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April2012 Vol.49 Issue:      2 Table of Contents
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Surgical Results and Clinical Outcome of Medially Located Cerebello-Pontine Angle Meningiomas

Omar M. El-Falaky


Department of Neurosurgery, Cairo University; Egypt




ABSTRACT

Background: Meningiomas are the second most common tumor occupying the cerebello-pontine angle (CPA). Medially located tumors are more difficult to remove. A preoperative anticipation of the exact location of these tumors and relation to the neighboring neurovascular structures enables a proper surgical planning and thus better clinical outcome  Objective: The aim of this study is to analyze the results of a group of patients harboring cerebello-pontine angle meningiomas originating from the posterior petrous bone in relation with, or extending anterior to the internal auditory meatus, regarding the clinical presentation, surgical outcome, and complications. Methods: In a series of 9 patients with antero-medially located CPA meningiomas operated upon in Cairo University Hospitals between 2007 and 2011, data was collected and reviewed. A special emphasis was directed to tumor size, neurological presentation, site of tumor origin and extent of resection and post operative clinical outcome. Results: Gross total resection of the tumor (Simpson G I and II) was achieved in 78% (7/9 cases), subtotal resection in 2 cases. Acquired permanent facial nerve deficit occurred in one case (11%). No Acquired post operative hearing impairment was recorded. Conclusion: A thorough preoperative radiological evaluation anticipates the relationship of the tumor with the facial vestibulo-cochlear complex and coupled with intra operative microscopic view, helps a great deal in sparing injury of these nerves and thus minimizing the postoperative morbidity. The lateral sub occipital approach proved to be a reliable approach in such tumors. [Egypt J Neurol Psychiat Neurosurg.  2012; 49(2): 99-104]

 

Key Words: cerebello-pontine angle, meningioma, microsurgery, sub occipital approach

Correspondence to Omar M. El-Falaky, Department of Neurosurgery, Cairo University; Egypt.

E-mail: omarfalaky@hotmail.com   Tel.: 01223954993




 

INTRODUCTION

 

Meningiomas of the posterior cranial fossa comprise approximately 9% of all intracranial meningiomas.1 Of those posterior fossa meningiomas, 42% arise from the posterior surface of the petrous bone, and those are generally called CPA meningiomas in most series described in the literature.2 Meningiomas are considered the second most common tumors of the cerebelo-pontine-angle (CPA), accounting for 6.5% of cerebello-pontine angle (CPA) tumors with vestibular Shwanomas comprising the majority of tumors in this region. Although these lesions share the characteristic of critical relationships with neurovascular structures of the posterior fossa, they encompass a wide spectrum of distinct clinical and radiological situations linked to distinct prognoses.3 Cases included in this study are among the more surgically challenging, medially located CPA meningiomas.

 

 

PATIENTS AND METHODS

 

Patient Selection 

Between 2007 and 2011, 9 patients harboring meningiomas of the posterior surface of the petrous bone having their dural base related to or extending antero-medially beyond the internal auditory meatus were selected. The tumor localization was done by preoperative radiology and verified by intra-operative findings. Tumors mainly arising from the lateral surface of the clivus or extending from the cavernous sinus or the tentorium cerebelli were excluded from this study.

 

Pre operative assessment:

The patients included had a thorough neurological examination with documentation of pre operative data including assessment of the facial nerve functions and auditory functions. Computed Tomography (CT) Brain and Magnetic Resonance Imaging (MRI) with and without contrast were done for all cases preoperatively. Magnetic Resonance Angiography (MRA), CT Angiography or four vessel angiography were also done in case of vascular involvement. Radiological analysis of the exact tumor location, size and extension, were done, and the associated relation with near structures as the adjacent vascular structures, the tentorium cerebelli, the Trigeminal nerve, Facial nerve, vestibule-cochlear complex and the internal auditory meatus, and lower extension to the jugular foramen were all thoroughly studied.

Auditory assessment was done clinically and with pure tone audiometry in cases which presented with auditory impairment, followed by post operative assessment using the Gardner-Robertson hearing scale. Grades I and II are considered "useful hearing" and  Grade V for “Deaf”.4 Assessment of facial nerve function preoperatively and at postoperative follow up was based on the House–Brackmann scoring system.5

 

Surgical Approach

All cases were operated upon microscopically using the lateral sub occipital retro mastoid approach, surgical steps of the procedure have been previously well described in the literature.6,7 As a routine, the rim of the petrous bone adjacent to the sigmoid sinus up to the transverse-sigmoid junction, was drilled completely in order to improve exposure and visualization in all the cases. Lumbar drain was not used yet, whenever possible, drainage of the CPA cistern was done, to minimize cerebellar retraction.

 

Post operative clinical outcome and follow up:

All patients following the surgeries were kept in an intensive care unit at least for the first 24 hours. Patients received third generation cephalosporins intravenously for 3 days unless infection or wound collection was noted, in such situation antibiotics continued. A complete post operative neurological evaluation was performed for assessing the level of consciousness, cranial nerve deficits or any other neurological deficit. Morbidities such as wound infection, seizers, medical problems or neurological deterioration were also recorded.

Routine follow up CT Brain was done immediately post operative with a follow up MRI with contrast after 1 month of surgery. Assessment of the extent of resectability, tumor size, and clinical functional outcome focusing on the facial nerve and the cochlear functions, are also done.

 

RESULTS

 

Nine patients were included in the study: 7 females 78% and 2 males 22%. Age range 44-65 years mean age (52 years). Most prominent presenting symptom was headache in 89% (8/9 cases) of cases followed by hearing impairment and tinnitus in 56% (5/9 cases). Table (1) shows the clinical symptoms and signs found in the studied group of patients.

 

Operative Results

All patients were operated upon by the lateral sub occipital retro mastoid approach. Tumor sizes ranged between 2.5 and 5 cm (mean 3.6 cm). In 7 of 9 cases 78%, Gross total resection was achieved, in the remaining two patients it was decided to leave some tumor behind, in one of them the tumor was attached firmly to the brainstem and in the other case the tumor was extremely tough and difficult to excise totally without endangering the neighboring structures. Cases with subtotal resection were sent to radio surgery. Pathological analysis revealed Meningiothelial meningioma in 5 cases, transitional type in 2 cases and fibroblastic type in 2 cases.

 

Clinical Outcome and Complications

No mortality was recorded in this studied group, CSF leak occurred in 3 cases (33%), which resolved following the insertion of a post operative temporary lumbar drain and in 2 cases wound infection took place and responded well to antibiotic treatment. One case suffered a mild post operative hematoma at the site of surgery, yet resolved spontaneously without the need for surgical evacuation.

Incomplete bulbar palsy occurred in 2 cases, but improved with time with no permanent deficit. One patient developed post operative hydrocephalic changes 6 days following surgery and a ventriculo-peritoneal shunt was inserted.

Facial and auditory outcomes: Five cases suffered impaired hearing before surgeries and this was unchanged after surgery as no new hearing deficit was acquired. As for the facial nerve: one patient suffered facial weakness before surgery (G II) and was unchanged after surgery, New facial deficit was acquired in 3 cases post operatively (33%), one was permanent severe  facial  deficit (G V) and the other 2 were temporary (G II) and resolved within a month following surgery. Only one patient developed a permanent facial deficit (11%).

Table (2) demonstrates operative data and results of the studied patients. Illustrative cases of performed operations seen in Figures (1-5).


 

Table 1. Preoperative clinical presentation of the studied patients.

 

Symptoms

Patients

%

 

Signs

Patients

%

Hearing impairment

5

56%

 

CN. 5

3

33%

Headache

8

89%

 

CN. 7

1

11%

Gait disturbance

3

33%

 

CN. 8

5

56%

Facial pain

3

33%

 

Bulbar

-

--

Dizziness

-

-

 

Ataxia

3

33%

(CN: cranial nerve-Bulbar: Bulbar nerve palsy)

 
Tinnitus

5

56%

 

Nystagmus

-

--

Table 2. Demonstrating Tumor size, extent of resection, and Surgical Outcome and complications of the studied patients.

 

Patient

1

2

3

4

5

6

7

8

9

Age/sex

48/F

52/F

48/F

44/M

65/F

55/F

52/M

56/F

50/F

Tumor size (cm)

3 cm

2.5 cm

4 cm

2.5 cm

3.5 cm

4.8 cm

2.8 cm

4 cm

5 cm

Resection

Total

Total

Subtotal

Total

Total

Subtotal

Total

Total

Total

Outcome:

 

CN 7

+ temporary

 

 

 

 

+ as pre op.

 

+ temporary

+

CN 8*

 

 

+

+

 

+

 

+

+

Bulbar N

 

 

 

 

 

+ partial

 

+ partial

 

Complications:

 

Motor weakness

 

 

+

 

 

 

 

 

 

Hydrocephalus

 

 

+

 

 

 

 

 

 

CSF Leak

+

 

 

+

+

 

 

 

 

Infection

+

 

 

 

+

 

 

 

 

Hematoma

+

 

 

 

 

 

 

 

 

Adjuvant therapy

 

 

+

 

 

+

 

 

 

 (- Bulbar N: Bulbar nerve palsy- CN: Cranial Nerve –T: Total resection- ST: Subtotal resection)

*The 5 cases of hearing loss were manifesting preoperatively.

 

 

 

 

Figure 1. Illustrative case: MRI Brain with contrast axial cuts showing a CPA Meningioma originating from the antero medial portion of the posterior Surface of the petrous bone, situated Antero-Medial to the internal auditory meatus.

 

 

 

Figure 2. Post operative Ct Brain of the same patient revealing total removal of the tumor.

 

 

Figure 3. Intra operative photograph of the same patient showing tumor, Cranial nerves 5 and 7 and the internal auditory meatus (IOM). A safe working channel between the fifth and seventh cranial nerves is also demonstrated, through which, the tumor was totally resected.


 

Figure 4. Preoperative MRI Brain with contrast axial cut of another case revealing an enhancing

Right CPA Meningioma opposing the right internal auditory meatus.

 

 

 

Figure 5. Post operative CT Brain, of the same patient revealing total resection of the tumor.


DISCUSSION

 

The first CPA meningioma was described by Rokitansky in 1855.7 Yasargil, et al., asserted that meningiomas in this region should be classified into anterior petroclival meningiomas and posterior CPA meningiomas. 8 Samii and Ammirati, used the term CPA meningiomas in referring to the meningiomas arising from the posterior surface of the petrous bone, and based on the anatomical relationship with the IAC (internal auditory canal) they, classified them into two types: those anterior to the IAC and those posterior to the IAC.9 Schaller et al. divided them into pre meatal and retro meatal meningiomas, with worse surgical results in the pre meatal variety.10 Due to the complex anatomy of this region many other classifications have been suggested by other authors. Desgeorges et al. classified the posterior surface of the petrous bone into three equal zones according to imaging manifestation: zones A, M, and P (anterior, middle and posterior).11 Recently, Bassiouni et al. divided these lesions into five groups: retromeatal, premeatal, suprameatal, inframeatal, and centered on the internal acoustic meatus.12

In this study, the nine tumors   originated from the posterior surface of the petrous bone, at the internal auditory meatus or extending antero-medially beyond the meatus, which might coincide with the anterior group of Samii and Ammirati. Tumors totally originating posterior to the internal auditory meatus were not included. In this study, tumor size ranged between 2.5 to 5 cm with a mean of 3.6 cm which was similar to the anterior group of CPA meningiomas in the series of Samii and Ammirati were tumor size ranged between 2.5 to 6 cm. 9

Headache was the most common presentation in 89% of our cases, preoperative impaired hearing was present in 56% of cases compared to Bassiouni et al where impaired hearing presented in 54% of cases.12 The presence of facial pain in 34% of our cases (3/9 cases) preoperatively could be explained by the direct compression caused by the medially situated tumors on the trigeminal nerve. Preoperative facial nerve affection was present in only one case in this study (11%), which coincides with the series of Bassiouni et al. it was found in 6% of cases. This coincides with the literature were it is considered as a rare preoperative finding, in even in the presence of large tumors extending to the meatus.12  

Preoperative MRI Brain used in our cases proved to have a superior role in evaluating the exact tumor origin, and extensions around the meatus; it has also illuminated us about the degree of tumor vascularity and relation to eloquent neighboring neurovascular structures.

               Many surgical approaches have been described in the literature for resection of CPA meningiomas, like the Standard lateral sub occipital (retro sigmoid) approach, transpetrosal approach, trans labyrinthine, transcochlear, and middle fossa approach.13 -14

I used the standard lateral sub occipital approach in all our cases with emphasis on proper head positioning and routine drilling of the petrous bone during the craniectomy flush with the sigmoid sinus up to the transverse sigmoid junction. This allowed us to gain maximal exposure and visualization of the regional anatomy and tumor, improving our outcome. The direction and extent of displacement of the cranial nerves by the tumors in this study was quite variable, especially depending on the tumor size area of dural attachment, yet in the majority of cases, the facial vestibulo-cochlear complex was encountered in early stages of dissection. This early exposure should help in preserving those nerves yet we are forced to resect the tumor from in between those nerves. Dissecting through a window between the facial and trigeminal nerve as seen in Figure (3) seemed to be the safest maneuver in handling those nerves, compared to working below the facial and jeopardizing the bulbar nerves.

In this study total resection was achieved successfully in 78% of cases (7/9 cases), (Simpson G I and II) This extent of resectability compared Bassiouni et al who achieved total resection in 84% of their cases12, and to Samii and Ammirati who achieved total resection in 91% of their cases.9 A satisfactory facial nerve outcome was perceived in this study following the surgeries: 2 temporary deficits of GII which returned to normal within a month and only one permanent facial deficit 11% of our cases, with no new post operative hearing deficit.

 

Conclusion

Anterior CPA meningiomas remain a challenging and a difficult task to the neurosurgeon.  A thorough preoperative radiological evaluation anticipates the relationship of the tumor with the facial vestibulo-cochlear complex and coupled with intra operative microscopic view, and meticulous dissection, helps a great deal in sparing injury of these nerves and thus minimizing the postoperative morbidity.

The retro-sigmoid lateral sub-occipital approach has proved to be a safe and reliable approach in handling such tumors even in the more difficult   ane-meatal variety where the facial nerve gets in the way of removing the tumor.

Meticulous localization and delicate intra-operative handling of the cranial nerves crossing the CP angle is a crucial step for alleviating the surgical outcome of these tumors.

 

[Disclosure: Authors report no conflict of interest]

REFERENCES

 

1.      Quest DO. Meningiomas: an update. Neurosurgery. 1978; 3: 219-22.

2.      Al-Mefty O, Smith RR. Clival and petroclival meningiomas. In: Al-Mefty O,editor. Meningiomas. New York: Raven Press; 1991 pp. 517-37.

3.      Carney S, Ward V, Malluci C, O’Donoghue G, Robertson I, Baldwin D, Maw R, Coakham H. Meningioma involving the internal auditory canal: A diagnostic and surgical challenge. Skull Base Surgery. 1996; 9: 87-94.

4.      Gardner G, Robertson JH. Hearing preservation in unilateral acoustic neuroma surgery. Ann Otol Rhinol Laryngol. 1988; 97: 55-66.

5.      House JW, Brackmann DE.  Facial nerve grading system. Otolaryngol Head Neck Surg. 1985, 93: 146-147.

6.      Castellano F, Ruggiero G. Meningiomas of the posterior fossa. Acta Radiol .1953; 104: 1-177.

7.      Wu ZB, Yu CJ, and Guan SS. Posterior petrous meningiomas: 82 cases. J Neurosurg. 2005; 102: 284-289.

8.      Yasargil MG, Mortara RW, Curcic M. Meningiomas of the basal posterior cranial fossa. Adv Tech Stand Neurosurg. 1980; 7: 1-115.

9.      Samii M, Ammirati M. Cerebellopontine angle meningiomas. In: Al-Mefty O,editor. Meningiomas. New York Raven Press; 1991. pp. 503-15

10.    Schaller B, Merlo A, Gratzl O, Probst R. Premeatal and retromeatal cerebellopontine angle meningioma, Two distinct clinical entities. Acta Neurochir. 1999, 141: 465-71.

11.    Desgeorges M, Sterkers O, Poncet JL, Rey A, Sterkers JM. Chirurgie des meningiomes de la partie posterieure de la base du crane, 135 cas. Choix de la voie d’abord et resultats. Neurochirurgie 1995; 41: 265-94.

12.    Bassiouni H, Hunold A, Asgari S, Stolke D. Meningiomas of the posterior petrous bone: functional outcome after microsurgery. J Neurosurg. 2004; 100: 1014-24.

13.    Sekhar LN, Jannetta PJ. Cerebellopontine angle meningiomas; microsurgical excision and follow-up results. J Neurosurg. 1984; 60: 500-5.

14.    Roche PH, Lubrano V, Noudel R, Melot A,Regis J.  Decision making for the surgical approach of posterior petrous bone meningiomas. Neurosurg Focus. 2011; 30(5): 100-14.


 

الملخص العربي

 

النتائج الإكلينيكية لجراحات الأورام السحائية الداخلية لمنطقة الزاوية المخيخية الجسرية

 

مقدمة:

تعتبر الأورام السحائية ثاني أكثر الأورام انتشاراً بالزاوية المخيخية الجسرية وعندما تنمو هذه الأورام بالجزء الداخلي للعظمة الصخرية يمثل ذلك تحدياً جراحياً أكبر كي تتم إزالتها بصورة آمنة.

الهدف:

تقييم الأداء الجراحي والنتائج الإكلينيكية لإزالة هذه الأورام الداخلية والمرتبطة بالأعصاب القحفية الملازمة للمدخل العظمي لقناة العصب السمعي.

أساليب البحث:

تم أدراج تسعة مرضى في هذا البحث يعانون من الأورام المذكورة بين عامي 2007|2009 بمستشفيات جامعة القاهرة. تم تجميع بيانات للتاريخ المرضي والعرض الإكلينيكي والمدخل الجراحي ونتائج الجراحات لهذه الأورام وتم تحليل هذه النتائج.

نتائج البحث:

تم إزالة الأورام بصورة كاملة في 78% من الحالات وبصورة جزئية في 12% من الحالات (وقد تلقت هذه الحالات العلاج الاشعاعي) كما حدث خدل بالعصب السابع في حالة واحدة بعد الجراحة ولم يحدث إصابات جديدة في العصب السمعي في أي من الحالات.

الاستنتاج:

تمثل الأورام السحائية الداخلية للزاوية الجسرية تحدياً جراحياً كبيراً فالفحص الدقيق لهذه الأورام وعلاقتها بالأعصاب القحفية والشرايين عن طريق فحص الرنين المغناطيسي قبل الجراحة ومقارنة ذلك بالصورة الواقعية أثناء الجراحة يساعد على تلافي إصابة هذه الأعصاب والشرايين مما يساعد على تحسين النتائج الجراحية.



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