Exam 1 - 002 Orbit and Paranasal Sinuses

Question 1

Bones of the orbit

Answer 1

maxillary
palatine
frontal
sphenoid
zygomatic
ethmoid
lacrimal

Question 2

Relationship of the medial walls of the orbit

Answer 2

 Roughly parallel

 About 25 mm apart

Question 3

Relationship of the lateral walls of the orbit

Answer 3

About 90 degrees from each other

Question 4

Angle where the lateral and medial walls meet at the apex of the orbit

Answer 4

45 degrees

makes the orbit pyramidal in shape

Question 5

Location of the widest part of the orbit

Answer 5

about 15 mm behind the orbital margin

Question 6

Depth of the orbit

Answer 6

45 mm

Question 7

Bones of the Roof

Answer 7

**The roof slope down from front to back
Frontal bone 
•	orbital plate
•	anterior part
•	Thin so can get blown out easily
Lesser wing of the sphenoid bone
•	Posterior part
•	Much thicker than the frontal bone

Question 8

Landmarks of the roof

Answer 8

•Lacrimal fossa
o Depression in the frontal bone
o In the superior temporal position behind the lateral aspect of the superior orbital margin (so anterior)
•Fovea trochlearis (AKA trochlear fossa)
o Medial depression on the frontal bone
o About 4 mm behind the medial aspect of the superior orbital margin
o Houses the cartilaginous pulley (trochlea) for the tendon of the superior oblique muscle

Question 9

Features of the lateral wall

Answer 9

 Roughly triangular
 Thickest orbital wall
 Separated from the roof of the orbit by the superior orbital fissure
 Separates orbit from temporal fossa (and the temporalis muscle) anteriorly
 Posteriorly the greater wing of sphenoid separates orbit from the middle cranial fossa

Question 10

Bones of the lateral wall

Answer 10

•Greater wing of the sphenoid bone
o Posterior 2/3
•Zygomatic bone
o Anterior 1/3

Question 11

Landmarks of the lateral wall

Answer 11

•Lateral orbital tubercle
o On the orbital surface of zygomatic bone
o Located just within the lateral orbital margin at its midpoint
o Attachment site for several structures
•Zygomatico-orbital foramen
o Opening in zygomatic bone
o Carries zygomatic nerve and blood vessels
o Leads to zygomaticotemporal and zygomaticofacial foramen

Question 12

Features of the medial wall

Answer 12

 Rectangular

 THINNEST orbital wall

Question 13

Bones of the medial wall

Answer 13

•Maxillary bone
•Lacrimal bone
•Lamina papyracea of ethmoid bone (largest part of the medial wall)
o	Paper thin
o	Separates orbit from ethmoid air cells
•Body of the sphenoid

Question 14

Landmarks of the medial wall

Answer 14

• Fossa for the lacrimal sac

* Nasolacrimal canal

Question 15

Fossa for the lacrimal sac

Answer 15

o Formed by the maxillary and lacrimal bones
o Anterior and posterior borders are the lacrimal crests
 Anterior lacrimal crest on maxillary bone
 Posterior lacrimal crest on lacrimal bone
o Contains the lacrimal sac

Question 16

Nasolacrimal canal

Answer 16

Bony canal within the maxilla that is continuous with the fossa for the lacrimal sac
o Below the level of the orbital floor
o Leads inferiorly into the inferior meatus of the nasal cavity
o Contains the nasolacrimal duct

Question 17

Features of the floor of the orbit

Answer 17

 Triangular
 Separated from the lateral wall by the IOF
 Frequently fractured due to the thinness of the floor and presence of the infraorbital groove and canal where the orbital floor is the thinnest

Question 18

Bones of the floor of the orbit

Answer 18

•	Maxillary bone
o	Largest part of the orbital floor
•	Zygomatic bone
•	Palatine bone
o	Smallest part of the orbital floor
o	Most posterior in the floor

Question 19

Landmarks of the floor of the orbit

Answer 19

• Infraorbital groove, canal and foramen
• Nasolacrimal canal
o Anterior-medial on the floor of the orbit

Question 20

Infraorbital groove

Answer 20

o Groove runs forward from the IOF
o Canal is formed when the groove acquires a roof with the maxillary bone
o Foramen is where the canal opens onto the face
o Transmits the infraorbital nerve, artery and vein

Question 21

Anatomical relationship of the roof of the orbit

Answer 21

 Can damage the frontal lobe and meninges of the brain
 Frontal sinus cyst can enlarge into the thin roof of the orbit
 Fracture of the superior orbital margin can damage the trochlea leading to superior oblique paralysis
 Lacrimal gland can be damaged

Question 22

Which two walls of the orbit are the weakest?

Answer 22

Floor and medial wall

Question 23

Inferior Orbital Fissure

Answer 23

 Separates lateral wall and floor of the orbit
 Lies between the greater and lesser wings of sphenoid
 Connects
• Pterygopalatine fossa and infratemporal fossa to the orbit
 Transmits
• Infraorbital artery and vein
• Infraorbital nerve
• Zygomatic nerve
o Postganglionic parasympathetic fibers to the lacrimal gland (hitch-hiking)
• Inferior Ophthalmic vein

Question 24

Supraorbital Foramen

Answer 24

AKA supraorbital notch
Transmits
• Supraorbital artery, vein and nerve

Question 25

Anterior Ethmoidal foramen

Answer 25

Transmits | • Anteriror ethmoidal artery and nerve

Question 26

Posterior Ethmoidal Foramen

Answer 26

Transmits | • Posterior ethmoidal artery and nerve

Question 27

Zygomatic Foramina

Answer 27

``` Zygomatico-orbital foramen •Transmits oZygomatic nerve Zygomaticofacial foramen • Transmits o Zygomaticofacial nerve Zygomaticotemporal foramen • Transmits o Zygomaticotemporal nerve ```

Question 28

Orbital Rim

Answer 28

the sharp edge of the orbital opening, which is the peripheral border of the base of the pyramid-shaped orbit

Question 29

Orbital Margin

Answer 29

o It is quadrangular in shape with rounded corners o The dimensions of the margin (height, width, depth)  Horizontal diameter – 40 mm  Vertical diameter – 35 mm

Question 30

Bones of the superior orbital margin

Answer 30

* Superior orbital margin | * Frontal bone

Question 31

Bones of the inferior orbital margin

Answer 31

* Zygomatic bone | * Maxillary bone

Question 32

Bones of the lateral orbital margin

Answer 32

* STRONGEST and most exposed part of margin * Frontal bone * Zygomatic bone * Weakest part is at the suture between the frontal and zygomatic bones

Question 33

Bones of the medial orbital margin

Answer 33

* Maxillary bone | * Frontal bone

Question 34

Why is the orbital margin the strongest part of the orbit?

Answer 34

 All three bones are usually thick at the orbital margin |  The sutures by which the bones connect are extensive

Question 35

What is a blow out fracture?

Answer 35

o Refers to the rupture of the orbital bones o The margin will remain intact but the bones will fracture away from the site of impact  The orbital plates within the orbit are relatively thin and easily broken, which leads to a blow out fracture o Usually occurs when an object larger than the orbit strikes the orbital margin  Causes compression of the orbital contents and a sudden increase in intraorbital pressure  The shock wave of this travels through the site of impact and: • Causes a fracture in one of the orbital walls at one of the weaker points in the bone • May cause expulsion of the soft tissue through the fracture site o The blow out fracture is a safety mechanism to prevent the rupture of the eyeball

Question 36

Most common sites of a blowout fracture?

Answer 36

 Maxillary bone by the infraorbital groove |  Lamina paprycea of ehtmoid

Question 37

Symptoms of a blow out fracture

Answer 37

 Black eye (ecchymosis)  Loss of sensation along the distribution of nerves on the floor or medial wall of orbit  Diplopia, due to restriction of ocular motility  Enophthalmos – posterior displacement of the eye in the orbit • Leads to a smaller palpebral fissure on the affected side

Question 38

Treatment of a blowout fracture

Answer 38

* Antibiotics * Steroids to reduce orbital edema if present * Resect perioorbita * Repair fracture using bone grafts, synthetic materials like silicone or MEDPOR

Question 39

Orbital openings

Answer 39

``` o Optic Canal  Connects orbit to middle cranial fossa oSuperior Orbital Fissure  Connects the middle cranial fossa to the orbit o Inferior Orbital Fissure  Connects PP fossa ```

Question 40

What does the optic canal transmit

Answer 40

Optic nerve | Ophthalmic artery

Question 41

What does the Superior Orbital Fissure transmit?

Answer 41

```  Lacrimal N (CN V1)  Frontal N (CN V1)  Trochlear N (CN IV)  Superior and inferior division of oculomotor nerve (CN III)  Nasociliary N (CN V1)  Abducens N (CN VI)  Superior Opthalmic V  Inferior Ophthalmic V ```

Question 42

What does the inferior orbital fissure transmit?

Answer 42

???

Question 43

What is the periorbita?

Answer 43

It is the orbital periosteum  Covers all of the bones of the orbit, the entire inner surface of the orbit  Contains nerves and blood vessels that can penetrate the bone and provide innervation and nutrients  Bands of CT that extend from the periorobita to CT surrounding the eyeball provide structural support for the eyeball • Has extensions to hold the trochlea in place, enclose the lacrimal sac and the lacrimal gland  Provides temporary resistance to the spread of infections and tumors from paranasal sinuses into the orbit

Question 44

Attachments of the periorbita?

Answer 44

```  Firmly attached • Orbital margin • Suture lines • Foramina • Fissures • Lacrimal fossa  Loosely attached • Everywhere else • Can be easily detached by accumulations of blood or pus from trauma, which will push on the eyeball and other orbital contents ```

Question 45

What is the periorbita directly continuous with?

Answer 45

```  Posteriorly •At the optic canal •Continuous with the periosteal layer of the dura surrounding the optic nerve  Anteriorly •Periosteum of skull bones of the face o Zygomatic bone o Frontal bone o Maxillary bone •Orbital septum ```

Question 46

What is the orbital septum?

Answer 46

o Connective tissue membrane that extends from the orbital margin towards the tarsal plates of the eyelids (through the center of the eyelid) o Separates the contents of the eyelids from the orbital contents

Question 47

Insertions of the orbital septum

Answer 47

 Upper eyelid • Aponeurosis of levator palpebrae superioris, NOT into the superior tarsal plate  Lower eyelid • Orbital septum fuses with the fascia of the inferior tarsal muscle and together they insert into the inferior border of the tarsal plate

Question 48

Functions of the orbital septum

Answer 48

 Anatomic barrier to infection, hemorrhage and edema  Prevents the spread of blood or inflammation from the eyelid to the orbit  Holds orbital fat in position  MAIN FUNCTION is to prevent infections from entering the orbit

Question 49

Preseptal cellulitis

Answer 49

* generalized inflammation or infection of the tissues of the eyelid anterior to the orbital deptum * Most commonly occurs secondary to a staphylococcal or streptococcal bacterial infection in the eyelid OR the extension of a paranasal sinus infection * The infection must involve the surrounding eyelid tissue

Question 50

Signs/symptoms of preseptal cellulitis

Answer 50

``` o Eyelids appear red and swollen, warm and may be painful or tender to the touch o Patient may be unable to open eyelid due to eyelid edema o NO:  No disturbance in visual acuity  No proptosis  No pain with eye movement  No restriction of eye movement  Pupils are normal ```

Question 51

Treatment of preseptal cellulitis

Answer 51

Oral antibiotics

Question 52

Orbital Cellulitis

Answer 52

• generalized inflammation or infection of the soft tissues posterior to the orbital septum • Most commonly occurs secondary to a staphylococcal or streptococcal bacterial infection o I.e. orbital trauma, paranasal sinus infections, complication of orbital or paranasal surgery, tooth infection spreading, penetrating injury, etc o Most common cause is paranasal sinus infections in children

Question 53

Signs/Symptoms of orbital cellulitis

Answer 53

``` o Eyelid edema o Redness and distension (swelling and tightness) of the lid and surrounding orbital skin o Difficulty opening the eyelid o Significant pain upon palpation o Swollen conjunctiva (chemosis) o Conjunctival vessels congested o Fever o There IS proptosis (forward displacement of the eyeball) o Pain on eye movement o Restriction of eye movement ```

Question 54

Which is more serious - preseptal or orbital cellulitis?

Answer 54

Orbital cellulitis • Considered a serious medical issue because if left untreated it could lead to severe vision-threatening complications and life threatening complications (like meningitis, intracranial abscesses or cavernous sinus infections)

Question 55

Treatment for orbital cellulitis

Answer 55

Hospitalization to receive antibiotics intravenously (IV)

Question 56

What nerves should pierce the orbital septum?

Answer 56

 Nerves and vessels that are trying to reach the eyelids, face, forehead that do NOT pass through a foramen or notch

Question 57

Annulus of Zinn

Answer 57

AKA common tendinous ring  The thickening of the periorbita posteriorly around the optic canal and central part of the superior orbital fissure  Located at the apex of the orbit  Oval tendinous ring  Attaches to the lesser and greater wings of the sphenoid  Surround the optic canal and a portion of SOF  Forms the origin for tendons of the four rectus muscles (LR, MR, SR, IR)

Question 58

What structures pass through the Superior orbital fissure and then ABOVE the common tendinous ring?

Answer 58

``` Mneumonic: LF STUNALI • Frontal nerve – in the orbit is when it divides into supraorbital and supratrochlear nerves • Trochlear Nerve (CN IV) • Lacrimal N • Superior Ophthlamic Vein ```

Question 59

What structures pass through the Superior orbital fissure and then THROUGH the common tendinous ring?

Answer 59

* Superior Division of CN III * Inferior Division of CN III * CN VI * Nasociliary N

Question 60

What structures pass through the Superior orbital fissure and then BELOW the common tendinous ring?

Answer 60

Inferior Ophthalmic Vein

Question 61

What structures pass through the optic canal and then THROUGH the common tendinous ring?

Answer 61

Optic Nerve | Ophthalmic artery

Question 62

Spaces lying above the orbit

Answer 62

Anterior cranial fossa | (In some people) frontal sinus

Question 63

Spaces lying medial to the orbit

Answer 63

 Ehtmoidal sinuses  Sphenoid sinus  Nasal cavity

Question 64

Spaces lying below the orbit

Answer 64

maxillary sinus

Question 65

Spaces lying posterior to the orbit

Answer 65

Middle cranial fossa

Question 66

Paranasal sinus locations

Answer 66

 Located in four bones of the skull

Question 67

Frontal sinuses

Answer 67

Right and Left • Superior to the orbits in the frontal bone • Behind the supracilliary arches • MAY extend posteriorly into the orbital plate of the frontal bone allowing infections to spread through the thin orbital roof into the orbit or anterior cranial fossa

Question 68

Frontal sinus relationships to other structures

Answer 68

o Posterior – anterior cranial fossa o Superior – anterior cranial fossa and meninges of the frontal lobe (if frontal sinus is in orbital plate) o Inferior-medial – drains into the middle meatus

Question 69

Ethmoid Air cells/sinuses

Answer 69

Right and left • Medial to the orbits • Separated by lamina papyracea

Question 70

Relationship of anterior ethmoid air cells to other structures

Answer 70

``` Anteriorly - nothing Posteriorly - Middle air cells Superiorly - anterior cranial fossa and meninges of the frontal lobe Medially - middle meatus laterally - orbit ```

Question 71

Relationship of Middle ethmoid air cells to other structures

Answer 71

``` Anteriorly - anterior ethmoid air cells Posteriorly - posterior air cells Superiorly - anterior cranial fossa and meninges of the frontal lobe Medially - middle meatus laterally - orbit ```

Question 72

Relationship of posterior ethmoid air cells to other structures

Answer 72

``` Anteriorly - middle air cells Posteriorly - sphenoid sinus Superiorly - anterior cranial fossa and meninges of the frontal lobe Medially - superior meatus laterally - orbit ```

Question 73

Sphenoid sinuses

Answer 73

Right and left | • Posterior and medial to the orbit

Question 74

Relationship of sphenoid sinus to other strucutres

Answer 74

``` o Pituitary gland superior o Cavernous Sinuses laterally o Optic nerves as they exit the orbit o Posterior ethmoid air cells anteriorly o Orbit laterally from the sinus o Posterior cranial fossa ```

Question 75

Maxillary Sinuses

Answer 75

Right and Left • In the maxillary bone below the orbital floor and inferolateral to the nasal cavities • Floor is formed by the alveolar bone of the upper teeth

Question 76

Relationship of maxillary sinuses to other structures

Answer 76

o Superior – orbit o Medial – drains into middle meatus o Inferior – teeth and gums

Question 77

Computerized tomography scan (CT scan)

Answer 77

o CT scans use ionizing radiation in the form of x-rays, creating an image as if the examiner was standing at the foot of the bed and looking towards the head of a patient lying down  The machine measures the amount of radiation that passes through the body, reconstructing an image  Dense tissues block the passage of x-rays (like bone, so it appears gray) vs. less dense tissues (like air or fluids, which appear black)

Question 78

What can you see with CT scans and when should you use them?

Answer 78

 EOMs, optic nerves and major blood vessels can be distinguished in conjunction with bone on CT scans  Orbital tumors can be well visualized • The orbit has thin bones and the orbital fat provides good background contrast so dye is not needed • Tumors appear whitish, especially those containing calcium  Locations to use when you suspect • Bone fractures • Foreign bodies in the orbit (especially metallic structures) • Orbital tumors  ***don’t use on pregnant women***

Question 79

MRI

Answer 79

 Creates an image as if the examiner was standing at the foot of a bed and looking up at the head (left side of the body is on the right side of the image)  Uses a magnetic field to align the hydrogen atoms present in water and fat in the body tissues (shows a proton/water? Gradient) • CAN NOT USE IF METAL IS ANYWHERE IN THE BODY • Then uses low frequency radio waves whose energy is absorbed by the hydrogen ions • When the radio waves are turned off, the hydrogen atoms return to their original position, emitting the energy they had absorbed as weak radio signals that are stored and reconstructed by the MRI computer

Question 80

What can be seen and when should you use an MRI?

Answer 80

 Soft tissues composed of a large amount of hydrogen atoms are well defined (like the brain and spinal cord) • Gray matter of the brain is gray, white matter and fat are white, CSF or water is black, bone and air are black • Compact bone plates are black but the bone marrow is white  When to use an MRI • Higher resolution imaging of the nervous system than CT scans • Brain tumors • Neurologic diseases of the brain (like multiple sclerosis)