Download Skull base approaches

Skull base approaches
 cranial base is classically divided into anterior, middle, and posterior segments.
 middle cranial base may be further subdivided into a single central and two lateral
compartments. These compartments may be distinguished when viewing the skull
base from extracranially if two imaginary parasagittal straight lines are drawn, one
on each side, through the medial pterygoid plate anteriorly and the occipital
condyle posteriorly. The central compartment lies medial to the two lines and the
lateral compartments lateral to them.
 Structures contained within the central compartment include the sella turcica,
lower sphenoid sinus and rostrum, nasopharynx, pterygopalatine fossa, and lower
clivus. Structures within the lateral compartments include the infratemporal fossa,
parapharyngeal space, and petrous portion of the temporal bone.
Spaces of the base of skull
 Parapharyngeal space
o potential space lateral to the upper pharynx.
o shaped like an inverted pyramid, extending from the skull base superiorly to
the greater horn of the hyoid bone inferiorly.
o fascia from the styloid process to the tensor veli palatini divides the PPS into
an anterolateral compartment (ie, prestyloid) and a posteromedial (ie,
poststyloid) compartment.
o The prestyloid compartment contains the retromandibular portion of the
deep lobe of the parotid gland, adipose tissue, and lymph nodes associated
with the parotid gland.
o The poststyloid compartment contains the internal carotid artery, the
internal jugular vein, CNs IX- XII, the sympathetic chain, and lymph nodes.
 Retropharyngeal space
o Extends behind the oesophagus into the posterior mediastinum to the
diaphragm
o located immediately posterior to the nasopharynx, oropharynx,
hypopharynx, larynx, and trachea.
o Boundaries
1. Anterior - Buccopharyngeal fascia which surrounds the pharynx,
trachea, esophagus, and thyroid
2. Posteriorly - alar fascia
3. Laterally by the carotid sheaths and parapharyngeal spaces. It
extends superiorly to the base of the skull and inferiorly to the
mediastinum at the level of the tracheal bifurcation
 Prevertebral space
o limited to T3
o Contains longus coli muscles, but also the paraspinous muscles, the vertebra,
the vertebral artery, and the spinal cord.
 Carotid space
o carotid artery, internal jugular vein, cranial nerves 9-11, internal. jugular
chain of nodes.
 Masticator space
o contains the muscles of mastication. These include the masticator,
temporalis, the medial and lateral pterygoids.
 Submandibular space
o contains the submandibular gland, submandibular nodes, and portions of the
facial vein and artery as well as the inferior branches of cranial nerve V
Infratemporal fossa
ITF is a potential space bounded
1. roof by the temporal bone and the greater wing of the sphenoid bone –
communicates with temporal fossa
2. medially by the superior constrictor muscle, the pharyngobasilar fascia, and the
pterygoid plates; tensor and levator palati
3. laterally by the zygoma, ramus of mandible, parotid gland, and masseter muscle
4. anteriorly, by the posterior surface of the mandible
5. posteriorly by the articular tubercle of the temporal bone, glenoid fossa, and
styloid process.
6. contains both the parapharyngeal space (ie, internal carotid artery [ICA],
internal jugular vein [IJV], cranial nerves [CN] IV to XII) and the masticator
space (ie, V3, internal maxillary artery [IMA], pterygoid venous plexus, pterygoid
muscles).
Skull base Approaches
 Modular disassembly of functional aesthetic units
Classification
1. Anterior
o Intracranial
i. Transfrontal (Level 1)
ii. Transfrontal nasal (Level 2)
iii. Transfrontal nasal orbital (Level 3)
o Extracranial
i. Transnasomaxillary (Level 4)
ii. Transmaxillary (level 5)
iii. Transpalatal (level 6)
2. Anterolateral
o Minifacial translocation
i. Medial
ii. Lateral
o Standard facial translocation
o Expanded facial translocation
i. Medial and inferior
ii. Posterior
iii. bilateral
 Advantage of anterior approaches over lateral and anterolateral
o Access is via avascular midline plane
o Vital neurovascular structures, TMJ and muscles of mastication avoided
o Avoid facial incisions (often)
Intracranial approaches
 Bicoronal incision
 Level 1 = frontal osteotomy
 Level 2 = frontal nasal osteotomy
 Level 3 = frontal-nasal, zygomaticoorbital osteotomy
 Frontogaleal flaps may be used to line defects
Extracranial approaches
 Level 4
o Modified Weber-Ferguson with extension across the the glabellar and opposite
subciliary margin
o Bilateral upper sulcus incisions
o Lefort II osteotomy
 Level 5
o Upper buccal sulcus incision
o Lefort I osteotomy with midline split
 Level 6
o Transpalatal
o U shaped cut around hard palate with septal split
Anterolateral approaches
Medial minifacial translocation
 Lesions of the medial orbit, sphenoid, ethmoid sinus and inferior clivus
 Incision along lateral side of nose
Lateral minifacial translocation
 Infratemporal fossa
 Incision from medial canthus to preauricular area and vertically along the
preauricular line
 Osteotomy of the zygomatic arch and malar eminence
Standard facial translocation
 Access to the entire anterolateral skull base
Medial Extended Facial Translocation
Inferior extended facial translocation
Posterior extended facial translocation
Approaches to Infratemporal fossa
1. extracranial
i. transtemporal
ii. infratemporal
iii. transfacial
2. intracranial
Infratemporal approaches
 preauricular incision
o approach provides inadequate exposure for the resection of tumors that
invade the tympanic bone and does not provide adequate access to the
intratemporal facial nerve or jugular bulb.
 postauricular approach
o better to expose and resect lesions that involve the temporal bone and that
extend into the ITF.
 transfacial approach
o best used to approach sinonasal tumors invading the ITF, the masticator
space, or the pterygomaxillary fossa and for tumors of the nasopharynx
extending into the ITF.
Approaches to Parapharyngeal space
 transoral
o removal of small, benign neoplasms that originate in the prestyloid PPS and
manifest as an oropharyngeal mass.
o limited exposure, inability to visualize the great vessels, and an increased
risk of facial nerve injury and tumor rupture
 transcervical
o method for removal of most poststyloid PPS tumors.
 Transcervical-transparotid approach
o For tumors arising from the deep lobe of the parotid, the transcervical
approach can be combined with a transparotid approach by extending the
incision superiorly as for parotidectomy. The facial nerve is identified and
dissected, superficial parotidectomy is performed, and the deep lobe portion
of the tumor is identified. The cervical incision allows access to the PPS
component of the tumor.
 Transcervical-transmandibular approach
o The transcervical approach may be combined with mandibulotomy when
better exposure is required. Such situations include very large tumors,
vascular tumors with superior PPS extension,
Approaches to Pterygomaxillary space
 Transfacial
 Transantral
 Transcervical with mandibular split