Describe the route of spread of nasopharyngeal carcinoma.

From the primary site the tumour may spread in one or more of the following directions:

1. Anteriorly to the nasal cavity and paranasal sinuses, pterygopalatine fossa and apex of the orbit.
2. Posteriorly to the retropharyngeal space and node of rouviers, destroying the lateral mass of the atlas.
3. Laterally into the parapharyngeal space:
   • Prestyloid compartment: Involvement of the mandibular nerve, pterygoid muscle and infiltration of the deep lobe of the parotid.
   • Post styloid compartment: vascular compression of the carotid sheath and vessels.
   • Invasion of the last four cranial nerves and cervical sympathetic nerves
   • Superiorly through the sphenoid  body and sinus involving the parasellar structures and optic nerve, petrous apex and foramen lacerum along the carotid canal into the cavernous sinus involving nerves III,IV,V and VI. The brain is affected by direct tumour extension and not haematogenous spread.
   • Inferiorly to the oral cavity and retrotonsillar regions.