Novel diagnostic approach to carpal tunnel syndrome Wang FC, Gérard P, Iserentant C CHU Liège...

Novel diagnostic approach to carpal tunnel syndrome

Wang FC, Gérard P, Iserentant CCHU Liège

RBSPRM Annual Congress, december 2, 2005RBSPRM Annual Congress, december 2, 2005

Background

The Carpal Tunnel Syndrome (CTS), a condition in which the median nerve is compressed within the carpal tunnel where it passed under the trans-carpal ligament (flexor retinculum), is the most frequent mononeuropathy in the world, with a prevalence in the adult population estimated at 3%.

RBSPRM Annual Congress, december 2, RBSPRM Annual Congress, december 2, 20052005

Objectives To answer this question : in patients clinically suspected of having CTS, what are the best electrodiagnostic (EDX) studies (with the highest sensitivity and specificity) to confirm the diagnosis ?


AAEM QualityAssurance Committe criteria

1. Prospective study design2. Diagnosis of CTS in patient

population based on clinical criteria independent of the EDX procedure under evaluation

3. EDX procedure described in sufficient detail to permit replication

4. Limb temperature monitored (> 32°C)

5. Reference values for EDX obtained with concomitant study of a reference population

6. Criteria for abnormal findings clearly stated and defined in statistically computed terms


Methods

Conduction slowing through the carpal tunnel was evaluated in 3 ways:

1. Absolute slowing : prolonged distal motor latency and

reduced sensory conduction velocity of the median nerve through the carpal tunnel2. Relative slowing : difference

between median and ulnar nerves3. Relative slowing : difference

between two distinct nerve segments of the median

nerve


Median palm-wrist mixed orthodromic conduction (med

SCV)• G1 : 3 cm bar electrode, at the proximal wrist crease, between the tendons of the flexor carpi radialis and palmaris longus• G2 : proximal to G1• Cathode : 8 cm distal to G1, in the mid-palm• Anode : distal to the cathode


Difference in velocity between the mixed orthodromic conductions of the ulnar and median nerves in the palm-wrist segment(med-uln SCV)


Orthodromic 14-7 distoproximal ratio (14-7 method or Twin Peak test)


• G2 : at the proximal wrist crease, between the tendons of the flexor carpi radialis and palmaris longus• G1 : mid-palm, 7 cm distal to G2• Cathode : 7 cm distal to G1,

(third digit)• Anode : distal to the cathode

Orthodromic 14-7 distoproximal ratio (14-7 method or Twin Peak test)


G1/G2

G2/G1

Peak II/Peak I3.2 ms/1.52 ms = 2.11

Median distal motor latency

(med DML)• G1 (APB muscle) : halfway between the midpoint of the

distal wrist crease and the first metacarpophalangeal joint (MPJ)• G2 : slightly distal to the MPJ• Cathode : 8 cm proximal to G1, in a line measured first to the midpoint of the distal wrist crease and then to a point slightly ulnar to the tendon of the flexor carpi radialis• Anode : proximal to the cathode


Difference in distal motor

latency between ulnar and median

nerves with thenar

recordings (uln-med

DML)• G1 and G2 : as for medDML• Cathode : over the median

nerve, than over the ulnar nerve at the wrist on the same line • Anode : proximal to the cathode


Difference in distal motor

latency between ulnar and median

nerves with thenar

recordings (uln-med

DML)


Groups • 22 dominant and 22 non dominant hands from healthy volunteers (45 ± 11 y.o. ; 170 ± 7 cm ; female : 59%)

• 29 dominant and 24 non dominant hands from patients with paresthesia in the territory of the median nerve worsening at night or upon awakening (at least at the onset) (53 ± 16 y.o. ; 163 ± 8 cm ; female : 75%)

• 20 dominant and 20 non dominant hands from patients without paresthesia (39 ± 14 y.o. ; 167 ± 6 cm : female : 70%)


Reference values (from healthy volunteers)

Normal distributionUnilateral tests

• Mean ± 1.65SD : = 0.05

• Mean ± 1.96SD : = 0.025

• Mean ± 2.30SD : = 0.01


Mean

SD Mean±1.65

SD

Mean±1.96

SD

Mean±2.30

SD

med SCV• domi• non domi

5959

5.55.6

5050

4948

4747

uln-med SCV• domi• non domi

3.43.9

6.34.7

1412

1613

1815

14-7 method• domi• non domi

1.91.9

0.11

0.10

2.092.09

2.132.12

2.162.15

med MDL• domi• non domi

3.33.3

0.32

0.26

3.83.7

3.93.8

4.03.9

med-uln MDL• domi• non domi

0.50.5

0.26

0.21

0.90.8

1.00.9

1.11.0

His togram m e : LDM dr + g

K -S d= ,19830, p< ,10 ; Lilliefors p< ,01

S hapiro-W ilk W = ,95329, p= ,07299

2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0

X < = B orne de c atégorie

0

2

4

6

8

10

12

14

Nom

bre d'observations

med MDL

Sensitivity and specificity (established by confronting patients, with and without paresthesia, to the reference values)

• Relative methods are more sensitive and specific than absolute measurements

• Motor axons are less vulnerable to compression than sensory axons


Specificity fixed at 97%

Mean±1.65

SD

Mean±1.96

SD

Mean±2.30

SD

med SCV• sensitivity• specificity

77% 87%90%

85%92%

83%92%

uln-med SCV• sensitivity• specificity

91% 88%100%

87%100%

81%100%

14-7 method• sensitivity• specificity

70% 73%95%

70%95%

70%97%

med MDL• sensitivity• specificity

57% 75%90%

70%92%

64%92%

med-uln MDL• sensitivity• specificity

70% 79%87%

72%95%

66%100%

0 10 20 30 40 5045

56

67

78

89

100

1-specificity

sensi

bili

tyROC curves


med MDLmed-uln MDLmed SCVuln-med SCV14-7 method

• Relative methods are more sensitive and specific than absolute measurements

• Motor axons are less vulnerable to compression than sensory axons

Sen

siti

vit

y

Novel Diagnostic Approach : 100% of specificity

89% of sensitivity

med SCV and uln-med SCV

(LN : 50 m/s and 14 ms)Both abnormal One normal, one

abnormalBoth normal

14-7 method(LN : 2.09)

Abnormal Normal

med DML and med-uln DML

(LN : 3.8 ms and 0.9 ms)

Both abnormal One normal, one abnormal

Both normal

Sensory CTS

Sensory motor CTS

No CTS

Novel diagnostic approach to carpal tunnel syndrome Wang FC, Gérard P, Iserentant C CHU Liège...

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