Significant differences often are present in patients with carpal tunnel syndrome, despite the subjective flattening of the median nerve at the lateral and distal carpal row. Flattening ratios have been used to document statistically significant flattening of the median nerve at the level of the hamate. The median nerve may display enlargement or dilation at the level of the pisiform and concomitant compression and flattening at the level of the hook of the hamate.

False Positives/Negatives

Since carpal tunnel involvement is bilateral in as many as 50% of patients, comparison with the contralateral wrist can be misleading. Alterations in the median nerve signal intensity may represent edema or demyelination within neural fibers, thus are somewhat nonspecific. Both T1 and T2 signal intensities may be decreased when fibrosis of the median nerve is present. Evaluation of swelling is accomplished by comparing the cross sectional area of the median nerve at the level of the pisiform and hamate to the cross sectional area of the median nerve at the level of the distal radius.

ULTRASOUND

Section 6 of 8  

• Authors and Editors
• Introduction
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Multimedia
• References

Findings

The development of high-resolution ultrasound (US) transducers (7-15 MHz) has allowed evaluation of normal and abnormal US appearances of the median nerve and adjacent tendons. High-resolution US allows noninvasive imaging of the carpal tunnel and its contents. It has several advantages over MRI, including being relatively fast and inexpensive and allowing additional dynamic and blood flow imaging with relatively little additional time.

On transverse US scans, the normal median nerve is elliptical and flattens progressively as it courses distally. On US, median nerve compression reveals the classic triad of nerve flattening in the distal tunnel, nerve swelling at the level of the distal radius (less frequently in the proximal tunnel), and palmar bowing of the flexor retinaculum.

Since the shape of the nerve varies as it passes through the tunnel, indexes have been introduced to better quantify abnormal findings; a nerve cross sectional area greater than 9 mm² at the level of the proximal tunnel is reported to be the best criterion for the diagnosis.

Degree of Confidence

A good correlation has been demonstrated between the measured US area of the median nerve and the degree of findings of electromyography or functional outcome after surgery. Reduced transverse sliding of the nerve beneath the retinaculum during flexion and extension of the index finger also may be seen, but this sign is harder to quantify and may be too subjective. Only a few studies have compared US and MRI in evaluating carpal tunnel syndrome, but these demonstrated that US is capable of producing results similar to MRI. MRI has been shown to be superior to US in identification of subtle cases and MRI demonstrates better sensitivity than color and power Doppler US in showing changes caused by nerve edema and blood perfusion abnormalities.

MULTIMEDIA

Section 7 of 8  

• Authors and Editors
• Introduction
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Multimedia
• References

Media file 1:  Carpal tunnel syndrome. Normal findings on an axial spin-echo T1 MRI of the carpal tunnel showing the intermediate signal intensity of the median nerve (arrow).
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Media type:  MRI

Media file 2:  Carpal tunnel syndrome. Normal findings of isointense-to-hypointense appearance of the median nerve on fast spin-echo T2-weighted MRI (arrow). Note the fairly well-defined nerve fascicles within the median nerve sheath.
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Media type:  MRI

Media file 3:  Carpal tunnel syndrome. Axial fast spin-echo T2-weighted MRI with fat saturation. Note the increased T2-weighted signal within the median nerve (arrow). A slightly increased cross sectional area of the nerve is noted but the nerve architecture is preserved, consistent with early or mild inflammation.
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Media type:  MRI

Media file 4:  Carpal tunnel syndrome. Fast spin-echo T2-weighted MRI illustrates more pronounced increased signal within the median nerve (arrow). Note the small amount of fluid within the carpal tunnel, a secondary sign of inflammation. Slightly less optimal fat saturation is noted than on other images, which is a common occurrence.
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Media type:  MRI

Media file 5:  Carpal tunnel syndrome. Axial fast spin-echo T2-weighted MRI with greater increase in signal and loss of definition within the nerve (arrow). Inflammatory change is noted within the carpal tunnel, adjacent to the flexor digitorum superficialis tendons. The appearance is consistent with pronounced inflammatory change within the carpal tunnel.
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Media type:  MRI

Media file 6:  Carpal tunnel syndrome. Carpal and Guyon tunnels. Drawing showing the proximal level of the carpal tunnel delimited by the pisiform (P) and the scaphoid (S). The flexor retinaculum (medium gray region) forms the roof of the carpal tunnel and the floor of the Guyon tunnel. The palmar carpal ligament (dark gray region) forms the volar boundary of the Guyon tunnel. * = flexor pollicis longus tendon, * = flexor carpi radialis tendon. From Martinoli C, Bianchi S, et al. US of nerve entrapments in osteofibrous tunnels of the upper and lower limbs. Radiographics 2000; 20:S199-S217. Used by permission of the authors and RSNA.
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Media type:  Graph

Media file 7:  Carpal tunnel syndrome. Carpal and Guyon tunnels. Transverse 5-12-MHz ultrasound scan corresponding to Image 6 shows the proximal level of the carpal tunnel delimited by the pisiform (P) and the scaphoid (S). The flexor tendons and median nerve (MN) extend through the carpal tunnel, with the nerve lying palmar and radial. The flexor retinaculum (open arrowhead) forms the roof of the carpal tunnel and the floor of the Guyon tunnel. At the level of the pisiform, the ulnar nerve (U) courses medial to the ulnar artery (solid arrowhead) within the Guyon tunnel. From Martinoli C, Bianchi S, et al. US of nerve entrapments in osteofibrous tunnels of the upper and lower limbs. Radiographics 2000; 20:S199-S217. Used by permission of the authors and RSNA.
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Media type:  Image

Media file 8:  Carpal tunnel syndrome. Carpal and Guyon tunnels. Drawing showing the distal level of the carpal tunnel delimited by the hook of the hamate (H) and the tubercle of the trapezium (T). The flexor retinaculum (medium gray region) forms the roof of the carpal tunnel. From Martinoli C, Bianchi S, et al. US of nerve entrapments in osteofibrous tunnels of the upper and lower limbs. Radiographics 2000; 20:S199-S217. Used by permission of the authors and RSNA.
	View Full Size Image
Media type:  Image

Media file 9:  Carpal tunnel syndrome. Carpal and Guyon tunnels. Transverse 5-12-MHz ultrasound scan corresponding to Image 8 shows the distal level of the carpal tunnel delimited by the hook of the hamate (H) and the tubercle of the trapezium (T). The flexor retinaculum (open arrowhead) forms the roof of the carpal tunnel. The flexor tendons and median nerve (MN) extend through the carpal tunnel, with the nerve lying palmar and radial. At the level of the pisiform, the ulnar nerve (U) courses medial to the ulnar artery (solid arrowhead) within the Guyon tunnel. At the level of the hamate, the ulnar nerve divides into two terminal branches, a deep motor branch (curved arrow) and a superficial sensory branch (straight arrow). From Martinoli C, Bianchi S, et al. US of nerve entrapments in osteofibrous tunnels of the upper and lower limbs. Radiographics 2000; 20:S199-S217. Used by permission of the authors and RSNA.
	View Full Size Image
Media type:  Image

REFERENCES

Section 8 of 8

• Authors and Editors
• Introduction
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Multimedia
• References

• Allmann KH, Horch R, Uhl M, et al. MR imaging of the carpal tunnel. Eur J Radiol. Sep 1997;25(2):141-5. [Medline].
• Andre V, Zagnoli F, Andre M, et al. [Clinical, electrophysiological and MRI correlations in carpal tunnel syndrome]. J Radiol. Jul 1999;80(7):721-6. [Medline].
• Bonel HM, Heuck A, Frei KA, et al. Carpal tunnel syndrome: assessment by turbo spin echo, spin echo, and magnetization transfer imaging applied in a low-field MR system. J Comput Assist Tomogr. Jan-Feb 2001;25(1):137-45. [Medline].
• Britz GW, Haynor DR, Kuntz C, et al. Carpal tunnel syndrome: correlation of magnetic resonance imaging, clinical, electrodiagnostic, and intraoperative findings. Neurosurgery. Dec 1995;37(6):1097-103. [Medline].
• Buchberger W, Judmaier W, Birbamer G, et al. Carpal tunnel syndrome: diagnosis with high-resolution sonography. AJR Am J Roentgenol. Oct 1992;159(4):793-8. [Medline].
• Buchberger W, Schon G, Strasser K, Jungwirth W. High-resolution ultrasonography of the carpal tunnel. J Ultrasound Med. Oct 1991;10(10):531-7. [Medline].
• Cavallaro MC, Taylor JA, Gorman JD, et al. Imaging findings in a patient with fibrolipomatous hamartoma of the median nerve. AJR Am J Roentgenol. Oct 1993;161(4):837-8. [Medline].
• Chen P, Maklad N, Redwine M, Zelitt D. Dynamic high-resolution sonography of the carpal tunnel. AJR Am J Roentgenol. Feb 1997;168(2):533-7. [Medline].
• Coyle MP. Nerve entrapment syndromes in the upper extremity. In: Dee R, et al, eds. Principles of Orthopaedic Practice. Vol 1. McGraw-Hill Pub;1989:672.
• Duncan I, Sullivan P, Lomas F. Sonography in the diagnosis of carpal tunnel syndrome. AJR Am J Roentgenol. Sep 1999;173(3):681-4. [Medline].
• Gelberman RH, Eaton RG, Urbaniak JR. Peripheral nerve compression. Instr Course Lect. 1994;43:31-53. [Medline].
• Healy C, Watson JD, Longstaff A, Campbell MJ. Magnetic resonance imaging of the carpal tunnel. J Hand Surg [Br]. May 1990;15(2):243-8. [Medline].
• Keberle M, Jenett M, Kenn W, et al. Technical advances in ultrasound and MR imaging of carpal tunnel syndrome. Eur Radiol. 2000;10(7):1043-50. [Medline].
• Kleindienst A, Hamm B, Hildebrandt G, Klug N. Diagnosis and staging of carpal tunnel syndrome: comparison of magnetic resonance imaging and intra-operative findings. Acta Neurochir (Wien). 1996;138(2):228-33. [Medline].
• Lee D, van Holsbeeck MT, Janevski PK, et al. Diagnosis of carpal tunnel syndrome. Ultrasound versus electromyography. Radiol Clin North Am. Jul 1999;37(4):859-72, x. [Medline].
• Martinoli C, Derchi LE, Bertolotto M, et al. US and MR imaging of peripheral nerves in leprosy. Skeletal Radiol. Mar 2000;29(3):142-50. [Medline].
• Martinoli C, Serafini G, Bianchi S, et al. Ultrasonography of peripheral nerves. J Peripher Nerv Syst. 1996;1(3):169-78. [Medline].
• Martinoli C, Bianchi S, Gandolfo N. US of nerve entrapments in osteofibrous tunnels of the upper and lower limbs. Radiographics. Oct 2000;20 Spec No:S199-213; discussion S213-7. [Medline].
• Mesgarzadeh M, Schneck CD, Bonakdarpour A. Carpal tunnel: MR imaging. Part I. Normal anatomy. Radiology. Jun 1989;171(3):743-8. [Medline].
• Mesgarzadeh M, Schneck CD, Bonakdarpour A, et al. Carpal tunnel: MR imaging. Part II. Carpal tunnel syndrome. Radiology. Jun 1989;171(3):749-54. [Medline].
• Monagle K, Dai G, Chu A, et al. Quantitative MR imaging of carpal tunnel syndrome. AJR Am J Roentgenol. Jun 1999;172(6):1581-6. [Medline].
• Papanicolaou GD, McCabe SJ, Firrell J. The prevalence and characteristics of nerve compression symptoms in the general population. J Hand Surg [Am]. May 2001;26(3):460-6. [Medline].
• Sugimoto H, Miyaji N, Ohsawa T. Carpal tunnel syndrome: evaluation of median nerve circulation with dynamic contrast-enhanced MR imaging. Radiology. Feb 1994;190(2):459-66. [Medline].
• Zeiss J, Jakab E, Khimji T, Imbriglia J. The ulnar tunnel at the wrist (Guyon''s canal): normal MR anatomy and variants. AJR Am J Roentgenol. May 1992;158(5):1081-5. [Medline].

Article Last Updated: Jul 2, 2004