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The Carpal Tunnel

CTSDysfunction of median nerve in the carpal tunnel resulting in

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Symptoms in CTS

– pain and numbness in the abd– worse on finger activity– aggravated by forceful grippinggg y g pp g– symptoms more prominent at night-morning

(flexed fingers)

Signs of CTS

2-point discrimination > 3.4 mmPhalen sign digit 3Tinel signTinel signweakness of thenar muscles wrist ratio (lat vs dors-volar) > 0.7

EDX in CTS; principles

• Motor:– Absolute values– Comparison with ulnarComparison with ulnar

• Sensory:– Absolute values– Comparison with other nerves

• med-uln• med-rad

– Transcarpal tunnel compared to distal segment

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EDX in CTS: pathophysiology

Test motor and sensory Median nerve for :Demyelination (slowing)Axonal degeneration (low ampl+ denerv)Axonal degeneration (low ampl+ denerv)Conduction block (prox-dist stim)

Motor: APB,ADM

80 mm

80 mm

Stimulation in the palm

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Motor: APB transcarpal

CTS, motor(normal amplitude/increased distal lat. at wrist)

Stimulation site:

palm

wrist

above elbow

Demyelination, no axonal loss

CTS, motor (low amplitude/increased distal lat. at wrist )

Stimulation site:

palm

wrist

above elbow

Demyelination + conduction block

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CTS, motor (low amplitude/increased distal lat. at wrist )

Stimulation site:

lpalm

wrist

above elbow

Demyelination +severe axonal loss

Summary motor

Practical approach: Motor 1med (APB) and uln (ADM) comparison

Stimulate at wrist; median and ulnarRecord from APB and ADM (80 mm)Normal lat diff APB-ADM < 1 3 msecNormal lat diff APB-ADM < 1.3 msec

If low APB amplitude, also stimulate in the palmNormal increase < 25%

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Motor: Lumbr I-IOD II

CTS; mainly motor- demo of IOD, lumbr

Uln; 2.7 Med; 4.0

Practical approach: Motor 2med (lumbrical I) and uln (IOD II) comparison

- performed in severe casesStimulate median and ulnar at wrist crest Record between metacarp II and III

Normal diff < 0.7 msec (Tromsö + Normal diff < 0.7 msec (Tromsö + littlitt))< 0.5 msec (B.S < 0.5 msec (B.S KherzriKherzri, K , K LindblomLindblom, BMA), BMA)

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7

6

5

4

Motor: corr Medlat-Ulnlat vs lumbr1-IOD230 controls, 30 CTS Tromsö

lub-iod

76543210-1

med

-uln

3

2

1

0

-1

P atient Diagnos is

p n p

n o rm a l

cts

Comparison lumb/IOD is not better than APB/ADM

lumb-IOD

Median nerve, sensoryDemyelination, slowing across CT:

a) dig to wrist or wrist to dig. CV compared to ulnar (IV) or radial (base of thumb)

b) palm to wrist (med and uln)c) 14-7 antidromicd) 14-7 CT tester

Axonal degeneration, general loss of ampl:sensory amplitudes distal to CT lig

Conduction block, amplitude drop across CT:

Sensory: orthodromic dig IV and mixed from palm

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Practical approach: SensoryMedian dig IV and ulnar dig IV comparison

Stimulate wrist median and ulnarRecord base of dig IVgCalculate CV

Normal diff (IV-IV) < 16 m/sec

32 controls, 24-69 y

Sensory: antidromic med-uln

Sensory antidromic med-rad

10

1010

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Antidromic stim of med + rad nerve (ring electrodes) Bactrian sign CTS

normal CTS

Med + Rad stim (ring el), Bactrian sign in CTS

20 uV/div1ms/div

antidromic

normal CTSrad + medrad med

antidromic

orthodromic

CTS

Practical approach: SensoryMedian thumb and radial thumb comparison

Stimulate wrist; median and radialRecord base of thumb (ring el)Di t 10Distance 10 cm

Normal diff < 0.3 ms

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Sensory antidromic 14-7 cm

77

+

Reference values14-7measured to neg peak

Segment 95% limit source

140 mm: 3.5 ms Örebro3 7 ms Johnson3.7 ms Johnson

palm-digIII 1.9 ms Örebro trans- CT 1.6 ms Örebro

Sensory orthodromic, “CT tester”

77

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NormalT2/T1 = 1T2T1

CTT2/T1 > 1

T2T1

Diagnostic output CT-tester

A i di i 70% ”N i l” 30%Automatic diagnosis 70% ”No signal” 30%

CTS 88%PNP 9%

Normal 3%

CTS, CT tester

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Left

Late

ncy

[ms]

Tra

ce1 10

9

8

7

6

M-latmed

SNCS Medianus Left CV [m/s] Trace4

80706050403020

MNC

SM

edia

nus

L

5

4

3

2

SIDE

s

d

b

only motor

only sensory

Sens CV III

CTS; CT index vs sens CV diff dig 4- 450

40

30

6 5%

CT Tester CT Index cts

3,53,02,52,01,51,0,5

SDI4

_4C

T

20

10

0

-10

24.4%

6.5%

CT tester

CV

um

ed 4

-uln

4

Definitions of CTS(Luca Padua)

• Slight only sensory abnormalies• Moderate sens +motor abnormal• Pronounced no sens responses• Pronounced no sens responses• Very severe no sens or motor responses

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CTS; additional methods

* pron quadr/APB amplp q p* centimetering* ultrasound

N Interosseus antRec Pron quadr

Stim median nerve

rec 45 mm prox linel diiproc styl.radii-

proc styl. ulna

ref

Use of PQ in severe CT69 y trauma, hand drop. Plexus? Focal nerve? PNP?

Stiff pers. Syndr.

APB = 0lumb1 and IOD2

Normal PQ response indicates normal median proximally. CT.Pat has also pnp.

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Median nerve SSS - method

Median nerve centimetering, normal finding

SSS in very mild CTS

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Ultrasound

All pictures with Courtesy

Lisa Hobson-Webb M DLisa Hobson-Webb, M.D.Advanced Fellow in Neuromuscular DiseaseDuke University Medical Center

A Normal Median Nerve

Asymptomatic vs. CTS

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12cmElbow Hand

Imaging TechniqueForearm measurement

Wristmeasurement

Normal median nerve in sagittal plane

Measurement in CTS

D=12cmElbow Hand

Focal enlargementat carpal tunnel

Median nerve insagittal plane

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CommentsComments

• Both sensory (more than one test) and motor nerve should be tested

• Sensitivity and specificity:Sensitivity and specificity:– single ref values (sens)– inter-nerve comparison (spec)– transcarpal tunnel conduction (spec)

• Additional tests to detect:– cond block; motor and sensory (antidromic)

Pooled sensitivity and specificity of EDX techniques for CTS

Pooled Pooledsensitivity specificity

A Median sensory and mixed nerve conduction: wrist and palm segmentcompared to forearm or digit segment 0.85 0.98

B Comparison of median and ulnar sensory conduction between wrist andring finger 0.85 0.97

C Median sensory and mixed nerve conduction between wrist and palm 0.74 0.97

D Comparison of median and ulnar mixed nerve conduction between wristand palm 0.71 0.97

AAEM M&N 2002

p

E Median motor nerve conduction between wrist and palm 0.69 0.98

F Comparison of median and radial sensory conduction between wrist andThumb 0.65 0.99

G Median sensory nerve conduction between wrist and digit 0.65 0.98

H Median motor nerve distal latency 0.63 0.98

I Median motor nerve terminal latency index 0.62 0.94

J Comparison of median motor nerve distal latency (second lumbrical) to theulnar motor nerve distal latency (second interossei) 0.56 0.98

K Sympathetic skin response 0.04 0.52

CTS standards, guidelines, optionsMedian sensory NCS across the wrist (13 cm to 14 cm) (Technique G). If abnormal, compare median

sensory NCS to sensory NCS of one other adjacent sensory nerve in the symptomatic limb (Standard).

If the initial median sensory NCS across the wrist (distance greater than 8 cm) is normal, one of the following studies is recommended:

comparison of median sensory or mixed nerve conduction across the wrist over a short (7 cm to 8 cm) conduction distance (Technique C) with ulnar sensory nerve conduction across the wrist over the same short (7 cm to 8 cm) conduction distance (Technique D) (Standard), or

comparison of median sensory conduction across the wrist with radial or ulnar sensory conduction across the wrist in the same limb (Techniques B and F) (Standard), or

comparison of median sensory or mixed nerve conduction through the carpal tunnel to sensory or mixed NCSs of proximal (fore arm) or distal (digit) segments of the median nerve in the same limb (Technique A) (Standard).

AAEM M&N 2002

( q ) ( )

Motor NCS of the median nerve recording from the thenar muscle (Technique H) and of one other nerve in the symptomatic limb to include measurement of distal latency (Guideline).

Supplementary NCS: comparison of the median motor nerve distal latency (second lumbrical) to the ulnar motor nerve distal latency (second interossei) (Technique J); median motor terminal latency index (Technique I); median motor nerve conduction between wrist and palm (Technique E); median motor nerve compound muscle action potential (CMAP) wrist-to-palm amplitude ratio to detect conduction block; median sensory nerve action potential (SNAP) wrist-to-palm amplitude ratio to detect conduction block; short segment (1 cm) incremental median sensory nerve conduction across the carpal tunnel (Option).

Needle electromyography (EMG) of a sample of muscles innervated by the C5 to T1 spinal roots, including a thenar muscle innervated by the median nerve of the symptomatic limb (Option).

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MOTOR:MOTOR:

APB (full exam – CV, F) ADM (uln only distally)

in case of exceptional situation:in case of exceptional situation:Lumbr I, IOD IIPron quadr, ADMEMG

•• SENSORY:SENSORY:

• Orthodromic method: (rec wrist, calc CV)– med dig 4, uln dig 4 and– med dig 3, uln dig 4– med palm uln palmmed palm, uln palm

• CT tester

• In case of exceptional situation (uln trauma, cut fingers)

– 7-14 antidromic wrist to dig 3– orthodromic thumb to radial and median (Bactrian sign)– digital branch:antidromic to individual digits (tennis, golfer)