Correlation of electrodiagnostic findings and the disabilities of arm, shoulder and hand questionnaire in ulnar neuropathy at the elbow

Aim: We aimed to find out whether there is a relationship between the electrodiagnostic findings and disabilities of arm, shoulder and hand (DASH) questionnaire in the ulnar neuropathy at the elbow (UNE). Material and Methods: Patients whose clinical and electrodiagnostic findings were compatible with UNE were included in this retrospective cohort study. UNE patients were divided into mild, moderate and severe UNE according to the neurophysiological classification. DASH-disability / symptom (DASH-DS) scores of all patients were calculated. In addition, DASH work module (DASH-W) and DASH sports / performing arts module (DASH-SP) questionnaire were applied to some patients. Results: Thirty-nine UNE patients were included in the study. There were 26 mild UNE patients, 8 moderate UNE patients, and 5 severe UNE patients. There was a positive correlation between neurophysiological classification of UNE and DASHDS / DASH-W scores (p = 0.002 r = 0.491, p = 0.012 r = 0.453). An inverse correlation was found between DASH-W scores and ulnar nerve compound muscle action potential / sensory nerve action potential amplitudes (p = 0.036 r = -0.413, p = 0.006 r = -0.492). When the moderate and severe UNE group was evaluated as a single group, DASH-DS and DASH-W scores of mild UNE patients were low in those of moderate-severe UNE patients (p = 0.001, p = 0.012). Conclusion: This study showed a positive correlation between the DASH scores and the neurophysiological classification in the UNE. In addition to the DASH-DS questionnaire, the use of the DASH-W questionnaire can be useful in UNE.


Introduction
Ulnar neuropathy at the elbow (UNE) is the second most common entrapment neuropathy. The diagnosis can be made by clinical features, electrodiagnostic tests and imaging methods. Sensory abnormalities in the ulnar nerve dermatome or weakness or atrophy in the muscles innervated by the ulnar nerve may be observed in UNE [1,2,3,4]. Although ultrasonography is also used in the diagnosis of UNE, nerve conduction studies have a more important place in the diagnosis of UNE [1,3,5]. In nerve conduction studies, the slowing of the ulnar motor nerve conduction velocity (NCV) across the above elbow-below elbow segment or the detection of a conduction block in this segment supports the diagnosis of UNE [1,6,7,8,9,10]. Within the electrodiagnostic tests, short segment motor nerve conduction studies across the elbow segment is considered as the gold standard [1,4,7,8,9]. With this method, UNE can be diagnosed and lesion localization can be found. UNE can be mild or moderate, or it can be severe enough to cause disability. Therefore, it is important to diagnose and follow up UNE. In addition to physical therapy, some patients with a lesion under the humeroulnar aponeurotic arcade (HUA) may be operated [1,5,11]. The upper limb disability can be evaluated with the disabilities of arm, shoulder and hand questionnaire (DASH) questionnaire [12,13]. The DASH questionnaire was used for postoperative evaluation in patients with UNE under HUA [14,15]. It was aimed to find the relationship between DASH questionnaire and electrodiagnostic findings of UNE. Thus, we also aimed to evaluate the use of DASH in UNE.

Material and Methods
Individuals who applied to the electromyography (EMG) laboratory between July 2018 and December 2019 and whose clinical and electrodiagnostic features were compatible with UNE were included in this retrospective cohort study. Patients were excluded from the study if they had polyneuropathy or a disease such as diabetes mellitus that would cause polyneuropathy, or a family history of hereditary polyneuropathy, or a history of surgery of the extremity, if there were findings compatible with polyneuropathy in nerve conduction studies. If the clinical and electrodiagnostic findings were compatible with UNE, the patient was considered to have UNE [3,4,16]. The patient was considered to have clinically UNE when one of the following criteria was: 1) Continuous paresthesia in the ulnar nerve dermatome 2) Hypoesthesia in the ulnar nerve dermatome 3) Weakness in the muscles innervated by the ulnar nerve. Turkish version of DASH questionnaire was applied to all patients. This questionnaire consisted of 30 questions [12,13]. DASH disability / symptom (DASH-DS) score was calculated in patients. If the patient did not answer more than 1 questions, the DASH-DS score was not calculated. DASH work module (DASH-W) and DASH sports / performing arts module (DASH-SP) questionnaire was also applied to some patients, and in this optional questionnaire, the score was calculated if all questions were answered.
Cadwell Sierra Summit EMG unit (Cadwell laboratories, Kennewick, Washington, USA) was used for nerve conduction studies and needle EMG. Median, ulnar, peroneal, posterior tibial, sural nerve sensory and motor nerve conduction studies and needle EMG were applied to all patients. Electrodiagnostic tests were performed if the temperature of the extremities was above 32 degrees, otherwise the extremities were heated. Stimulation and recording were made using surface electrodes. Nerve stimulation was performed supramaximally. Low-high filters for sensory and motor nerve conduction studies were set at 20Hz-2kHz and 20Hz-10kHz, respectively. In motor and sensory nerve conduction studies, sweep speed and sensitivity were 5 ms / division, 1 ms / division and 2 mV / division and 10 µV / division, respectively. Compound muscle action potential (CMAP) and sensory nerve action potential (SNAP) amplitudes were obtained by measuring peak to peak. Ulnar nerve CMAP was obtained from the abductor digiti quinti (ADQ) and first dorsal interosseous (FDI) muscles, and the median nerve CMAP was obtained from the abductor pollicis brevis muscle. Median and ulnar nerves were stimulated at wrist, 5 cm proximal to the recording electrode. The stimulation site was 12 cm proximal from the recording electrode to obtain ulnar nerve CMAP recording from FDI muscle (the pathway of the ulnar nerve was taken into account). Ulnar motor nerve conduction was performed based on Buschbacher's method [17,18]. Kanakamedala's method was used for short segment motor nerve conduction in the elbow [8]. Short segment motor nerve conduction study across the elbow was performed at 2 cm intervals. The stimulation points were 2 cm (D2) and 4 cm (D4) distal to the medial epicondyle, medial epicondyle (ME), 2cm (P2), 4cm (P4) and 6 cm (P6) proximal to the medial epicondyle. Ulnar and median sensory nerve conduction studies were performed orthodromically. Peak latency was used in sensory nerve conduction studies. Sural nerve SNAP was obtained antidromically. The posterior tibial and peroneal nerve CMAPs were obtained using conventional methods. Stimulation points for obtaining the peroneal nerve CMAP were the ankle, below the head of the fibula, and the popliteal fossa. For reference values of nerve conduction studies, previous studies were considered [4,19]. For the diagnosis of UNE, it should have been one of the following electrodiagnostic criteria; 1) Ulnar motor NCV above elbowbelow elbow segment <45 m/s, 2) In motor nerve conduction study, presence of conduction block across elbow segment (CMAP amplitude obtained by above elbow stimulation reduced by more than 50% compared to CMAP obtained by below elbow stimulation) 3) the velocity difference between motor NCV of the forearm and elbow segments (FEVD) > 14 m/s, 3) latency difference in the short segment motor nerve conduction study > 0.6 ms [4,16]. The lower reference limits of ulnar SNAP amplitude of 5th digit-wrist segment and distal ulnar nerve CMAP amplitude recorded from the ADQ muscle were considered as 7.5 µV and 7.0 mV, respectively [4,19]. UNE patients were divided into mild, moderate, severe and extreme UNE according to the classification proposed by Padua [2]. Extreme UNE patients were excluded from the study because ulnar CMAP could not be obtained in extreme UNE. Patients were considered to be mild UNE if there was a slowing of ulnar motor NCV across elbow segment, and a moderate UNE if SNAP amplitude was reduced in addition to slowing of ulnar motor NCV across elbow segment, and severe UNE if the ulnar SNAP could not be obtained in addition to slowing of ulnar motor NVC across elbow segment. Concentric needle electrodes were used for needle EMG. Positive sharp wave and fibrillation potentials were carefully examined. When the motor unit action potential amplitude was > 4 mV, it was considered neurogenic. This study was approved by institutional ethical committee (number 45/621). Informed consent was obtained from all patients and the principles of the Helsinki Declaration were followed.

Statistical Analysis
The Shapiro-Wilk test was used to determine the distribution of the data. Comparisons were made using Kruskal-wallis and Mann-Whitney u tests for independent samples. Tamhane's T2 test was used as post-hoc analysis. Pearson's Chi-squared test was used to analyze categorical variables. Spearman's test was used for correlation. Mean ± standard deviation (SD) and median of numeric data were calculated for descriptive statistics. Statistical Package for the Social Sciences (SPSS IBM Corp; Armonk, NY, USA) 22.0 was used to perform the statistical analysis.

Results
Forty-one UNE patients who met clinical and electrodiagnostic criteria were reviewed. Since 2 patients did not answer too many questions in the DASH questionnaire, these patients were excluded from the study. Thirty-nine patients were included in the study. 27 patients (69%) were male. The mean age of the patients was 42.5 ± 14.4 (range 18-77) years. The mean height, weight and body mass index were 171.4 ± 8.5 cm, 76.9 ± 12.6 kg, 26.2 ± 4.0 kg/m2, respectively. The mean duration of the symptoms was 8.6 ±14.3 (1-60) months. The symptoms and neurological examination findings of the patients are shown in Table 1. The most common symptom was paresthesia in the 4th and/or 5th digits (100%), and the most common neurological examination finding was hypoesthesia in the 4th and/or 5th digits (95%). Electrodiagnostic findings of the patients are shown in table 1. The most abnormality in nerve conduction studies was in short segment motor nerve conduction studies. All patients had prolonged latency difference in the short segment motor nerve conduction study recorded from ADQ or FDI muscles. There were more neurogenic needle EMG findings in ADQ and FDI muscles than flexor carpi ulnaris and flexor digitorum profundus (ulnar nerve) muscles. 18

Discussion
UNE can cause mild to severe neuropathy. It may cause disability in some patients. In addition to physical therapy, surgical treatment is also a treatment option for some patients with lesions at HUA [11,14,15,20]. For this reason, it is important to diagnose and follow up UNE. Our primary goal in this study was to evaluate the correlation between electrodiagnostic findings and DASH questionnaire scores of UNE and to evaluate the use of the DASH questionnaire in the UNE.
The most common symptom in this study was paresthesia in 4th and/or 5th digits and the most frequent neurological examination finding was hypoesthesia in 4th and/or 5th digits.
These findings were consistent with the literature [1,2,3,4]. Pain was a less common symptom. This finding was important because some of the questions in the DASH questionnaire were associated with pain. Tinel's sign and elbow flexionpressure test were 36% and 59% positive, respectively, which supported the low diagnostic value of provocative tests reported in the literature [21]. The findings of nerve conduction studies in this study showed the importance of short segment motor nerve conduction studies in the diagnosis of UNE. All patients had abnormalities in the short segment motor nerve conduction study. This may be because the ulnar motor nerve conduction studies were performed by recording from both ADQ and FDI muscles. In previous studies, it was reported that ulnar motor nerve conduction studies performed by recording both muscles increased sensitivity for the diagnosis of UNE [1,3,4]. Consistent with the literature, in this study, ulnar nerve lesions at retroepicondylar groove were observed more than lesions at HUA in UNE [1,4,5]. Needle EMG findings were more abnormal in ADQ and FDI muscles than in proximal muscles innervated by ulnar nerve. These findings were consistent with the previous studies [4,22]. This can be explained by the topographic distribution of the ulnar nerve fascicles [23].
According to the Leeds assessment of neuropathic symptoms and signs (LANSS) pain scale, it was reported that electrodiagnostic findings did not differ in patients with and without neuropathic pain [24]. This may mean that the use of LANSS pain scale in UNE is limited. In addition, as we mentioned earlier in this study, pain was a less common symptom. In the DASH questionnaire, although there were questions about pain, the number of questions containing the word "pain" was less than five. The DASH questionnaire has been used in many studies related to UNE. DASH questionnaire is important in postoperative evaluation of patients operated for UNE [14,15]. The DASH questionnaire was used in Padua's study for the neurophysiological UNE classification [2]. There was a positive correlation between DASH function scores and neurophysiological classification in that study. A similar positive correlation was found in this study. In this case, a positive correlation between neurophysiological classification and DASH scores can be mentioned. A significant difference was found in DASH scores between mild UNE and moderate UNE. Interestingly, while the DASH score of two severe UNE patients was 25, the DASH scores of some mild UNE patients were high (up to 58). It would be appropriate to interpret these findings as there may be mild UNE patients with high DASH scores as well as severe UNE patients with a low DASH scores. When UNE patients were divided into two groups, mild and moderate-severe, DASH-W scores were found to be significantly different in addition to DASH-DS scores. In this study, an inverse correlation was found between DASH-W and ulnar CMAP / SNAP amplitudes. Reduced CMAP or SNAP amplitudes are indicative of axonal degeneration. For this reason, it will be useful to use DASH-W in addition to DASH-DS in UNE. There was some limitations in this study. The low number of patients in the moderate and severe UNE group was one of the limitations of the study. The retrospective nature of the study was another limitation.

Conclusion
A positive correlation between DASH-DS / DASH-W scores and the neurophysiological classification of UNE, an inverse correlation between DASH-W and ulnar CMAP / SNAP amplitudes were found. In addition to DASH-DS, evaluation of UNE with DASH-W may increase the value of the DASH questionnaire. Some mild UNE patients may have high DASH scores, while some moderate and severe UNE patients may have low DASH scores.

Declaration of conflict of interest
No conflict of interest was declared by the authors. The authors declared that this study has received no financial support.