Lateral skull base
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LATERAL SKULL BASE. AMOLENDA, Patricia G. Anatomy. Internal auditory canal with the facial nerve Jugular Foramen Foramen lacerum Foramen ovale Foramen spinosum. Clinical Examination. The symptoms of the diseases of the lateral skull base may cause deficits of CN 7, 8, 9, 10, 11

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Lateral skull base


AMOLENDA, Patricia G.


  • Internal auditory canal with the facial nerve

  • Jugular Foramen

  • Foramen lacerum

  • Foramen ovale

  • Foramen spinosum

Clinical examination
Clinical Examination

  • The symptoms of the diseases of the lateral skull base may cause deficits of CN 7, 8, 9, 10, 11

  • CN testing

    • Oral cavity examination: CN 9 & 12

    • Indirect laryngoscopy: CN 10, recurrent laryngeal nerve

Clinical examination1
Clinical Examination

  • Cochleovestibular Syndrome

    • Sensorineural HL

    • Tinnitus

    • Dysequilibrium and vertigo

Clinical examination2
Clinical Examination

  • Jugular Foramen Syndrome

    • CN 9: palatal deviation

    • CN 10: unilateral vocal cord paralysis and dysphagia

    • CN 12: tongue deviation toward the affected side, lingual atrophy, lingual fasciculations

Clinical examination3
Clinical Examination

  • Petrous Apex Syndrome

    • Triad

      • Purulent otorrhea

      • Stabbing ipsilateral facial pain (Trigeminal nerve irritation)

      • Diplopia (CN 6 palsy in petrous apex abscess)

Imaging studies
Imaging Studies

  • CT Scan

    • Best for defining infiltration and destruction of bony structures

  • MRI

    • Better for defining and differentiating lesions especially tumor and inflammatory processes

  • Conventional Angiography

    • Assess disease processes in close proximity to major vessels

    • Embolization

Surgery of the lateral skull base
Surgery of the Lateral Skull Base

  • Intracranial-intradural

    • Most common: suboccipital and retrosigmoid approach

  • Intracranial-extradural (Transtemporal)

    • Exposes the petrous pyramid through a temporal craniotomy

    • The dura is separated from the surface of the petrous pyramid and elevated away from it with the temporal lobe

    • Used in surgical treatment of temporal bone fractures or tumors of the internal auditory canal

Surgery of the lateral skull base1
Surgery of the Lateral Skull Base

  • Extracranial-extradural (Transmastoid and infratemporal)

Classification of temporal bone fractures
Classification of Temporal Bone Fractures

  • Squama-mastoid Fractures

  • squLongitudinal temporal bone fracture

  • Transverse temporal bone fracture

  • Isolated meatal fracture

Squama mastoid fractures
Squama-mastoid Fractures

  • Confined to the temporal squama and mastoid air cells

  • Auditory and tympanic cavity may also be involved

Isolated meatal fracture
Isolated Meatal Fracture

  • Most often caused by a posterior displacement of the mandibular condyle

  • Usually due to a fall onto the chin

  • The fracture penetrates the posterior wall of the glenoid fossa and the anterior wall of the ear canal and is often associated with a condylar neck fracture

Longitudinal temporal bone fractures
Longitudinal Temporal bone Fractures

  • Most common burst fracture

  • Caused by a diffuse, lateral traumatizing force (ex. Falls, brain trauma)

  • Fracture along the EAC and the anterior border of the petrous pyramid

  • Symptoms: otorrhea (blood or blood with CSF), hearing loss, bloody rhinorrhea, facial paralysis

Longitudinal temporal bone fracture
Longitudinal Temporal Bone Fracture


  • Otoscopy: tearing of the meatal skin and TM, with bleeding into the ear canal

  • Clinical auditory testing (Weber test): lateralized to affected ear

  • Neurography: facial nerve function

  • Thin slice CT scan

  • Pure tone audiometry

Longitudinal temporal bone fracture1
Longitudinal Temporal Bone Fracture


  • Meningitis, OM w/ TM perforation, facial nerve paralysis


  • Cover the ear with sterile dressing

  • Corticosteroids: facial paralysis

  • Surgical exploration

Transverse temporal bone fractures
Transverse Temporal Bone Fractures

  • Fracture that runs across the petrous pyramid along the internal auditory canal and//or through the labyrinth

  • Caused by a traumatizing force in the frontal plane

  • Symptoms: severe vertigo, nausea and vomiting, deafness

Transverse temporal bone fracture
Transverse Temporal Bone Fracture


  • Clinicalexamination:

    • Weber Test-Lateralized to the normal ear

    • spontaneous nystagmus towards normal side

    • Otoscopy: hemotympanum

  • CT Scan

Transverse temporal bone fracture1
Transverse Temporal Bone Fracture


  • Meningitis, Facial nerve paralysis


  • Surgical closure

Otitis media
Otitis Media

  • most common inflammation and infection that affect the lateral skull base region

  • Cholesteatoma is one of its complications which arises from the middle ear and spreads to the lateral skull base

Tumors of the temporal bone
Tumors of the Temporal Bone

  • Paraganglioma

  • Primary Cholesteatoma or Epidermoid

  • Carcinoma of the Mucosa

  • Sarcoma

  • Lymphoma


  • Also glomustumor, chemodectoma

  • Most common tumor of the middle ear and adjacent lateral skull base

  • Arises from the paraganglia of the temporal region, most commonly in the area of the jugular bulb and along the neural plexus of the tympanic cavity

  • It may be located in the middle ear, jugular bulb, carotid bifurcation, and along the vagus nerve, and often extend to the temporal bone region


  • Manifestations: pulsatile tinnitus and conductive hearing loss, possible SNHL

  • Diagnosis: MRI, CT Scan, Angiography

  • Treatment: Surgery-subtotal petrosectomy

Tumors of the internal auditory canal and cerebellopontine angle
Tumors of the Internal Auditory Canal and Cerebellopontine Angle

  • Vestibular Schwanomma

  • Meningioma

  • Hemangioma

  • Lipoma

Vestibular schwanomma
Vestibular Schwanomma

  • Slow-growing, benign, tumor arising from the Schwann cells of CN 8, affecting more commonly the vestibular nerve

  • Medial tumors arise from the intracranial part of CN8 while the lateral tumors are located in the internal auditory canal

  • Clinical hallmark is a unilateral hearing disorder which may consist of tinnitus, hearing loss and dysacusis

Vestibular schwannoma
Vestibular Schwannoma

  • Medial schwannomas can occasionally produce trigeminal nerve symptoms such as facial pain or numbness in the jaw

  • Large tumors present with signs of brainstem compression and/or hydrocephalus with ataxia, nausea & vomiting

  • Diagnosis:

    • clinical examination: shows unilateral cochleovestibular d/o

    • Audiometry: shows retrocochlear impairment with lengthening of auditory brainstem reposnses

    • gadolinium enhanced MRI

Vestibular schwanomma1
Vestibular Schwanomma

  • <1cm: observe

  • 1-2.5cm: streotactic radiosurgery/ open surgery

  • >2.5cm: open surgery