Ann Thorac Surg 2009;88:1335-1337. doi:10.1016/j.athoracsur.2009.01.063
© 2009 The Society of Thoracic Surgeons
Case Reports
Paralysis of the Upper Rectus Abdominis Muscle After Video-Assisted or Open Thoracic Surgery: An Underdiagnosed Complication?
Tommi Pätilä, MDa,
Eero I. Sihvo, MD, PhDa,
Jari V. Räsänen, MD, PhDa,
Raimo Ramstad, MDb,
Ari Harjula, MD, PhDa,
Jarmo A. Salo, MD, PhDa,*
a Department of Cardiothoracic Surgery, Helsinki University Central Hospital, Helsinki, Finland
b Department of Clinical Neurophysiology, Helsinki University Central Hospital, Helsinki, Finland
Accepted for publication January 26, 2009.
* Address correspondence to Dr Salo, Division of General Thoracic and Esophageal Surgery, Department of Cardiothoracic Surgery, Helsinki University Central Hospital, P.O. Box 340, Haartmaninkatu 4, Helsinki, FIN-00029 HUS, Finland (Email: jarmo.salo{at}hus.fi).
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Abstract
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In open or video-assisted thoracic surgery, injury to one to four intercostal sensory nerves is a well-recognized complication. This nerve damage is a well-defined cause for chronic postoperative pain. In this discussion, the motor innervation of the rectus abdominis muscle with the T7 to T12 intercostal nerves has been neglected. Paralysis of rectus abdominis might pose significant burden on patients, delay recovery, and thus warrants exploration.
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Introduction
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Thoracotomy and thoracoscopy commonly lead to intercostal nerve damage [1, 2]. The nerve conduction blocks are often due to indirect injury, and application of the retractor in open thoracic surgery might cause conduction disturbances in the nerves up to two intercostal spaces from the incision [1]. When the innervation of the rectus abdominis muscle is from the seventh to the twelfth intercostal nerves, lower incisions evidently pose a risk of rectus paralysis. Although intercostal nerve damage is well documented, rectus abdominis paralysis is uncommonly reported, and here we present two cases and review the literature accordingly.
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Case Reports
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Patient 1
A 17-year-old man had a known alpha-1 anti-trypsin deficiency. He had sustained several episodes of left-sided pneumothorax. A computed tomographic scan revealed no bullae. During triple-port video-assisted thoracic surgery superficial apical lesions were observed and stapled. Parietal pleurectomy was performed above the sixth rib. The patient recovered well and was discharged on postoperative day 3. One week later, at a regular postoperative follow-up, the patient complained of paralysis of the upper left side of the rectus abdominis muscle. Electromyography indicated major acute loss of motor axons (scale: major, moderate, minor, none) in the T7 intercostal nerve and minor injury to the T8 nerve. The upper part of the rectus muscle was atrophic (Fig 1). Three months later, electromyography demonstrated regeneration of the nerves without clinical improvement. After a year, function of the intercostal nerves had recovered, with a recovery of the function of the rectus muscle.
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Fig 1. (A) Upper, left-sided rectus abdominis paralysis caused muscular atrophy at 10 days after thoracoscopy for pneumothorax (*). On the right side, a normal contracted muscle can be seen (**). (B) Sites of thoracoscopic ports.
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Patient 2
A 51-year-old man complained of dyspnea on exertion. A computed tomographic scan revealed pleural effusion and thickened parietal pleura. Due to tenacious adhesions, thoracoscopic biopsy was converted to a thoracotomy in the sixth intercostal space. No malignancy was detected, and the lung was decorticated with parietal pleurectomy. The lung expanded well, and the patient was discharged on postoperative day 4. After 2 weeks in outpatient care, uncomplicated recovery was considered. Two months later, the patient returned complaining of discomfort, pain, and a lump in the anterior abdominal wall (Fig 2). Clinically, a paralysis of the upper right side of the rectus abdominis muscle was detected. Electromyography revealed major acute loss of motor axons in T7 and T8, and minor damage in T9 intercostal nerves. After a year, electromyography showed strong and subtotal lesion with some regeneration in T7 and T8 motor axons, and with T9 showing a normal finding.
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Fig 2. Hernia-like protrusion of paralyzed upper rectus abdominis muscle (*) was observed several months after thoracotomy through the sixth intercostal space.
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Comment
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Innervation of the rectus abdominis muscle is by T7 to T12 intercostal nerves. Direct damage of these nerves in most thoracotomies, performed through the fourth, fifth, or sixth intercostal spaces, seems unlikely. After removal of the rib retractor, neural dysfunction at the opened intercostal space has been reported to be 100% in the study by Rogers and colleagues [1]. They also described a conduction block in the nerve immediately below the incision in 11 of 12 patients [1]. Furthermore, in the next nerve below, conduction abnormalities were found in 4 patients, total conduction block in 2 patients and partial in 2. Therefore, not only the direct injury, such as laceration of the intercostal nerve, but also indirect injury, such as compression by the retractor can occur. When a low intercostal space is opened or used as a port-site, the innervation to the upper rectus muscle is in danger. Also the extent of the thoracotomy incision might contribute to nerve damage. Impaired function of low intercostal nerves, reflected by superficial abdominal reflexes, after standard posterolateral thoracotomy through the fifth or sixth intercostal space has been recorded in 45% to 64% of patients [3, 4]. Overall, indirect nerve injuries might, therefore, be a more common cause of upper rectus abdominis muscle paralysis.
The prevalence of this complication is obscure, as is the prevalence of permanent injury. Indirect nerve damage is more prone to recovery. Of 19 patients without superficial abdominal reflexes after thoracotomy, only 2 had absent reflexes 2 to 3 months postoperatively [4]. Because none of these patients had measurable reflexes at 1 week after surgery, rapid recovery of nerve function after indirect injury is unlikely. With nerve continuity, axonal regeneration takes place at a rate of 1 to 3 mm/day [5]. Therefore, the permanency of paralysis can only be assessed several months after surgery. The paralysis is probably functionally minor, not affecting the primary postoperative recovery. For the patient, it is of course an unnecessary burden, and in the case of permanent damage, patients may experience significant discomfort and loss of quality of life. Also the possibilities of using paralyzed muscle for the transverse rectus abdominis musculocutaneous flap in breast reconstruction are uncertain.
Both of our patients complained of postoperative symptoms. The younger man was unsatisfied primarily for esthetic reasons. The lump in the older man was located anterior to the abdomen, which caused disability and prevented fitness exercises. In overweight patients, or in patients without prominent abdominal musculature the paralysis of the upper part of the rectus abdominis muscle might be missed.
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References
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- Rogers ML, Henderson L, Mahajan RP, Duffy JP. Preliminary findings in the neurophysiological assessment of intercostal nerve injury during thoracotomy Eur J Cardiothor Surg 2002;21:298-301.[Abstract/Free Full Text]
- Maguire MF, Latter JA, Mahajan R, Beggs FD, Duffy JP. A study exploring the role of intercostal nerve damage in chronic pain after thoracic surgery Eur J Cardiothorac Surg 2006;29:873-879.[Free Full Text]
- Benedetti F, Vighetti S, Ricco C, et al. Neurophysiologic assessment of nerve impairment in posterolateral and muscle-sparing thoracotomy J Thorac Cardiovasc Surg 1998;115:841-847.[Abstract/Free Full Text]
- Benedetti F, Amanzio M, Casadio C, et al. Postoperative pain and superficial abdominal reflexes after posterolateral thoracotomy Ann Thorac Surg 1997;64:207-210.[Abstract/Free Full Text]
- Beazley RM, Bagley DH, Ketcham AS. The effect of cryosurgery on peripheral nerves J Surg Res 1974;16:231-234.[Medline]
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Abstract
Introduction
