J Neurosurg 47:113-114, 1977
Anomalous course of the recurrent motor branch of the median nerve in a patient with carpal tunnel syndrome Case report
J. DOUGLAS WERSCHKUL, M.D. Division of Neurosurgery, University of Oregon Medical School Hospital and Clinics, Portland, Oregon v' A case is discussed in which carpal tunnel syndrome with an unusual course of the motor recurrent branch was discovered at operation. The importance of a careful dissection of the median nerve in this condition is emphasized. KEY WORDS
9 carpal tunnel syndrome
HIS case report describes an anatomical variant encountered in the carpal tunnel syndrome. The importance of this finding is discussed as regards surgical technique. y
C a s e Report
A 45-year-old construction worker was admitted to the Portland Veterans Administration Hospital on April 20, 1975, for evaluation. Over the last 4 years he had suffered pain in the forearms and hands which was worse after heavy physical labor, and often awakened him at night. The pain was worse on the right side. Over the few months before admission he noted numbness along the volar aspect of the second and third digits of the right hand and weakness of grip in the right hand. Examination. The pertinent findings were positive Tinel's sign at the wrist and positive Phelan's sign bilaterally. There was a mild hypesthesia over the ulnar aspect of the index J. Neurosurg. / Volume 47 / July, 1977
9 m e d i a n nerve
finger on the right and weakness of abduction of the right thumb. Nerve conduction studies showed a terminal m o t o r latency of the median nerve across the wrist of 6.0 msec on the right and 5.1 msec on the left (normal is less than 5.0 msec). Operation. On April 22, 1975, the right median nerve was explored through a vertical incision in the mid-palm, extending proximally along the base of the thenar eminence to the last wrist crease. During inspection of the operative field a nerve was visualized passing ventrally and directly through the midportion of the transverse carpal ligament to the thenar muscles laterally. After careful division of the ligament, this nerve was shown to be the m o t o r recurrent branch (Fig. 1). In addition to passing directly through the ligament, the m o t o r branch arose from the ulnar aspect of the median nerve. The fact that this was the m o t o r division was verified by bipolar stimulation, which produced contraction of the thenar eminence. ] 13
j. D. W e r s c h k u l operation for carpal tunnel syndrome. 2,*-7 T w o i m p o r t a n t v a r i a t i o n s h a v e been observed: either the m o t o r branch takes origin from the ulnar aspect of the median nerve crossing anterior to it within the carpal tunnel, or the m o t o r branch passes directly through the transverse carpal ligament instead of around its distal margin. Both of these features were present in the case reported here which is similar to that reported by G r a h a m ? In such a case, the m o t o r branch would be at increased risk of d a m a g e during operation, particularly if "blind" section of the transverse carpal ligament were utilized. Although anomalies in the course of the m o t o r recurrent branch seem to be uncommon, they will doubtless be encountered from time to time considering the frequency of surgery for carpal tunnel syndrome. Because of the i m p o r t a n c e of preserving the m o t o r recurrent branch, a careful, open dissection of the transverse carpal ligament with full visualization of the median nerve is encouraged. FIG. 1. Operative photograph of the right median nerve (plain arrow), showing the course of the motor branch (single-crossed arrow) in relation to the divided transverse carpal ligament (doublecrossed arrow).
Postoperative Course. The patient was readmitted on M a y 15, 1975, at which time the left median nerve was explored for continuing complaints of the left carpal tunnel syndrome. The anatomical arrangement of the left side was normal. Discussion
The m o t o r recurrent branch has a consistent relationship to the transverse carpal ligament in the majority of cases, x,3 It arises from the anterolateral aspect of the median nerve near the distal edge of the ligament around which it passes to muscles of the thenar eminence. The author is not aware of any statistical analysis of anatomical variations in this area. However, there have been occasional reports of abnormalities in the course of the m o t o r recurrent branch during
] ]4
References
1. Boyes JH: Bunnell's Surgery of the Hand, ed 5. Philadelphia: JB Lippincott, 1970, p 348 2. Entin MA: Carpal tunnel syndrome and its variants. Surg Clin North Am 48 No. 5: 1097-1112, 1968 3. Goss CM (ed): Gray's Anatomy of the Human Body, ed 28. Philadelphia: Lea and Febiger, 1966, p 975 4. Graham WP III: Variations of the motor branch of the median nerve at the wrist. Case report. Plast Reconstr Surg 51:90-92, 1973 5. Mannerfelt L, Hybbinette C-H: Important anomaly of the thenar motor branch of the median nerve. A clinical and anatomical report. Bull Hosp Joint Dis 33:15-21, 1972 6. Ogden JA: An unusual branch of the median nerve. J Bone Joint Surg 54:1779-1781, 1972 7. Papathanassiou BT: A variant of the motor branch of the median nerve in the hand. J Bone Joint Surg 50-B:156-157, 1968
Address reprint requests to." J. Douglas Werschkul, M.D., Maj., MC, Neurosurgery Service HSW-SN, Department of the Army, Walter Reed Army Medical Center, Washington, D.C. 20011.
J. Neurosurg. / Volume 47 / July, 1977
Anomalous course of the recurrent motor branch of the median nerve in a patient with carpal tunnel syndrome Case report
J. DOUGLAS WERSCHKUL, M.D. Division of Neurosurgery, University of Oregon Medical School Hospital and Clinics, Portland, Oregon v' A case is discussed in which carpal tunnel syndrome with an unusual course of the motor recurrent branch was discovered at operation. The importance of a careful dissection of the median nerve in this condition is emphasized. KEY WORDS
9 carpal tunnel syndrome
HIS case report describes an anatomical variant encountered in the carpal tunnel syndrome. The importance of this finding is discussed as regards surgical technique. y
C a s e Report
A 45-year-old construction worker was admitted to the Portland Veterans Administration Hospital on April 20, 1975, for evaluation. Over the last 4 years he had suffered pain in the forearms and hands which was worse after heavy physical labor, and often awakened him at night. The pain was worse on the right side. Over the few months before admission he noted numbness along the volar aspect of the second and third digits of the right hand and weakness of grip in the right hand. Examination. The pertinent findings were positive Tinel's sign at the wrist and positive Phelan's sign bilaterally. There was a mild hypesthesia over the ulnar aspect of the index J. Neurosurg. / Volume 47 / July, 1977
9 m e d i a n nerve
finger on the right and weakness of abduction of the right thumb. Nerve conduction studies showed a terminal m o t o r latency of the median nerve across the wrist of 6.0 msec on the right and 5.1 msec on the left (normal is less than 5.0 msec). Operation. On April 22, 1975, the right median nerve was explored through a vertical incision in the mid-palm, extending proximally along the base of the thenar eminence to the last wrist crease. During inspection of the operative field a nerve was visualized passing ventrally and directly through the midportion of the transverse carpal ligament to the thenar muscles laterally. After careful division of the ligament, this nerve was shown to be the m o t o r recurrent branch (Fig. 1). In addition to passing directly through the ligament, the m o t o r branch arose from the ulnar aspect of the median nerve. The fact that this was the m o t o r division was verified by bipolar stimulation, which produced contraction of the thenar eminence. ] 13
j. D. W e r s c h k u l operation for carpal tunnel syndrome. 2,*-7 T w o i m p o r t a n t v a r i a t i o n s h a v e been observed: either the m o t o r branch takes origin from the ulnar aspect of the median nerve crossing anterior to it within the carpal tunnel, or the m o t o r branch passes directly through the transverse carpal ligament instead of around its distal margin. Both of these features were present in the case reported here which is similar to that reported by G r a h a m ? In such a case, the m o t o r branch would be at increased risk of d a m a g e during operation, particularly if "blind" section of the transverse carpal ligament were utilized. Although anomalies in the course of the m o t o r recurrent branch seem to be uncommon, they will doubtless be encountered from time to time considering the frequency of surgery for carpal tunnel syndrome. Because of the i m p o r t a n c e of preserving the m o t o r recurrent branch, a careful, open dissection of the transverse carpal ligament with full visualization of the median nerve is encouraged. FIG. 1. Operative photograph of the right median nerve (plain arrow), showing the course of the motor branch (single-crossed arrow) in relation to the divided transverse carpal ligament (doublecrossed arrow).
Postoperative Course. The patient was readmitted on M a y 15, 1975, at which time the left median nerve was explored for continuing complaints of the left carpal tunnel syndrome. The anatomical arrangement of the left side was normal. Discussion
The m o t o r recurrent branch has a consistent relationship to the transverse carpal ligament in the majority of cases, x,3 It arises from the anterolateral aspect of the median nerve near the distal edge of the ligament around which it passes to muscles of the thenar eminence. The author is not aware of any statistical analysis of anatomical variations in this area. However, there have been occasional reports of abnormalities in the course of the m o t o r recurrent branch during
] ]4
References
1. Boyes JH: Bunnell's Surgery of the Hand, ed 5. Philadelphia: JB Lippincott, 1970, p 348 2. Entin MA: Carpal tunnel syndrome and its variants. Surg Clin North Am 48 No. 5: 1097-1112, 1968 3. Goss CM (ed): Gray's Anatomy of the Human Body, ed 28. Philadelphia: Lea and Febiger, 1966, p 975 4. Graham WP III: Variations of the motor branch of the median nerve at the wrist. Case report. Plast Reconstr Surg 51:90-92, 1973 5. Mannerfelt L, Hybbinette C-H: Important anomaly of the thenar motor branch of the median nerve. A clinical and anatomical report. Bull Hosp Joint Dis 33:15-21, 1972 6. Ogden JA: An unusual branch of the median nerve. J Bone Joint Surg 54:1779-1781, 1972 7. Papathanassiou BT: A variant of the motor branch of the median nerve in the hand. J Bone Joint Surg 50-B:156-157, 1968
Address reprint requests to." J. Douglas Werschkul, M.D., Maj., MC, Neurosurgery Service HSW-SN, Department of the Army, Walter Reed Army Medical Center, Washington, D.C. 20011.
J. Neurosurg. / Volume 47 / July, 1977
