The cricopharyngeal muscle is a small, ring-like muscle situated deep within the neck. It is the primary component of the upper esophageal sphincter (UES), acting as a muscular gatekeeper between the throat and the feeding tube, known as the esophagus. This muscle regulates the passage of food and liquid while also protecting the airway. Malfunction can lead to significant difficulty with swallowing and related health issues.
Anatomical Placement and Structure
The cricopharyngeal muscle is located at the bottom of the pharynx, marking the transition point into the cervical esophagus. Specifically, it is the lower, horizontally oriented part of the inferior pharyngeal constrictor muscle. Its location is described as being at the C5-C6 vertebral level, approximately below the Adam’s apple.
This muscle wraps around the back of the throat like a muscular collar, forming a complete sling. Its fibers originate from the sides of the cricoid cartilage, a ring-shaped structure in the larynx. Unlike the other constrictor muscles, the cricopharyngeus fibers do not meet at a central seam but blend directly with the circular muscle layers of the esophagus below. This structure allows it to maintain the resting tension that characterizes the upper esophageal sphincter.
Primary Function in the Esophagus
The muscle’s primary function is to maintain a state of near-constant contraction, keeping the entrance to the esophagus closed. This continuous tension serves two protective purposes: preventing air from entering the esophagus during breathing, and guarding against the reflux of stomach contents back up into the throat and airway.
During swallowing, this muscle must rapidly and completely relax to allow the food or liquid bolus to pass from the pharynx into the esophagus. This relaxation is precisely coordinated with the contraction of the pharyngeal muscles and the elevation of the larynx, which helps widen the opening. Once the swallowed material has passed, the muscle swiftly contracts again to restore the high-pressure barrier.
When the Muscle Fails to Relax
When the cricopharyngeal muscle fails to relax during swallowing, a condition known as cricopharyngeal dysfunction or cricopharyngeal achalasia occurs. This blocks the smooth passage of food into the esophagus. This issue is often associated with aging, neurological conditions, or scarring from treatments like radiation therapy.
The most common symptom is dysphagia, or difficulty swallowing, often described as a sensation of food sticking in the neck shortly after the swallow is initiated. Patients may also experience a feeling of a lump in the throat, known as globus sensation, or the need to wash down every bite with liquid.
Persistent high pressure above the unyielding muscle can force the inner lining of the throat to bulge outward through a weak spot, creating a pouch called a Zenker’s diverticulum. This pouch traps food, leading to symptoms like regurgitation of undigested food, foul breath, and coughing or choking. Diagnosing this dysfunction often involves a modified barium swallow study or pharyngeal manometry to visualize the muscle’s failure to relax.
Common Treatments for Dysfunction
Therapeutic interventions for cricopharyngeal muscle dysfunction are aimed at reducing the muscle’s excessive tension. One non-surgical approach involves the targeted injection of Botulinum Toxin (Botox) directly into the muscle. This neurotoxin temporarily paralyzes the muscle fibers, forcing them to relax and remain open longer during swallowing.
Botox injections are often considered a first-line treatment. However, the effect is temporary, usually lasting several months, and requires repeated injections. The more definitive treatment is a surgical procedure called cricopharyngeal myotomy.
During a cricopharyngeal myotomy, a surgeon cuts the tight muscle fibers to permanently reduce the tension and resistance at the upper esophageal sphincter. This procedure can be performed through an incision in the neck or endoscopically (operating through the mouth). Myotomy is particularly effective for persistent dysfunction and is often performed alongside the repair of an existing Zenker’s diverticulum.