Ultrasound of Carpel tunnel syndrome

1. Carpal Tunnel syndrome ( CTS(
Ultrasound criteria
Presented By
DR Laith Fadhel

2. 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%.

3. 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

4. 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

5. 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 )

6. 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

7. Imaging technique
• In the longitudinal imaging plane the never is
demonstrated coursing parallel and superficial
to the flexor digitorum tendons

8. 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 criteria
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
Volar bulging of the flexor retinaculum is greater than 3.1 mm

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

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

11. 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

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

13. 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 criteria
The 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 ) mm²
The 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)

14. Moderate degree Bilateral CTS more on the right side

15. RT hand / flatting of MN + decrease mobility

16. Volar bulging of FR / 2.7mm

17. Mean CS area of MN (10.2 mm2(

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

19. LT hand / no flatting of MN + no decrease mobility

20. Volar bulging of FR / 2.3mm

21. Mean CS area of MN (11.2 mm2(

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

23. Other things seen with ultrasound
Of 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:

24. 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.