update on the use of ultrasound in the diagnosis of carpal tunnel syndrome renato a. sernik, md, phd

Update on the Use of Ultrasound in the Diagnosis of Carpal Tunnel

Syndrome

Renato A. Sernik, MD, PhD

t

Flexor retinaculum

median nerve

median nerve

carpal tunnel

• Common compressive neuropathy.• Initially, pain and sensitivity changes in the median nerve territory.• Advanced stages – weakness and atrophy of the thenar muscles.

Carpal Tunnel Syndrome

Carpal Tunnel Syndrome

- useful as a screening test, reducing the cost of diagnosis of carpal tunnel syndrome.

Fowler JR, Maltenfort MG, Ilyas AM. Ultrasound as a first-line test in the diagnosis of carpal tunnel syndrome: a cost-effectiveness analysis. Clin Orthop Relat Res. 2013 Mar;471(3):932-7.

Ultrasonography

Linear transducers:-12 –18 MHz.-High resolution.

PERIPHERAL NERVE ANATOMY

fiber

fasciclenerve

perineurium

scaphoid pisiform

trapeziumhamate

flexor retinaculum

Carpal Tunnel

PIS

CARPAL TUNNEL

* a

n

scaphoidpisiform

a u fu

* PIS

scaphoid pisiform

trapezium

hamatetrapezium

hamate

ULTRASONOGRAPHY

Median Nerve Evaluation

• Qualitative• Quantitative

Qualitative Evaluation

- shape-echogenicity-structure

Echogenicity / structures

Shape

• COMPRESSION• EDEMA HOURGLASS SHAPE

carpal tunnel

median nerve

proximal distal

Quantitative Evaluation

In 1991, Buchberger et al. proposed 3 criteria for sonographic diagnosis of the carpal tunnel syndrome:

- increase in cross-sectional area of the median nerve, proximal to the compression.- thinning of the median nerve at the site of the compression, measured by the ratio of two diameters of the nerve.- bulging of the flexor retinaculum.

Carpal Tunnel Syndrome

In 1991, Buchberger et al. proposed 3 criteria for sonographic diagnosis of the carpal tunnel syndrome:

- increase in cross-sectional area of the median nerve, proximal to the compression.- thinning of the median nerve at the site of the compression, measured by the ratio of two diameters of the nerve.- bulging of the flexor retinaculum.

Carpal Tunnel Syndrome

Quantitative Evaluation

 The measurement of the area must be made where it is greater

At the entrance carpal tunnel or in the proximal carpal tunnel

Median Nerve Área

Fowler JR, Gaughan JP, Ilyas AM. The sensitivity and specificity of ultrasound for the diagnosis of carpal tunnel syndrome: a meta-analysis. Clin Orthop Relat Res. 2011 Apr;469(4):1089-94.

Tai TW, Wu CY, Su FC, Chern TC, Jou IM. Ultrasonography for diagnosing carpal tunnel syndrome: a meta-analysis of diagnostic test accuracy. Ultrasound Med Biol. 2012 Jul;38(7):1121-8.

Fowler JR, Gaughan JP, Ilyas AM. The sensitivity and specificity of ultrasound for the diagnosis of carpal tunnel syndrome: a meta-analysis. Clin Orthop Relat Res. 2011 Apr;469(4):1089-94.

- increase the area of the median nerve used as diagnostic criteria. - Cutoff 9 -11mm².- sensitivity 77.6% and specificity 86.8%.

Tai TW, Wu CY, Su FC, Chern TC, Jou IM. Ultrasonography for diagnosing carpal tunnel syndrome: a meta-analysis of diagnostic test accuracy. Ultrasound Med Biol. 2012 Jul;38(7):1121-8.

Mhoon JT, Juel VC, Hobson-Webb LD. Median nerve ultrasound as a screening tool in carpal tunnel syndrome: correlation of cross-sectional area measures with electrodiagnostic abnormality. Muscle Nerve. 2012 Dec;46(6):871-8.

Ultrasonography in Carpal Tunnel Syndrome

Fowler JR, Maltenfort MG, Ilyas AM. Ultrasound as a first-line test in the diagnosis of carpal tunnel syndrome: a cost-effectiveness analysis. Clin Orthop Relat Res. 2013 Mar;471(3):932-7.

Cutoff- 10 mm2 sensitivity – 85.0%

specificity – 92.1%

accuracy – 89.3%

Tai TW, Wu CY, Su FC, Chern TC, Jou IM. Ultrasonography for diagnosing carpal tunnel syndrome: a meta-analysis of diagnostic test accuracy. Ultrasound Med Biol. 2012 Jul;38(7):1121-8.

pronador quadratus

Comparative Evaluation

carpal tunnel

A1

A2

Normal Nerve:A1- A2 ≤ 2mm²

Thickened Nerve:A1- A2 ≥ 2mm²

pronador quadratus

A1

A2

carpal tunnel

Palmar Cutaneus Branch(PCB) of the Median Nerve

antebrachial fascia

flexor retinaculum

median nerve median nerve

FCRT

palmaris longus t

Palmar Cutaneus Branch of the Median Nerve

• Compression in the tunnel.• Stretching as a consequence to reduced mobility of the

median nerve.

FCRT

median nerve

PCB

median nerve FCRT

palmaris longus t

Median nerve

median nerve

median nerve

Post-Operative - Carpal Tunnel Syndrome

Post-Operative - Carpal Tunnel Syndrome

median nerve

median nerve

CONCLUSION

Ultrasound in Carpal Tunnel Syndrome

• The method doesn’t predict severity.• useful as a screening test, reducing the cost of diagnosis

of carpal tunnel syndrome.• post-operative evaluation.

rasernik@uol.com.br