AMOLENDA, PATRICIA G.
LATERAL SKULL BASE
Anatomy
Internal auditory canal with the facial nerveJugular ForamenForamen lacerumForamen ovaleForamen 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 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)
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 FracturessquLongitudinal temporal bone fractureTransverse temporal bone fractureIsolated 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 chinThe 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 fractureCaused by a diffuse, lateral traumatizing
force (ex. Falls, brain trauma)Fracture along the EAC and the anterior
border of the petrous pyramidSymptoms: otorrhea (blood or blood with
CSF), hearing loss, bloody rhinorrhea, facial paralysis
Longitudinal Temporal Bone Fracture
DiagnosisOtoscopy: tearing of the meatal skin and TM,
with bleeding into the ear canal Clinical auditory testing (Weber test):
lateralized to affected earNeurography: facial nerve functionThin slice CT scanPure tone audiometry
Longitudinal Temporal Bone Fracture
ComplicationsMeningitis, OM w/ TM perforation, facial
nerve paralysisTreatmentCover the ear with sterile dressingCorticosteroids: facial paralysisSurgical 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
DiagnosisClinical examination:
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
ParagangliomaPrimary Cholesteatoma or EpidermoidCarcinoma of the MucosaSarcomaLymphoma
Paraganglioma
Also glomus tumor, chemodectomaMost common tumor of the middle ear and
adjacent lateral skull baseArises 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, AngiographyTreatment: Surgery-subtotal petrosectomy
Tumors of the Internal Auditory Canal and Cerebellopontine Angle
Vestibular SchwanommaMeningiomaHemangiomaLipoma
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: clinical examination: shows unilateral cochleovestibular
d/o Audiometry: shows retrocochlear impairment with
lengthening of auditory brainstem reposnses gadolinium enhanced MRI
Vestibular Schwanomma
<1cm: observe1-2.5cm: streotactic radiosurgery/ open
surgery>2.5cm: open surgery
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