3406jum937-1114 copy_Layout 1 5/22/15 8:08 AM Page 1027
ORIGINAL RESEARCH
Sonographic Findings in the Ulnar Nerve According to the Electrophysiologic Stage of Carpal Tunnel Syndrome Young In Eom, MD, Moon Hee Choi, MD, Yue Kyung Kim, MD, In Soo Joo, MD
Article includes CME test
Objectives—Involvement of the ulnar nerve in patients with carpal tunnel syndrome is controversial. The aim of our study was to evaluate sonographic findings in the ulnar nerve in patients with carpal tunnel syndrome. Methods—We performed median and ulnar nerve conduction studies with sonography in 109 hands of 60 patients with clinically suspected carpal tunnel syndrome. Sonographic findings were analyzed with regard to electrophysiologic stages of carpal tunnel syndrome. Results—We found that the sensory conduction velocity of the ulnar nerve decreased as the electrophysiologic stage of carpal tunnel syndrome increased (P = .038), but there was no change in the cross-sectional area of the ulnar nerve at the wrist. The median-toulnar nerve cross-sectional area ratio at the wrist showed a significant correlation with the electrophysiologic stage of carpal tunnel syndrome (Spearman r = 0.431; P < .0001), in addition to the median nerve cross-sectional area at the wrist and the wrist-to-forearm median nerve cross-sectional area ratio. Conclusions—In our study, ulnar nerve involvement in patients with carpal tunnel syndrome was shown electrophysiologically but not sonographically. These results suggest that morphologic changes in the ulnar nerve do not occur in carpal tunnel syndrome, although functional changes may occur. Key Words—carpal tunnel syndrome; electrophysiologic stage; nerve conduction study; sonography; ulnar nerve
C Received August 1, 2014, from the Department of Neurology, Ajou University School of Medicine, Suwon, Korea. Revision requested August 17, 2014. Revised manuscript accepted for publication September 8, 2014. Address correspondence to In Soo Joo, MD, Department of Neurology, School of Medicine, Ajou University, 5 San, Woncheon-dong, Yongtong-gu, Suwon-si, Kyunggi-do 442-749, Korea. E-mail: [email protected] doi:10.7863/ultra.34.6.1027
arpal tunnel syndrome, the most common entrapment neuropathy, is caused by compression of the distal median nerve resulting from increased pressure in the carpal tunnel. Carpal tunnel syndrome can be diagnosed by the presence of symptoms, such as numbness, tingling, burning, and pain in the median territory of the hands, and by nerve conduction studies. In addition to nerve conduction studies, sonography has been extensively used to evaluate carpal tunnel syndrome, owing to its noninvasiveness and utility in patients with discrepancies between clinical and electrophysiologic findings. Previous sonographic findings in patients with carpal tunnel syndrome have shown an increase in the cross-sectional area of the distal median nerve at the wrist,1–5 an elevated wrist-to-forearm cross-sectional area ratio,5–7 and an elevated wrist-to-forearm difference8 in the median nerve crosssectional area.
©2015 by the American Institute of Ultrasound in Medicine | J Ultrasound Med 2015; 34:1027–1034 | 0278-4297 | www.aium.org
3406jum937-1114 copy_Layout 1 5/22/15 8:08 AM Page 1028
Eom—Ulnar Nerve Sonography in Carpal Tunnel Syndrome
Although the median nerve innervates the first 3 fingers and half of the fourth finger, many patients with carpal tunnel syndrome report symptoms throughout the whole hand, including the fifth finger. These variations have contributed to inconsistent results in studies of ulnar nerve involvement in carpal tunnel syndrome.9–13 However, most literature to date have reported only findings from nerve conduction studies of the ulnar nerve in patients with carpal tunnel syndrome. To our knowledge, no study has evaluated sonographic findings of the ulnar nerve according to the electrophysiologic stage of carpal tunnel syndrome. The objective of this study was to use sonography to determine whether there is a relationship between the ulnar nerve and the electrophysiologic stage of carpal tunnel syndrome.2
Materials and Methods Participants We conducted a retrospective study of 109 hands in 60 patients (40 women and 20 men; mean age ± SD, 54.37 ± 13.86 years; range, 25–82 years) who were referred to our electrophysiology laboratory in 2012 and 2013 with paresthesia of one or both hands. If clinical carpal tunnel syndrome was suspected, patients were recruited to our carpal tunnel syndrome registry and underwent nerve conduction studies and peripheral nerve sonography the same day. Bilateral median and ulnar nerves were investigated using both nerve conduction studies and sonography in all patients. The global symptom score,14 the sum of numeric quantifications from 0 to 10 of 5 symptoms (pain, numbness, paresthesia, weakness, and nocturnal awakening), was used to quantify the carpal tunnel syndrome symptom severity. Patients had no clinical or electrophysiologic signs of other neuromuscular diseases and had no conditions that would predispose to carpal tunnel syndrome (eg, wrist fracture or pregnancy). Patients with a bifid median nerve were excluded. However, we did not exclude participants with diabetes mellitus unless electrophysiologic evidence of diabetic polyneuropathy coexisted because we wanted to obtain a full spectrum of carpal tunnel syndrome presentations. This study was approved by the hospital’s Institutional Review Board, and written consent was obtained from all participants. Nerve Conduction Studies All nerve conduction studies were performed by a single well-trained examiner. We investigated the sensory conduction velocity, sensory nerve action potential amplitude, distal motor latency, motor conduction velocity, and compound muscle action potential amplitude of the median
1028
and ulnar nerves. In sensory conduction studies, median and ulnar orthodromic sensory nerve conduction was measured by stimulating the second and fourth fingers and then recording at the wrist. For motor conduction studies, a surface recording electrode was placed over the belly of the adductor digiti minimi muscle for the ulnar nerve and over the abductor pollicis brevis muscle for the median nerve. Distal motor latency was measured with the stimulation point 7 cm proximal to the adductor digiti minimi and abductor pollicis brevis muscles. When symptoms were atypical of carpal tunnel syndrome, additional electrodiagnostic studies were performed to exclude radiculopathy, brachial plexopathy, polyneuropathy, and ulnar neuropathy at the elbow. The ground electrode was placed between the stimulating and recording points. Skin temperature was kept above 32°C. All electrophysiologic studies were performed with a Medelec Synergy system (Oxford Instruments Medical, Hawthorne, NY). The electrophysiologic severity of carpal tunnel syndrome was assessed by means of a previously reported classification by Padua et al.15 This classification was simplified to the following 3 classes: mild (including minimal), moderate, and severe (including extreme). Regardless of symptoms, patients without nerve conduction study abnormalities were included in the electrophysiologically normal group. Sonography Sonography was performed either just before or immediately after the electrophysiologic studies. All examinations were performed in the supine position with the palm up in the neutral position. Transverse sonograms of the median nerve were collected at the distal wrist crease and mid forearm of the symptomatic limb in patients with a 7–12-MHz linear array transducer (ML6-15; GE Healthcare, Milwaukee, WI). The ulnar nerve was also examined at the distal wrist crease, mid forearm, and elbow with a hockey stick transducer (L8-18i; GE Healthcare) for the distal wrist crease and a linear array transducer for the mid forearm and elbow. Sonographic examinations of the ulnar nerve were performed with the arm extended and hands resting in a horizontal supine position on the examination table for measurement at the distal wrist crease and mid forearm. When the ulnar nerve was measured at the level of the elbow, the upper limb was abducted to 90° from the body, and the elbow was flexed to 30° with maximal supination. If focal entrapment of the ulnar nerve at the elbow was suspected, we excluded the case, considering the influence of possible concurrent pathologic conditions. Subluxation of the ulnar nerve at the elbow was not considered a
J Ultrasound Med 2015; 34:1027–1034
3406jum937-1114 copy_Layout 1 5/22/15 8:08 AM Page 1029
Eom—Ulnar Nerve Sonography in Carpal Tunnel Syndrome
pathologic condition unless entrapment was suspected. All cross-sectional areas were measured twice and averaged. All sonographic studies were performed by the same physician, who was blinded to the nerve conduction data. Statistical Analysis Descriptive statistics, including means and standard deviations, were applied to nerve conduction and sonographic studies of each nerve. Correlations were assessed by the Spearman coefficient. Values in each electrophysiologic group were compared by the Kruskal-Wallis test. We did not consider minimum detected differences because ulnar and median nerves are known to have low minimum detected differences compared to other nerves.16 All analyses were performed with the SPSS version 19.0 statistical software package (IBM Corporation, Armonk, NY). Results were considered statistically significant at P < .05.
Results Among the 60 patients examined, we detected 49 (81.7%) bilateral and 11 (18.3%) unilateral symptoms in cases of clinically suspected carpal tunnel syndrome. As a whole, 109 hands were evaluated. According to the electrophysiologic stage, normal, mild, moderate, and severe carpal tunnel syndrome occurred in 31 (28.4%), 22 (20.2%), 38 (34.9%), and 18 (16.5%) hands, respectively.
Electrophysiologic and sonographic data for each carpal tunnel syndrome stage are shown in Tables 1 and 2. Ulnar nerve sensory conduction velocity values were within the normal range in all 109 hands, but there were significant differences in the velocities among the groups (P = .038). Other nerve conduction study findings for the ulnar nerve, including the sensory nerve action potential amplitude, compound muscle action potential amplitude, distal motor latency, and motor conduction velocity, were normal and showed no differences between groups (Table 1). Table 2 shows means and standard deviations of sonographic values for patients with carpal tunnel syndrome separated by electrophysiologic stage. The mean median nerve crosssectional area at the distal wrist crease and median nerve wrist-to-forearm cross-sectional area ratio were significantly higher with increasing stage (P < .0001 for median nerve cross-sectional area at the wrist; P = .003 for median nerve wrist-to-forearm cross-sectional area ratio). Figure 1 shows sonograms of the median nerve according to the electrophysiologic stage of carpal tunnel syndrome. However, there was no difference in the ulnar nerve cross-sectional area at the distal wrist crease. A sonogram of the ulnar nerve is shown in Figure 2. In addition to the median nerve crosssectional area at the distal wrist crease and the median nerve wrist-to-forearm cross-sectional area ratio, the median-toulnar nerve cross-sectional area ratio at the distal wrist crease was measured, and the value increased significantly according to the electrophysiologic stage (P < .0001).
Table 1. Ulnar Nerve Conduction Values According to the Electrophysiologic Stage of Carpal Tunnel Syndrome Parameter USCV, m/s USNAPa, μV UDML, ms UMCV, m/s UCMAPa, mV
Normal (n = 31)
Mild (n = 22)
Moderate (n = 38)
Severe (n = 18)
P
46.02 ± 3.34 21.51 ± 7.87 2.35 ± 0.20 59.44 ± 3.73 15.09 ± 2.30
45.68 ± 4.17 20.76 ± 10.77 2.29 ± 0.25 59.58 ± 4.31 17.25 ± 2.17
44.52 ± 3.40 17.59 ± 6.33 2.40 ± 0.24 59.32 ± 3.65 15.81 ± 2.91
43.23 ± 4.29 20.04 ± 7.38 2.46 ± 0.24 58.27 ± 5.06 16.07 ± 4.25
.038 .244 .096 .052 .620
Data are presented as mean ± SD. UCMAPa indicates ulnar nerve compound motor action potential amplitude; UDML, ulnar nerve distal motor latency; UMCV, ulnar nerve motor conduction velocity; USCV, ulnar nerve sensory conduction velocity; and USNAPa, ulnar nerve sensory nerve action potential amplitude. Table 2. Sonographic Findings According to the Electrophysiologic Stage of Carpal Tunnel Syndrome Parameter MCSAd, mm2 UCSAd, mm2 MWFR MUR
Normal (n = 31)
Mild (n = 22)
Moderate (n = 38)
Severe (n = 18)
P
7.94 ± 1.58 3.92 ± 0.97 1.68 ± 0.34 2.16 ± 0.53
10.44 ± 2.56 3.89 ± 0.93 1.94 ± 0.42 2.77 ± 0.81
11.11 ± 2.18 4.18 ± 1.01 2.03 ± 0.48 2.75 ± 0.64
13.22 ± 3.92 4.13 ± 0.83 2.46 ± 1.08 3.27 ± 0.98
ORIGINAL RESEARCH
Sonographic Findings in the Ulnar Nerve According to the Electrophysiologic Stage of Carpal Tunnel Syndrome Young In Eom, MD, Moon Hee Choi, MD, Yue Kyung Kim, MD, In Soo Joo, MD
Article includes CME test
Objectives—Involvement of the ulnar nerve in patients with carpal tunnel syndrome is controversial. The aim of our study was to evaluate sonographic findings in the ulnar nerve in patients with carpal tunnel syndrome. Methods—We performed median and ulnar nerve conduction studies with sonography in 109 hands of 60 patients with clinically suspected carpal tunnel syndrome. Sonographic findings were analyzed with regard to electrophysiologic stages of carpal tunnel syndrome. Results—We found that the sensory conduction velocity of the ulnar nerve decreased as the electrophysiologic stage of carpal tunnel syndrome increased (P = .038), but there was no change in the cross-sectional area of the ulnar nerve at the wrist. The median-toulnar nerve cross-sectional area ratio at the wrist showed a significant correlation with the electrophysiologic stage of carpal tunnel syndrome (Spearman r = 0.431; P < .0001), in addition to the median nerve cross-sectional area at the wrist and the wrist-to-forearm median nerve cross-sectional area ratio. Conclusions—In our study, ulnar nerve involvement in patients with carpal tunnel syndrome was shown electrophysiologically but not sonographically. These results suggest that morphologic changes in the ulnar nerve do not occur in carpal tunnel syndrome, although functional changes may occur. Key Words—carpal tunnel syndrome; electrophysiologic stage; nerve conduction study; sonography; ulnar nerve
C Received August 1, 2014, from the Department of Neurology, Ajou University School of Medicine, Suwon, Korea. Revision requested August 17, 2014. Revised manuscript accepted for publication September 8, 2014. Address correspondence to In Soo Joo, MD, Department of Neurology, School of Medicine, Ajou University, 5 San, Woncheon-dong, Yongtong-gu, Suwon-si, Kyunggi-do 442-749, Korea. E-mail: [email protected] doi:10.7863/ultra.34.6.1027
arpal tunnel syndrome, the most common entrapment neuropathy, is caused by compression of the distal median nerve resulting from increased pressure in the carpal tunnel. Carpal tunnel syndrome can be diagnosed by the presence of symptoms, such as numbness, tingling, burning, and pain in the median territory of the hands, and by nerve conduction studies. In addition to nerve conduction studies, sonography has been extensively used to evaluate carpal tunnel syndrome, owing to its noninvasiveness and utility in patients with discrepancies between clinical and electrophysiologic findings. Previous sonographic findings in patients with carpal tunnel syndrome have shown an increase in the cross-sectional area of the distal median nerve at the wrist,1–5 an elevated wrist-to-forearm cross-sectional area ratio,5–7 and an elevated wrist-to-forearm difference8 in the median nerve crosssectional area.
©2015 by the American Institute of Ultrasound in Medicine | J Ultrasound Med 2015; 34:1027–1034 | 0278-4297 | www.aium.org
3406jum937-1114 copy_Layout 1 5/22/15 8:08 AM Page 1028
Eom—Ulnar Nerve Sonography in Carpal Tunnel Syndrome
Although the median nerve innervates the first 3 fingers and half of the fourth finger, many patients with carpal tunnel syndrome report symptoms throughout the whole hand, including the fifth finger. These variations have contributed to inconsistent results in studies of ulnar nerve involvement in carpal tunnel syndrome.9–13 However, most literature to date have reported only findings from nerve conduction studies of the ulnar nerve in patients with carpal tunnel syndrome. To our knowledge, no study has evaluated sonographic findings of the ulnar nerve according to the electrophysiologic stage of carpal tunnel syndrome. The objective of this study was to use sonography to determine whether there is a relationship between the ulnar nerve and the electrophysiologic stage of carpal tunnel syndrome.2
Materials and Methods Participants We conducted a retrospective study of 109 hands in 60 patients (40 women and 20 men; mean age ± SD, 54.37 ± 13.86 years; range, 25–82 years) who were referred to our electrophysiology laboratory in 2012 and 2013 with paresthesia of one or both hands. If clinical carpal tunnel syndrome was suspected, patients were recruited to our carpal tunnel syndrome registry and underwent nerve conduction studies and peripheral nerve sonography the same day. Bilateral median and ulnar nerves were investigated using both nerve conduction studies and sonography in all patients. The global symptom score,14 the sum of numeric quantifications from 0 to 10 of 5 symptoms (pain, numbness, paresthesia, weakness, and nocturnal awakening), was used to quantify the carpal tunnel syndrome symptom severity. Patients had no clinical or electrophysiologic signs of other neuromuscular diseases and had no conditions that would predispose to carpal tunnel syndrome (eg, wrist fracture or pregnancy). Patients with a bifid median nerve were excluded. However, we did not exclude participants with diabetes mellitus unless electrophysiologic evidence of diabetic polyneuropathy coexisted because we wanted to obtain a full spectrum of carpal tunnel syndrome presentations. This study was approved by the hospital’s Institutional Review Board, and written consent was obtained from all participants. Nerve Conduction Studies All nerve conduction studies were performed by a single well-trained examiner. We investigated the sensory conduction velocity, sensory nerve action potential amplitude, distal motor latency, motor conduction velocity, and compound muscle action potential amplitude of the median
1028
and ulnar nerves. In sensory conduction studies, median and ulnar orthodromic sensory nerve conduction was measured by stimulating the second and fourth fingers and then recording at the wrist. For motor conduction studies, a surface recording electrode was placed over the belly of the adductor digiti minimi muscle for the ulnar nerve and over the abductor pollicis brevis muscle for the median nerve. Distal motor latency was measured with the stimulation point 7 cm proximal to the adductor digiti minimi and abductor pollicis brevis muscles. When symptoms were atypical of carpal tunnel syndrome, additional electrodiagnostic studies were performed to exclude radiculopathy, brachial plexopathy, polyneuropathy, and ulnar neuropathy at the elbow. The ground electrode was placed between the stimulating and recording points. Skin temperature was kept above 32°C. All electrophysiologic studies were performed with a Medelec Synergy system (Oxford Instruments Medical, Hawthorne, NY). The electrophysiologic severity of carpal tunnel syndrome was assessed by means of a previously reported classification by Padua et al.15 This classification was simplified to the following 3 classes: mild (including minimal), moderate, and severe (including extreme). Regardless of symptoms, patients without nerve conduction study abnormalities were included in the electrophysiologically normal group. Sonography Sonography was performed either just before or immediately after the electrophysiologic studies. All examinations were performed in the supine position with the palm up in the neutral position. Transverse sonograms of the median nerve were collected at the distal wrist crease and mid forearm of the symptomatic limb in patients with a 7–12-MHz linear array transducer (ML6-15; GE Healthcare, Milwaukee, WI). The ulnar nerve was also examined at the distal wrist crease, mid forearm, and elbow with a hockey stick transducer (L8-18i; GE Healthcare) for the distal wrist crease and a linear array transducer for the mid forearm and elbow. Sonographic examinations of the ulnar nerve were performed with the arm extended and hands resting in a horizontal supine position on the examination table for measurement at the distal wrist crease and mid forearm. When the ulnar nerve was measured at the level of the elbow, the upper limb was abducted to 90° from the body, and the elbow was flexed to 30° with maximal supination. If focal entrapment of the ulnar nerve at the elbow was suspected, we excluded the case, considering the influence of possible concurrent pathologic conditions. Subluxation of the ulnar nerve at the elbow was not considered a
J Ultrasound Med 2015; 34:1027–1034
3406jum937-1114 copy_Layout 1 5/22/15 8:08 AM Page 1029
Eom—Ulnar Nerve Sonography in Carpal Tunnel Syndrome
pathologic condition unless entrapment was suspected. All cross-sectional areas were measured twice and averaged. All sonographic studies were performed by the same physician, who was blinded to the nerve conduction data. Statistical Analysis Descriptive statistics, including means and standard deviations, were applied to nerve conduction and sonographic studies of each nerve. Correlations were assessed by the Spearman coefficient. Values in each electrophysiologic group were compared by the Kruskal-Wallis test. We did not consider minimum detected differences because ulnar and median nerves are known to have low minimum detected differences compared to other nerves.16 All analyses were performed with the SPSS version 19.0 statistical software package (IBM Corporation, Armonk, NY). Results were considered statistically significant at P < .05.
Results Among the 60 patients examined, we detected 49 (81.7%) bilateral and 11 (18.3%) unilateral symptoms in cases of clinically suspected carpal tunnel syndrome. As a whole, 109 hands were evaluated. According to the electrophysiologic stage, normal, mild, moderate, and severe carpal tunnel syndrome occurred in 31 (28.4%), 22 (20.2%), 38 (34.9%), and 18 (16.5%) hands, respectively.
Electrophysiologic and sonographic data for each carpal tunnel syndrome stage are shown in Tables 1 and 2. Ulnar nerve sensory conduction velocity values were within the normal range in all 109 hands, but there were significant differences in the velocities among the groups (P = .038). Other nerve conduction study findings for the ulnar nerve, including the sensory nerve action potential amplitude, compound muscle action potential amplitude, distal motor latency, and motor conduction velocity, were normal and showed no differences between groups (Table 1). Table 2 shows means and standard deviations of sonographic values for patients with carpal tunnel syndrome separated by electrophysiologic stage. The mean median nerve crosssectional area at the distal wrist crease and median nerve wrist-to-forearm cross-sectional area ratio were significantly higher with increasing stage (P < .0001 for median nerve cross-sectional area at the wrist; P = .003 for median nerve wrist-to-forearm cross-sectional area ratio). Figure 1 shows sonograms of the median nerve according to the electrophysiologic stage of carpal tunnel syndrome. However, there was no difference in the ulnar nerve cross-sectional area at the distal wrist crease. A sonogram of the ulnar nerve is shown in Figure 2. In addition to the median nerve crosssectional area at the distal wrist crease and the median nerve wrist-to-forearm cross-sectional area ratio, the median-toulnar nerve cross-sectional area ratio at the distal wrist crease was measured, and the value increased significantly according to the electrophysiologic stage (P < .0001).
Table 1. Ulnar Nerve Conduction Values According to the Electrophysiologic Stage of Carpal Tunnel Syndrome Parameter USCV, m/s USNAPa, μV UDML, ms UMCV, m/s UCMAPa, mV
Normal (n = 31)
Mild (n = 22)
Moderate (n = 38)
Severe (n = 18)
P
46.02 ± 3.34 21.51 ± 7.87 2.35 ± 0.20 59.44 ± 3.73 15.09 ± 2.30
45.68 ± 4.17 20.76 ± 10.77 2.29 ± 0.25 59.58 ± 4.31 17.25 ± 2.17
44.52 ± 3.40 17.59 ± 6.33 2.40 ± 0.24 59.32 ± 3.65 15.81 ± 2.91
43.23 ± 4.29 20.04 ± 7.38 2.46 ± 0.24 58.27 ± 5.06 16.07 ± 4.25
.038 .244 .096 .052 .620
Data are presented as mean ± SD. UCMAPa indicates ulnar nerve compound motor action potential amplitude; UDML, ulnar nerve distal motor latency; UMCV, ulnar nerve motor conduction velocity; USCV, ulnar nerve sensory conduction velocity; and USNAPa, ulnar nerve sensory nerve action potential amplitude. Table 2. Sonographic Findings According to the Electrophysiologic Stage of Carpal Tunnel Syndrome Parameter MCSAd, mm2 UCSAd, mm2 MWFR MUR
Normal (n = 31)
Mild (n = 22)
Moderate (n = 38)
Severe (n = 18)
P
7.94 ± 1.58 3.92 ± 0.97 1.68 ± 0.34 2.16 ± 0.53
10.44 ± 2.56 3.89 ± 0.93 1.94 ± 0.42 2.77 ± 0.81
11.11 ± 2.18 4.18 ± 1.01 2.03 ± 0.48 2.75 ± 0.64
13.22 ± 3.92 4.13 ± 0.83 2.46 ± 1.08 3.27 ± 0.98
