Chapter 45 - Temporal Bone Trauma

Question 1

Most common site of injury to VII in T-bone trauma

Answer 1

perigeniculate region

Question 2

How often to patients with a skull fx after head trauma get a T bone fx?

Answer 2

14-22%

Question 3

How many T bone fxs are associated with intracranial injury? What about cervical spine injury?

Answer 3

90%

9%

Question 4

Name all structures passing near/through temporal bone that can be affected by Fx

Answer 4

VI, VII, VIII, IX, X, XI
ICA
IJ

Question 5

What type of membrane lines the mastoid?

Answer 5

Mucous membrane

Question 6

Longitudinal Fxs

Answer 6

80% of all
95% are otic capsule-sparing
Blunt trauma
Disrupt ossicles
Parallel to long axis of petrous pyramid to foramen lacerum
30% extend to opposite T bone
20% VII injury (usually bony impinge/intraneural hematoma)
Often produce CHL
TM may rupture, so possible CSF otorrhea
EAC often lacerated

Question 7

Transverse Fx

Answer 7

Less common, more morbid
20% of all
Severe blunt trauma occiput or frontal
More otic capsule disruption
50% VII injury rate (usually transection)
Severe SNHL or mixed, vertigo
TM likely intact, so CSF leak would present with rhinorrhea

Question 8

How otic capsule disruption presents

Answer 8

Sudden severe vertigo, SNHL

Question 9

What causes Battle’s sign

Answer 9

bleeding from mastoid emissary vein

Question 10

What causes raccoon eyes

Answer 10

Periorbital ecchymosis from middle and anterior cranial fossa fx
meningeal tears –> venous sinus bleeding into orbit

Question 11

Which arteries may be injured with T bone fx

Answer 11

Carotid, vertebral, middle meningeal

Question 12

Where can CN V be injured with T bone fx

Answer 12

surface of petrous bone in Meckel’s cave

Question 13

Where can CN VI be injured in T bone fx

Answer 13

Dorello’s canal

Question 14

How does cholesteatoma occur after T bone fx?

Answer 14

late finding, displaced canal skin or Tm skin into middle ear or mastoid space

Question 15

When to get T bone thin section HR CT after head trauma

Answer 15

facial paralysis, CSF leak, EAC fx/canal disruption, vascular injury, CHL, preop

Question 16

When to get carotid angiography/MRA/CTA after T bone fx

Answer 16

transient or persistent neurological deficit

Question 17

Findings that may warrant early surgical intervention with T bone Fx

Answer 17

facial nerve injury (esp immediate onset)
CSF leak
hearing loss
vertigo

Question 18

Slices necessary prior to facial nerve exploration

Answer 18

1mm (fine cut)

Question 19

How to examine VII in unconscious patient

Answer 19

Grimace in resp to pain
NET or MST 3-7d after injury…if lose stimulability within 1 wk injury, consider exploration
ENoG…if >90% degen at 6d and >95% in 14d, consider exploration

Question 20

Approaches for facial nerve decompression

Answer 20

If involve otic capsule, loss of hearing: translab
If hearing, otic sparing: transmastoid/supralab if well aerated mastoid or ossicular discontinuity, and transmastoid/mid cranial fossa if poorly aerated mastoid

Question 21

Percentage of T bone FXs with CSF leak

Answer 21

17%

Question 22

Will CSF leaks lead to meningitis with T bone fx?

Answer 22

If 7d or less leak, then 5-10% risk meningitis
If >7d, then 50-90% meningitis
Otic capsule fxs have greater meningitis risk due to inability of endochondral bone to remodel/heal

Question 23

Why not use prophy ABx with CSF leak

Answer 23

mask early infection

develop resistance

Question 24

What to do if CSF leak doesn’t resolve in 7d

Answer 24

lumbar drain 72 hr

consider surgical exploration

Question 25

How to treat otic disrupting fxs with profound HL

Answer 25

mastoidectomy

middle ear obliteration (w/ fat graft)

Question 26

Types of post-traumatic vertigo

Answer 26

• Concussion to membranous labyrinth: positional vertigo, NL VNG, tx sxs
• Ablative vertigo: otic capsule disrupting, intensity decreases after 7-10d then decreases over following 1-2 mo, unsteady 3-6 mo, with nystagmus beating away from fx side
• BPPV: delayed
• vertigo and fluctuating SNHL: perilymphatic fistula, initial tx conservatively
• endolymphatic hydrops: presents with sx of meniere’s, tx the same

Question 27

Which ossicle is most prone to injury with T bone fx

Answer 27

incus

minimal stabilizing elements

Question 28

How many CHL patients with T bone fx eventually return to NL

Answer 28

75%

So don’t explore surgically until 3-6mo later

Question 29

Causes of traumatic SNHL

Answer 29

otic capsule disruption
perilymphatic fistula
noise injury
concussion injury
direct injury to central auditory system

Question 30

Types of HL caused by different fx types

Answer 30

Long: CHL, high tone SNHL (inner ear concussion)
Trans: severe SNHL or mixed

Question 31

Which three things cause you to consider facial nerve exploration with paralysis post-trauma

Answer 31

immediate onset
ENoG 90% destroyed day 6, 95% destroyed day 14
evidence of nerve transection or bony impingement on CT
More than 90% of people without these factors recover to HB 1-2 without surgery

Question 32

Percentage of patients with immediate onset complete paralysis who will eventually return to normal

Answer 32

50%

Question 33

Algorithm to decide on facial nerve exploration

Answer 33

If acute onset and complete or progresses to complete, then do ENoG, and if >95% degen at 14d do exploration
If delayed onset, then observe