1/Anatomy
The nasopharynx is the superior portion of the tubular pharynx Fig. 1 ,its limits are:
·Superior: Central skull base.
·Inferior: The soft palate,
separating it from oropharynx.
·Posterior: The clivus and the two first cerical vertebrae.
·Anterior: Nasal cavity and choane.
·Lateral: The lateral walls of the nasopharynx are in continuity with the lateral oropharyngeal walls.
The pharyngobasilar fascia forms the wall of the nasopharynx.
Foramen of morgani is a small lateral attachment in pharyngobasilar fascia skull base,
through which the Eustachian tube pass between the levatorveli-palatini muscle and the tensorveli-palatini muscle Fig. 2 .
Foramen of morgani is a weak spot and may favor neoplasm progression to the skull base.
Rosenmuller recessus is superior and postero-lateral to the torus tubarius and the first site of neoplasm arising.
2/Histology and epidemiology:
NPC is a tumor arising from the epithelial cells that cover the surface and line the nasopharynx.
The incidence is particularly high in Tunisian population.
There are three groups of nasopharyngeal carcinoma
-Type 1 : keratininzing or epidermoidcarcinoma,
associated with tobacco,
alcohol,
and Human papilloma virus infection
-Type 2 : differentiated non-keratinizing carcinoma,
-Type 3 : undifferentiated carcinoma,
the most common (95%) and associated with Epstein Bar Virus infection,
high incidence between 40 and 60 yearsold (sex ratio = 2.5).
Less common tumors are lymphoma (15%),
plasmocytma,
adenocarcinoma.
3/ Symptoms :
Patients may present with epistaxis,
blocked nose,
hearing loss,
otalgia,
headache,
and less often with cranial nerves involvement.
the first presentation may be with cervical nodal or distant metastasis due to the silent spread of the disease.
4/ Imaging tools :
MRI
The protocol of MRI includes:
- Unenhanced T1 weighted images in axial and sagittal planes : detect the skull base involvement and the fat of the deep facial spaces.
- T2-weighted fast spin-echo sequence in axial and coronal planes : for assessment of early parapharyngeal tumor spread,
paranasal sinus invasion and middle ear effusions.
- Contrast-enhanced T1-weighted images in axial and coronal planes with fat suppression : to detect tumor extent,
includingperineuralspread and intracranial extension of the tumor
- T2 fat spin echosequence on the neck in axial or cornal plane : to detect lymphnodes.
CT
CT has now largely been replaced by MRI but still used for the detection of skull base tumor involvement with lytic or sclerotic lesions