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8/13/2015
1
Ultrasound Imaging of the Median Nerve
Carpal Tunnel Syndrome
Benjamin M. Sucher, D.O., FAOCPMR-D, FAAPMR
EMG LABs of [email protected]
North Phoenix, Mesa, Glendale, West Phoenix
Disclosure
Benjamin M. Sucher, D.O.
has no relevant financial disclosures.
Why Ultrasound and EDX?
1. Collaborative/Supplemental – provides anatomic info about the nerve;correlate with EDX and clinical exam
2. Provides dynamic physiologic information about the nerve during motion
3. Provides functional info about surrounding structures (mm, tendon, etc), and how they interact with the nerve during activity
4. Do the Ultrasound findings correlate (degree and location of swelling)?
5. EDX is still the ‘gold standard’; perform EDX first to plan US imaging
6. Use the Ultrasound findings to optimize management decisions
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DIAGNOSTIC TESTS FOR CTS
Anatomic v. Physiologic Vascular v. Neurologic
X-Ray
MRI Scan
EDX
Ultrasound Ultrasound
MRI Scan
EDX
Ultrasound Ultrasound
The Thumb
‘The human thumb emerges as a compromise at one point in evolutionary time, a locomotor organ that has been transformed into a manipulative organ
(by stone tool use).
Frank Wilson, The Hand, 1998
The Thumb‘…the modern human brain came into being after the hominid hand became “handier” with tools, …the human brain was the last
organ to evolve”.
Frank Wilson, The Hand, 1998
“….both the most delicate and the most dangerous of the primates”.
“Because of its unique capabilites…the thumb, if need be,
can carry on as a solo act”.
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The ThumbJust how important and powerful is it?
ETIOLOGY OF CTS• IDIOPATHIC
• INFLAMMATORY: Tendonitis/Rheumatoid
• ARTHRITIC: DJD/OA
• CARPAL CANAL STENOSIS / FIBROSIS
• WORK-RELATED: Trauma, Repetition,
Awkward Posturing, Vibration, Cold
• MISCELLANEOUS: Connective Tissue,
Endocrine, Amyloid, etc.
- is it really?
DIAGNOSTIC EVALUATION OF CTS
• HISTORY
• PHYSICAL EXAM
• EDX-ELECTRODIAGNOSIS (EMG/NCS)
• X-RAY-Carpal Canal Views
• ULTRASOUND (high resolution, 12+ MHz)
• MRI“Electrodiagnostic studies remain the gold standard for
verification and diagnosis of a median neuropathy”Vender, et al: Upper extremity compressive neuropathies, In:
Derebery and Kasdan: Injuries and Rehabilitation of the Upper
Extremity, Physical Medicine and Rehab State of Art Reviews,June, 1998; and Strakowski, 2014
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ULTRASOUND EVALUATION OF CTS1. a. CSA at pisiform
2. Digit flexion – lumbrical intrusion
3. Digit + wrist extension – sublimus intrusion
1. b. CSA Forearm (if 9-11mm2)
W-F Ratio > 1.5
10-12cmproximal
ULTRASOUND EVALUATION OF CTS
4. Longitudinal MN diameter pre-stress
5. Longitudinal MN diameter stress
6. Transverse MN diameter (optional)
‘Open-Mouth’ view
7. Video MN stress (optional)
a. longitudinal
b. transverse
DIAGNOSTIC ULTRASOUND OF CTS
Normalm = median nervet = flexor tendons
AbnormalEnlarged + loss of fascicular echotexture = nerve edema
Max normal cross-sectional area <12mm2
Lee, Radiol Clin NA, 7/99
Visser, JNNP, Jan 2008‘Accuracy’ similar to EDX
Walker, AANEM, 9/08US and EDX complementary
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DIAGNOSTIC ULTRASOUND OF CTS
Normalm = median nervet = flexor tendons
AbnormalEnlarged + loss of fascicular echotexture = nerve edema
Max normal cross-sectional area <12mm2
Median DML = 7.3msDistal (palmar) Amp = 8.9mV, prox = 1.7mV
80% conduction block
Median DSL = 6.6ms to D1Amplitude = 2mcv
US and EDX complementary
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DIAGNOSTIC ULTRASOUND OF CTSBifid Median Nerve (high division)
DIAGNOSTIC ULTRASOUND OF CTS
NormalLongitudinal View
NormalAxial View(‘open-mouth’)
Thenar muscles
TCL
TCL
Median nerve
Median nerve
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CTS Case #1
70 y/o female with right UE pain, numbness, tingling, and weakness, for
the past 2mos. Symptoms worse at night and with gripping activity.
PE: palpatory restriction over carpal canal, intact sensation
positive Tinel and Phalen tests
EDX:
Median DML 4.8ms (7mV) [Ulnar 2.7 (10mV)]
Median DSL D-1 3.9ms (11mcv) [Radial 2.7 (10mcv)]
DIAGNOSTIC ULTRASOUND Case #1Lumbrical muscle intrusion
More frequent muscle intrusion in CTS
[46-100%]
Cartwright, Holtzhausen
Larger volume of muscleintrusion in CTS
[8mm2 vs. 4mm2]
Cartwright
lumbricals
CSA = 13mm2
CTS Case #2
44 y/o female with UE pain, numbness, tingling, and weakness, R>L, for the past 2 years; employed as a
spa tech with wrists extended as performing pedicures.
PE: normal, except palpatory restriction over carpal canal
EDX:
Median DML 4.5ms [ Ulnar 2.7 ]
Median DSL D-1 4.2ms [ Radial 2.5]
______________________________________________
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DIAGNOSTIC ULTRASOUND Case #2
Sublimus muscle intrusion
CTS Case #342 y/o male with UE pain, numbness, and tingling, R>L, for the
past 2 years. Treatment with wrist braces provided some relief. Works as computer programmer.
PE: normal, except for Tinel & Phalen tests positive bilaterally
EDX:
Median DML 2.8ms R; 2.9ms L [ Ulnar 2.5 R+L]
Median DSL D-1 2.8ms R; 2.7ms L [ Radial 2.4 R+L] (.4/.3)
Median DSL D-4 3.2ms R+L [Ulnar 3.0 R+L] (.2/.2)
Median mixed 1.8ms R; 1.9ms L [Ulnar 1.8 R; 1.9 L]
__________________________________________________
CSI = .6ms R; .5ms L
DIAGNOSTIC ULTRASOUND Case #3Sublimus muscle intrusion
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DIAGNOSTIC ULTRASOUND OF CTS
‘Notching’ of the median nerveon longitudinal/sagittal view
Lee, Radiol Clin NA, 7/99
Beekman and Visser, Muscle & Nerve, Jan 2003,
‘Only in severe cases’
Transverse carpal ligament
Maximal site of compression,at distal tunnel
DDDDDD
Median nerve Stress testing - Normal
Thenar Digital Flexion Stress Test
No median nerve narrowing
Pre-Stress (neutral)
Actual increase in diameter 30%!
Stress
Median Nerve Stress Testing - CTSCompression of the median nerve
on longitudinal/sagittal view
Median nerve narrowing (58%)
(Maximal site of compression at mid-distal tunnel)
Pre-stress
Stress
No compression
Med DSL = 3.4msRadial DSL = 2.5ms
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DIAGNOSTIC ULTRASOUND OF CTS
PRE-StressMed DML = 5.3ms; 75%CBMed DSL = NR
StressMedian nerve compression
(46% narrowing)
DIAGNOSTIC ULTRASOUND OF CTS
PRE-StressMed DML = 5.2msMed DSL = 4.4ms
StressMedian nerve compression
(41% narrowing)
capitate #3 metacarpal
#3CMC
DYNAMIC STRESS TESTING OF CTS
Longitudinal Imaging - video
40 y/o female, Left UE pain, numb, tingling, weak, x 3mos, 1st 3 digits, worse at nite+activity, + Tinel/Phalen, palp restricLeft DML = 5.3ms (ulnar 2.8), DSL (D-1) = 4.4ms 7mcv,
needle exam normal
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Median Nerve Stress Testing for CTS
Pre-stress
Stress(Median nerve flattening - 36%)
Compression of the median nerveon axial ‘open-mouth’ imaging
During dynamic thenar stress
(Transverse Imaging)
DYNAMIC STRESS TESTING OF CTS
Transverse Imaging - video
Hx: typical CTS x 2mos
PE: + Tinel, Phalen, mild thenar weaknessdec median sensat; palp restrict
Med DML = 6.0ms (Ulnar 3.0ms)Med Mot Amp = 15mV
Med DSL = 4.6ms (Radial 2.9ms); amp wnl
Needle emg: inc insert activity thenar mm
DIAGNOSTIC ULTRASOUND OF CTSPost-op – scar tissue
Korstanje, et al: M&N, May, 2012
‘Thickening and fibrosis of the SSCT(subsynovial connective tissue),
Increased adhesions and decreased excursion of the median nerve andFDP tendons’.
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Anatomy of Carpal Tunnel
Variations of Thenar Muscle Attachment
TCL Myofibroblasts in CTS
Electron-microscopy of the TCL
Myofibroblasts detected in the TCL; fibroblasts with properties of smooth muscle cells
Faster growth rate in TCL cells of CTS patients, may be due to cellular response to trauma.
Allampallan, et al: JOEM, 1996
Constant state of contraction:Decrease in the volume of the carpal tunnel
Increasing pressure on the median nerve
Etiology of CTS
Sucher: JAOA + Curr Rev Musculoskel Med, 2009; Korstanje: M&N, 2012
Multifactorial:
1. Increased intracarpal pressure (+ muscle intrusion during activity)
2. Decreased median nerve mobility (fibrous fixation, SSCT adhesions)
3. Median nerve deformation (traction, stretching, compression; SSCT?)
4. Increased ‘stiffness’ of synovium (and SSCT) and TCL
5. Thenar muscle mass effect +TCL protrusion into the carpal tunnel
6. Flexor tendon thickening and tightening during activity; SSCT ‘tethering’?
7. Combine #5-6: direct compression between muscle and tendon
[Lower the ‘Roof’ (TCL, thenar muscle) + Raise the ‘Floor’ (tendons)]
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CTS is Not IdiopathicIt does not just ‘happen to you’
It is a self-defense mechanism, nature’s way of protecting itself from overuse:
The activity compresses the nerve supplying the muscle that generates the activity, leading to weakness and
atrophy of the muscle, which causes the compression to
‘back-off’, and allows the nerve to recover.
Sucher: JAOA + Curr Rev Musculoskel Med, 2009; PM&R Clinics NA, 2014
Treatment Implications:
1. Myofascial release
2. Modified thumb spica
3. Botox thenar muscle?
4. Avoid vigorous or sustained grasping/pinching (padded handgrips)
CTS Stress Testing Pre+Post OM
Pre-stress
Stress Stress Post OM
THE ELECTRODIAGNOSTIC REPORT
Report the abnormality (Interpretation):“…moderate prolongation of the median distal motor and sensory latencies,
consistent with slowing across the wrist due to focal demyelination…loss of amplitude consistent with conduction block (or axon loss)….”
Summarize with ‘Impressions’ or ‘Conclusions’:“Median mononeuropathy (consistent with carpal tunnel syndrome); mild-
moderate on the right and mild on the left, electrically”
Diagnostic ultrasound imaging (high resolution, 4-15MHz linear transducer) of the right wrist reveals moderate increase in the cross-sectional area of the median nerve (18mm2;
normal <12mm2) at the level of the pisiform (transverse imaging), and partial loss of fascicular echotexture, consistent with nerve edema and carpal tunnel syndrome. The flexor tendons appear normal. Thenar flexion stress test (longitudinal imaging) reveals median nerve
compression between the thenar muscles and flexor tendons in the distal carpal canal. Motion studies (transverse imaging) reveal mild lumbrical muscle intrusion into the carpal canal during digit flexion (grasp), with mild median nerve compressive effect; but no muscle intrusion
during wrist and digit extension.
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Ultrasound v. EDXUS is painless, lower cost, less time
US provides detailed anatomic information:Muscle atrophy
Nerve mobility (sliding in sagittal and axial planes)Precise localization/extent of edema
Anomalous nerve branching
Anomalous muscle penetration into the canalPost-op incomplete TCL transection
Presence of cysts, tumor, persistent median artery
EDX provides physiologic information:
Specific – axon v. myelin, CB; prognosis
EDX is painful
Both have fairly high specificity and sensitivity for CTS
Key References:
1. Strakowski JA: Ultrasound Evaluation of Focal Neuropathies:
Correlation with Electrodiagnosis. New York, Demos Medical
Publishing, 2014.
2. Walker FO and Cartwright MS: Neuromuscular Ultrasound.
Philadelphia, Elsevier Saunders. 2011
3. Peer S and Bodner G: High-Resolution Sonography of the
Peripheral Nervous System, 2nd Ed. Berlin, Springer-Verlag, 2008
4. Ahuja AT: Diagnostic and Surgical Imaging Anatomy Ultrasound.
Salt Lake City, Amirys. 2007
3. Jacobson JA: Fundamentals of Musculoskeletal Ultrasound.
Philadelphia, Saunders, 2012.
8/13/2015
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References:1. Sucher BM and Schreiber AL: Carpal tunnel syndrome diagnosis. Phys Med Rehabil Clin N
Am 2014;25:229-247.
2. Strakowski JA: Ultrasound Evaluation of Focal Neuropathies: Correlation with
Electrodiagnosis. New York, Demos Medical Publishing, 2014.
3. Sucher BM: Ultrasound imaging of the carpal tunnel during median nerve compression.
Curr Rev Musculoskelet Med 2009; DOI 10.1007/s12178-009-9056-5 (online).
4. Sucher BM: Carpal tunnel syndrome: Ultrasonographic imaging and pathologic
mechanisms of median nerve compression. JAOA 2009;109:641-647.
5. Lee D, van Holsbeeck MT, Janevski PK, et al: Diagnosis of carpal tunnel syndrome:
Ultrasound versus electromyography. In: Musculoskeletal Ultrasound. Radiologic Clinics
of North America. 1999;37 (No. 4): 859-872,
6. Beekman R and Visser LH: Sonography in the diagnosis of carpal tunnel syndrome: A
critical review of the literature. Muscle and Nerve. 2003;27:26-33.
7. D’Costa S, Jiji, Nayak SR, Sivanadan R, Abhishek: Anomalous muscle belly to the index
finger. Ann Anat. 2006 Sep; 188(5):473-5.
8. Holtzhausen LM, Constand D, de Jager W: The prevalence of flexor digitorum superficialis
and profundus muscle bellies beyond the proximal limit of the carpal tunnel: A cadaveric
study. J Hand Surg Am. 1998;23:32-7.
9. Robinson D, Aghasi M, Halperin N: The treatment of carpal tunnel syndrome caused by
hypertrophied lumbrical muscles: Case reports. Scand Hand Surg. 1989;23(2):149-51.
10. Siegel DB, Kuzma G, Eakins D: Anatomic investigaton of the lumbrical muscles in carpal
tunnel syndrome. J Hand Surg Am. 1995;20:860-3.
11. Cobb TK, An K-N, Cooney WP: Effect of lumbrical muscle incursion within the carpal tunnel
on carpal tunnel pressure: A cadveric study. J. Hand Surg Am. 1995;20(2)186-92.
12. Caress JB and Walker, FO: Ultrasound of peripheral nerves: An AANEM Workshop.
AANEM, 2006.
13. Robinson LR, Micklesen PJ, and Wang L: Strategies for analyzing nerve conduction data:
Superiority of a summary index over single tests. Muscle & Nerve. 1998;21:1166-1171.
References (cont):14. Robinson LR, Micklesen PJ, and Wang L: Optimizing the number of tests for carpal tunnel syndrome.
Muscle & Nerve. 2000;23:1880-1882.
15. Klauser AS, Halpern EJ, DeZordo T, et al: Carpal tunnel syndrome assessment with ultrasound: Value of
additional cross-sectional area measurements of the median nerve in patients versus healthy volunteers.
Radiology 2009;250(1);171-7.
16. Hobson-Webb L and Paduca L: Median nerve ultrasonography in carpal tunnel syndrome: Findings from
two laboratories. Muscle & Nerve. 2009;40:94-97.
17. Wilson, F: The Hand, How Its Use Shapes The Brain, Language, and Human Culture. New York, Pantheon
Books. 1998.
18. Cartwright MS, et al. : Muscle intrusion into the tunnel in carpal tunnel syndrome. AANEM 2010 Annual Meeting
Abstract Guide.
19. Joshi SD, Joshi SS, and Athavale SA: Lumbrical muscles and carpal tunnel. J Anat Soc India. 2005;54:12-15.
20. Walker FO and Cartwright MS: Neuromuscular Ultrasound. Philadelphia, Elsevier Saunders. 2011
21. Walker FO and Cartwright MS: Neuromuscular ultrasound: Emerging from the twilight. Muscle & Nerve.
2011;43:777-779.
22. Padua L: Repeated ultrasound studies may help us understand what’s going on inside the nerve. Muscle &
Nerve. 2012;44:6-7.
23. Therimadasamy A, Peng YP, and Wilder-Smith EP (Letter to Editor): Carpal tunnel syndrome – Median nerve
enlargement restricted to the distal carpal tunnel. Muscle & Nerve. 2012;46: 455-7.
24. Mhoon JT, Juel VC, and Hobson-Webb LD: Median nerve ultrasound as a screening tool in carpal tunnel
syndrome: Correlation of cross-sectional area measures with electrodiagnostic abnormality. Muscle & Nerve.
2012;46:871-878.
25. Cartwright MS, Hobson-Webb LD, Boon AJ, et.al: Evidence-based guideline: Neuromuscular ultrasound for the
diagnosis of carpal tunnel syndrome. Muscle & Nerve. 2012;46:287-293.
26. Korstanje JH, et al: Ultrasonographic assessment of longitudinal median nerve and
hand flexor tendon dynamics in carpal tunnel syndrome. Muscle & Nerve. 2012;45:721-729.