Download 1. You are testing the extraocular muscles and their innervation in a

1. You are testing the extraocular muscles and their innervation in a
patient who periodically experiences double vision. When you ask
him to turn his right eye inward toward his nose and look
downward he is able to look inward, but not down. Which nerve is
most likely involved?
Abducens
Nasociliary
Oculomotor, inferior division
Oculomotor, superior division
Trochlear
2. The outermost layer of the optic nerve sheath is a continuation of
the:
Arachnoid membrane
Meningeal dura
Periosteal dura
Pia mater
Retina
3. The inner lining of the eyelid is called the:
Orbital septum
Palpebral conjunctiva
Periorbita
Sclera
Tarsal plate
4. What would the examining physician notice in the eye of a person
who has taken a sympathetic blocking agent?
Exophthalmos and dilated iris
Enophthalmos and dry eye
Dry eye and inability to accommodate for reading
Wide open eyelids and loss of depth perception
Ptosis and miosis (pin-point pupil)
5. You are examining a patient who has a pituitary tumor involving
the cavernous sinus. While doing a preliminary eye exam, you
suspect the right abducens nerve of the patient has been damaged
by the tumor. In which direction would you have the patient turn his
right eye to confirm the defect?
Inward
Outward
Downward
Down and out
Down and in
Upward
Up and out
Up and in
6. You have a patient with a drooping right eyelid. You suspect
Horner's syndrome. Which of the following signs on the right side
would confirm this diagnosis?
Constricted pupil
Dry eye (lack of tears)
Exophthalmos
Pale, blanched face
Sweaty face
7. Following endarterectomy on the right common carotid, a patient is
found to be blind in the right eye. It appears that a small thrombus
embolized during surgery and lodged in the artery supplying the
optic nerve. What artery would be blocked?
Central artery of the retina
Infraorbital
Lacrimal
Nasociliary
Supraorbital
8. You are asked to check the integrity of the trochlear nerve in the
right eye of a patient. Starting with the eyes directed straight
ahead, you would have the patient look:
Inward, toward the nose and downward
Inward, toward the nose and upward
Toward the nose in a horizontal plane
Laterally in a horizontal plane
Outward, away from the nose and downward
Outward, away from the nose and upward
9. The ducts of the lacrimal gland open into the:
Superior fornix of the conjunctiva
Inferior fornix of the conjunctiva
Lacrimal puncta
Lacrimal canaliculi
Lacrimal lake
10.
Starting from a position gazing straight ahead, to direct the
gaze downward, the inferior rectus muscle must be active along
with the:
Superior oblique
Inferior oblique
Medial rectus
Lateral rectus
Superior rectus
11.
During a physical examination it is noted that a patient has
ptosis. What muscle must be paralyzed?
Orbicularis oculi, lacrimal part
Orbicularis oculi, palpebral part
Stapedius
Superior oblique
Superior tarsal (smooth muscle portion of levator palpebrae)
12.
The extraocular muscle that does not originate at or near the
apex of the orbit is the :
Inferior oblique
Inferior rectus
Levator palpebrae superioris
Superior oblique
Superior rectus
13.
An adolescent boy suffers from severe acne. As is often the
case he frequently squeezed the pimples on his face. He
subsequently develops a fever and deteriorates into a confused
mental state and drowsiness. He is taken to his physician and after
several tests a diagnosis of cavernous sinus infection and
thrombosis is made. The route of entry to the cavernous sinus
from the face was most likely the:
Carotid artery
Mastoid emissary vein
Middle meningeal artery
Ophthalmic vein
Parietal emissary vein
14.
If a person looking inward towards their nose is unable to
look down, which nerve may be injured?
Abducens (CN VI)
Inferior division of oculomotor (III)
Optic (II)
Superior division of oculomotor (III)
Trochlear (IV)
15.
If a person is taking a sympathetic blocking agent, what
would you notice in her or his eyes?
Dry eyes and inability to accommodate for reading
Enophthalmos and teary eyes (III)
Exophthalmos and dilated pupil
Ptosis and constricted pupil
Wide open eyes and loss of depth perception (IV)
1. The correct answer is:
trochlear
To understand this question, you need to understand how the motions of
the eye are tested. Since the actions of the extraocular muscles are
complex, it is necessary to turn the eye to a position where a single
action of each muscle predominates when evaluating the individual
muscles. A key principle for muscle testing is: if a muscle has two
actions and you perform one of those two, then it can't perform its other
action. Superior and inferior recti turn the eye in and up or in and down.
Superior and inferior oblique turn the eye out and down or out and up.
So, if you turn your eye in (with the superior and inferior rectus as well
as medial rectus), then only superior and inferior oblique can move the
eye down or up (because the superior and inferior recti are already
shortened by turning the eye in - they can't shorten any more). Similarly,
if you turn the gaze out (with the obliques and lateral rectus) then only
superior and inferior rectus can turn the eye up or down.
In this case, the patient has the eye turned inward, so the doctor must
be testing the oblique muscles. The superior oblique muscle is the
muscle that lowers the eye when it is turned inward. Since the patient
can't do this, the superior oblique must not be functioning, and this
muscle is innervated by the trochlear nerve.
Abducens (CN VI) innervates the lateral rectus muscle, which is not
involved in the eye test. The nasociliary nerve comes from the
ophthalmic division of the trigeminal nerve (V1). It is a sensory nerve to
the eyeball that also carries some sympathetic fibers. The inferior
division of the oculomotor nerve innervates inferior rectus, inferior
oblique, and medial rectus. All of these muscles appear to be
functioning. Finally, the superior division of the oculomotor nerve
innervates levator palpebrae superioris and superior rectus. These are
not the muscles that appear to be malfunctioning.
2. The correct answer is:
meningeal dura
The optic nerve comes off the base of the brain and passes through the
optic canal. As it leaves the brain, it still retains all of the meningeal layer
coverings. So, it is covered by meningeal dura, arachnoid membrane,
and pia mater. This is significant, because an increase in intracranial
pressure will increase the pressure in the subarachnoid space. This may
squeeze the optic nerve and make the optic nerve bulge into the eye, a
condition known as papilledema.
The periosteal dura is the layer of periosteum covering the internal
surface of the calvaria. The retina is the inner layer of the eyeball which
receives and absorbs visual light rays.
3. The correct answer is:
palpebral conjunctiva
The palpebral conjunctiva is the thin membrane that lines the eyelid. It is
continuous with the bulbar conjunctiva which lines the eyeball. The
orbital septum is a weak membrane that spans from the tarsal plates to
the margins of the orbit where it becomes continuous with the
periosteum. It contains orbital fat and can limit the spread of infection in
the orbit. The periorbita is the periosteum lining covering the bones
forming the orbit. The sclera is the outer fibrous layer of the eyeball.
Finally, the tarsal plate is a thin, cardboard-like layer of connective tissue
in the eyelids which forms the "skeleton" of the eyelids.
4.
The correct answer is:
Ptosis and miosis (pin-point iris)
Start this question out by thinking about what a sympathetic blocker
would do to the pupil of the eye. Since sympathetic nerves allow the
pupil to dilate, a sympathetic blocker would stop the eye from dilating
and make the pupil constrict. Now think about the other issues. First,
remember that sympathetic nerves innervate the superior tarsal muscle,
which elevates the eyelids. If there is a problem with the regional
sympathetics (as is the case with Horner's syndrome), the superior tarsal
muscle will be paralyzed, and the eyelid will droop (ptosis). If the
sympathetic nervous system is inhibited, sweating will cease, and you
will observe the eye sinking back into the orbit.
Accomodation is not mediated by the sympathetic system;
accomodation is a function of parasympathetic nerve so this should not
be affected. Finally, the lacrimal gland is innervated by
parasympathetics, so there should not be a major change in eye
secretions after a sympathetic blocker. Putting all of these factors
together, answer choice E is the only one that fits!
5. The correct answer is:
outward
To understand this question, you need to understand how the motions of
the eye are tested. Since the actions of the extraocular muscles are
complex, it is necessary to turn the eye to a position where a single
action of each muscle predominates when evaluating the individual
muscles. For the superior and inferior recti, turning the eye outward
(abduction) by approximately 25 degrees places the superior rectus in
position to raise the eye and the inferior rectus to lower the eye.
Similarly, turning the eye inward (adduction) approximately 50 degrees
places the inferior oblique in position to raise the eye and the superior
oblique to lower the eye. The medial and lateral recti may be checked
while the eye is staring straight ahead since they have simple planar
actions.
In this case, you're interested in testing an "easy" muscle. Since the
lesion appears to be in the abducens, which innervates the lateral rectus
muscle, you could just ask the patient to turn the eye outward. If the
patient could not do this, it would confirm that there was a lesion in the
abducens nerve, since the muscle responsible for lateral movement of
the eye would be paralyzed.
Also remember--a tumor in the cavernous sinus could affect many
nerves. The oculomotor nerve (CN III), trochlear (CN IV), ophthalmic
division of trigeminal (CN V1), and abducens (CN VI) all pass through the
cavernous sinus.
6.
The correct answer is:
constricted pupil
Horner's syndrome is a disorder involving damage to the sympathetic
trunk in the neck. This means that the sympathetics of the head will be
disrupted. This causes a variety of very characteristic symptoms,
including a constricted pupil. Remember--sympathetic nerves innervate
the dilator pupillae muscle. This muscle allows the eye to dilate. If these
sympathetic nerves are lost, the pupil will contract.
Several of the other listed symptoms are the opposite of what you would
expect with Horner's syndrome. Exophthalmos is the protrusion of the
eye, but in Horner's syndome the eye sinks in, possibly due to the
paralysis of a smooth muscle in the floor of the orbit. The face does not
become blanched and sweaty with Horner's syndrome--instead, it
becomes red and dry. Without the sympathetic nerve supply, the
vasculature of the face cannot constrict. So, the arterioles in the patient's
face are vasodilated, making the face red. Sympathetic nerves also
innervate sweat glands; if these nerves are interrupted, the patient will
not sweat and the face will appear very dry. Finally, the lacrimal gland is
innervated by parasympathetics, not sympathetics. So, Horner's
syndrome should produce no appreciable changes in tearing.
Make sure to know the different symptoms and signs of Horner's
syndrome!
7. The correct answer is:
Central artery of the retina
The central artery of the retina is a branch of the ophthalmic artery. It is
the sole blood supply to the retina; it has no significant collateral
circulation and blockage of this vessel leads to blindness. The branches
of this artery are what you view during a fundoscopic exam. The
infraorbital artery is a branch of the maxillary artery. It comes through the
infraorbital foramen, inferior to the eye. It supplies the maxillary sinus,
the maxillary incisors, canine and premolar teeth, and the skin of the
cheek below the orbit. The supraorbital artery is another branch of the
ophthalmic artery. It comes through the supraorbital foramen or notch
and supplies blood to the muscles, skin and fascia of the forehead. The
lacrimal artery is a branch of the ophthalmic artery that supplies the
lacrimal gland. The nasociliary artery doesn't exist, but there is a
nasociliary nerve (the third and lowest branch of the ophthalmic division)
that travels with the continuation of the ophthalmic artery.
8. The correct answer is:
Inward, toward the nose and downward
To understand this question, you need to understand how the motions of
the eye are tested. Since the actions of the extraocular muscles are
complex, it is necessary to turn the eye to a position where a single
action of each muscle predominates when evaluating the individual
muscles. To test the superior and inferior recti, a patient needs to turn
the eye outward approximately 25 degrees. At this postion, the superior
rectus will simply act to raise the eye, and the inferior rectus will lower
the eye. To test the superior and inferior obliques, a patient needs to
turn the eye inward approximately 50 degrees. When the eye is in this
position, the superior oblique muscle will act to lower the eye, and the
inferior oblique will act to raise the eye.
So, now that you understand how to the test the eye, you have to decide
which muscle is innervated by the trochlear nerve. And that's the
superior oblique. So, to test this muscle, the eye needs to turn inward
(toward the nose) and downward.
What nerves innervate the other muscles? The abducens nerve (CN VI)
innervates the lateral rectus muscle. The oculomotor nerve (CN III)
innervates the superior rectus, inferior rectus, medial rectus, and inferior
oblique muscles.
9. The correct answer is:
Superior fornix of the conjunctiva
Lacrimal fluid is produced by the lacrimal gland, which lies in a fossa in
the superolateral part of each orbit. The fluid from this gland enters the
conjunctival sac through up to 12 lacrimal ducts that open into the
superior conjunctival fornix. The tears then flow to the medial angle of
the eye and collect in the lacrimal lake. The lacrimal papilla are small
elevations on the eyelids, found near the lacrimal lake. These papillae
have small openings called the lacrimal puncta; tears flow from the
lacrimal lake into these puncta. From there, the lacrimal fluid goes into
small canniliculi which drain the fluid into the lacrimal sac. The lacrimal
sac continues on as the nasolacrimal duct and drains tears into the
inferior nasal meatus. Take a look at Netter Plate 77 and try to follow the
path of tears from the lacrimal gland to the inferior meatus!
10. The correct answer is:
Superior Oblique
The inferior rectus muscle depresses the eye and medially rotates it. So,
to direct the gaze downward, you want to find a muscle that will depress
the eye while counterbalancing the medial rotation with lateral rotation.
And, the superior oblique, innervated by the trochlear nerve (CN IV),
does just that--it depresses the eye while laterally rotating it. The inferior
oblique muscle laterally rotates the eye and elevates the eye. The
medial rectus adducts the eye--it does not raise or lower the eye. The
lateral rectus abducts the eye--it also does not raise or lower the eye.
Finally, the superior rectus elevates the eye and draws it medially.
11. The correct answer is:
Superior tarsal
The superior tarsal muscle is a smooth muscle which is sympathetically
innervated. It is an involuntary muscle that elevates the eyelid. It is
innervated by the cervical sympathetic trunk, and this muscle's
functioning provides a good indication of the integrity of the cervical
sympathetic trunk. If the cervical sympathetic trunk has been damaged,
a patient will have ptosis, a droopy eyelid. Orbicularis oculi is innervated
by the facial nerve. If this muscle is paralyzed, the problem won't be a
droopy eyelid--instead, the patient won't be able to close the eyelid. This
is why patients with Bell's palsy are prescribed lubricating eye drops--if
they can't close the eyelid, they may be at risk for corneal irritation.
Stapedius is another muscle innervated by the facial nerve -- it serves to
dampen the vibrations of the stapes and the tympanic membrane.
Finally, the superior oblique muscle depresses the eyeball and turns it
laterally. It does not affect the eyelid.
12. The correct answer is:
Inferior oblique
The inferior oblique muscle does not originate at the apex of the orbit. It
takes origin from the floor of the orbit, lateral to the lacrimal groove. The
inferior rectus and superior rectus muscles take origin from the common
tendinous ring at the apex of the orbit. The levator palpebrae superioris
takes origin from the apex of the orbit above the optic canal. The
superior oblique muscle takes origin from the apex of the orbit, above
the optic canal. For a picture of this, see Netter Plate 79.
13. The correct answer is:
Ophthalmic vein
The ophthalmic veins are continuous with the facial vein and the
pterygoid plexus of veins. These veins drain the face toward the
cavernous sinus. They are valveless, so infections from the face can
drain into the cavernous sinus. Besides causing fever and confusion,
thrombotic congestion and edema in the cavernous sinus can compress
the nerves that traverse that space to exit through the superior orbital
fissure(CN III, CN IV, CN V1, and CN VI). This can affect the function of
the ocular muscles, so one symptom of a cavernous sinus infection
might be an inability to perform different eye movements.
The carotid artery and middle meningeal artery would not be the source
of the infections. Infections do not tend to enter through arterial
circulation. Remember--the common carotid is the major source of blood
to the head and neck, and the middle meningeal artery is the branch of
the maxillary artery that supplies blood to the dura. The emissary veins
are valveless veins of the scalp. These veins can carry blood from the
scalp to the dural venous sinuses or in the reverse direction depending
on blood pressure. These veins may carry infectious materials from the
scalp into the dural venous sinuses, but they are not important for
carrying infections to the cavernous sinus.
14. The correct answer is:
Trochlear (IV)
To understand this question, you need to understand how to evaluate
the muscles of the eye. Since the actions of the extraocular muscles are
complex, it is necessary to turn the eye to a position where a single
action of each muscle predominates. To isolate the superior and inferior
recti, the patient needs to turn the eye outward by approximately 25
degrees. This places the superior rectus in position to raise the eye and
the inferior rectus in position to lower the eye. Turning the eye inward
approximately 50 degrees places the inferior oblique in position to raise
the eye and the superior oblique in position to lower the eye. The medial
and lateral recti are the easy muscles -- they may be checked while the
eye is staring straight ahead since they have simple planar actions
So, this patient is looking inward, which means that the obliques are
being tested. The patient can't look downward, which shows that the
superior oblique is not functional. This is the only muscle innervated by
the trochlear nerve (CN IV).
Abducens (CN VI) innervates the lateral rectus muscle, which is tested
by asking the patient to move the eye outward. The inferior division of
the oculomotor nerve innervates inferior rectus, inferior oblique, and
medial rectus. The superior branch of the oculomotor nerve innervates
levator palpebrae superioris and superior rectus muscles. Finally, the
optic nerve (CN II) provides the special sense of vision, and it is not
tested in the eye-movement tests.
Are you getting the idea that you really need to know about testing the
eye muscles? Take the time and really understand this concept--you'll
be glad that you did!
15. The correct answer is:
Ptosis and constricted pupil
To understand this question, it's important to look at all the different
choices and determine which ones fit with a sympathetic block. First, the
lacrimal gland is innervated parasympathetically, so a sympathetic
blocker should have no effect on eye secretions. Accomodation is also a
function of the parasympathetic nervous system; it should not be altered
by a sympathetic blocker. Enophthalmos is the name for the eye sinking
into its orbit. A sympathetic block does cause enophthalmos, due to the
paralysis of a smooth muscle in the floor of the orbit. Exophthalmos is
the opposite of enophthalmos--it is the protrusion of the eye from the
orbit. You would not see exophthalmos with a sympathetic blockade.
Sympathetic nerves allow the eye to dilate--if you blocked these nerves,
the eye would constrict. A sympathetic blocker would also cause ptosis-it would paralyze the superior tarsal muscle, which holds the lids up
involuntarily and receives sympathetic innervation. Finally, the
sympathetic blocker should not affect depth perception. If you put all of
these things together, answer choice D is the correct one.
If it helps to remember, taking a sympathetic blocking agent will lead to
similar symptoms in the head and neck as Horner's syndrome, a disease
characterized by a loss of sympathetic innervation to the head and neck.