orbital, frontal sinus anatomy, trauma, and surgical approaches

Question 1

each bony orbit is composed of __ # of bones
list them

Answer 1

seven
1. frontal bone
2. zygoma
3. maxilla
4. lacrimal
5. ethmoid
6. sphenoid
7. palatine bone

Question 2

orbital landmarks
medial orbital wall disection is safe ___mm from rim?
anterior ethmoid artery location in relation to lacrimal crest?
posterior ethmoid artery?
optic canal?

Answer 2

Medial orbital wall dissection is safe 25-30 mm from the rim
Anterior ethmoid artery is 24 mm from anterior lacrimal crest
Posterior ethmoid artery is 36 mm from anterior lacrimal crest
Optic canal is 42mm from the anterior lacrimal crest

Question 3

thinnest wall of orbit

Answer 3

medial wall - gets some strength from ethmoid air cells la

Question 4

lateral orbital wall anatomy

Answer 4

composed of zygoma, sphenoid and frontal bones

Question 5

orbital floor anatomy

Answer 5

composed of maxilla and zygomatic bone
roof of maxillary sinus
thin, anatomitcally weakened due to the passing of the infraorbital nerve

Question 6

inner / outer canthus?

Answer 6

corners of the eyes

Question 7

orbital blood supply from which artery

Answer 7

opthalmic artery from internal caroti

Question 8

nerves to orbit? number? innervation? course?

Answer 8

optic nerve : CN II
courses through optic canal / foramen into the sphenoid bone

opthalmic nerve : CN V: division I
branches just before entering the orbit via the superio orbital fissure

motor nerves: III (oculomotor) , IV (trochlear) , VI (abducens)

Question 9

gold standard for imaging if suspect orbital fracture

Answer 9

CT imaging

when isolated fracture, the mechanism of injury is likely due to increased intra-ocular pressure

identification is important - as changes in orital volume can affect vision and extra-occular movements
- diplopia, enopthalmos (sunken eyes), vertical diplopia

Question 10

orbital fractures involve which bone / wall most of the time?
indications for surgical intervention?

Answer 10

orbital floor fracture, medial wall (second most common) is involved 20 % of the time

usually not clinically notable until several weeks when diplopia is noted
clinical exam can be obscured by edema
CT axial allows most visualization

indications for surgical intervention?
- non resolving diplopia within 2-3 weeks
- enopthalmos greater than 2 mm
- defects larger than 1 cm
- clincially notable hypoglobus

if medial wall fractured - usually dx is made on limitations of abduction of the globe due to entrapment of the medial rectus muscle

Question 11

oculocardiac reflex

Answer 11

initiated by stretch receptors in the ocular and periorbital tissues – short and long ciliary nerves conduct impulses carrying sensory messages to ciliary ganglion

• causes severe bradycardia usually when traction is applied to extra-ocular eye muscles, esp the medial rectus, which can be caused by pressure on the globe, ocular trauma, traction on conjunctiva, or ocacasionally placement of a retorbulbar block
  affarent - ciliary nerves
  efferent- vagus (X)

Question 12

frontal sinus anatomy
arterial supply?

Answer 12

composed of anterior table, posterior table, and sinus floor

anterior tabnle is 2-12 mm thick
posterior is 0.1-4 mm thick
general capacity is 5-16 mL and height / width is 32x26 mm

arterial supply: anterior ethmoid, supraorbital and supratrochlear arteries

Question 13

frontal sinus drains where in most people?

Answer 13

frontal sinus drains directly into the middle meatus via an ostium for 85% of people
15% of people hve a true nasal frontal duct

Question 14

main goal in tx of frontal sinus trauma

Answer 14

protect intracranial contents and prevent post op infectious complications

anterior frontal sinus requires greater force to fracture than any other facial bone

Question 15

anterior table fracture NON displaced management?

Answer 15

observation and sinus precautions
- if no nasofrontal duct trauma / obstruction

Question 16

anterior table fracture displaced management?
include details of nasofrontal duct

Answer 16

if displaced anterior table but no nasofrontal duct obstruction manage with ORIF and sinus precautions

if displaced anterior table with nasofrontal duct obstruction manage with ORIF and obliteration

Question 17

T/F posterior table displacement will always have nasofrontal duct obstruction?

Answer 17

true - treat with ORIF, dural repair and cranialization, and nasofrontal duct obliteration
(posterior table displacement also always involves anterior table displacement)

Question 18

arterial supply to the frontal sinus

Answer 18

from anterior ethmoid artery and branches of the sphenopalatine artery via the mussel meatus

the supraorbital, anterior superficial temporal, anterior cerebral and middle meningeal arteries all supply the frontal bone

sinus is innervated by nerves that follow arterioles including the lateral posterior superior nasal branch of V2 (maxillary branch), and the anterior ethmoid nerve branch of V1( ophthalmic branch) of CN V

Question 19

preferred method of frontal sinus surgical approach

Answer 19

coronal flap
- rapidly and more bloodlessly provides complete access to the frontal bone
- more desirable esthetic outcome

or in area of existing laceration

Question 20

anterior table fracture of frontal sinus surgiacl managment

Answer 20

if anterior table fracture exists:
- if minimally displaced - does not require surgical management and usually largerly driven by cosmetic concerns

*use of sinus decongestants are useful

Question 21

inferior orbital fissure permits passage of

Answer 21

1. maxillary division of trigeminal nerve
2. infraorbital artery
3. branches of spenopalatine ganglion
4. branches of the inferio ophthalmic vein to pterygoid plexus