Figure :Normal nasopharyngeal anatomy - computed tomography Transverse section through the nasopharynx at the level of the mandibular condyle (k). The lateral pterygoid muscle (m) runs from the lateral pterygoid plate (black arrow) to the insertion along the medial aspects of the mandibular neck. Air is seen in the eustachian tube close to the opening in torus tubarius (open arrow). The fossa of Rosenmüller is partly collapsed (arrowhead). (a=internal carotid artery; v=internal jugular vein; s=styloid process)
Nasopharynx
Technique
The nasopharynx, the nasal cavities and the paranasal sinuses are in close contact with the skull base, the parapharyngeal space and the infratemporal fossa. All these areas should therefore be assessed when examining nasopharyngeal lesions by cross-sectional imaging. Superficial lesions of the nasopharyngeal mucosa are best evaluated by direct inspection while computed tomography or magnetic resonance imaging is needed to depict deep tumor extension and possible skull base involvement.
Anatomy
The nasopharynx communicate forward with the posterior choanal openings of the nasal cavities and downward with the oropharynx. The roof and posterior margins of the nasopharynx is formed by the sphenoid bone and the clivus and the insertion of the prevertebral muscles into the skull base. The lateral margins are made up by the pharyngeal constrictors and the torus tubarius in the center of which the opening of the eustachian tube can be found. The nasopharyngeal mucosa is rich in lymphoid tissue. The nasopharynx is surrounded and formed by the strong pharyngobasilar fascia. The fascia is only penetrated by the eustachian tubes and the levator veli palatine muscles and is a tight barrier between the superficial and deep structures of the nasopharynx (Fig. 18). Behind the torus tubarius the fossa of Rosenmüller is found being a deep recess beyond which the internal carotid artery can be found.
Technique
The nasopharynx, the nasal cavities and the paranasal sinuses are in close contact with the skull base, the parapharyngeal space and the infratemporal fossa. All these areas should therefore be assessed when examining nasopharyngeal lesions by cross-sectional imaging. Superficial lesions of the nasopharyngeal mucosa are best evaluated by direct inspection while computed tomography or magnetic resonance imaging is needed to depict deep tumor extension and possible skull base involvement.
Anatomy
The nasopharynx communicate forward with the posterior choanal openings of the nasal cavities and downward with the oropharynx. The roof and posterior margins of the nasopharynx is formed by the sphenoid bone and the clivus and the insertion of the prevertebral muscles into the skull base. The lateral margins are made up by the pharyngeal constrictors and the torus tubarius in the center of which the opening of the eustachian tube can be found. The nasopharyngeal mucosa is rich in lymphoid tissue. The nasopharynx is surrounded and formed by the strong pharyngobasilar fascia. The fascia is only penetrated by the eustachian tubes and the levator veli palatine muscles and is a tight barrier between the superficial and deep structures of the nasopharynx (Fig. 18). Behind the torus tubarius the fossa of Rosenmüller is found being a deep recess beyond which the internal carotid artery can be found.
Pathology
Benign lesions
Adenoid hyperplasia :commonly found in childhood can remain up into the late teens. The benign adenoidal pad has a characteristic appearance on computed tomography and magnetic resonance imaging and it should not be mistaken for a malignant tumor. The adenoidal pad has a typical lobulated surface. On contrast enhanced computed tomography images the pad is seen superficial to the pharyngobasilar fascia which is outlined by the enhancing lamina propria. On magnetic resonance imaging the high signal lymphoid tissue is seen superficial to the low signal fascia.
Congenital remnants high in the nasopharynx can give rise to a midline cyst , the so called Thornwald cyst. This cyst is discovered in the young adult and on cross sectional imaging it can be seen as a smooth well demarcated midline cyst.
Juvenile angiofibroma occurs in teenage boys and is characterized by uncontrollable nosebleeds. This benign but expansile and highly vascularized tumor originates from the lateral wall of the nasopharynx close to the pterygopalatine fossa. The tumor will expand the fossa as it grows both out into the nasopharynx and into the nasal cavity, as well as, out into the infratemporal fossa. From the pterygopalatine fossa the tumor can grow up through the infraorbital fissure into the orbit and continue intracranially through the superior orbital fissure. On computed tomography the tumor shows intense homogenous contrast enhancement and on magnetic resonance imaging the tumor will show characteristic flow voids both findings compatible with a highly vascularized tumor. This together with the location and the expansion of the pterygopalatine fossa contributes to the diagnosis of a juvenile angiofibroma.
Malignant tumors
Squamous cell carcinoma accounts for more than 90% of all malignant tumors of the nasopharynx. The tumor often originating laterally fills out the fossa of Rosenmüller and will cause obstruction of the eustachian tube. Serous otitis and a metastatic neck mass are the most common presenting symptoms of a nasopharyngeal carcinoma. The nasopharynx should therefore be included in the imaging study for the work-up of these symptoms. Contrary to benign adenoid tissue, squamous cell carcinoma will penetrate the pharyngobasilar fascia early in the course reaching the parapharyngeal space and the skull base. Metastatic lymph nodes are often found in the posterior triangle posterior to the stemocleidomastoid muscle.
Lymphoma found in the nasopharynx is often of the non-Hodgkin type and coexisting bilaterallymphadenopathy can therefore often be found in the neck as well as below the diaphragm. The lymphoma can be of considerable size and direct extension up into the skull base is often along the neurovascular bundles.
Rhabdomysosarcoma is the most common malignant nasopharyngeal tumor in children. These tumors are often of considerable size when they are detected and the exact origin can be difficult to discern.
Computed tomography with intravenous contrast is often sufficient to diagnose and evaluate the extent of any nasopharyngeal tumor. Magnetic resonance imaging is the primary tool, however, because it shows the overall extent relative to the skull base, cavernous sinus and brain better than CT in most cases. Coronal non-contrast CT is required in selected cases to exclude subtle skull base invasion.
Adenoid hyperplasia :commonly found in childhood can remain up into the late teens. The benign adenoidal pad has a characteristic appearance on computed tomography and magnetic resonance imaging and it should not be mistaken for a malignant tumor. The adenoidal pad has a typical lobulated surface. On contrast enhanced computed tomography images the pad is seen superficial to the pharyngobasilar fascia which is outlined by the enhancing lamina propria. On magnetic resonance imaging the high signal lymphoid tissue is seen superficial to the low signal fascia.
Congenital remnants high in the nasopharynx can give rise to a midline cyst , the so called Thornwald cyst. This cyst is discovered in the young adult and on cross sectional imaging it can be seen as a smooth well demarcated midline cyst.
Juvenile angiofibroma occurs in teenage boys and is characterized by uncontrollable nosebleeds. This benign but expansile and highly vascularized tumor originates from the lateral wall of the nasopharynx close to the pterygopalatine fossa. The tumor will expand the fossa as it grows both out into the nasopharynx and into the nasal cavity, as well as, out into the infratemporal fossa. From the pterygopalatine fossa the tumor can grow up through the infraorbital fissure into the orbit and continue intracranially through the superior orbital fissure. On computed tomography the tumor shows intense homogenous contrast enhancement and on magnetic resonance imaging the tumor will show characteristic flow voids both findings compatible with a highly vascularized tumor. This together with the location and the expansion of the pterygopalatine fossa contributes to the diagnosis of a juvenile angiofibroma.
Malignant tumors
Squamous cell carcinoma accounts for more than 90% of all malignant tumors of the nasopharynx. The tumor often originating laterally fills out the fossa of Rosenmüller and will cause obstruction of the eustachian tube. Serous otitis and a metastatic neck mass are the most common presenting symptoms of a nasopharyngeal carcinoma. The nasopharynx should therefore be included in the imaging study for the work-up of these symptoms. Contrary to benign adenoid tissue, squamous cell carcinoma will penetrate the pharyngobasilar fascia early in the course reaching the parapharyngeal space and the skull base. Metastatic lymph nodes are often found in the posterior triangle posterior to the stemocleidomastoid muscle.
Lymphoma found in the nasopharynx is often of the non-Hodgkin type and coexisting bilaterallymphadenopathy can therefore often be found in the neck as well as below the diaphragm. The lymphoma can be of considerable size and direct extension up into the skull base is often along the neurovascular bundles.
Rhabdomysosarcoma is the most common malignant nasopharyngeal tumor in children. These tumors are often of considerable size when they are detected and the exact origin can be difficult to discern.
Computed tomography with intravenous contrast is often sufficient to diagnose and evaluate the extent of any nasopharyngeal tumor. Magnetic resonance imaging is the primary tool, however, because it shows the overall extent relative to the skull base, cavernous sinus and brain better than CT in most cases. Coronal non-contrast CT is required in selected cases to exclude subtle skull base invasion.
Reference : Medcyclopedia.
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