Persistent intolerable abdominal pain in patients with Parkinson's disease

In Parkinson's disease (PD), pain is common, increases motor disability, and makes daily life unpleasant. Few patients reportedly have a low prevalence of abdominal pain. The pathophysiology of such abdominal pain has not been confirmed. We clinically studied patients with PD and persistent intolerable abdominal pain to determine the pathophysiology and effective therapy.

We obtained detailed clinical information from medical records, including the disease course before and after the onset of abdominal pain. The maximal thickness of the rectus muscle at the L4 and L5 corpus vertebral level of the abdomen on axial computed tomography was calculated, and the relative muscle thickness ratio was calculated by dividing the maximal thickness by the distance from the fascia between the bilateral rectus muscles of the abdomen and the dorsal part of the corpus vertebrae.

In six patients with PD (three men, age range 71-85 years), the Hoehn-Yahr stage, disease duration, and daily levodopa equivalent dose were 3.1 ± 0.7, 107 ± 44 months, and 636.7 ± 451.4 mg/day, respectively. The pain occurred daily and often during the night and was not related to the timing of food intake. The pain in two patients was related to wearing-off. One patient showed constant hypertonic activity in the rectus abdominis on surface electromyography. The rectus abdominis showed that the maximal thickness and relative muscle thickness ratio of patients with abdominal pain were significantly higher than those of patients without pain. Therapeutic usefulness of antiparkinsonian medications was short and limited.

Although intolerable abdominal pain is likely to be infrequent, it alleviates the quality of life of patients with PD. The pathophysiology seems to vary, and our observations found wearing-off of related pain and muscle contraction, suggesting dystonia. Among persistent abdominal pain, organic abnormalities, such as the precursor state of megacolon, may be lurking.