Chapter 45 - Temporal Bone Trauma Flashcards
Most common site of injury to VII in T-bone trauma
perigeniculate region
How often to patients with a skull fx after head trauma get a T bone fx?
14-22%
How many T bone fxs are associated with intracranial injury? What about cervical spine injury?
90%
9%
Name all structures passing near/through temporal bone that can be affected by Fx
VI, VII, VIII, IX, X, XI
ICA
IJ
What type of membrane lines the mastoid?
Mucous membrane
Longitudinal Fxs
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
Transverse Fx
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
How otic capsule disruption presents
Sudden severe vertigo, SNHL
What causes Battle’s sign
bleeding from mastoid emissary vein
What causes raccoon eyes
Periorbital ecchymosis from middle and anterior cranial fossa fx
meningeal tears –> venous sinus bleeding into orbit
Which arteries may be injured with T bone fx
Carotid, vertebral, middle meningeal
Where can CN V be injured with T bone fx
surface of petrous bone in Meckel’s cave
Where can CN VI be injured in T bone fx
Dorello’s canal
How does cholesteatoma occur after T bone fx?
late finding, displaced canal skin or Tm skin into middle ear or mastoid space
When to get T bone thin section HR CT after head trauma
facial paralysis, CSF leak, EAC fx/canal disruption, vascular injury, CHL, preop
When to get carotid angiography/MRA/CTA after T bone fx
transient or persistent neurological deficit
Findings that may warrant early surgical intervention with T bone Fx
facial nerve injury (esp immediate onset)
CSF leak
hearing loss
vertigo
Slices necessary prior to facial nerve exploration
1mm (fine cut)
How to examine VII in unconscious patient
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
Approaches for facial nerve decompression
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
Percentage of T bone FXs with CSF leak
17%
Will CSF leaks lead to meningitis with T bone fx?
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
Why not use prophy ABx with CSF leak
mask early infection
develop resistance
What to do if CSF leak doesn’t resolve in 7d
lumbar drain 72 hr
consider surgical exploration
How to treat otic disrupting fxs with profound HL
mastoidectomy
middle ear obliteration (w/ fat graft)
Types of post-traumatic vertigo
- 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
Which ossicle is most prone to injury with T bone fx
incus
minimal stabilizing elements
How many CHL patients with T bone fx eventually return to NL
75%
So don’t explore surgically until 3-6mo later
Causes of traumatic SNHL
otic capsule disruption perilymphatic fistula noise injury concussion injury direct injury to central auditory system
Types of HL caused by different fx types
Long: CHL, high tone SNHL (inner ear concussion)
Trans: severe SNHL or mixed
Which three things cause you to consider facial nerve exploration with paralysis post-trauma
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
Percentage of patients with immediate onset complete paralysis who will eventually return to normal
50%
Algorithm to decide on facial nerve exploration
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
