Anatomy of the Carpal Tunnel. Carpal Tunnel Syndrome. Ultrasound: Normal Nerve. Ultrasound: Median Nerve/Carpal Tunnel

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1 Courses In Diagnostic Ultrasound Wake Forest School of Medicine US for Carpal Tunnel Syndrome Lecture Outline Steven Shook, MD Staff, Neuromuscular Center Cleveland Clinic Neurological Institute April 11, 2013 Overview of CTS Ultrasound of Normal Median Nerve US findings in CTS Is NM US an accurate test for CTS diagnosis? What is the sensitivity of US for CTS? What does US add to EMG in CTS? Can US predict outcome after surgical release? Questions Carpal Tunnel Syndrome Anatomy of the Carpal Tunnel CTS is the most common entrapment neuropathy worldwide Prevalence up to 9.2% in women, 6.0% in men Incidence 276/100,000 year Risk factors: Obesity, Female Gender, Pregnancy, Renal Failure, Thyroid Disease, Diabetes, Mechanical Injury/Trauma Diagnosis: Clinical with electrodiagnostic support Sensitivity of EMG/NCS estimated from 80-95% Surgical literature suggests 16-34% of patients with clinical CTS have normal NCS Formed by the transverse carpal ligament (a.k.a., flexor retinaculum) ventrally, carpal bones dorsally The proximal end of the carpal tunnel is marked by the pisaform bone (medially) and scaphoid bone (laterally) The tunnel contains the 8 tendons of the flexor digitorum superficialis and profundus, and the flexor pollicis longus tendon The median nerve lies superficial and parallel to the flexor tendons of digits II-III Reduced anatomic space is thought to play a role in the clinical symptoms of carpal tunnel syndrome Shook, SJ CTS 5 Minute CC 2012 Ultrasound: Normal Nerve Normal nerves appear as hypoechoic fascicles with hyperechoic perineurium Surrounding tissue borders the hyperechoic epineurium Nerves can be differentiated from surrounding tissue Ultrasound: Median Nerve/Carpal Tunnel High resolution linear array probe Small parts, Musculoskeletal (MSK) Probe Assessment to include: Cross-sectional evaluation at the distal wrist crease Sagittal/longitudinal view of the median nerve Comparison at the forearm (around 12 cm proximal to the wrist crease) Measurements to include: Largest CSA proximal to and/or within the carpal tunnel CSA at approximately 12 cm proximal to the distal wrist crease Internal control measurement; Index calculation Contralateral assessment for comparison Additional measurements/assessment as clinically appropriate Walker and Cartwright NM US

2 Normal Median Nerve Cross Sectional Area (CSA) Fifty asymptomatic volunteers (100 arms) evaluated Cross-sectional area of the nerve was consistent along its course (7.5 to 9.8 mm2): Distal wrist crease 9.8 (2.4) Mid-forearm 7.5 (1.6) Proximal forearm 7.6 (1.7) Antecubital fossa 8.6 (2.3) Mid-humerus 8.9 (2.1) Axilla 7.9 (1.9) Cartwright, et al J Neuroimaging 2009 Normal Median Nerve CSA The upper limit of normal (mean + 2 SD) for side-to-side difference at the individual sites were: Distal wrist crease 3.4 mm2 Mid-forearm 2.6 mm2 Pronator teres 2.8 mm2 Antecubital fossa 4.3 mm2 Mid-humerus 3.0 mm2 Axilla 3.5 mm2 Nerve size at the wrist correlated with: Weight (correlation coefficient of.411, P =.0030) Age (r =.413, P =.0029) Cartwright, et al J Neuroimaging 2009 Nerve Ultrasound: Abnormal Findings Ultrasound Findings in CTS Limited range of abnormality can be identified Swelling (increased CSA) Abrupt changes in course due to entrapment, or surrounding pathology Laceration/trauma Focal changes in echotexture Increases in blood supply (power/color Doppler) Adjacent pathology Why do entrapped nerves swell? Based on experimental animal studies, etiology likely varies over the period of compression: Early: Endoneurial edema, fibroblasts and capillary endothelial cell proliferation, fibrin deposition, damming of axon transport, and Schwann cell proliferation/apoptosis Later: Endoneurial invasion (mast cells/macrophages), demyelination/remyelination, axon degeneration/regrowth, fibrosis, and thickening of the perineurium Similar, albeit more mild, changes at entrapment sites have been identified in asymptomatic human cadavers suggesting a possible threshold symptoms Differential Diagnosis of Nerve Enlargement Entrapment neuropathies Peripheral nerve tumors/neuromas Acquired amyloid neuropathy Sarcoidosis Inflammatory neuropathies GBS, CIDP, MMNCB, MADSAM Hereditary neuropathies HNPP, CMT, Refsum s, Familial amyloidosis Neuropathy in leprosy Rempel et al, Gupta, et al, Neary, et al,

3 Carpal Tunnel Syndrome: Other US Findings Bowing and thickening of the flexor retinaculum Changes in the echotexture beneath flexor retinaculum Loss of fascicular discrimination Abrupt caliber change ( notch sign ) at proximal tunnel Flattening of the nerve within the distal tunnel (w/d > 3) Reduced mobility with wrist flexion Increased vascularization within the nerve (Doppler) Is US an accurate test for the diagnosis of CTS? Wright et al. 1996, Beekman et al. 2003, Mallouhi et al Evidence-Based Guideline AANEM AANEM expert panel systematic review of articles published from 1990 to May 2011 (724 articles) Review of 240 abstracts yielded 121 articles for full review and rating by AAN criteria, 67 included in the guideline Key questions to be answered: (1) What is the accuracy of median nerve cross-sectional area enlargement as measured with ultrasound for the diagnosis of CTS? (2) What added value, if any, does neuromuscular ultrasound provide over electrodiagnostic studies alone for the diagnosis of CTS? AANEM Guideline: Accuracy of US in CTS Calculated probability that a patient will be correctly classified by a screening or diagnostic test Definition of accuracy Sensitivity x prevalence + specificity x (1-prevalence) Panel considered an accuracy of > 70% supportive of neuromuscular ultrasound for the diagnosis of CTS AANEM Guideline: Accuracy of US in CTS AANEM Guideline: Accuracy of US in CTS Class I Quality of evidence Class I 4 studies (prospective cohort) Class II 2 studies (retrospective case-control) Class III 27 studies 18 studies due to spectrum bias (e.g., controls = healthy volunteers) 6 studies due to failure to blind US examiner to clinical data or other diagnostic information 2 studies due to both spectrum bias and failure to blind the US examiner Class IV 12 3

4 AANEM Guideline: Accuracy of US in CTS Class II AANEM Guideline: Accuracy of US in CTS Based Class I and Class II evidence US measurement of median nerve CSA at the wrist is established as accurate for the diagnosis of CTS Recommendation: If available, US measurement of median nerve CSA at the wrist may be offered as an accurate diagnostic test for CTS (Level A) Note: No single cut-off for diagnosis is provided Scanning protocols and reference values for median nerve CSA should be established by each laboratory Class I and II studies utilized a CSA of 9 to 12 mm2 (measured at the level of the pisaform bone in most cases) Carpal Tunnel Syndrome: Nakamichi 2002 Symptomatic idiopathic CTS (n=414) v. volunteers (n=408) Gold standard: Clinical history and neurologic examination Nerve conduction criteria Sensitivity 73%: Specificity 96% Mean CSA >0.12 cm 2 Sensitivity 67%: Specificity 97% NCS or US abnormalities Sensitivity 84%: Specificity 94% Note: When median motor and sensory responses were both absent (8%) US was localizing to the CT in all cases Carpal Tunnel Syndrome: Ziswiler 2005 Prospective study of 74 consecutive patients (110 wrists) with suspected CTS Compared median nerve CSA in patients with and without EMG evidence of CTS Post test probability of CTS: Median CSA > 12 mm2: > 90% Median CSA > 14 mm2: approaches 100% Good correlation between median distal motor latency and largest median nerve CSA within the carpal tunnel Nakamichi et al Ziswiler, et al Carpal Tunnel Syndrome: Additional Data Studies have confirmed the accuracy of using increased median nerve CSA at the wrist: Meta-analysis Fowler 2011 (19 studies, unrated quality of evidence) Sensitivity and specificity of ultrasound in the diagnosis of CTS Composite: 77.6% and 86.8% EDX = gold standard 80.2% and 78.7% Clinical diagnosis = gold standard 77.0% and 93.0% Conclusion: US compares favorably with the EDX sensitivity and specificity defined by Graham (69% and 97%, respectively) Correlations also exist between ultrasonographic findings and electrophysiological stage, as well as MUNE Median wrist-to-forearm CSA ratio (>1.5) may be of additional value, although the utility of this measurement is debated What does US add to EMG in CTS? Fowler, et al, Clin Orthop Relat Res 2011; Hobson-Webb

5 Can Ultrasound Replace EMG? EMG is the diagnostic gold standard in most disorders of the peripheral nervous system Information derived from EMG, not from US Evaluation of the neuromuscular junction Localization of a lesion within the intraspinal canal Characterizing axon loss versus demyelination Estimation of lesion duration US is a valuable adjunct to EMG, adding valuable and often diagnostic structural information Ultrasound Complements EMG in Mononeuropathy Recent study examined outcomes when US was added to the EMG/NCS in evaluation of mononeuropathy 20 cases (26%) medical approach was impacted by US Nerve tumors, adjacent pathology, and variant anatomy 35 cases (47%), findings supported the electrodiagnostic impression, but did not impact treatment Focal nerve swelling at an entrapment site identified by EDX 20 cases (26%) cases were considered inconclusive Findings no abnormalities was clinically useful Conclusion: US can meaningfully impact patient care when combined with the EDX in selected patients Padua, L., et. al Ultrasound Added-Value AANEM Guideline: Added Value of US in CTS Class II Clinically-relevant anatomical variants Aneurysms Cysts Non-neural soft tissue tumors Scar tissue Bone Fragments Tendon rupture/hypertrophy AANEM Guideline: Added Value of US in CTS Screening for structural abnormalities at the wrist higher yield in those with atypical CTS Unilateral symptoms and signs History of trauma Presence of anatomical variants such as persistent median arteries, bifid median nerves and accessory muscles may alter management Added Value of US in CTS: Persistent median artery Estimated incidence 10 26% 15% in a retrospective study at Cleveland Clinic; bilateral 31% Found adjacent to the ligament and is often associated with a variant (bifid) median nerve 77% in a retrospective study at Cleveland Clinic Can complicate an endoscopic CT release or an open release if a tourniquet is used Imaging can help to guide CTS surgical planning and may improve patient outcomes Gassner, et. al. JUltraMed. 2002; John, et. al. J Neuroimag

6 Predicting responders to CTR Surgery Data Supporting Can US predict outcome after surgical release? Mondelli et. al (n=67 patients) CSA reduced after CTR: Pre-CTR 15.5 mm2 (range , SD 5.8) 1 month 13.8 mm2 (range , SD 4.8) 6 months 13.6 mm2 (range , SD 5.0) Reduction in area correlated with NCS and clinical improvement Logistic regression analysis: Smaller pre-cts CSA correlated with post-ctr satisfaction/improvement Predicting responders to CTR Surgery Data against Smidt and Visser 2008 (n=172 patients, 88 CTR) Main outcome: Satisfaction scales at 6 months Good Outcome: n=66 76% decreased CSA Poor Outcome: n=10 60% decreased CSA No difference in median change in CSA Pre-operative CSA did not predict outcome Naranjo A et. al (n = 88 patients, 104 hands) Main outcome: Five-point Likert scale at 3 months Clinical Improvement: mean CSA decreased 14.2 to 13.3 mm2 No/Slight Improvement: mean CSA decreased 12.5 to 11.6 mm CASES DIFFERENTIAL DIAGNOSIS OF CTS Case 1: Carpal Tunnel Syndrome? Case 1: Carpal Tunnel Syndrome? 35 year old woman with a history of NF1 Presenting with burning, lightening shocks and other sensory changes in digits 1 through 3 bilaterally, right > left, questionable carpal tunnel syndrome Neurological examination: mild sensory loss in digits 1 3 on both sides; no APB weakness/atrophy. Tinel's and Phalen's signs were positive on the right. EMG: Normal without median sensory or motor response abnormalities MRI C-spine: Unremarkable 6

7 Case 1: Carpal Tunnel Syndrome? Case 1: Carpal Tunnel Syndrome? Case 1: Median Nerve Neurofibromas Case 2: Progressive APB Atrophy 33 year old right-handed white man, history of CMT Slowly progressive right thumb weakness for 10 years, with atrophy of the thenar eminence Examination: motor > sensory deficits and foot deformity consistent with CMT, and left APB atrophy EMG: Severe demyelinating neuropathy, and absent right median sensory and motor responses; interpreted as CMT +/- an unlocalizable right median neuropathy Case 2: Progressive APB Atrophy in CMT Case 2: Progressive APB Atrophy in CMT 7

8 Case 2: Median neuropathy, forearm; ganglion cyst Case 3: Cop with hand weakness 40 year old right-handed policeman Intermittent right hand "numbness" and paresthesias, distal digits 1 through 3, 18 months prior to our consultation Progressive right hand numbness and weakness No wrist pain, nighttime worsening, improvement with shaking, etc. No neck, shoulder or arm pain Carpal tunnel release at an OSH did not improve symptoms EMG: Absent median motor and sensory responses, and fibrillation potentials throughout the median myotome, including the pronator teres Case 3: Median Neuropathy, Above the Elbow Case 3: Median Neuropathy, Above the Elbow Case 3: Median Neuropathy, Above the Elbow Case 4: Post Median Nerve Graft Wrist Pain 45 year old woman with a history of CTS, status-post bilateral carpal tunnel release at an OSH She noted immediate numbness in the palm and digits 3 and 4 and Tinel's sign at the wrist Neuroma was subsequently identified, excised, and four fascicles of the median nerve were grafted At 6 month post-graft she experienced minimal wrist pain with flexion She was concerned about neuroma recurrence 8

9 Case 4: No Evidence of Neuroma Recurrence Thank you 9