novel diagnostic approach to carpal tunnel syndrome wang fc, gérard p, iserentant c chu liège...
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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 ?
RBSPRM Annual Congress, december 2, RBSPRM Annual Congress, december 2, 20052005
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
RBSPRM Annual Congress, december 2, RBSPRM Annual Congress, december 2, 20052005
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
RBSPRM Annual Congress, december 2, RBSPRM Annual Congress, december 2, 20052005
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
RBSPRM Annual Congress, december 2, RBSPRM Annual Congress, december 2, 20052005
Difference in velocity between the mixed orthodromic conductions of the ulnar and median nerves in the palm-wrist segment(med-uln SCV)
RBSPRM Annual Congress, december 2, RBSPRM Annual Congress, december 2, 20052005
Orthodromic 14-7 distoproximal ratio (14-7 method or Twin Peak test)
RBSPRM Annual Congress, december 2, RBSPRM Annual Congress, december 2, 20052005
• 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)
RBSPRM Annual Congress, december 2, RBSPRM Annual Congress, december 2, 20052005
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
RBSPRM Annual Congress, december 2, RBSPRM Annual Congress, december 2, 20052005
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
RBSPRM Annual Congress, december 2, RBSPRM Annual Congress, december 2, 20052005
Difference in distal motor
latency between ulnar and median
nerves with thenar
recordings (uln-med
DML)
RBSPRM Annual Congress, december 2, RBSPRM Annual Congress, december 2, 20052005
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%)
RBSPRM Annual Congress, december 2, RBSPRM Annual Congress, december 2, 20052005
Reference values (from healthy volunteers)
Normal distributionUnilateral tests
• Mean ± 1.65SD : = 0.05
• Mean ± 1.96SD : = 0.025
• Mean ± 2.30SD : = 0.01
RBSPRM Annual Congress, december 2, RBSPRM Annual Congress, december 2, 20052005
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
RBSPRM Annual Congress, december 2, RBSPRM Annual Congress, december 2, 20052005
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
RBSPRM Annual Congress, december 2, RBSPRM Annual Congress, december 2, 20052005
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