Tumor-Induced Oblique Abdominal Muscle Paralysis Syndrome: A Case of Position-Dependent Abdominal Distension and Umbilical Displacement

Our plain-English summary of Tumor-Induced Oblique Abdominal Muscle Paralysis Syndrome: A Case of Position-Dependent Abdominal Distension and Umbilical Displacement, by Y. Ishikawa, K. Sakai, S. Teramura, et al (Curēus, 2024).

The study

• Authors: Y. Ishikawa, K. Sakai, S. Teramura, K. Ito, T. Yamada
• Journal: Curēus
• Published: 2024;16(12):e75341
• Type of article: Case report
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Unilateral paralysis of the oblique abdominal muscles is commonly linked to non-malignant conditions, such as herniated discs, shingles, and phrenic nerve injury, each leading to localized muscle weakness through nerve impairment. However, oblique abdominal muscle paralysis caused by malignant tumors is exceedingly rare. This report presents a unique case of left oblique abdominal muscle paralysis induced by malignant pleural mesothelioma (MPM), demonstrating a distinct pattern of position-dependent abdominal bulging and umbilical displacement. The patient, a male in his 70s, was initially treated with chemotherapy for left-sided MPM and later received radiation therapy (RT) for pleural lesions causing pain. As the disease progressed, he developed a visible bulging of the left lateral abdomen, which was more pronounced in upright positions (standing or sitting) and resolved in the supine position. CT imaging showed atrophy of the left oblique abdominal muscle and a displacement of the umbilicus to the right, findings were consistent with intercostal nerve impairment due to tumor invasion. This case underscores the importance of conducting abdominal examinations in various positions when nerve impairment by a tumor is suspected. The presence of position-dependent lateral abdominal bulging, lateral displacement of the umbilicus, and lack of intraperitoneal abnormalities should raise suspicion for tumor-induced oblique abdominal muscle paralysis. We propose defining such cases as "tumor-induced oblique abdominal muscle paralysis syndrome" to improve diagnostic accuracy and aid in the effective management of malignancy-associated abdominal neuropathies.

Copyright © 2024, Ishikawa et al.

In plain English

This case report described a man in his 70s with malignant pleural mesothelioma on the left side. The article did not report whether he had been exposed to asbestos. He was treated with chemotherapy (cisplatin and pemetrexed, then pemetrexed alone) and later with nivolumab, but the pleural lesions grew and a right adrenal metastasis appeared. He then had several courses of radiation therapy, the first being 39 Gy in 13 fractions to pleural lesions near the 10th and 11th intercostal spaces. About six to nine months after that first radiation, a bulge developed on the left side of his abdomen. It appeared when he sat or stood and was absent lying flat. On standing, his navel shifted to the right. CT showed no clear abnormality inside the abdomen, but the left external and internal oblique muscles had wasted. The authors attributed this to paralysis of those muscles from tumor-related intercostal nerve impairment. They noted that radiation damage could not be entirely excluded and that, as a single case, the relative roles of radiation and tumor could not be settled. They proposed naming such cases "tumor-induced oblique abdominal muscle paralysis syndrome".

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Case report (one patient)
• Who was studied: One male patient in his 70s with left-sided malignant pleural mesothelioma (MPM), diagnosed by thoracoscopic lung biopsy. The authors are from Tohoku Medical and Pharmaceutical University, Sendai, Japan.
• Exposure: The article did not report any asbestos exposure or occupational history for this patient. It said only, as general background, that MPM is primarily caused by asbestos exposure. The case concerns the effects of the tumor and its treatment: chemotherapy, nivolumab, and several courses of radiation therapy.
• Main results:
  • At diagnosis, CT showed a 3.7 cm mass in the left lower lobe next to the diaphragm. Thoracoscopic lung biopsy confirmed MPM.
  • The patient received cisplatin and pemetrexed, then pemetrexed alone, and from the third year after diagnosis nivolumab, continued until the fifth year (50 courses).
  • Despite treatment, the patient's pleural lesions grew and a right adrenal metastasis appeared.
  • The first radiation therapy, 39 Gy in 13 fractions to pleural lesions in the 10th and 11th intercostal spaces of the left chest wall, relieved the patient's pain.
  • Around six to nine months after the first radiation therapy, the patient developed a bulge on the left side of the abdomen.
  • The patient's abdomen was flat when lying down, and the bulge appeared only when standing or sitting. On standing, his navel shifted to the right.
  • CT showed no significant abnormality inside the abdomen. It did show atrophy of the patient's left external and internal oblique abdominal muscles and a rightward displacement of the navel.
  • The authors attributed these findings to paralysis of the left oblique abdominal muscles caused by impairment of the intercostal nerve.
  • Other causes were considered unlikely in this patient: there was no shingles rash and no history of diabetes.
  • Regulating bowel movements and reducing intestinal gas gave the patient partial relief, but the symptoms persisted.
• The authors' conclusion: The authors concluded that abdominal examination should also be done in seated or standing positions, not only lying down. They said tumor-induced oblique abdominal muscle paralysis should be suspected in the following situations: abdominal distension that increases when standing or sitting and decreases when lying down; a navel that shifts toward the unaffected side; or no organic abnormality on imaging together with visible thinning of the oblique muscles. They proposed the name "tumor-induced oblique abdominal muscle paralysis syndrome" for such cases.
• Limitations the authors state:
  • The patient received a relatively high radiation dose of 39 Gy in 13 fractions. The authors said radiation-induced nerve damage or muscle atrophy could not be entirely excluded, although they believed tumor effects likely played a more significant role.
  • Because this is a single case report, the authors said no definitive conclusions can be drawn about how much radiation versus the tumor contributed.

Topics

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Chemotherapy, Standing.

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