To clarify both the mechanism of parapharyngeal involvement of head and neck cancers and the clinical usefulness of parapharyngeal dissection, the routes of lymphatic flow from the oral cavity and oropharynx to the parapharyngeal space were studied using activated carbon particles CH40.
The following results were obtained:
1. Lymphatic flow from the posterior portion of the oral cavity and that from the oropharynx reach the parapharyngeal space through lymphatic channels in the submucosa.
2. Among 6 routes of direct parapharyngeal spread of head and neck cancers, the anteromedial inferior, anteromedial superior, medial central, and anterolateral routes were found to have direction-specific routes of lymphatic flow. The flow of the former 3 routes is high, and that of the later route is low. These routes of lymphatic flow were considered to be responsible for the frequent spread of cancers into the parapharyngeal space by direct extension.
3. Lymphatic flow to the parapharyngeal space drains not only into the node of Kuttner but also into the parapharyngeal and retropharyngeal nodes through lymphatic vessels in the parapharyngeal space.
4. Anatomically, these findings suggest that parapharyngeal dissection is very useful in the management of cancers that involve the parapharyngeal space.