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General Anatomy and Embryology with Radiology Correlates


Key Points

  • 1.

    Eight branches of the external carotid artery:

    • Superior thyroid

    • Ascending pharyngeal

    • Lingual

    • Facial

    • Occipital

    • Posterior auricular

    • Maxillary

    • Superficial temporal

  • 2.

    Layers of fascia in the neck:

    • Superficial cervical fascia

    • Superficial layer of deep cervical fascia

    • Middle layer of deep cervical fascia

    • Deep layer of deep cervical fascia

  • 3.

    Characteristics of malignant lymph nodes on neck CT with contrast:

    • Size >1.5 centimeters

    • Round shape

    • Necrotic center

    • Ill-defined margins

  • 4.

    Facial nerve landmarks:

    • Tragal pointer

    • Tympanomastoid suture line

    • Insertion of the posterior belly of digastric muscle onto the mastoid

  • 5.

    Best imaging study by region:

    • Cerebellopontine angle – MRI with contrast

    • Neck and salivary glands – CT with contrast or MRI with contrast

    • Sinus – CT without contrast

    • Temporal bone – CT without contrast

    • Thyroid – Ultrasound

Pearls

  • 1.

    CT scan is best for visualizing temporal bone masses and lesions, but MRI (of the internal auditory canal with contrast) is best for evaluating acoustic neuromas.

  • 2.

    When a temporal bone fracture is suspected, the best test is a fine cuts CT of temporal bones without contrast.

  • 3.

    If the nasal turbinates light up on T1 MRI, imaging was performed with contrast.

  • 4.

    MRI scans commonly over diagnose sinus disease and do not provide detail on outflow obstruction. The most appropriate method to determine chronic sinus disease is CT without contrast ( Fig. 1.1 ).

  • 5.

    The best imaging method for evaluating thyroid nodules is ultrasound.

Fig. 1.1
Chronic sinusitis with nasal polyposis on CT scan.

Questions

1

When do the sinuses develop?

The maxillary sinus is the first to develop in utero. After birth, this sinus enlarges in two stages, once at the age of 3 years and then again between the ages of 7 and 12 years. Neonates have three to four ethmoid cells at birth, which multiply to become 10 to 15 cells by the age of 12 years. The sphenoid sinus begins pneumatization at 3 years of age, and the frontal sinus is the last to develop at approximately 5 years of age. The sphenoid and frontal sinuses do not reach adult size until the teenage years.

2

What is the difference between agger nasi, Onodi, and Haller ethmoid cells?

The agger nasi cell is the most anterior of the ethmoid cells. It is found anterior and superior to the attachment of the middle turbinate to the lateral wall. The Onodi cell is an ethmoid cell that pneumatizes laterally or posteriorly to the anterior wall of the sphenoid. This cell can be adjacent to the optic nerve or carotid artery, so it is important to recognize this variation during sinus surgery. A Haller cell forms when the ethmoid pneumatizes into the medial and inferior orbital walls. If this cell is large, it can cause obstruction of the maxillary ostium.

3

Name the branches of the internal carotid artery in the neck.

Trick question! The internal carotid artery does not branch in the neck.

4

Name the eight branches of the external carotid artery in the neck.

From proximal to distal, the branches are: the superior thyroid, ascending pharyngeal, lingual, facial, occipital, posterior auricular, maxillary, and superficial temporal arteries.

5

Name the four types of tongue papillae. Where are they located?

The four types are circumvallate, fungiform, foliate, and filiform papillae. The circumvallate are located at the junction of the anterior two thirds and posterior one third of the tongue in a “V” shape. Fungiform papillae are found at the tip and lateral edges of the anterior two thirds of the tongue. Foliate papillae are found at the posterolateral base of tongue. Filiform papillae are found all over the tongue and do not participate in taste sensation.

6

Describe the landmarks used to locate the facial nerve during parotid surgery.

Typical landmarks include the tragal pointer, tympanomastoid suture line, and posterior digastric muscle. The tragal pointer refers to the tragus cartilage, which “points” to the location of the nerve 1 centimeter anterior, inferior, and deep to the cartilage. Another method of identification is to follow the tympanomastoid suture line inferiorly to its drop-off point. Six to eight millimeters medial to this point, the facial nerve can be found passing through the stylomastoid foramen. Finally, the nerve can be located just medial to the insertion of the posterior belly of the digastric on the mastoid.

7

Name each of the major salivary glands and describe the types of saliva produced by each.

There are three paired major salivary glands: the parotid, submandibular, and sublingual glands. Each gland has acinar cells that produce either serous or mucinous solution. The parotid glands produce mostly serous saliva. The sublingual glands produce mostly mucinous saliva, and the submandibular glands produce a mixture of the two.

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