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Anconeus epitrochlearis as a source of chronic compressive ulnar neuropathy: A new treatment |
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Department of Rehabilitation Medicine, Gangnam Severance Hospital, Rehabilitation Institute of Neuromuscular Disease, Yonsei University College of Medicine, Seoul, Republic of Korea1, Department of Physical and Rehabilitation Medicine, Armed Forces Capital Hospital, Seongnam, Korea2, Department and Research Institute of Rehabilitation Medicine, Severance Hospital, Yonsei University College of Medicine3 |
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Jinyoung Park1*, Yewon Lee1, Sun Woong Kim2, Young Seok Kim1, Min Cheol Ha3, Jung Hyun Park1† |
Introduction: Anconeus epitrochlearis muscle originates from the inferior surface of the medial epicondyle of the humerus and inserts to olecranon process. As ulnar nerve runs beneath this muscle, this anatomical relationship provides the chance to develop entrapment or compression of the ulnar nerve by this muscle (Figure 1). There is no report that the nerve conduction velocity recovered right after the muscle releasing, especially using electrical twitch obtaining intramuscular stimulation (ETOIMS).
Case: In May 16, 2019, a 26-year-old male patient visited a neuromuscular clinic complaining of tingling pain (visual analogue scale, VAS 4-5) on ulnar side of Rt. hand and hypersensitivity of Rt. 4th and 5th fingers which has been persisted after suture of the lacerated lesion in Rt. elbow after a pedestrian traffic accident occurred 2 years ago. He had no weakness and deep tendon reflex of biceps and triceps were normal. Lhermitte and spurling sign was negative. The magnetic resonance image of Rt. elbow taken after the accident revealed no specific lesion in the joint. The first electrodiagnostic study (EDx) performed in January 18, 2018. The motor nerve conduction study (NCS) for Rt. ulnar nerve demonstrated decreased velocity (38.4 m/sec) in the segment between 2cm above and below lateral epicondyle of humerus. Sensory NCS revealed normal for Rt. ulnar nerve. Needle electromyography (EMG) showed increased insertional activities in Rt. flexor carpi ulnaris and adductor digiti minimi muscles. These results were suggestive of Rt. ulnar neuropathy at elbow level. In June 14, 2019, on following 2nd EDx, the motor NCS revealed increased amplitude and increased velocity at the segment between the epicondyle and 2cm above the epicondyle. However, the conduction velocity between the epicondyle and 2cm below the epicondyle was still slow (38.4 m/sec) (Table 1).
By physical examination, slight compression of the Rt. anconeus epitrochlearis triggered the tingling pain on the ulnar aide of Rt. hand. Presuming that the anconeus epitrochlearis muscle compresses the ulnar nerve, ETOIMS was applied using Clavis (Alpine Biomed ApS, Denmark) for the muscle releasing. After confirming the bony landmarks by palpation, a monopolar needle electrode was inserted into the Rt. anconeus epitrochlearis as reference electrode attached onto the nearby skin. The stimulations were delivered with 2-mA intensity, 0.2-ms pulse duration, 2-Hz frequency with unipolar negative square waves for 10 seconds at two stimulation points (Figure 2). Right after the ETOIMS, the conduction velocity got faster from 38.4 m/sec to 66.7 m/sec (Table 1). The tingling pain was relieved (VAS 0) and the hypersensitivity was disappeared. After 1 week, only the minimal hypersensitivity remained.
Conclusion: The anconeus epitrochlearis muscle can cause a chronic compressive ulnar neuropathy. The ETOIMS is effective in releasing the anconeus epitrochlearis and even can restore the conduction velocity. |
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Table 1. Serial electrodiagnostic studies before and after ETOIMS.
Figure 1. Anatomical relationship between anconeus epitrochlearis muscle and ulnar nerve.
Figure 2. ETOIMS in the Rt. anconeus epitrochlearis muscle.
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