Download Imaging of the anterior and central skull base as a guide

Imaging of the anterior and central skull base as a guide for
endoscopic skull surgery
Poster No.:
C-0264
Congress:
ECR 2015
Type:
Educational Exhibit
Authors:
L. Oleaga Zufiría, I. Alobid, J. Berenguer, I. Valduvieco, E. Verger;
Barcelona/ES
Keywords:
Head and neck, Anatomy, MR, CT, Diagnostic procedure,
Education, Image registration, Pathology, Image verification
DOI:
10.1594/ecr2015/C-0264
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Learning objectives
To learn the relevant anatomy to guide minimally invasive surgery of the anterior and
central skull base
To be aware of the most important imaging findings that influence treatment options
To evaluate CT and MRI imaging protocols, advantages and disadvantages of both
techniques
Background
ANATOMY OF THE ANTERIOR SKULL BASE
The anterior skull base separates the anterior cranial fossa superiorly from the paranasal
sinuses and orbits below.
The boundaries of the anterior skull base are anterolaterally the frontal bones, inferiorly
the ethmoid and frontal sinuses, orbit and orbital canals. Superiorly the frontal lobes and
the first cranial nerve and the boundaries with the central skull base are the lesser wing
of sphenoid bone and planum sphenoidale.
In the anterior skull base we have to identify different landmarks on imaging. The cribiform
plate, the lateral lamella and the orbital roof, on MRI we can identify the olfactory bulbs.
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Fig. 1: Sagittal CT image. Anatomic landmarks for endoscopic skull surgery
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
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Fig. 2: Coronal CT and Coronal T2W MRI. Anterior Skull base anatomy
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
There are five entry points in the skull base for anterior skull base minimally invasive
surgery, it is important to become familiar with the anatomy, to select the best entry point,
depending on the pathology.
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Fig. 3: Sagittal CT image with showing the entry points of surgical corridors for
endoscopic skull surgery
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
•Transfrontal 1
•Transcribriform 2
•Transplanum sphenoidale 3
•Transsellar 4
•Transclival 5
ANATOMY OF THE CENTRAL SKULL BASE
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The central skull base makes up the floor of the middle cranial fossa. It is composed
of the sphenoid and temporal bone anterior to the petrous ridge. It can be divided into
midline sagittal, parasagittal and lateral compartments.
It is separated from the anterior skull base by a line that follows the tubercullym sella,
the anterior clinoid processess, the posterior margin of the lesser sphenoid wings, and
the anterior and superior rim of the greater sphenoid wings. It is separated posteriorly
from the posterior skull base by a line that follows the dorsum sella and posterior clinoid
processes and petrous ridges laterally.
The central skull base might be divided in compartments: midline sagittal (MLS),
parasagittal (PS) and lateral (L) compartments.
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Fig. 4: Axial CT demonstrating the anatomic landmarks in central skull base
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
Fig. 5: Coronal T2W MRI demonstrating the anatomy of central skull base
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
Images for this section:
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Fig. 1: Sagittal CT image. Anatomic landmarks for endoscopic skull surgery
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Fig. 4: Axial CT demonstrating the anatomic landmarks in central skull base
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Fig. 3: Sagittal CT image with showing the entry points of surgical corridors for
endoscopic skull surgery
Page 10 of 28
Findings and procedure details
CT and MRI provide detailed anatomy of the skull base. Both are complementary
techniques. CT is an excellent modality for delineation of the bone structures and MRI
provides superior soft tissue contrast it is better to evaluate the intracranial extension of
the lesions.
The sagittal plane provides a good vision of the skull base to decide the best surgical
approach.
It is important to be aware of the contraindications to surgery that include, invasion of the
cavernous sinuses, optic nerves and chiasm.
ASSESSMENT OF LESION EXTENSION
CHECKLIST
•
•
•
•
•
•
•
Location and extention of the lesion
Amount of bony skull base involvement
Intracranial and orbital invasion
Cavernous sinus invasion
Cranial nerve and vessel involvement
Dural invasion
Optic nerve or quiasm invasion
ANTERIOR SKULL BASE LESIONS
Anterior skull base defects
•
Ethmoid meningoencephalocele
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Fig. 9: Meningoencephalocele
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
Fig. 10: Close up view of surgery of the meningoencephalocele
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
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Fig. 11: Repair and closure of the anterior skull defect with fascia lata
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
Fig. 12: Repaired meningoencephalocele
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
Ethmoid sinuses infections
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•
•
Rhinosinusitis
Mucocele
Fig. 19: Fungal rhinosinusitis with orbital and cranial invasion (yellow arrows)
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
Fig. 20: Right ethmoidal mucocele with orbital invasion (yellow arrows)
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References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
Esthesioneuroblastoma
Fig. 15: Esthesioneuroblastoma arising from the olfatry groove and invading the
ethmoid sinuses (red arrows) and extending into the nasopharynx
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
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Fig. 16: Close up view of the esthesioneuroblastoma at surgery
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
Fig. 17: Follow up MRI one year after surgery. Surgical changes with linear
enhancement in the ethmoid region extending to anterior skull base
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
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Fig. 18: Endoscopic image of the surgical cavity. The mucosa is vascularized and
shows a normal appearance
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
Ethmoid sinuses neoplasms
•
•
Benign (osteoma, fibrous dysplasia, meningioma)
Malignant (squamous cell, adenocarcinoma, lymphoma, undifferentiated
carcinoma, sarcoma)
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Fig. 21: Meningioma of the olfatory groove. Large mass in the anterior cranial fossa,
pushing the brain superiorly, invading the ethmoid sinuses below and extending to the
planum sphenoidale posteriorly (yellow arrows)
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
Page 18 of 28
Fig. 13: Sinonasal adenocarcinoma involving the right ethmoid sinuses and nasal
fossa. The anterior skull base is not invaded
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
Fig. 14: Close up view of the adenocarcioma at surgery
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
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Fig. 22: Lymphma involving the left ethmoidal cells (asterisk) infiltrating the lamina
papiracea and extending into the orbit (red arrows)
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
IMAGING ASSESMENT OF ASB INVASION
Invasion of the anterior cranial fossa is better depicted by MRI
When the tumor extends to de anterior cranial fossa three different situations can be
seen on imaging:
1.
2.
3.
The neoplasm contacts the ASB but there is not invasion
The neoplasm encroaches the cribriform plate, the dura is thickened but not
invaded (linear thickening <5mm and enhancement)
The neoplasm encroaches the dura (dural thickening >5mm, nodular
enhancement, pial enhancement)
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Fig. 6: Ethmoid sinuses squamous cell carcinoma CT demostrates the soft tissue
mass involving and destroying the sinuses, with orbital invasion. The bone window
shows destruction of the cribiform plate (red arrows) MRI shows the mass with no dural
thickening or enhancement (green arrows). MRI is superior to CT to rule out dural or
brain invasion
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
Page 21 of 28
Fig. 7: Intestinal-type sinonasal adenocarcinoma. MRI shows extension of the tumor to
the anterior skull base. The neoplasm encroaches the cribriform plate, T1W gadolium
enhanced MRI depicts the linear dural thickening (<5mmm) and enhancement (red
arrows). The dura is thickened but not invaded
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
Fig. 8: Intestinal-type adenocarcinoma MRI shows the neoplasm encroaching and
invading the dura. The dura is thickened (>5mm). T1W MRI with gadolinium depicts the
nodular dural and pial enhancement(red arrows)
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
Midline Sagittal CSB LESIONS
Originate from the greater sphenoid wing, cavernous sinus, cranial nerves and petroclival
synchondrosis
•
•
•
•
Sphenoid body, sphenoid sinus (infections, neoplasms)
Clivus (metastasis,plasmacytoma,chordoma,chondrosarcoma)
Sella turcica (macroadenoma, meningioma, craniopharyngioma)
Nasopharynx (infections, neoplasms)
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Fig. 23: Macroadenoma with suprasellar extension (red arrows)
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
Fig. 24: Intrasphenoid macroadenoma.The tumor originates in the pituitary gland with
intrasphenoid growth
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
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Fig. 25: Intrasellar and suprasellar lung metastasis
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
Fig. 26: Craniopharyngioma. Heterogeneous midline suprasellar mass with solid and
cystic components.The midline, the pituitary gland is displaced downward
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
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Fig. 27: Close up view of the clival chordoma surgery
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
Fig. 28: Clival chordoma. Midline soft tissue mass with cystic and low signal intensity
areas, with a characteristic pop corn type of enhancement
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References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
Parasagittal CSB LESIONS
Originate from the greater sphenoid wing, cavernous sinus, cranial nerves and petroclival
synchondrosis
•
•
Developmental lesions ( trans-sphenoidal cephaloceles)
Cavernous sinus lesions (primary and secondary cranial nerve tumors,
vascular lesions, meningiomas and inflammatory conditions)
Fig. 29: Chordoma arising at the petroclival junction. Parasagittal central skull
bilobulated enhancing mass
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
Lateral CSB LESIONS
The lateral CSB includes the lateral aspect of the greater sphenoid wings, the lateral
aspect of the temporal bone and the TMJ. It is a crossroads between the orbit, the middle
cranial fossa and temporal fossa
•
•
•
Meningiomas
Osteosarcomas
Metastasis
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•
•
Lymphoma
Synovial chondromatosis (TMJ)
Fig. 30: Masticator space lymphoma. Infiltrating process on the left masticator space
(red arrows),normal masticator space on the right (green arrows)
References: Dept. of Radiology, Hospital Clinic Barcelona - Barcelona/ES
Conclusion
CT and MRI have a key role in the evaluation of ASB and CSB
Cross sectional imaging has an important role in the evaluation of the skull base, it
provides important information about the location and extension of the lesions to allow a
better surgical planning and patient management
Personal information
References
1- DeMonte F. Management considerations for malignant tumors of the skull base.
Neurosurg Clin N Am 2013; 24:1-10
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2- Ivan M.E., Jahangiri A., El-Sayed I.H., MDb,c, Aghi M.K. Minimally invasive
approaches to the anterior skull base. Neurosurg Clin N Am 2013; 24:19-37
3- Choudhri AF1, Parmar HA, Morales RE, Gandhi D. Lesions of the skull base: imaging
for diagnosis and treatment. Otolaryngol Clin North Am. 2012; 45:1385-404
4- Borges A. Imaging of the central skull base. Neuroimaging Clin N Am. 2009;
19:669-696
5- Parmar H1, Gujar S, Shah G, Mukherji SK. Imaging of the anterior skull base.
Neuroimaging Clin N Am. 2009; 19:427-439
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