Carpal Tunnel syndrome ( CTS ( Ultrasound criteria

Presented By DR Laith Fadhel

Introduction • Carpal tunnel syndrome (CTS) is the most

common entrapment neuropathy, affecting 9% of women, 6% of men and it is responsible for significant morbidity and occupational absence. Clinical assessment is used for initial diagnosis and nerve conduction (Nerve Conductive ) studies are currently the principal test used to confirm the diagnosis. There is now good evidence that US can be used as an alternative to NC studies to diagnose CTS. US can assess the anatomy of the median nerve and also identify pathology of the surrounding structures that may compress the nerve. US sensitivity has been reported to be as high as 80-90%.

Signs & symptoms • Paresthesia in the hand through

the distribution of median nerve

• Night paresthesia in the fingers / pain in the forearm and arm

• Weakness and atrophy of thenar muscle

• + Ve (Tinel's sign ) a sensation of tingling or pins and needles in the distal extremities of a limb when percussion in made over the site of an injured nerve

• Phalen’s sign : reproduction of pain or paresthesia with flexion of the wrist for one minute or more

Etiology of CTS • The carpel tunnel is fibro-

osseous space between the carpel bones and the flexor retinaculum . It contains the eight flexor digitorum tendons . The flexor pollicus longus , the median nerve

• The etiology of CTS is primarily the encroachment on the median nerve , this can be due either a decrease in size of tunnel , or increase in the volume of tunnel content

• The most recently described common cause of CTS is repetitive stress injury as in computer keyboard operators

Common Cases of CTS • Osseous causes of tunnel

narrowing • Misalignment of carpel bones • Displaced fractures • Hypertrophic bone changes

and callus formation • Increase content volume

causes of tunnel narrowing • Tendon sheath enlargement

(traumatic synovitis )• Synovial proliferation ( RA ) • Hypertrophied muscle

( occupational ) • Increase fat ( obesity )

Imaging technique • Patient positioning / the forearm should rest

comfortably and the wrist is in supination • In the transverse imaging plane the ulnar artery

is the medial landmark of the carpel tunnel • Imaging must be performed with the transducer

in plane perpendicular to the tendon surface to eliminate the anisotropic effect

• The tunnel contains the flexor digitorum tendons which are hyper echoic

• Anterior to the tendons is the median nerve • The median nerve has a characteristic

appearance which differentiates it from the fibillar hyper echoic tendons

• The nerve is hypo echoic with a hyper echoic borders and show multiple bright reflectors in the transverse imaging plane

• The median nerve is rounded or oval in the proximal wrist and flattens progressively as it courses through the carpel tunnel

• Within the tunnel the nerve is in intimate contact with the flexor retinaculum , its size remains constant but its shape is quite variable

Imaging technique • In the longitudinal imaging plane the never is

demonstrated coursing parallel and superficial to the flexor digitorum tendons

  Ultrasound finding :Subjective criteria 

Flattening of the nerve, especially at the level of the hamate bone Volar bulging of the flexor retinaculum                                                   Enlargement of the median nerve as it enters the carpal tunnel       Large fluid or fat layer surrounding the tendons                                    Decreased mobility of the median nerve on flexion and extension  of the fingers 

Objective criteriaThe mean cross sectional area of the median nerve is greaterThan 10 mm squared at the pisiform bone level                               The flattening ratio of the nerve (transverse diameter divided by AP diameter) is greater than 4:1 at the level of the hamate bone  Volar bulging of the flexor retinaculum is greater than 3.1 mm      

Flattening of the nerve, especially at the level of the hamate bone

Volar bulging of the flexor retinaculum Volar bulging of the flexor retinaculum is greater than 3.1 mm

Enlargement of the median nerve as it enters the carpal tunnel The mean cross sectional area of the median nerve is greater

Than 10 mm squared at the pisiform bone level

The flattening ratio of the nerve (transverse diameter divided by AP diameter) is greater than 4:1 at the level of the hamate bone

Case study / 49 y female presented with paresthesia in RT hand with pain extended from RT arm down to the wrist , with miner complying within LT hand for 3 years duration Age : 49 years Gender : female Hospital : Baghdad .T.H Date of examination : 26-3-2015 Hand RT -LT Diagnostic Imaging Finding / Ultrasound finding :Subjective criteria Flattening of the nerve, especially at the level of the hamate bone ( RT – present ) ( LT – not ) Volar bulging of the flexor retinaculum ( RT – present ) ( LT – present ) Enlargement of the median nerve as it enters the carpal tunnel ( RT – present ) ( LT – present ) Large fluid or fat layer surrounding the tendons ( RT – not ) ( LT – not ) Decreased mobility of the median nerve on flexion and extension ( RT – present ) ( LT – not ) of the fingers, hand or wrist Objective criteriaThe mean cross sectional area of the median nerve is greater Than 10 mm squared at the pisiform bone level RT ( 10.2 ) mm² LT ( 11.2 ) mm²The flattening ratio of the nerve (transverse diameter divided by AP diameter) is greater than 4:1 at the level of the hamate bone RT ( 3.7 :1 ) LT ( 3.5:1 ) Volar bulging of the flexor retinaculum is greater than 3.1 mm RT ( 2.7 m ) LT ( 2.3 m)

Moderate degree Bilateral CTS more on the right side

RT hand / flatting of MN + decrease mobility

Volar bulging of FR / 2.7mm

Mean CS area of MN (10.2 mm2(

Flatting ratio of MN must be grater than (4:1) of Transverse :AP { 3.7:1 {

LT hand / no flatting of MN + no decrease mobility

Volar bulging of FR / 2.3mm

Mean CS area of MN (11.2 mm2(

Flatting ratio of MN must be grater than (4:1) of Transverse :AP { 3.5:1 {

Other things seen with ultrasoundOf course evidence of CTS is not the only thing seen on the ultrasound scans of hand and wrist and a variety of other lesions may be seen in the surrounding tissues. The scanner can also be used to study other nerve lesions. Ganglion cysts appear as very hypo-echoic (dark) spaces, sometimes with internal subdivisions yet without any evidence of flow on Doppler imaging:

This lesion below, clearly seen at the base of the little finger as a soft, somewhat lobulated, swelling, extending into the proximal phalanx of the little finger...

...is probably a lipoma, showing as a fairly uniform, evenly speckled, slightly encapsulated structure on ultrasound, again without evidence of internal flow on Doppler imaging.