The Carpal Tunnel CTS. Stålberg 1. Dysfunction of median nerve in the carpal tunnel resulting in

Transcription

1 The Carpal Tunnel CTS Dysfunction of median nerve in the carpal tunnel resulting in 1

2 Symptoms in CTS pain and numbness in the abd worse on finger activity aggravated by forceful gripping g symptoms more prominent at night-morning (flexed fingers) Signs of CTS 2-point discrimination > 3.4 mm Phalen sign digit 3 Tinel sign weakness of thenar muscles wrist ratio (lat vs dors-volar) > 0.7 EDX in CTS; principles Motor: Absolute values Comparison with ulnar Comparison with ulnar Sensory: Absolute values Comparison with other nerves med-uln med-rad Transcarpal tunnel compared to distal segment 2

3 EDX in CTS: pathophysiology Test motor and sensory Median nerve for : Demyelination (slowing) Axonal degeneration (low ampl+ denerv) Conduction block (prox-dist stim) Motor: APB,ADM 80 mm 80 mm Stimulation in the palm 3

4 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 4

5 CTS, motor (low amplitude/increased distal lat. at wrist ) Stimulation site: palm wrist above elbow Demyelination +severe axonal loss Summary motor Practical approach: Motor 1 med (APB) and uln (ADM) comparison Stimulate at wrist; median and ulnar Record from APB and ADM (80 mm) Normal lat diff APB-ADM < 1.3 msec If low APB amplitude, also stimulate in the palm Normal increase < 25% 5

6 Motor: Lumbr I-IOD II CTS; mainly motor- demo of IOD, lumbr Uln; 2.7 Med; 4.0 Practical approach: Motor 2 med (lumbrical I) and uln (IOD II) comparison - performed in severe cases Stimulate median and ulnar at wrist crest Record between metacarp II and III Normal diff < 0.7 msec (Tromsö + litt) < 0.5 msec (B.S Kherzri, K Lindblom, BMA) 6

7 Motor: corr Medlat-Ulnlat vs lumbr1-iod2 30 controls, 30 CTS Tromsö Patient Diagnosis pnp med-uln 0-1 normal cts lumb-iod lub-iod Comparison lumb/iod is not better than APB/ADM Median nerve, sensory Demyelination, 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 antidromic d) 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 7

8 Practical approach: Sensory Median dig IV and ulnar dig IV comparison Stimulate wrist median and ulnar Record base of dig IV Calculate CV Normal diff (IV-IV) < 16 m/sec 32 controls, y Sensory: antidromic med-uln Sensory antidromic med-rad

9 Antidromic stim of med + rad nerve (ring electrodes) Bactrian sign CTS normal CTS Med + Rad stim (ring el), Bactrian sign in CTS normal CTS antidromic rad + med rad med 20 uv/div 1ms/div antidromic orthodromic CTS Practical approach: Sensory Median thumb and radial thumb comparison Stimulate wrist; median and radial Record base of thumb (ring el) Distance 10 cm Normal diff < 0.3 ms 9

10 Sensory antidromic 14-7 cm Reference values14-7 measured to neg peak Segment 95% limit source 140 mm: 3.5 ms Örebro 37ms 3.7 Johnson palm-digiii 1.9 ms Örebro trans- CT 1.6 ms Örebro Sensory orthodromic, CT tester

11 T1 T2 T1 T2 T2/T1 = 1 Normal T2/T1 > 1 CT Diagnostic output CT-tester Automatic diagnosis i 70% No signal 30% CTS 88% PNP 9% Normal 3% CTS, CT tester 11

12 M-lat med MNCS Medianus Left Latency [ms] Trace only sensory only motor SIDE s d b 80 SNCS Medianus Sens Left CV III CV [m/s] Trace4 CTS; CT index vs sens CV diff dig % 6.5% 10 SDI4_4CT CV umed 4-uln ,5 1,0 1,5 24.4% 2,0 2,5 3,0 3,5 CT CT Tester tester CT Index cts Definitions of CTS (Luca Padua) Slight Moderate Pronounced Very severe only sensory abnormalies sens +motor abnormal no sens responses no sens or motor responses 12

13 CTS; additional methods * pron quadr/apb ampl * centimetering * ultrasound N Interosseus ant Rec Pron quadr Stim median nerve rec 45 mm prox line proc styl.radiiproc styl. ulna ref Use of PQ in severe CT 69 y trauma, hand drop. Plexus? Focal nerve? PNP? Stiff pers. Syndr. APB = 0 lumb1 and IOD2 Normal PQ response indicates normal median proximally. CT. Pat has also pnp. 13

14 Median nerve SSS - method Median nerve centimetering, normal finding SSS in very mild CTS 14

15 Ultrasound All pictures with Courtesy Lisa Hobson-Webb, M.D. Advanced Fellow in Neuromuscular Disease Duke University Medical Center A Normal Median Nerve Asymptomatic vs. CTS 15

16 Elbow Imaging Technique Forearm measurement 12cm Wrist measurement Hand Normal median nerve in sagittal plane Measurement in CTS Elbow D=12cm Hand Median nerve in sagittal plane Focal enlargement at carpal tunnel 16

17 Comments Both sensory (more than one test) and motor nerve should be tested 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) AAEM M&N 2002 Pooled sensitivity and specificity of EDX techniques for CTS Pooled Pooled sensitivity specificity A Median sensory and mixed nerve conduction: wrist and palm segment compared to forearm or digit segment B Comparison of median and ulnar sensory conduction between wrist and ring finger C Median sensory and mixed nerve conduction between wrist and palm D Comparison of median and ulnar mixed nerve conduction between wrist and palm E Median motor nerve conduction between wrist and palm F Comparison of median and radial sensory conduction between wrist and Thumb G Median sensory nerve conduction between wrist and digit H Median motor nerve distal latency I Median motor nerve terminal latency index J Comparison of median motor nerve distal latency (second lumbrical) to the ulnar motor nerve distal latency (second interossei) K Sympathetic skin response CTS standards, guidelines, options AAEM M&N 2002 Median 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). 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). 17

18 MOTOR: APB (full exam CV, F) ADM (uln only distally) in case of exceptional situation: Lumbr I, IOD II Pron quadr, ADM EMG SENSORY: Orthodromic method: (rec wrist, calc CV) med dig 4, uln dig 4 and med dig 3, uln dig 4 med 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) 18