KMDS
E-submission
Articles
- Page Path
- HOME > J Mov Disord > Volume 18(1); 2025 > Article
-
Letter to the editor
Muscle Dystonia Manifesting as Unilateral Rectus Abdominis Hypertrophy and Abdominal Pain in Parkinson’s Disease: A Case Report -
Chengjian Wu1,2*
, Yanhui Meng1,3*, Ming Yang1
-
Journal of Movement Disorders 2025;18(1):108-110.
DOI: https://doi.org/10.14802/jmd.24230
Published online: December 10, 2024
1Center of Gerontology and Geriatrics, West China Hospital, Sichuan University, Chengdu, China
2Department of Gastroenterology and Hepatology, Sichuan University-University of Oxford Huaxi Joint Centre for Gastrointestinal Cancer, West China Hospital, Sichuan University, Chengdu, China
3Department of Geriatrics, Meishan City People’s Hospital, Meishan, China
- Corresponding author: Ming Yang, MD, PhD Center of Gerontology and Geriatrics, West China Holspital, Sichuan Unviersity, No.37 Guoxue Lane, Chengdu 610041, China / Tel: +86-28-85422321 / E-mail: yangmier@gmail.com; yangmier@scu.edu.cn
- *These authors contributed equally to this work.
• Received: November 14, 2024 • Revised: November 27, 2024 • Accepted: December 10, 2024
Copyright © 2025 The Korean Movement Disorder Society
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
- 1,148 Views
- 52 Download
Dear Editor,
Pain is a common nonmotor symptom in Parkinson’s disease (PD), affecting 24% to 85% of PD patients [1]. Although musculoskeletal and central pain symptoms are frequently reported, abdominal pain is relatively rare, with a prevalence of only 3.4% [2]. The pathophysiology of PD-related abdominal pain remains poorly understood, particularly when it is associated with muscle dystonia. Herein, we report a unique case of a PD patient presenting with severe intractable abdominal pain and unilateral rectus abdominis hypertrophy that responded to combined muscle relaxant and antiparkinsonian therapy.
A 77-year-old woman presented with severe paroxysmal abdominal pain that started 2 days before admission. She experienced episodes of severe cramping pain, which predominantly occurred in the left periumbilical region, lasting from several minutes to hours. The pain severity was rated as 7–8 points on the visual analog scale (VAS). Her symptoms typically worsened at night and were not related to food intake. The pain intensified with standing and walking but was partially improved with bending forward and lying in a supine position. She also reported tenesmus and a sensation of incomplete evacuation that improved after defecation. There was no nausea, vomiting, diarrhea, fever, radiating pain, cardiorespiratory symptoms, or history of abdominal trauma.
The patient first noticed right-sided resting tremor and bradykinesia in early 2020. She was diagnosed with PD in February 2021. She had been taking 250 mg carbidopa/levodopa three times daily since the diagnosis, and 1.5 mg pramipexole once daily was added in February 2022. The patient maintained this medication regimen until the onset of abdominal pain, which occurred approximately 2 years and 10 months after the initial diagnosis; moreover, she did not experience significant motor fluctuations. Her nonmotor symptoms included constipation (2–3 spontaneous bowel movements per week), dysphagia, and nocturnal sleep disorder. She had no relevant medical or family history. At the time of presentation with abdominal pain, her Hoehn-Yahr stage was three, and her total Unified Parkinson’s Disease Rating Scale score was 60, thus indicating moderate disease progression.
Physical examination revealed stable vital signs. Neurological examination revealed a reduced speech rate. Resting tremors (predominantly right-sided), bilateral limb rigidity (more pronounced on the right), slow gait with reduced arm swinging, and difficulty with body turning were observed. Bradykinesia was evident with respect to finger tapping, grip strength, and pronation-supination movements. Her posture exhibited mild forward flexion. Abdominal examination revealed a soft abdomen with palpable cord-like thickening of the left rectus abdominis muscle; although this muscle was not visually apparent, it was firm and tender without rebound tenderness. Murphy’s sign was negative. Muscle strength and physiological reflexes were normal, and pathological reflexes were absent.
The results of laboratory tests, including complete blood count, electrolytes, liver and renal function, and coagulation profile, were within normal ranges. Brain magnetic resonance imaging revealed multiple ischemic foci in the bilateral basal ganglia and periventricular regions with cerebral atrophy. Enhanced abdominal computed tomography (CT) and CT angiography demonstrated marked thickening of the left rectus abdominis measuring approximately 10 mm (with a mean CT value of 46 Hounsfield unit [HU]), whereas the contralateral muscle was thin at 3.7 mm (with a mean CT value of 12 HU) (Figure 1). Both pancreatic fatty infiltration and atherosclerotic changes in the abdominal aorta and its branches were observed. Capsule endoscopy revealed chronic atrophic gastritis and prominent small bowel vessels, with normal findings observed in the colon and rectum.
Initial symptomatic treatment with 40 mg esomeprazole daily, 40 mg trimebutine three times daily, and 100 mg tramadol twice daily showed limited efficacy. The patient’s pain score (VAS) remained at 7–8 points. When considering the imaging findings of unilateral rectus abdominis hypertrophy and based on previous reports in the literature [3,4], we suspected that PD-related dystonia was the cause of her abdominal pain. Although the original antiparkinsonian medication regimen was not changed, the patient was started on 10 mg oral eperisone hydrochloride three times daily. After 3 days of treatment, her abdominal pain almost completely resolved; moreover, the left rectus abdominis muscle became notably softer on palpation, although muscle hypertrophy persisted. This temporal correlation between physical sign changes and symptom improvement provides compelling evidence supporting dystonia as the mechanism underlying intractable abdominal pain.
Previous case reports have described bilateral rectus abdominis hypertrophy in PD patients with abdominal pain [3,4]. Kataoka et al. [4] reported two cases of bilateral muscle hypertrophy with constant hypertonic activity on surface electromyography. In contrast, our patient demonstrated marked unilateral hypertrophy that precisely corresponded with the distribution of pain. The distinct CT density difference between the affected and unaffected sides provided objective evidence of sustained muscle contraction. Additionally, the significant response to skeletal muscle relaxants (rather than due to dopaminergic medication adjustment) suggested a mechanism that is distinct from classic “off-period” dystonia. This unique presentation expands our understanding of the spectrum of PD-related muscle dystonia.
Previous studies have shown that α-synuclein pathology in PD affects not only the central nervous system but also the enteric nervous system [5]. Both brainstem autonomic nuclei and enteric nervous system dysfunction may contribute to the occurrence of gastrointestinal symptoms in PD patients. In our case, rather than being a simple manifestation of gastrointestinal dysfunction or classic “off-period” dystonia, we hypothesize that the symptoms resulted from complex pathophysiological mechanisms. The central dysregulation of muscle tone control, which potentially involves both dopaminergic and nondopaminergic pathways, may specifically affect the rectus abdominis muscle. This hypothesis is supported by several observations. First, the symptoms demonstrated a circadian rhythm but had no correlation with medication timing. Second, specific postures were able to modulate symptom severity. Finally, a considerable response was elicited with the use of skeletal muscle relaxants rather than due to dopaminergic medication adjustment.
In conclusion, this case highlights several important aspects. First, it describes a unique presentation of unilateral rectus abdominis hypertrophy in PD-related abdominal pain, which differs from previously reported bilateral cases [3,4]. Second, it emphasizes the importance of circadian rhythm and postural dependence in recognizing dystonia-related pain. Third, this study demonstrates the effectiveness of skeletal muscle relaxants as a treatment strategy. These findings not only deepen our understanding of nonmotor symptoms in PD but also provide valuable insights for clinical practice. When evaluating refractory abdominal pain in PD patients, clinicians should consider morphological changes in the abdominal muscles and utilize imaging studies to assist in diagnosis and treatment decisions. However, the lack of follow-up CT images prevents us from documenting potential radiological changes corresponding to clinical improvement.
-
Ethics Statement
The study protocol was approved by the medical ethics committee of West China Hospital, Sichuan University (IRB No. 2024-0977). Informed consent was obtained from the patient.
-
Conflicts of Interest
The authors have no financial conflicts of interest.
-
Funding Statement
None
-
Author Contributions
Conceptualization: Ming Yang. Data curation: Chengjian Wu, Yanhui Meng. Formal analysis: Chengjian Wu. Investigation: Chengjian Wu, Yanhui Meng. Methodology: Ming Yang. Software: Ming Yang. Supervision: Ming Yang. Writing—original draft: Chengjian Wu. Writing—review & editing: Yanhui Meng, Ming Yang.
Notes
Acknowledgments
None
Figure 1.
CT findings of asymmetric rectus abdominis hypertrophy in a patient with Parkinson’s disease. An axial CT scan parallel to the L4 vertebral endplate revealed marked thickening of the left rectus abdominis muscle (white arrow, maximum thickness of 10.0 mm) with well-defined borders and homogeneous density, in contrast to the thin right rectus abdominis muscle (hollow arrow, thickness of 3.7 mm). The mean CT attenuation values were 46 HU and 12 HU for the left and right rectus abdominis muscles, respectively, thus indicating increased tissue density on the left side, which was consistent with sustained muscle contraction. CT, computed tomography; HU, Hounsfield unit.
- 1. Nardelli D, Gambioli F, De Bartolo MI, Mancinelli R, Biagioni F, Carotti S, et al. Pain in Parkinson’s disease: a neuroanatomy-based approach. Brain Commun 2024;6:fcae210.ArticlePubMedPMCPDF
- 2. Sung HY, Park JW, Kim JS. The frequency and severity of gastrointestinal symptoms in patients with early Parkinson’s disease. J Mov Disord 2014;7:7–12.ArticlePubMedPMC
- 3. Kataoka H, Sugie K. Persistent intolerable abdominal pain in patients with Parkinson’s disease. Clin Neurol Neurosurg 2023;224:107558.ArticlePubMed
- 4. Kataoka H, Tonomura Y, Eura N, Terashima M, Kawahara M, Ueno S. Painful abdominal contractions in patients with Parkinson disease. J Clin Neurosci 2012;19:624–627.ArticlePubMed
- 5. Yang R, Gao G, Yang H. The pathological mechanism between the intestine and brain in the early stage of Parkinson’s disease. Front Aging Neurosci 2022;14:861035.ArticlePubMedPMC
REFERENCES
Figure & Data
References
Citations
Citations to this article as recorded by 
Comments on this article
PubReader
ePub Link
Cite
XML DownloadMuscle Dystonia Manifesting as Unilateral Rectus Abdominis Hypertrophy and Abdominal Pain in Parkinson’s Disease: A Case Report
Figure 1. CT findings of asymmetric rectus abdominis hypertrophy in a patient with Parkinson’s disease. An axial CT scan parallel to the L4 vertebral endplate revealed marked thickening of the left rectus abdominis muscle (white arrow, maximum thickness of 10.0 mm) with well-defined borders and homogeneous density, in contrast to the thin right rectus abdominis muscle (hollow arrow, thickness of 3.7 mm). The mean CT attenuation values were 46 HU and 12 HU for the left and right rectus abdominis muscles, respectively, thus indicating increased tissue density on the left side, which was consistent with sustained muscle contraction. CT, computed tomography; HU, Hounsfield unit.
Figure 1.
Muscle Dystonia Manifesting as Unilateral Rectus Abdominis Hypertrophy and Abdominal Pain in Parkinson’s Disease: A Case Report
