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Previous Volume 356:1381-1382 March 29, 2007 Number 13 Next

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The medical mystery in the February 1 issue¹ involved a 70-year-old man who presented with a history of increasing abdominal distention. The patient was evaluated by means of computed tomography (CT) after an abdominal radiograph raised concern about a sigmoid volvulus. The diagnosis of a colonic pseudo-obstruction was made after the CT scan and a follow-up contrast enema study showed dilated loops of colon extending to the rectum, without evidence of blockage or perforation. An underlying parasitic infection was ruled out by means of additional laboratory testing.

The CT scout image, however, provided a clue to the patient's disease. With the patient lying still on a CT-scanner table, the scout image was acquired on a 64-detector–row CT scanner. The scout image was used to preview the area of interest for subsequent CT imaging. It revealed an unusual sinusoidal artifact involving the patient's right forearm (Figure 1A). The patient's concurrent electrocardiogram (Figure 1B) showed an analogous artifact, mimicking an atrioventricular block. This rhythm is in fact a normal sinus rhythm with superimposed, sharp pseudoflutter waves (Figure 1B) that are not associated with the QRS complex.

View larger version (53K): [in this window] [in a new window]   Figure 1. Parkinson's Disease in a 70-Year-Old Man. Panel A shows a magnified CT scout image of the patient's right forearm. The bar represents one cycle (27 mm). Panel B shows an electrocardiogram of lead I with arrows pointing to pseudoflutter waves. The bar represents 5 mm.

 
This case shows several features of a Parkinsonian tremor, while highlighting the association between Parkinson's disease and a colonic pseudo-obstruction. The tremor is present at rest and is often confined to one limb. Besides the classic "pill-rolling" tremor, pronation–supination of the hand and forearm, as seen in this patient, is a common presentation. The frequency of the tremor is typically between 3 and 5 cycles per second. In this case, on the basis of a CT scout table velocity of 79 mm per second and an electrocardiographic sweep speed of 25 mm per second, the tremor frequency was estimated to be 3 and 4 Hz by means of CT and electrocardiography, respectively — findings ultimately confirmed by direct visual observation.

Jason Handwerker, M.D.
Vassilios D. Raptopoulos, M.D.
Beth Israel Deaconess Medical Center
Boston, MA 02215
jhandwer{at}bidmc.harvard.edu

Editor's note: We received 1475 responses to this medical mystery — 53% from physicians in practice, 26% from physicians in training, 16% from medical students, and 5% from other readers. Responses were received from 82 countries. Many of the responses reflect pathophysiological thinking as well as a team effort — such as the results of a discussion of the case during a teaching conference.

Ten percent of the respondents correctly diagnosed Parkinson's disease, with tremor-induced changes in the right arm (on the scout film) and on the electrocardiogram, and the dilated bowel. Thirty-four percent diagnosed Chagas' disease, which was probably due to the dilated bowel and presumed cardiac dysfunction. Twenty-one percent of the responses suggested a toxic metabolic cause, such as hypokalemia, hypomagnesemia, or adverse effects of medication (e.g., from digitalis or calcium-channel blockers); 11% suggested atrial fibrillation with mesenteric ischemia due to an embolic event; 5% diagnosed Ogilvie's syndrome; and the remaining 19% diagnosed a variety of other conditions, such as toxic megacolon, amyloidosis, and Hirschsprung's disease.

References

1. Handwerker J, Raptopoulos VD. A medical mystery: dilated bowel. N Engl J Med 2007;356:503-503. [Free Full Text]

PDF PDA Full Text Add to Personal Archive Add to Citation Manager Notify a Friend E-mail When Cited E-mail When Letters Appear Related Article by Handwerker, J. PubMed Citation