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

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Lateral skull base

LATERAL SKULL BASE

AMOLENDA, Patricia G.


Anatomy

Anatomy

  • 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)


Laterobasal fractures

Laterobasal Fractures


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

Diagnosis

  • 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

Complications

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

    Treatment

  • 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

Diagnosis

  • 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

Complication

  • Meningitis, Facial nerve paralysis

    Treatment

  • Surgical closure


Inflammations and tumors of the lateral skull base

Inflammations and Tumors of the Lateral Skull Base


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


Paraganglioma

Paraganglioma

  • 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


Paraganglioma1

Paraganglioma

  • 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


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