Anterior Triangle

Question 1

A person receives a shallow knife wound just behind the sternocleidomastoid muscle and about 1 1/2 inches above the clavicle. There is an immediate numbness of the skin below the wound and over the acromion and clavicle. The nerve most likely severed was the

Answer 1

The supraclavicular nerves come from C3 and C4 in the cervical plexus. These cutaneous nerves provide sensory innervation to the skin of the root of the neck, upper chest, and upper shoulder. These nerves innervate the skin right above the clavicle, so they are the correct answer.

Question 2

Which muscle is innervated by a branch of the ansa cervicalis?

Answer 2

The sternohyoid muscle is one of the strap muscles which runs from the manubrium and the sternal end of the clavicle to the hyoid bone.

Question 3

The layer of encircling cervical fascia that splits to enclose sternocleidomastoid and trapezius muscles is the:

Answer 3

The superficial layer of deep cervical fascia extends between trapezius and sternocleidomastoid in the posterior triangle and between the paired sternocleidomastoid muscles in the anterior triangle.

Question 4

Which of the following is a dorsal ramus of a spinal nerve?

Supraclavicular n.
Transverse cervical n.
Great auricular n.
Greater occipital n.
Lesser occipital n.

Answer 4

The greater occipital nerve is the cutaneous branch of the dorsal primary ramus of spinal nerve C2 - it provides cutaneous innervation to the posterior scalp.

Question 5

Which of the following is true of the inferior thyroid arteries?

-They arise from the external carotid arteries
-They cross over the superior cervical sympathetic ganglion
-They supply most of the anterior surface of the thyroid gland
-They often supply all four parathyroid glands

Answer 5

They often supply all four parathyroid glands

Question 6

A 20 year old man was brought into the emergency room with a stab wound in the upper part of the neck. Although there was no major damage done, he lost sensation from the skin over the angle of the jaw. Which nerve has been cut?

Answer 6

The great auricular nerve comes from C2 and C3 branches of the cervical plexus; it provides sensory innervation to the ear and the skin below the ear, including the angle of the jaw.

Question 7

The triangle in which the superior branch of the ansa cervicalis separates from the hypoglossal nerve is the:

Answer 7

The superior branch of ansa cervicalis runs with the hypoglossal nerve until the carotid triangle. In this triangle, the superior branch of ansa cervicalis separates from the hypoglossal nerve and runs in the carotid sheath, anterior to the carotid artery.

Question 8

Exploration of the tracheoesophageal groove at the level of the thyroid gland would reveal what important structure bilaterally?

Answer 8

The left and right recurrent laryngeal nerves can be found in the left and right tracheoesophageal grooves.

Question 9

A 35 year old woman was diagnosed with an adenoma of the thyroid gland. This required excision of the lower pole (left lobe) of the gland and ligation of the artery supplying that region. Which of the following nerves accompanying the artery is most likely to be damaged if the surgeon is not careful?

Answer 9

The inferior thyroid artery supplies the lower lobes of the thyroid. It is a branch of the thyrocervical trunk. Branches of this artery cross the recurrent laryngeal nerve, so this is the nerve that might be damaged during the surgery.

Question 10

One of the motor components of the cervical plexus, the ansa cervicalis, innervates all of the following muscles except the:

Answer 10

The stylohyoid muscle runs from the posterior portion of the digastric muscle to the body of the hyoid bone. It elevates and retracts the hyoid, and it is innervated by the facial nerve (CN VII).

Question 11

A man has metastatic carcinoma and enlarged deep cervical lymph nodes. One of his symptoms is a hoarse voice, barely heard above a whisper. Subsequently he succumbs to the disease and at autopsy it is found that one of the enlarged nodes has put pressure on a nerve in the tracheoesophageal groove. Presumably this was the reason for the hoarse voice. What nerve was involved?

Answer 11

Damage to the recurrent laryngeal nerve is one possible cause of hoarseness. The recurrent laryngeal nerve changes its name to the inferior laryngeal nerve at the level of the inferior border of the cricoid cartilage. The inferior laryngeal nerve goes on to innervate all the intrinsic muscles of the larynx except cricothyroideus. So, if this nerve innervating all the muscles of the larynx was damaged, a patient would have a hoarse voice. A very significant piece of information that tells you that the recurrent laryngeal nerve was injured is the location of the injury– remember, recurrent laryngeal travels in the tracheoesophageal groove.

Question 12

You are called on to do a venous catheterization to measure central venous pressure in the heart. Which muscle of the neck would provide the best area of approach to the internal jugular vein?

Answer 12

The internal jugular vein is found in the carotid triangle, which is bounded medially by omohyoid, laterally by sternocleidomastoid, and superiorly by the posterior belly of digastric.

Of these three muscles, sternocleidomastoid is the easiest landmark to find on the neck and the most practical muscle to find when looking for the carotid triangle and the internal jugular vein

Question 13

A patient is brought into the Emergency Room in respiratory distress. It is quickly decided to create an emergency airway to restore respiration. At what level could you rapidly create an airway below the vocal cords with a minimum danger of hemorrhage?

Answer 13

To create an emergency airway, a midline cut can be made through the cricothyroid ligament and membrane. So, an opening is created between the thyroid cartilage and the cricoid cartilage. Since this is below the glottis and the tracheal inlet (which is the usual place where things get lodged), this is a good spot to make the cut. It is also easy to find the thyroid cartilage on a patient and make the incision right below that spot.

Question 14

A 47-year-old woman is diagnosed as having a thyroid tumor. Surgery to remove the cancerous growth is undertaken. In which triangle of the neck will the surgeon make an incision to gain access to the gland?

Answer 14

The muscular triangle is found in the anterior triangle of the neck. It is bounded by the midline as its medial border, the superior belly of the omohyoid as its superolateral border, and sternocleidomastoid as its inferolateral border. The strap muscles, thyroid, and parathyroids are found in this triangle. Since the thyroid is found at the midline, deep to the strap muscles, you would need to cut into this triangle to perform surgery on the thyroid gland.

Question 15

A 50-year-old woman is brought to the operating room for a biopsy of a suspicious looking nevus (mole) which is found along the anterior border of her sternocleidomastoid muscle at about its midlength. What nerve must be locally anesthetized for the operation to proceed without pain?

Answer 15

To answer this question, you want to figure out which nerves supply sensory innervation to the skin of the anterior neck. The transverse cervical nerves, which come off the C2 and C3 roots of the cervical plexus, are the nerves that supply the skin of the neck anteriorly. So, these nerves would need to be anesthetized.

Question 16

Following surgery on the upper pole of the right lobe of the thyroid gland, a patient complains of hoarseness and weakness of voice. What nerve may have been injured?

Answer 16

The external branch of the superior laryngeal nerve travels with the superior thyroid artery toward the superior pole of the thyroid. So, it’s in the right place to be injured by surgery on the upper pole of the gland.

Question 17

These structures are all located in the superficial fascia of the neck EXCEPT
- External jugular vein
- Platysma muscle
- Cervical branch of the facial nerve
- Omohyoid muscle
- Transverse cervical nerve

Answer 17

The omohyoid muscle is a muscle found in the anterior and posterior triangle of the neck. It depresses and stabilizes the hyoid bone.

Question 18

The superior belly of the omohyoid forms the anterior border of which cervical triangle?

Answer 18

The carotid triangle is bounded anteriorly by the superior belly of the omohyoid muscle, laterally by the sternocleidomastoid, and superiorly by the posterior belly of the digastric.

Question 19

The cervical plexus innervates all of the following structures EXCEPT:
- Diaphragm
- Omohyoid muscle
- Platysma
- Skin over thyroid cartilage
- Skin over clavicle

Answer 19

Platysma is a muscle of facial expression. It inserts into the skin and helps lower the angle of the mouth and depress the mandible. It is innervated by the cervical branch of the facial nerve (CN VII).

Question 20

An emergency room patient presented with considerable bleeding from a shallow stab wound in the omoclavicular triangle. Which vessel was most likely cut?

Answer 20

The external jugular vein is a superficial vein on the lateral side of the neck. It is in the superficial fascia, so it could be easily injured by a superficial wound. Since this vein travels in the omoclavicular triangle, this is the structure that was injured.

Question 21

Which structure or area receives NO nerve fibers from the cervical plexus?

• Diaphragm
• Skin over the angle of the mandible
• Skin over the external occipital protuberance
• Thyrohyoid muscle

Answer 21

The skin over the external occipital protuberance is innervated by the greater occipital nerve, which is from the dorsal primary ramus of C2. Since the cervical plexus is made of the ventral primary rami of C1 through C4, the greater occipital nerve has no connection with the cervical plexus.

Question 22

A six-year-old child, whose medical history includes a rather difficult birth, has a permanently tilted head posture, with the right ear near the right shoulder and the face turned upward and to the left. Which of the following muscles was very likely damaged during birth?

Answer 22

If the **sternocleidomastoid **is damaged at birth and becomes shortened, a patient may have muscular torticollis. The neck will appear twisted and the chin elevated because the sternocleidomastoid muscle will be too short on one side. This patient has an injured right sternocleidomastoid, since his head is turned down on the right side where the sternocleidomastoid is too short.

Question 23

Any irritation of the diaphragm (e.g. infection, tumor) may create referred pain that seems (to the patient) to originate in the area atop the shoulder. This is due to the fact that the phrenic nerve shares spinal segments with what cutaneous nerve in the shoulder region?

Answer 23

The phrenic nerve consists of contributions from the ventral primary rami of C3, C4, and C5. The supraclavicular nerves come from the C3 and C4 roots of the cervical plexus. So, these nerves share spinal segments.

Question 24

Which of the following statements about the cervical plexus is true?
- It comprises spinal segments C1-C3
- It consists solely of cutaneous nerves
- It consists solely of ventral rami of spinal nerves
- It supplies motor innervation to platysma

Answer 24

The cervical plexus consists solely of the ventral primary rami of spinal nerves C1-C4. It supplies cutaneous innervation through nerves like the lesser occipital, great auricular, supraclavicular and transverse cervical. It also supplies motor innervation to the strap muscles through the ansa cervicalis.