Tegmen Defects (Tympani and Mastoideum)

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Associated articles
Intracranial Hypotension

FACTS

Tegmen anatomy review: Tympanum vs. Mastoideum
  • Tegmen is the roof of the middle ear/mastoid
  • It is divided into the tympanum and mastoidum, which are continuous thin plates of bone forming parts of the tegmen, but associated with a different air space in the temporal bone.
Feature
Tegmen Tympani
Tegmen Mastoideum
Location
Roof of the tympanic cavity (middle ear)
Roof of the mastoid antrum and mastoid air cells
Position
Medial, Anterior
Lateral, posterior
Part of temporal bone
Petrous part
mastoid part
Function
Separates the middle ear cavity from the middle cranial fossa
Separates the mastoid antrum and air cells from the middle cranial fossa
Clinical relevance
Defects here can lead to CSF otorrhea, meningitis, or brain herniation into the middle ear
Defects can cause intracranial spread of mastoid infections (e.g., meningitis or brain abscess)
Development
Usually ossifies earlier; thinner and more prone to congenital defects
Often thicker but can also be dehiscent or eroded in chronic infections
Helpful website to explore temporal bone structures:
http://uwmsk.org/temporalbone/atlas.html

HPI

universal ROS
  • congenital risk factors: any syndromic craniofacial anomalies at birth?
  • acquired risk factors
    • chronic otitis media / cholesteatoma / mastoiditis with resultant infection/inflammation can lead to bony erosion / sclerosis of bony roof
  • iatrogenic risk factors
    • any history of ear surgery (mastoidectomy or tympanoplasty)
  • elevated ICP review of symptoms (pressure erosion of tegmen)
  • obesity (IIH associated CSF leaks)
  • any head / facial trauma

PHYSICAL EXAM

universal neuro exam
  • careful assessment for facial symmetry
  • evaluate for rhinorrhea on chest to chin provocation
  • evaluate for otorrhea from both ears
  • evaluate for diplopia, upgaze palsy
  • evaluate for meningismus
  • evaluate for hearing loss

IMAGING

CTH thin cut from vertex to to evaluate for any fractures / defects in anterior/middle cranial fossa
  • include temporal bone sequences (thin-cut coronal through EAC/IAC)
  • include max-face sequences (thin-cut coronal through face)
MRI skull base w/wo (with fat sat images)
  • FIESTA sequences (non-con) are adequate to see encephocele
  • contrasted fat-sat sequences are reasonable to evaluate for radiographic meningitis
A/P
Operative options:
  • Middle cranial fossa craniotomy to approach the defect and repair it
  • reconstruction options: deep temporalis fascia, Surgicel, bone plug
 

Examples

6 year old child with severe TBI and numerous skull fractures

6 year old child who suffered fall off a bicycle with bilateral temporal bone fractures including displaced fracture of the L parietal calvarium with associated longitudinal fracture through L temporal bone sparing otic capsule. He underwent operative primary repair of fracture with cautery of a subtemporal meningoencephalocele and repair using tepmoralis fascia.
6 year old child who suffered fall off a bicycle with bilateral temporal bone fractures including displaced fracture of the L parietal calvarium with associated longitudinal fracture through L temporal bone sparing otic capsule. He underwent operative primary repair of fracture with cautery of a subtemporal meningoencephalocele and repair using tepmoralis fascia.
 

Middle aged male with history of L ear surgery

Normal tegmen tympanum and mastoideum on the right and defective tympanum/mastoideum on the left in a patient with history of a left cholesteatoma with a left canal, wall down tympanomastoidectomy who presented years later with CSF otorrhea on the left and underwent a L temporal craniotomy with temporal fascia repair.
Normal tegmen tympanum and mastoideum on the right and defective tympanum/mastoideum on the left in a patient with history of a left cholesteatoma with a left canal, wall down tympanomastoidectomy who presented years later with CSF otorrhea on the left and underwent a L temporal craniotomy with temporal fascia repair.
An associated encephalocele is demonstrated in the coronal plane on this patient’s pre-operative MRI skull-base with contrast fat-sat sequence (LEFT) and FIESTA (RIGHT).
An associated encephalocele is demonstrated in the coronal plane on this patient’s pre-operative MRI skull-base with contrast fat-sat sequence (LEFT) and FIESTA (RIGHT).