DIPARTIMENTO DI NEUROCHIRURGIA SECONDA UNIVERSITÀ … · 25/06/2010 Scaricato da 1 DIPARTIMENTO DI...

25/06/2010

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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


Thorough cranial nerve examExtra-ocular movementsExtra ocular movementsFunduscopic examFacial motor and sensory functionPneumatic otoscopy/Weber/RinneHitselberger’s signGag/TVC/SCM and trapezius


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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)


CT

MRI


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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


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


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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)


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


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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


Several histologic subtypessyncytialtransitionalfibrousangioblasticsarcomatous

Surgical excision with removal of underlying bonebone


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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


Facial nerve schwannoma

Cholesteatoma (epidermoid)

Lipoma

Arachnoid cyst


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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


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


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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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