Carcinoma of Tongue: Lymphatics & Swallowing

(i) Lymph Node Involvement and Distribution – Flowchart

The principal lymph nodes involved in carcinoma of the tongue are the cervical lymph nodes, specifically those in levels I-IV. The spread typically follows predictable patterns. Here’s a flowchart illustrating this:

Explanation of Levels:

• Level I: Submental nodes (below the mandible)
• Level II: Submandibular nodes (along the inferior border of the mandible)
• Level III: Mid-jugular nodes (along the internal jugular vein)
• Level IV: Low-jugular nodes (along the internal jugular vein, inferior to the omohyoid muscle)
• Level V: Posterior cervical nodes (posterior triangle of the neck)

Metastasis often occurs sequentially, starting with Level I and progressing to Levels II, III, and IV. Skip metastasis (direct spread to distant nodes) can also occur, though less commonly. The flowchart illustrates the most common pathway. Histopathological examination of sentinel lymph nodes is increasingly used to determine the extent of disease and guide treatment decisions.

(ii) Role of Tongue in Swallowing

Swallowing, or deglutition, is a complex physiological process divided into four phases. The tongue plays a critical role in all phases:

1. Oral Preparatory Phase (Voluntary)

This phase involves preparing the bolus (food mass) for swallowing. The tongue manipulates the food, mixing it with saliva to form a cohesive bolus. The superior longitudinal muscle of the tongue shapes the bolus, while the hyoglossus and styloglossus muscles help position it. This phase is under voluntary control.

2. Oral Phase (Voluntary)

The tongue propels the bolus towards the oropharynx. The tongue tip elevates and presses against the hard palate, squeezing the bolus posteriorly. The palatoglossus muscle assists in directing the bolus. This phase is also largely voluntary, initiating the swallowing reflex.

3. Pharyngeal Phase (Involuntary)

This is the critical phase where the swallowing reflex is triggered. The tongue base retracts, contributing to bolus propulsion. The hyoglossus, styloglossus, and palatoglossus muscles contract to move the bolus into the pharynx. Simultaneously, the soft palate elevates to close off the nasal cavity, and the epiglottis inverts to protect the airway. This phase is involuntary and coordinated by the swallowing center in the brainstem.

4. Esophageal Phase (Involuntary)

The bolus enters the esophagus, and peristaltic waves propel it downwards towards the stomach. While the tongue doesn’t directly participate in this phase, its efficient propulsion of the bolus into the pharynx is essential for initiating esophageal peristalsis. The upper esophageal sphincter relaxes to allow passage of the bolus.

Damage to the tongue, as seen in carcinoma, can disrupt all phases of swallowing, leading to dysphagia (difficulty swallowing), aspiration (food entering the airway), and malnutrition.