How common is abnormal relaxation of the upper esophageal sphincter (UES) during radiographic examination ?
T. Lerut, W. Coosemans, E. Ponette, J. Coolen (Leuven)
One of the major difficulties in assessing the upper esophageal sphincter (UES) is the complexity of its normal anatomy and its normal function. Therefore, the term abnormal relaxation requires a definition of a normal relaxation.
Anatomically there is indeed not a well defined UES. Although most investigators seem to agree upon the cricopharyngeal muscle as a part of the UES, this muscle is only approximately 1 cm in width and therefore cannot account by itself for the entire UES, as the length of the UES zone is indeed 2-4 cm on manometry. These manometric studies, as well as electromyographic ones, suggest that the cricopharyngeal and inferior pharyngeal constrictor muscles may constitute the UES .
Functionally, the passage of the bolus from the pharynx into the esophagus consists in a delicate sequence of contractions by the many different muscles involved in the swallowing act at this level. The in time relaxation and closure of the so called UES is of course of paramount importance in this process. The whole phase is however very rapid, and takes only one second or less .
Manometry, electromyography, cine-fluoroscopy and videorecording are the classic methods used to investigate the pharyngoesophageal region, but the execution and interpretation of all these methods require a lot of expertise. This is due, partly to technical shortcomings of each method, partly to the specific anatomical and functional inter relationships with the surrounding structures, and partly to the age of the patient [2, 3, 4].
As far as the radiological characteristics of the UES, and more specifically of the cricopharyngeal muscle, are concerned, there is a divergence of opinion regarding the radiological defect commonly seen in the pharyngo-esophageal area: a posterior indentation of the esophageal lumen is often observed at the level of the lower cervical spine, most often visible at C5-6 disk-space level, but it can be encountered from the body of C4 down to the body of C7. This impression has several names, including esophageal lip, spasm, hypopharyngeal bar or hypertrophy of the cricopharyngeal muscle. This indentation has been seen as an obstruction to the pharyngeal bolus, as an indentation appearing early, throughout or late in the swallowing phase, or with a varying appearance from one swallow to another [5, 6, 7].
What is the significance of this indentation ? According to Cricklow , there is no normal radiologic picture of the cricopharyngeal muscle because this muscle is never visualized if the esophagus is acting normally and several authors have claimed that it is abnormal to observe an indentation on the posterior wall of the pharyngo-esophageal junction, due to the cricopharyngeal muscle. However, Asherson reported individuals cases who did not complain of swallowing difficulties but had a typical indentation. Seaman , in a cinematographic investigation of swallowing in 200 patients without dysphagia, reported an indentation in 5 p. cent.
To time the relaxed phase of the cricopharyngeal muscle and to evaluate its coordination with the pharyngeal swallow, manometry, electromyography and cineradiology have been compared by Curtis : electromyographic studies show a relaxation potential lasting 500 msec, and manometric studies show a relaxation phase of 500-1,400 msec. The study of Curtis correlates well radiologic and manometric timing, showing the relaxation lasting nearly the 383 msec found by Christrup , and upwards the 1,440msec found by Knuff . Moreover, indentations seen early, throughout and late in the swallow, also allowed the required time for the bolus to pass the cricopharyngeal muscle.
All these findings just illustrate how difficult it is to define normal distention of the cervical esophagus and abnormal relaxation.
For practical purposes, an indentation occurring before the contraction of the pharynx, if complete or persisting during the phase of pharyngeal distention, has been suggested as cricopharyngeal dysfunction (incoordinated or abnormal relaxation) .
One of the most in depth studies on the incidence of cricopharyngeal dysfunction in patients with and without dysphagia has been performed by Ekberg and Nylander [13, 14]: with the aid of cineradiography, the pharyngeal stage of deglutition was examined at a speed of 50 and 100 frames per second among 150 individuals without dysphagia. In 83 p. cent the swallowing act had a symmetrical and synchronous pattern. Different types of aberrations were seen in 26 individuals (17%). Seven (4,6 %) of them had dysfunction of the cricopharyngeal muscle which did not relax properly. None of them showed any concomitant abnormality. The indentation did not exceed half of the diameter of the adjacent gullet. In 4 individuals, the cricopharyngeal indentation remained visible during passage of contrast medium. In the remaining two, it was a transient phenomenon at the beginning.
These results can be compared with a series of 250 patients with dysphagia where 55 (22 %) had dysfunction of the cricopharyngeal muscle, the indentation here being > 50 p. cent of the esophageal diameter in 8 patients, and continuous in 19.
From October 1988 until December 1989, 168 videorecorded swallowing acts have been performed in our institution for various reasons: most of them obviously were related to some sort of pharyngoesophageal symptomatology. Out of them, 136 (81 %) examinations showed a normal function of the UES. Nine patients (5,3 %) had a delayed but complete relaxation, while 9,5 p. cent of the patients (16) had an incomplete relaxation. Finally 7 patients (4,2 %) had a Zenker's diverticulum in which, as expected, UES relaxation was incomplete. This survey confirms the data obtained by Ekberg and Nylander.
The definition of the radiologic visualization of a cricopharyngeal dysfunction remains a controversial field requiring a great expertise to define it. Its incidence in patients without dysphagia seems to be inferior to 5 p. cent and, in these individuals, it appears as a solitary phenomenon.