Download LATERAL SKULL BASE

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
 CN testing
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Oral cavity examination: CN 9 & 12
Indirect laryngoscopy: CN 10, recurrent laryngeal nerve
Clinical Examination
 Cochleovestibular Syndrome
 Sensorineural HL
 Tinnitus
 Dysequilibrium and vertigo
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 Examination
 Petrous Apex Syndrome
 Triad
Purulent otorrhea
 Stabbing ipsilateral facial pain (Trigeminal nerve irritation)
 Diplopia (CN 6 palsy in petrous apex abscess)
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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
• 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 Base
 Extracranial-extradural (Transmastoid and
infratemporal)
Laterobasal Fractures
Classification of Temporal Bone Fractures
 Squama-mastoid Fractures
 squLongitudinal temporal bone fracture
 Transverse temporal bone fracture
 Isolated meatal fracture
Squama-mastoid Fractures
 Confined to the temporal squama and mastoid air
cells
 Auditory and tympanic cavity may also be involved
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
 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
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 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
 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
Diagnosis
 Clinical examination:
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Weber Test-Lateralized to the normal ear
spontaneous nystagmus towards normal side
Otoscopy: hemotympanum
 CT Scan
Transverse Temporal Bone Fracture
Complication

Meningitis, Facial nerve paralysis
Treatment

Surgical closure
Inflammations and Tumors of
the Lateral Skull Base
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
 Paraganglioma
 Primary Cholesteatoma or Epidermoid
 Carcinoma of the Mucosa
 Sarcoma
 Lymphoma
Paraganglioma
 Also glomus tumor, 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
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
 Vestibular Schwanomma
 Meningioma
 Hemangioma
 Lipoma
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
 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:
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clinical examination: shows unilateral cochleovestibular d/o
Audiometry: shows retrocochlear impairment with lengthening of
auditory brainstem reposnses
gadolinium enhanced MRI
Vestibular Schwanomma
 <1cm: observe
 1-2.5cm: streotactic radiosurgery/ open surgery
 >2.5cm: open surgery