Structural abnormalities of the cricopharyngeus muscle in patients with pharyngeal (Zenker's) diverticulum.

Recent manometric and radiological studies suggest that the upper oesophageal sphincter has poor compliance in patients with a pharyngeal (Zenker's) diverticulum. To test the hypothesis that this phenomenon is related to structural changes within the cricopharyngeus muscle we examined, histologically, muscle strips from 14 patients with a Zenker's diverticulum and compared them with control tissue obtained at autopsy from 10 non-dysphagic individuals. The cricopharyngeus muscle from patients and controls differed from inferior constrictor muscle by virtue of type 1 fibre predominance and greater fibre size variability. Ragged red fibres and nemaline bodies are a normal finding in the cricopharyngeus. Marked differences were observed in the cricopharyngeus muscle of Zenker's patients which demonstrated fibro-adipose tissue replacement and fibre degeneration. It is concluded that these structural changes may account for the observed diminished upper oesophageal sphincter opening and dysphagia in patients with Zenker's diverticulum.