The pyriform sinuses are recesses within the hypopharynx, the lower part of the throat. They sit on either side of the laryngeal inlet, the opening to the voice box. They form part of the pathway through which food and liquids travel during swallowing.
Anatomy and Role in Swallowing
The pyriform sinuses are positioned lateral to the larynx. Their name comes from the Latin “pirum,” meaning pear. These structures are bordered medially by the aryepiglottic fold and laterally by the thyroid cartilage, forming a defined pathway. The superior extent of each sinus is marked by the pharyngoepiglottic mucosal fold, which connects the lateral pharyngeal wall to the epiglottis, while their apex reaches down below the vocal cords. Deep to their mucous membrane, the internal laryngeal nerve, responsible for sensation in the area, is located.
These sinuses function as guiding channels. They facilitate the movement of food and liquids from the back of the mouth, directing them around the airway opening and into the esophagus. This passive channeling is a protective mechanism, helping to prevent the accidental entry of food or liquid into the lungs, a process known as aspiration. Impairment in their function, such as reduced opening of the upper esophageal sphincter, can lead to retention of swallowed material in these sinuses, increasing the risk of aspiration.
Associated Medical Conditions
The pyriform sinuses can sometimes temporarily trap small foreign bodies, such as fragments of food or even pills. When this occurs, individuals may experience a sensation known as “globus sensation,” a feeling that something is lodged in their throat, even though no obstruction is present. This discomfort typically resolves as the trapped material passes naturally or with further swallowing efforts.
A less common but notable condition is a pyriform sinus fistula, which represents an abnormal, often congenital, channel. These fistulas are thought to arise from remnants of embryonic pharyngeal pouches and can lead to recurrent neck infections, particularly observed in pediatric populations. Such infections can manifest as acute thyroiditis, a condition more frequently noted on the left side of the neck.
The pyriform sinuses are a significant site for the development of hypopharyngeal cancers, which are malignancies originating in the lower part of the throat. In the United States, a substantial majority, approximately 60-70%, of hypopharyngeal tumors begin in the pyriform sinus. These cancers are predominantly squamous cell carcinomas and are strongly associated with long-term exposure to risk factors such as heavy alcohol consumption and tobacco smoking.
Symptoms associated with pyriform sinus cancer can include a persistent sore throat, often localized to one side, and pain that may radiate to the ear on the same side. Individuals might also experience dysphagia, which is painful or difficult swallowing, or changes in their voice, such as hoarseness. A palpable lump in the neck may also be present, indicating potential spread. Tumors originating in the medial wall of the pyriform sinus can spread along the mucosal surface to the aryepiglottic folds and may invade the larynx. Tumors on the lateral wall and apex commonly invade the thyroid cartilage. Consulting a medical professional for evaluation is highly recommended if these symptoms persist.