dipartimento di neurochirurgia seconda universitÀ … · 25/06/2010 scaricato da 1 dipartimento di...
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DIPARTIMENTO DI NEUROCHIRURGIA SECONDA UNIVERSITÀ DI NAPOLI
DIRETTORE: PROF. ALDO MORACI
Processi espansivi
dell’angolo ponto-cerebellare
Borders of cerebellopontine angle
Internal auditory canal
Compartments of CN VII and VIII
CN V, VI, IX, X and XI
Vascular structrures
John K. Yoo, M.D. Jeffrey T. Vrabec, M.D., 1997
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Unilateral sensorineural hearing lossSudden sensorineural hearing lossSudde se so eu a ea g ossUnilateral tinnitusVestibular symptomsFacial hypesthesia and weaknessDiplopiaHoarseness, dysphagia, aspiration
John K. Yoo, M.D. Jeffrey T. Vrabec, M.D., 1997
Thorough cranial nerve examExtra-ocular movementsExtra ocular movementsFunduscopic examFacial motor and sensory functionPneumatic otoscopy/Weber/RinneHitselberger’s signGag/TVC/SCM and trapezius
John K. Yoo, M.D. Jeffrey T. Vrabec, M.D., 1997
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Pure tone and speech discrimination audiometryaudiometry
Rollover
Impedance audiometryacoustic reflextone decay
A dito b ainstem e oked esponse (ABR)Auditory brainstem evoked response (ABR)Vestibular testing (ENG)
John K. Yoo, M.D. Jeffrey T. Vrabec, M.D., 1997
CT
MRI
John K. Yoo, M.D. Jeffrey T. Vrabec, M.D., 1997
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Benign slow growing tumors from Schwann cells surrounding CN VIIIcells surrounding CN VIII10% of the intracranial tumors and >90% of the CPA tumorsIncidence 0.1 to 2.5 per 100,000Associated with neurofibromatosisRate of growth 0.2 to 4.0 mm per year
John K. Yoo, M.D. Jeffrey T. Vrabec, M.D., 1997
Centered on IAC, spherical, enlarge the medial IAC acute bone tumor angleIAC, acute bone-tumor angleCT: isodense and enhances with contrastInhomogeneous due to cystic degeneration or intratumoral hemorragingMRI: isointense or hypointense on T1 and T2, b t b k dl h d T1but becomes markedly enhanced on T1-gadolinium
John K. Yoo, M.D. Jeffrey T. Vrabec, M.D., 1997
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ObservationSurgery for small intracanalicular tumorsSurgery for small intracanalicular tumorsSurgery for medium-sized tumors (1-3 cm)Surgery for only-hearing earSurgery for bilateral acoustic neuromas (Neurofibromatosis-type II)
John K. Yoo, M.D. Jeffrey T. Vrabec, M.D., 1997
15% of intracranial tumors and 3% of CPA tumorstumorsArise from cells lining the arachnoid villaBenign and do not metastasize, but locally aggressive because they invade boneSigns and symptoms referable to site of involvement
John K. Yoo, M.D. Jeffrey T. Vrabec, M.D., 1997
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Eccentric to IAC hyperostosis at medial IACHemispherical and sessile with obtuse boneHemispherical and sessile with obtuse bone-tumor angleCT: hypodense with calcification with marked enhancement; homogeneous MRI: isointense/hypointense on T1, but only moderate enhancement on T1-gadg
John K. Yoo, M.D. Jeffrey T. Vrabec, M.D., 1997
Several histologic subtypessyncytialtransitionalfibrousangioblasticsarcomatous
Surgical excision with removal of underlying bonebone
John K. Yoo, M.D. Jeffrey T. Vrabec, M.D., 1997
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Hamartomatous vascular malformationsArise from geniculate ganglion or at the IACse o ge cu ate ga g o o at t e CClosely associated with the facial nerveMRI: hyperintense on T2CT: intratumoral bone spicules and “honeycomb” pattern of surrounding boneTreatment is surgical excisionTreatment is surgical excision
John K. Yoo, M.D. Jeffrey T. Vrabec, M.D., 1997
Facial nerve schwannoma
Cholesteatoma (epidermoid)
Lipoma
Arachnoid cyst
John K. Yoo, M.D. Jeffrey T. Vrabec, M.D., 1997
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AdvantagesNo retraction of cerebellumNo retraction of cerebellumAllows good identification of CN VIIAllows good exposure of IACLess risk of CSF leak
DisadvantagesHearing is sacrificed
Technique
John K. Yoo, M.D. Jeffrey T. Vrabec, M.D., 1997
AdvantagesExcellent for intracanalicular tumors especially atExcellent for intracanalicular tumors, especially at the lateral end of the IACHearing preservation is possibleExtradural with low risk of CSF leak
DisadvantagesLack of access to CPA and posterior fossaNeed to retract temporal lobe
Technique
John K. Yoo, M.D. Jeffrey T. Vrabec, M.D., 1997
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AdvantagesHearing preservation is possibleA CPAAccess to CPA
DisadvantagesLimited access to lateral IAC/FundusDifficult to repairing or grafting CN VIIIncreased risk of air embolism/CSF leak/post-op headache Cerebellar retraction is necessaryCerebellar retraction is necessary
Technique
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Epidermoid tumours are developmentaldevelopmentalEpidermoid tumours are developmental developmental anomaliesanomalies, presenting as benign masses
that arise when retained ectodermal
implants from the closing neural tube
(normal developmental cells) are trapped trapped withinwithin the growing brain, usually in the
third and fourth week of gestation.
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They are probably caused by incorrect incorrect disj nctiondisj nction of ne oectode mal cells f omdisjunctiondisjunction of neuroectodermal cells from
cutaneous ones, and thus are not not neoplastic massesneoplastic masses, but can be
considered, and are sometimes called, "ectodermal heterotopia""ectodermal heterotopia" In this senseectodermal heterotopiaectodermal heterotopia . In this sense they are similar to dermoid masses, with
the only difference being that dermoids also have mesodermal cells.
Epidermoids are uncommon primary intracranial, mainly extra-axial, intradural masses
(representing 0.2-1% of all intracranial neoplasms). They are benign and slowly-growing usually presenting, because of this
reason, in early to mid-adulthood. In this case the tumor had an intra axial localization which isthe tumor had an intra-axial localization, which is unusual. The most common location is the CPA CPA (40%),(40%), and these lesions represent 5-7% of all
CPA tumours.Osborn,1991
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Epidermoids grow very slowly, thus the patient often presents late in the course of the disease
with symptoms similar to those of any mass lesion in the same location. Additionally, they
may present with recurrent episodes of aseptic aseptic (nonbacterial) meningitis(nonbacterial) meningitis caused by rupture of the cyst contents Other symptoms include feverthe cyst contents. Other symptoms include fever,
headaches, and neck stiffness.
Osborn,1991
The treatment of ECs relies exclusively on surgery. In the cerebellopontine angle, it
may be a technical challenge Whilemay be a technical challenge. While approaching the cyst, the surgeon has to negotiate around particularly brittle cortex
and vessels.
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The lesion often is intimately adherent to intimately adherent to allall cranial nerves and vessels of the cranial nerves and vessels of the ii B id i i t t h d thregionregion. Bridging veins are stretched over the
tumor and may bleed after debulking of the cyst. Anatomical landmarks may be lost
because of the size of the tumor.
A 38-year-old man with a 12-month history oftinnitus in the right ear,tinnitus in the right ear, unsteady gait, and vestibular signs on theright. T1-weighted MRI(TR, 400 ms; TE, 12 ms;EX, 2). Careful study of the signal in the cyst and comparison with the CSFallow distinction fromarachnoid cysts.
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Proton-density MRI
(TR 2000 ms; TE(TR, 2000 ms; TE,
50 ms; EX, 2) in
the axial plane.
Note the different
signal of cystsignal of cyst
content (straight arrow) and CSF
(curved arrow).
T2-weighted MRI
(TR, 2000 ms; TE
100 ms; EX, 2) in
th i l lthe axial plane.
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The only definitive treatment of epidermoid tumours is surgery, and they are referred to astumours is surgery, and they are referred to as "pearly tumours" because of their glistening white appearance on surgery. Total removal is Total removal is considered the ideal optionconsidered the ideal option, as partial removal leads to recurrence. However, total removal is often associated with significant significant morbiditymorbidity in the postoperative period and there is controversy regarding the optimal extent of removal.
The whole of the capsule should ideally be p y
removed with microscopic dissection, but
adherence of the capsule to the adherence of the capsule to the
important neurovascular structuresimportant neurovascular structures in
and around the tumour such as cranialand around the tumour, such as cranial
nerves, brain stem, or important vessels in
the CPA, often leads to its incomplete leads to its incomplete
removalremoval.
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Management These meningiomas may arise from any area of the dura on the posterior surface of the petrous bone. At operation p p pfour general categories are found:
1.Anterior to the internal auditory meatus, displacing the seventh and eighth nerves posteriorly and inferiorly. 2.Between the internal auditory meatus and the jugular foramen, displacing the seventh and eighth nerves superiorly. 3 S i t th i t l dit t3.Superior to the internal auditory meatus, displacing the seventh and eighth nerves anteriorly in the large tumors. 4.Surrounding the internal auditory meatus, with the seventh and eighth nerves engulfed in the tumor.
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In the past I often utilized angiographyangiography when a cerebellopontine angle meningioma was suspected. However, for most of these meningiomas it is now not necessaryis now not necessary, because the MRI usually gives all the information needed and in most patients the blood supply comesand in most patients the blood supply comes primarily through the dural attachment. Embolization has not been a consideration. Embolization has not been a consideration.
This 41-year-old woman noted increased numbness in the left side of her face and decreased hearing in her left ear. MRI axial TI images after gadolinium show the typical appearance of a meningioma, with the flat flat surface against the petrous surface against the petrous bone and the dural "tails."bone and the dural "tails."This tumor is arising anterior to the left internal auditory meatus. It may extend into the internal auditory meatus, as seen here.
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This 40-year-old woman had progressively decreased hearing in herdecreased hearing in her left ear and discomfort around her ear and the side of her head. There was normal recovery. MRI axial TI images afterMRI axial TI images after gadolinium show a large meningioma arising posterior to the left internal auditory meatus.
The microsurgical removal of CPA meningioma can be done by a suboccipital, translabrynthine, or suboccipital, translabrynthine, or middle fossa approachmiddle fossa approach. Good results from all ppppthree approaches have been reported by experienced groups of neurosurgeons. For most For most patientspatients we have preferred the suboccipital (posterior fossaposterior fossa) approach because of the wide visualization it allows, the ability to save hearing in appropriate cases, and the good results we and app op ate cases, a d t e good esu ts e a dothers have reported. In a few patients with no In a few patients with no useful hearinguseful hearing and intracanalicular tumors or with tumors extending a few millimeters into the posterior fossa, we have used a translabrynthine translabrynthine approach.approach.
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I use the supine positionsupine position with the ipsilateral shoulder slightly elevated and the head turned toshoulder slightly elevated and the head turned to the opposite side.This approach has worked well for visualization of the important anatomical structures, tumor removal, comfort of the operator, and avoidance of problems with air embolism or hypotensionof problems with air embolism or hypotension.
Other surgeons have used the sitting positionsitting position andachieved good results.
The key considerations in the operation include:
1.1. ExposureExposure of the tumor as described in acoustic neurinoma.
2.2. Interruption of the blood supplyInterruption of the blood supply along the
dural attachments.
3.3. Internal decompressionInternal decompression combined with
careful dissection of the tumor capsule from
the brainstem and cranial nerves.
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Cerebellopontine Angle MeningiomasaRemoval bOutcome Complications Recurrenc
eeAnterior
Posterior
Anterior
Posterior
Anterior
PosteriorT 14 13 Good 34 15 Permane
ntdeficit
3 0 5 Anterior
RST
10 1 Fair 3 0 Cerebellarinfarction
1 0
ST 18 1 Poor 4 (4) 0 Meningitis 1 0 0 Posterior
Death
1 0 CSF leak 1 0
aT, total removal ,RST, radical subtotal removal ST, subtotal removal bGood, free of major neurological deficit and able to return to previous activity level Fair, independent but not able to return to full activity because of new neurologicaldeficit or significant preoperative deficit that did not fully recover Poor, dependent.
Yasargil et al. (1980)Yasargil et al. (1980)reported that 27 of 30 patients had a good result and in 27 the tumor was "radically excised "and in 27 the tumor was radically excised. Sekhar and Jannetta (1987)Sekhar and Jannetta (1987)reported total removal in 14 of 22 patients, with no operative mortality and a good outcome in 16.Samii and Ammirati (1991)Samii and Ammirati (1991)reported total removal of all 24 tumors located posterior to the internal auditory meatus with aposterior to the internal auditory meatus, with a good outcome for 22 patients. Of 32 patients with tumors anterior to the internal auditory meatus, 29 had the tumors totally removed and 28 had a good outcome.
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