The Value of Ultrasonographic Imaging in the Study of Carpal Tunnel Syndrome.

Transcription

1 Suez Canal Univ Med J Vol. 4 No. 1, March, The Value of Ultrasonographic Imaging in the Study of Carpal Tunnel Syndrome. Magdy A. Awadalla *, Ahmed F. El-Sera3 **. Amany Zakareya *, Noha Zaki**, Tarek Elbigurmie*", Ahmed Osama*** Rheumatology and Rehabilitation*, Radiology** and Neurology*** Departments Suez Canal and Ein Shams Universities Introduction Paget in 1854 and Cannon and Love in 1946 had described the carpal tunnel syndrome (CTS) as a compression neuropathy of the median nerve, occurring at the level of the fibro-osseous carpal tunnel in the wrist. The carpal tunnel is formed by the crossing of the fibrous flexor retinaculum in front of the anterior concavity of the carpus transferring it into a tunnel through which the flexor tendons of the digits as well as the median nerve gain access to the palm. The flexor retinaculum is medially attaches to the pisiform and hook of hamate and laterally it splits into two laminae. The superficial attached to the tubercle of scaphoid and trapezium, and deep attached to medial lip of a groove in the trapezium('). CTS have a variety of causes. It is often the result of a combination of factord2).the condition is attributed to compression of the median nerve in the carpal tunnel beneath the flexor 87 retinaculum at the wrist against the ligament due to hypertrophy or edema of the flexor synovium.. A frequent phenomenon encountered in rheumatic patients is tendon sheath enlargement caused by synovial proliferation(". In patients with rheumatoid arthritis (RA) finger flexor tenosynovitis varies from 5 to 55%(4). Among RA patients with finger flexor tenosynovitis, about 25-50% has CTS. Moreover a wide variety of systemic illnesses, metabolic diseases, overuse syndromes, fractures and aberrant anatomic structures have been also described as possible causes of CTS. Any pathological lesion that compromises the space available for the median nerve in the carpal tunnel can cause CTS. This could result in numbness, tingling in the hand, clumsiness, or pain described as CTS. Pain is thought to be due to nerve ischemia rather than direct physical damage of the nerve and the diagnosis should be

2 8 8 Magdy A. Awadalla, et al., considered for any patient with hand or wrist pain, weakness, or numbnesd5). In the majority of cases, CTS is idiopathic with no specific underlying cause detectedc6), meanwhile the syndrome can probably be produced by several mechanisms involving either an increase in the volume of tunnel content or decrease in tunnel diameter(7). Several investigations are used to evaluate cases of CTS. They are either electrophysiological studies or the various imaging techniques. Clinically accurate diagnosis of CTS relies on clinical symptoms and electromyography (EMG) despite that the sensitivity of the later does not exceed 25-35% (8). Diagnosis based on nerve conduction studies (NCS) is not always reliable. The usual criteria of sensory conduction velocity and motor latency fail to identify about 10% of the cased9). Plain radiographs are of very low yielding and are of important diagnostic value only when skeletal derangement might precipitate in the condition(i0). Computerized tomography (CT) study of the wrist displays changes in the carpal tunnel with possible measurement of cross sectional area of the carpal tunnel(l I). Magnetic resonance imaging (MRI)(12) and sonography (SG)(13) can be used to diagnose suspected CTS. Both have the advantage over NCS that they provide information about the possible causes of CTS, such as RA tenosynovitis or synovitis of the wrist joint(14). In the absence of CTS, SG might reveal the origin of hand pain in visualizing these changes. MRI may be used with the advantage of being noninvasive and more conclusive in the assessment of soft tissue pathology(15), it is reasonably accurate in diagnosing CTS, it can define the site of entrapment, it also may serve a role in postoperative evaluation of patients with recurrent symptoms(12) but due to its high cost, it should be restricted to special diagnostic problems and resistant cases(16) or when the clinical picture is confusing or there are equivocal or contradictory nerve conduction studies. The use of SG in the diagnosis of CTS although shows promises but it is currently still experimental. Ultrasonography owes a high sensitivity in the detection of fluid and alterations in shape and echogenecity of the median nerve and when quantitative analysis of its results were done, the results were significant(17). CTS is characterized by typical anatomic changes that can be shown SG(I8). The value of utilizing SG to directly scan the median nerve, was studied by several investigators, Some of them are still conservatives and find that it is still premature to promote or advertise carpal tunnel imaging as a diagnostic modality for CTS(19). While others can see it an encouraging useful tool. SG of the median nerve might allows for evaluation of the extrinsic causes of CTS and potentially facilitates therapeutic intervention. Enlargement of the median nerve, lack of deformability on real time and abnormalities of blood flow, swelling of the median nerve in the proximal part of the carpal tunnel, flattening of the median nerve in the distal part of the carpal tunnel, presence of a nodule and increased palmar bowing of the flexor retinaculum(18) are all imaging features that can be described by SG in evaluating cases with CTS. Buchberger et al. (20) compared the sonograms of 20 wrists with CTS with the their MR images and sonograms of normal wrists, and found that the results of SG were reliable and that diagnosis of CTS can be established on the basis of sonographic findings. Ferrari et al.(21) showed that SG exhibited 96% sensitivity, 95% specificity and 93% diagnostic accuracy and play a major role in the diagnosis of the CTS when compared to electromyography. The aim of this work was to investigate the reliability of high-resolution ~ltrason~graphy in the diagnosis of the carpal tunnel syndrome when comparing its findings with the results of commonly performed electrophysiological tests in cases with clinical evidence of carpal tunnel syndrome.

3 Ultrasonograpl~ic Imaging in Carpal Tunnel Syndrome Subjects and Methods This study comprised subjects attending the Rheumatology and Rehabilitation and Neurology Outpatient Clinics in Suez Canal University Hospitals. 32 wrists in 22 patients presented with clinical manifestations of carpal tunnel syndrome constitute the study group and a control group including 7 wrists in 4 normal asymptomatic subjects. Both groups constituted the material of our study. Both Female and male subjects were included in the study. Inclusion criteria: * Pain in one or both hands * Numbness in one or both hands * Weakness in one or both hands. Exclusion criteria: Cervical root compression confirmed by measurement of F wave latency. History of trauma at the wrist level or fracture at the lower third of forearm. Compression of the median nerve at higher level than the wrist, detected by clinical tests of pronator syndrome and for compression at flexor digitorum superficialis origin. Patients suspect$jd to have peripheral neuropathy. All Subjects included in the study were subjected to: A full history assessment. 2. General examination. 3. Neurological examination. 4. Local examination of both hands and forearm with comparison between both sides. 5. Motor power examination for the regional muscles. 6. Sensory examination including pinprick and point discrimination tests and comparison was made with ulnar enervated digits and with the other hand. 7. Some special tests were performed including : * Timed Phalen Test: was performed with the hands in gravity the examiner passively flexes assisted position and both wrists. * Reverse Phalen Tests: was performed with palms of both hands facing each other and elbows are elevated as high as possible. * Tine1 Sign: was performed after a period of 60 seconds of wrist hyperextension. *Tourniquet Test: was used by inflating sphygmomanometer cuff to above systolic blood pressure level for 60 seconds. * Pronator Teres Syndrome Test and Flexor Digitorum Superficialis Arch Test were also performed to excluded cases of proximal compression. After the clinical evaluation was completed the following electrophysio-logical procedures were performed: F- wave latency to exclude cases of cervical root compression. Distal Sensory Latency (DSL) of the median nerve with recording at index finger and stimulation 14 cm proximal. Distal Motor Latency (DML) of the median nerve with stimulation 8 cm proximal. EMG examination of the abductor pollicis brevis muscle with recording spontaneous, voluntary and maximal activity. Subjects were considered electrodiagnostically abnormal if one of the above electrodiagnosis test is abnormal considering values (3.8 and ( 4.3 as normal values for DSL and DML respectively. After a clinical and electrophysiological diagnosis was reached. Both groups were subjected to ultrasonographic examination of both wrists. With the subject sitting and his forearm resting comfortably on a flat surface, and the elbow in midflexion and the wrist on supination. Anatomic landmarks and imaging technique: In the transverse imaging plane, the ulnar artery is the medial landmark of the carpal tunnel. Imaging must be performed with the scan-head in a plane perpendicular to the tendon surface. The tunnel contains the flexor digitorum tendons, which are hyperechoic. 89

4 90 Magdy A. Awadalla, et al., Anterior to the tendons is the median nerve. Which has a characteristic appearance that differentiates it from the fibrillar hyperechoic tendons. The nerve is hypoechoic with a hypere~hoic border and shows multiple bright reflectors in the transverse imaging plane. The median nerve is rounded or oval in the proximal wrist and flattens progressively as it courses through the carpal tunnel. Within the tunnel the nerve is in intimate contact with the flexor retinaculum; its size remains constant but its shape is quiet variable. In the longitudinal imaging plane the nerve is demonstrated coursing parallel and superficial to the flexor digitorum tendons. The sonographic appearance of the nerve in this plane demonstrates hyperechoic continuos anterior and posterior borders (the nerve sheath). Sonographicfindings in carpal tunnel syndrome: Subjective criteria(18) Enlargement of the median nerve. Decreased mobility of the median nerve on flexion and extension of the fingers, hand and wrist. Abnormalities of blood flow. Swelling of the nerve in the proximal part of the carpal tunnel. Flattening of the nerve in the distal part of the carpal tunnel. Large fluid or fat layer surrounding the tendons. Presence of a nodule. Increased palmar bowing of the flexor retinaculum. The mean cross sectional area of the median nerve is greater than 10 mm at the pisiform bone level. The flattening ratio of the nerve (transverse diameter divided by the anteroposterior diameter) is greater than 4: 1 at the level of the hamate bone. Volar bulging of the flexor retinaculum is greater than 3.lmm. Results Our study comprised 22 patients (13 females and 9 males 1.44:l) with clinical evidence of CTS. Their ages ranged between years with the mean age for females of years slightly lower than that for males which was years. The overalls mean age was years. The duration of the disease ranged between 3-18 months. Pain was the presenting symptoms in 21 complaining hands corresponding to 65.1 % and clinical examination summary of results of patient group is illustrated in figure (1). The results of the Special Tests performed to subjects included in patient group are illustrated in figure (2). Among the 32 complaining hands included in the patients group, DSL detected changes in 27 hands corresponding to 84.4 %. Positive results were also obtained in 2 of the non-complaining hands and with no clinjcal evidence of CTS corresponding to 16.7 %. So DSL were able to detect changes in a total of 29 hands of the total number of hands included in patient group. Among the 32 complaining hands included in the patients group, EMG detected changes in 13 hands corresponding to approximately 40.6% while DML detected changes in 25 hands corresponding to 78.1 %. Both EMG and DML failed to detect any other significant abnormalities among hands included in patient group. Figures (3 and 4) showing abnormal DSL and DML and EMG respectively. From the above-mentioned results, we concluded that the DSL is the most sensitive electrophysiologic test, performed in our study, in the diagnosis of CTS. High resolution ultrasonography detected abnormalities in 22 hands (out of the 32 complaining hands) corresponding to 68.8% (Fig. 5,6,7). It also was able to show a moderate edema of the median nerve in 1 of the non-complaining hands and with no clinical evidence of CTS among the patient group.

5 Ultrasonographic Imaging in Carpal Tunnel Syndrome 9 1 El Bilateral Affection 81 Nmbness I Pain 3 Wasting W Phnlen II Hwersc Phalcn a Tinnel's l'oarniquet Fig. 1. Summary of results of patient group. Fig. 2. Results of special tests in patient group. R? A8D POL IRE Spon;an.uur PC5 SKAAP YAVE 1 llrcr \ FIBRILLATIONS a - -0 P, r-- -7,.-, 4.m r Trace 11 TertLng for medlen nerve coapxe#slon et the wrlst level by recording both dlst.1 sanrory ~atendv and terminal motor latency et both sldes Stlmulotlon at the medlao nerve ebovm the urlst vlth xecordlnq at dlqlt 1 lor sensory and ebductor p01lall bravls for motor REPORT : It Lt Z ll.0.c Sans: Dlstanoo 14.00~ Amplltudo JX CV 61 UV DLst Letanoy ~ ~ Worm<1.Ims WCV Not= > uc~ny fll.tmrr r Or. Amp1 l Ludr 13.1 IY iq.1 mr Tarmlnal latonsy 3.0 ms 3. 9% Nor. < 4.> ms Fig. 3. Testing for absolute distal motor latency and distal sensory latency of the median nerve across the wrist level. Upper two traces: Affected right hand. Lower two traces: Normal left hand. Fig. 4. Neuropathic EMG recording of Rt. abductor pollicis brevis muscle. Trace A: Combined fibrillations and positive sharp waves recorded during rest. TraceB: Neuropathic MUAP with marked polyphasia and increased amplitude. Trace C: Giant Neuropathic MUAP reaching 14.5 mv amplitude. Trace D: ~iscrete interference pattern with maximal contraction.

6 92 Magdy A. Awadalla, et al., Fig. 5. Ultrasound of the wrist showing compression of the median cerve by surrounding edema. Fig.6. Ultrasound of the wrist showing fibrosis and undistinguished layers of tendons due to adhesions (Previous operative procedure) Fig. 7a. Diagram showing transverse view of the entrance to the carpal tunnel with a swollen median nerve indicating carpal tunnel syndrome. Discussion Carpal tunnel syndrome is the commonest entrapment neuropathy resulting from compression of the median nerve at the level of the fibrous flexor retinaculum, with the resultant pain, tingling and numbness involving the distribution of the median nerve. Clinical examinations as well as the electrophysiological tests play the major role in its diagnosis@). In this work, comparison between results of different nerve conduction studies revealed that DSL was more sensitive than DML and EMG in detecting abnormalities in hands with clinical evidence of CTS. D~mitn.6~~) who reported that sensory fibers are usually affected first and to a greater extelit than motor fibers supports this opinion. Fig. 7b. Ultrasound of the wrist showing transverse view of the entrance to the carpal tunnel with a swollen median nerve indicating carpal tunnel syndrome. DSL is characteristically highly specific 95% and sensitive 93% in the diagnosis of CTS. DML can also detect the presence of CTS but with lesser degree of sensitivity and ~pecificity'~). In our study DSL was able to detect abnormalities in 84.4% of the complaining hands, such figures differs from the above mentioned, and this difference could be attributed to the difference between our patients series and that of Haloua et al.(9) in term of severity of cases where DSL is less sensitive in detecting moderate cases of CTS. And, from our work, we concluded that DSL was the most sensitive electrophysiologic test performed to diagnose cases with CTS.

7 Ultrasonographic Imaging in Carpal Tunnel Syndrome Clinical as well as electrophysiological tests can only diagnose the presence of CTS but can neither specify nor localize the pathology involving the median nerve. Moreover The usual criteria of sensory conduction velocity and motor latency fail to identify about 10% of the cased9). Utilizing ultrasound to directly image the median nerve may allows for evaluation of possible causes of CTS. High resolution ultrasonography has the advantage of localizing and specifying the pathology. Other imaging modalities such as plain x-ray or CT and MRI are deficient in either being unable to visualize the soft tissues or being unavailable and relatively expensive and hence reserved from problematic casedi2). Ultrasonography is fearly available, relatively inexpensive, involve no ionizing irradiation and can give valuable data comparable to that given with the classical and golden tools of diagnosis. When done properly high-resolution ultrasonography can detect median nerve compression with more than 93% of diagnostic accuracy and could play a major role in the diagnosis of the CTS(21). We agreed with the previous works discussing the values of ultrasonography in the diagnosis of CTS. Using US were able to detect compression of the nerve by surrounding edema (Fig. 5), fibrosis due to previous operative procedures (Fig. 6) and swollen median nerve at the entrance of the carpal tunnel indicating CTS (Fig. 7). In our study high resolution ultrasonography was able to detect abnormalities in 68.8 % of the complaining hands. Our figures differs from that of Ferrari et a~.(~') and this difference could be attributed to our lacking of experience in this field with newly adopted protocol and procedures. Moreover we did not consider measuring the cross diameter of the nerve. Taking in consideration that ultrasonography enabled us to directly image the median nerve, localize the pathology and determine its nature, we concluded that high resolution ultrasonography is definitely a step forward in the diagnosis and follow up of cases with clinical evidence of CTS. We recommend that high resolution ultrasound should be used for every case with clinical manifestation of CTS at the start and for follow up, also it might be of great when used for follow up and evaluation in post operative cases of CTS. References Delisa JA. Upper extremity nerves. In: Delisa JA, Lee HJ, Baran EM, Lai KS, Spielholz N, editors. Manual of nerve conduction velocity and neurophysiology. New York: Raven Press 1994; 68-71;. Franklin GM, Haug J, Heyer N, Checkoway H, Peck N. Occupational carpal tunnel syndrome in Washington State, Am J Public Health 1991; 81: Nashel DJ. Soft tissues: entrapment neuropathies. In: Klippel JH, Dieppe PA, editors. Rheumatology. London: Mosby, 1998; Paget J. Lectures on surgical pathology, edl, Lindsay Philadelphia, Blakiston, 40,1854. Quoted from Eversmann, Whitley-JM and McDonnell-DE : Post grad-med. Jan, 1995; 97(1) :89-92,956. Schuind F., Ventura M., Pasteels L., : J Hand Surg., 15 (A), 1990; Wand J, J Hand Surg. 15 (B),1990; Stevens JC. : Muscle Nerve,1987; Feb.: Haloua JP; Soulier F;Collin JP., : Ann Chir Main memb Super 1994; 13(1): Hart VL, and Gaynor VJ, Bone Joint Surg.; 23: , Quoted from Smith Liang CL., :Nippon-Seikeigeka Gakkai Zasshi 1987; 61(10): Mesgarzadeh M, Triolo J, Schneck CD. Magn Reson Imaging Clin N Am 1995; 3(2): Grassi W, Tittarelli E, Blasetti P, Pirani 0, Cervini C. Finger tendon involvement in rheumatoid arthritis. Arthritis Rheum 1995;38:

8 94 Magdy A. Awadalla, et al., 14.Nakamichi K, Tachibana S. The use of 20.Buchberger W, Judmaier W, Birbamer G, et al. ultrasonography in detection of synovitis in carpal AJR-AM-J-Rontgenol Oct 1992;159(4): tunnel syndrome. J Hand Surg [Br] 1993; 18: Ferrari FS, Della Sala, et al. Radiol Med (Torino) 15.Martin S, Zeiss J, Ibrahim N, et al.. J Hand Surg 1997; 93(4); ; 15 (A) : Dumitru D. Electrodiagnosis of CTS. 16. Seyfert S, Boegner F, Hamm B, et al. J Neurol 1994; Electrodiagnostic Medicine; Hanley and Belfus Inc 242(1):41-6, Dec. 1995; pp Buchberger - W, Judmaier - W, Schon - G, Strasser K, J-Ultrasound-Med 1991; lo(10): Buchberger W, Judmaier W, Birbamer G, et al. Rofo Fortschr Geb Rontgenstr Neuen Bildgeb Verfahr 1993; l59(2): Rosenbaum RB. Invest Radiol 1993; 28(11): Correspondence to: Dr. Magdy A. Awadalla, Department of Rheumatology and Rehablitation, Suez Canal University.

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