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Case Report: Unilateral Paresis of the Abdominal Wall with Associated Thoraco-Lumbar Pain.

A 53-year-old male with unremarkable past medical history presented with a new onset left lower abdominal wall swelling and pain. The pain radiated from his back, into the left iliac crest, groin, and testicle region. Patient reported a history of performing heavy physical work 2 weeks prior to presentation, and felt an unusual sensation in the left thorocolumbar region when lifting a stone. The pain progressively worsened over time and was exacerbated with weight-bearing activities such as standing and walking. Valsalva maneuver also increased the pain intensity, while traction relieved it. Patient's sleep was interrupted due to pain and symptoms were worse in the left lateral decubitus position. Aside from nausea with standing, there were no other gastrointestinal, urologic, neurological, inflammatory, or constitutional symptoms.

Physical examination revealed a sizeable left lower abdominal quadrant bulge/prominence which disappeared when recumbent and when extending to the right posterior quadrant (Figure 1). There was restricted range of motion in flexion and left lateral bending. There was significant left paralumbar muscle spasm extending to the thoraco-lumbar junction and tenderness over the iliac crest and posterior superior iliac spine. There was no specific tenderness to any one particular spinal segment. No neurological abnormalities could be detected, sensation over the left lower abdominal region was normal.

Upon initial presentation to the emergency room, the principle diagnosis was left inguinal hernia and mechanical low back strain for which he was referred to both general surgery and physiotherapy. Attempts at spinal manipulation did not relieve the pain; however, intramuscular stimulation helped ease the muscle spasm. The pain was controlled with ibuprofen 400 mg po tid prn and hydromorphone 1 mg po q4h prn.

Ultrasound of the left lower abdominal wall showed absence of inguinal hernia. An electromyographic study of the left lower abdominal wall was negative for signs of axonal denervation. An MRI of the lumbar spine showed a large disc herniation/sequestered disc fragment within the left lateral recess and left foraminal region at L1-L2, with significant narrowing of the left neural foramen and impingement on the exiting left L1 nerve root (Figure 2).

His pain resolved over a period of 3 weeks, and 3 months later his abdominal herniation disappeared. Spinal decompression surgery was not deemed necessary given the clinical improvement.

True abdominal hernias are the result of the protrusion of abdominal cavity contents through an opening, tear, or weakness in the abdominal wall musculature. (1) Abdominal wall bulging is the result of segmental denervation of abdominal muscles that can mimic a true abdominal hernia, and the patient could be exposed to unnecessary surgery.

Abdominal muscles such as rectus abdominis, oblique, and tranversus abdominis, are innervated by the lower 6 thoracic nerves iliohypogastric and ilio-inguinal nerves. Any pathology that affects these nerves could cause abdominal wall pain and bulging of the abdominal wall, mimicking a true abdominal hernia. In our case, the patient had a L1 nerve root compression, the ventral ramus of LI divides into iliohyoogastric and ilioinguinal nerves, both in charge of supplying the innervation of the lower segments of the transversus abdominis and the internal and external oblique muscle. (2) Thus, a far lateral lumbar disc herniation at L1-L2 can also present with abdominal pain and weakness causing abdominal wall paresis and bulge. (3) To our knowledge, there is only one previous cases report of abdominal wall bulging in a patient with a L1-L2 herniation. (4) Upper lumbar disc herniation most commonly presents with anterior thigh and or groin pain, not unilateral paresis of the abdominal wall. (5)

There are other entities that should also be considered as part of differential diagnosis of abdominal hernia. These can also involve damage to intercostal or upper lumbar nerves. For example, diabetic truncal radiculopathy can also present with unilateral abdominal wall herniation. The patient population consists of middle-aged or elderly diabetic men usually accompanied by a severe weight loss. The muscle bulging and pain resolve after 3-12 months. (6) In the literature, there are also a few case reports of abdominal muscle paralysis associated with herpes zoster, the incidence of abdominal muscle weakness varies between 0% and 6%. The most common presentation of herpes zoster is in the thoracic area; however, herpes zoster localized to the face and limbs are associated with motor complications. (7)

Other rare entities such as Lyme's disease (8) and thoracic syringomelia (9) can be associated with abdominal wall pain and paresis.

In conclusion, this case clearly illustrates that not all clinical presentation of inguinal masses are caused by abdominal/inguinal hernia subtypes. Other differential diagnosis such as acquired neurogenic abdominal wall weakness should be suspected when a unilateral bulging of the abdominal wall musculature is accompanied with position related spinal pain, and negative imaging tests for hernia. With a high index of suspicion for these clinical entities in mind during evaluation, unnecessary surgery can be prevented and appropriate work up and treatment can be provided.


(1.) Schwartz SI, Shires GT, Spencer FC, Storer EH. Principles of Surgery. 3rd ed. New York, NY: McGraw Hill Book Company; 1979.

(2.) Moore KL, Agur AMR, Dalley AF. Essential Clinical Anatomy. 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2013.

(3.) Bartolomei L, Carbonin C, Cagnin G, Toso V. Unilateral swelling of the lower abdominal wall. Unusual clinical manifestation of an upper lumbar disc herniation. Acta Neurochir (Wien). 1992;117(1-2):78-79.

(4.) Billet FP, Ponssen H, Veenhuizen Q. Unilateral paresis of the abdominal wall: a radicular syndrome caused by herniation of the L1-2 disc?. J Neurol Neurosurg Psychiatry. 1989;52:678.

(5.) Sanderson SP, Houten J, Errico T, et al. The unique characteristics of "upper" lumbar disc herniations. Neurosurgery. 2004;55:385-389.

(6.) Chaudhuri KR, Wren DR, Werring D, Watkins PJ. Unilateral abdominal muscle herniation with pain: a distinctive variant of diabetic radiculopathy. Diabet Med. 1997;14(9):803-807.

(7.) Gottschau P, Trojaborg W. Abdominal muscle paralysis associated with herpes zoster. Acta Neurol Scand. 1991;84(4):344-347.

(8.) Daffner KR, Saver JL, Biber MP. Lyme polyradiculoneuropathy presenting as increasing abdominal girth. Neurology. 1990;40(2):373-375.

(9.) Coleman RJ, Ingram DA. Abdominal wall weakness due to thoracic syringomyelia. Neurology. 1991;41(10):1689-1691.


Dr Elgueta is a Research Fellow in the Department of Anesthesia, Montreal General Hospital, and affiliated with the Pontificia Universidad Catolica de Chile, Santiago.

Dr Wang is a Resident in the Department of Anesthesia, Montreal General Hospital.

Dr Gupta, a physiatrist, works with the Canadian Forces Health Centre-Ottawa and the Alan Edwards Pain Management Unit of the Department of Anesthesia, Montreal General Hospital. He is also an adjunct professor at Mc-Gill University in Montreal, Quebec.

LCol Besemann, a physiatrist, is head of the Canadian Forces physical rehabilitation program at the Canadian Forces Health Services Group Headquarters in Ottawa. He also works at the Canadian Forces Health Centre and is a lecturer at the University of Ottawa.

Maria Francisca Elgueta, MD

Nina Nan Wang, MD

Gaurav Gupta, MD, FRCPC

LCol Markus Besemann, MD, FRCPC

Caption: Figure 1. Panel A shows the left lower quadrant bulge (arrow). Panel B shows reduction of the bulge in lumbar extension/ right side bending.

Caption: Figure 2. Left L1 nerve root compression from disc herniation (arrow). (MRI T2 weighted axial slice).
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Author:Elgueta, Maria Francisca; Wang, Nina Nan; Gupta, Gaurav; Besemann, Markus
Publication:U.S. Army Medical Department Journal
Date:Jul 1, 2018
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