MSP – Anatomy

PS #5 – 2nd Quarter

More Fun with the Head and Neck…

  1. You have been chosen to stand in as an extra in tonight’s taping of ER. Your character is a fourth year student rotating through their hospital. You and Dr. Ross are talking shop, when your first patient is rushed onto the set. He is a 25 year old male who has just fractured the base of his skull in an MVA (motor vehicle accident). He is quickly losing consciousness and his left eye is pulsating in and out in time with his radial pulse. Reading your cue cards, you confidently explain “Doug, this is clearly a result of a tear in the internal carotid artery within the cavernous sinus.”

Why would a rupture of the internal carotid within the cavernous sinus cause this pulsating exophthalmous?

WHEN THE INTERNAL CAROTID TEARS WITHIN THE CAVERNOUS SINUS, A ARTERIOVENOUS FISTULA IS PRODUCED. IN SUCH CASES, ARTERIAL BLOOD RUSHED INTO THE CAVERNOUS SINUS, ENLARGING IT AND FORCING BLOOD INTO THE CONNECTING VEINS, ESPECIALLY THE OPHTHALMIC VEINS THAT NORMALLY DRAIN THE ORBITAL CAVITY. AS A RESULT, THE EYE PROTRUDES AND THE CONJUNCTIVA BECOMES ENGORGED ON THE SIDE OF THE TORN ARTERY. IN THESE CIRCUMSTANCES, THE BULGING EYE PULSATES IN SYNCHRONY WITH THE RADIAL PULSE.

What nerves could be affected by injuries or infections of the cavernous sinus?

CRANIAL NERVES III, IV, V1, V2, VI (SEE MOORE, PP. 691-2)

  1. You are at your preceptor and a 34 year old man comes in because he has been suffering from double vision. On physical exam, you notice that his left pupil is really big and not responsive to light, his left eyelid is droopy, and his left eye is turned down and out. Your preceptor suspects an aneurysm in the proximity of the Circle of Willis and immediately sends the patient over to the hospital to have a cerebral angiography.

Where in or around the Circle of Willis could a bulging aneurysm cause these symptoms?

SINCE ALL OF THESE SYMPTOMS COULD BE EXPLAINED BY DAMAGE TO (COMPRESSION OF) CN III, THE MOST PROBABLE LOCATION OF THE ANEURYSM WOULD BE NEAR WHERE CN III PASSES BETWEEN THE SUPERIOR CEREBELLAR AND THE POSTERIOR CEREBRAL ARTERIES. THE POINTS WHERE THESE TWO ARTERIES BRANCH FROM THE BASILAR ARTERY ARE THE MOST LIKELY LOCATIONS (SEE MOORE, P. 698).

Draw the Circle of Willis

SEE MOORE, P. 698

  1. You are on your surgery rotation, when suddenly you hear a scream from a patient’s room. You know that Mrs. Horner just had a cancerous lymph node removed from the right side of her neck, but you can’t imagine what is so troubling at the moment. When you come in to the room, you find her staring at her mirror in horror. She is upset because her right eyelid is drooping, her right pupil is much smaller than the left, the right side of her face is flushed, and, even though the room is hot, she is only sweating on the left side of her face.

What nerve damage is at the root of her symptoms? Explain how this damage is responsible for each of the symptoms?

DAMAGE TO THE SYMPATHETIC TRUNK

  • THE PTOSIS IS CAUSED BY PARALYSIS OF THE SMOOTH MUSCLE IN THE LEVATOR PALPEBRAE SUPERIORIS (REMEMBER, THIS MUSCLE HAS BOTH SMOOTH AND STRIATED FIBERS. THE STRIATED FIBERS ARE INNERVATED BY CN III, AND THE SMOOTH ARE SYMPATHETIC.)
  • THE PUPILLARY CONSTRICTION IS CAUSED BY PARALYSIS OF THE DILATOR PUPILLAE MUSCLE IN THE IRIS
  • VASODILATION AND ABSENCE OF SWEATING OF THE FACE AND NECK IS DUE TO LACK OF SYMPATHETIC NERVE ACTIVITY TO THE BLOOD VESSELS AND SWEAT GLANDS.
  1. You are at your preceptors office, and you notice a woman with a very large mass in her neck sitting in the waiting room. You quickly make the diagnosis of a goiter.

Because she has a goiter, you know for sure that she is (euthyroid, hyperthyroid, hypothyroid) pick one. TRICK QUESTION!!! REMEMBER WHAT DR. GORSKI SAID: A GOITER COULD REPRESENT ANY ONE OF THE THREE OPTIONS.

When she comes into the examination room, you notice that she has exophthalmous of both eyes. When you take her history, you find that she has been extremely nervous lately, has lost a lot of weight without trying, and has noticed her heart racing a lot. After examining her, your preceptor concludes that she is hyperthyroid. Because of her other medical conditions, he concludes that the best option for her would be a partial thyroidectomy.

You know that this procedure is somewhat risky because of the many important structures around the thyroid.

The RECURRENT LARYNGEAL nerve can be accidentally severed when the surgeon attempts to cut the INFERIOR THYROID artery. What will this do to her voice? MAKE IT HOARSE

Another potential complication of this procedure is the development of a severe convulsive disorder (tetany) soon after the surgery. What would the surgeon have mistakenly removed to cause this disorder?

PARATHYROIDS – LEADING TO A FALL IN BLOOD CALCIUM LEVELS

What arteries supply the thyroid, and what arteries do they branch from?

SUPERIOR THYROID ARTERY – FROM EXTERNAL CAROTID

INFERIOR THYROID ARTERY – FROM THYROCERVICAL TRUNK

AND, IN 10% OF PEOPLE, THE THYROID IMA – FROM THE BRACHIOCEPHALIC TRUNK

  1. Match the following
  1. Sternohyoidi. Glossopharyngeal nerve
  2. Geniohyoidii. A branch of the mandibular nerve (V3)
  3. Stylopharyngeusiii. Ansa cervicalis
  4. Lies on the anterior aspect

of the scalenus anterior muscle iv. C-1 by way of hypoglossal nerve

  1. Mylohyoidv. Phrenic nerve

a. iii

b. iv (good illustration p. 256 BRS)

c. i

d. v

e. ii

STRUCTURE LIST

posterior triangle of neck

sternocleidomastoid muscle

trapezius

clavicle

supraclavicular nerves

XI spinal accessory nerve

lesser occipital nerve

great auricular nerve

transverse cervical nerve

external jugular vein

subclavius muscle

omohyoid muscle

transverse cervical artery and vein

suprascapular artery and vein

splenius capitis

levator scapulae

anterior, middle, posterior scalene muscles

phrenic nerve

anterior triangle of neck

hyoid bone

thyroid cartilage

thyrohyoid membrane

cricoid cartilage

cricothyroid membrane

trachea

common, external and internal carotid arteries

internal jugular vein

X vagus nerve

omohyoid, sternohyoid, sternothyroid, thyrohyoid muscles

ansa cervicalis

isthmus of thyroid gland

XI spinal accessory nerve

XII hypoglossal nerve

superior laryngeal nerve

internal laryngeal nerve

external laryngeal nerve

superior thyroid artery

superior laryngeal artery

lingual artery

facial artery

occipital artery

ascending pharyngeal artery

common facial vein

superior thyroid vein

anterior and posterior bellies of digastric muscle

mylohyoid muscle

submandibular gland

mylohyoid nerve

stylohyoid muscle

thyroid and parathyroid glands

superior and inferior thyroid arteries

recurrent laryngeal nerve

root of neck

common carotid artery

internal jugular vein

thoracic duct

subclavian artery and vein

X vagus nerve

phrenic nerve

thyrocervical, transverse cervical and suprascapular vessels

inferior thyroid artery

internal thoracic artery

vertebral artery

sympathetic chain and ganglia