Functional and morphological study of the cricopharyngeal muscle in patients with Zenker's diverticulum.

Pharyngo-oesophageal function was investigated in 12 patients with Zenker's diverticulum before and after cricopharyngeal myotomy with or without diverticulectomy using low-compliance, high-frequency oesophageal manometry. Nine healthy volunteers served as controls. The amount of muscle and connective tissue in the cricopharyngeal muscle was also measured by computerized morphometry and compared with findings in cadavers with no history of dysphagia. Preoperative manometry in patients with Zenker's diverticulum showed an incomplete relaxation of the upper oesophageal sphincter (UOS) (the residual UOS pressure at swallowing was 7.9 (range 1-20)mmHg in patients versus 0.2 (-12.5-14) mmHg in controls; P < 0.001) and increased pharyngeal intrabolus pressure (21 (range 0-52) versus 9 (range 0-16) mmHg; P < 0.01), with no pharyngo-oesophageal coordination abnormalities. Both parameters significantly decreased after myotomy. Patients with Zenker's diverticulum had significantly fewer muscle fibres in the cricopharyngeus and the muscle:connective tissue ratio was significantly lower (0.94 (range 0.8-1.4) in patients versus 1.5 (1.4-3.6) in controls; P < 0.05). This study supports the theory that Zenker's diverticulum is caused by an increased intrapharyngeal pressure at swallowing due to incomplete cricopharyngeal muscle relaxation resulting from localized sclerosis.