|Year : 2020 | Volume
| Issue : 1 | Page : 34-41
Surgical management of cerebellopontine angle tumors
Elsayed Sabah Mohammed Ali, Gasser Hasan Rabee Al Shyal, Abd Elfattah Abu El Fotoh Shehab
Department of Neurosurgery, Faculty of Medicine for Girls, Al-Azhar University, Cairo, Egypt
|Date of Submission||23-Dec-2019|
|Date of Decision||06-Jan-2020|
|Date of Acceptance||08-Jan-2020|
|Date of Web Publication||20-Apr-2020|
MD, PhD, IFAANS Gasser Hasan Rabee Al Shyal
Department of Neurosurgery, Faculty of Medicine for Girls, Al- Azhar University, Abbassyia St. Cairo
Source of Support: None, Conflict of Interest: None
Background Even though there is a high prevalence of tumors within the cerebellopontine angle (CPA), surgical management in this region remains a major obstacle owing to the critical neurovascular structures passing the CPA and constringed surgical access, with displayed complication rates.
Aims The current study was conducted to evaluate the various clinical and radiological modalities that are used for diagnosis of CPA tumors and planning of their surgeries. Additionally, it aimed to compare the various surgical strategies that have been used for excision of CPA tumors along with the assessment of cerebrospinal fluid diversion role in CPA surgery.
Patients and methods Patients with CPA tumor who have been diagnosed and treated surgically in 2-year interval between October 2017 and October 2019 were eligible for inclusion in the study. Surgeries were done via retrosigmoid or middle fossa approaches.
Results Patients experienced considerable improvement of the clinical symptoms especially intracranial tension, particularly those subordinated to preoperative shunt. Subsequent to that patients revealed dramatic improvement of the tinnitus, headache, vertigo, ataxia, and unsteadiness of gait after surgery. In addition, facial palsy was the most predominant complication succeeded by cerebellar ataxia, hematoma at the tumor bed, left-side hemiplegia, local wound infection, and meningitis.
Conclusion Retrosigmoid and middle fossa approaches accomplished significant outcome among patients with CPA tumors, counterpart hearing symptoms, bulbar affection, facial weakness, and cerebellar manifestations. Preoperative V-P shunt procedure improved noticeably the manifestations of increased intracranial tension.
Keywords: cerebellopontine angle tumors, middle fossa approach, retrosigmoid approach
|How to cite this article:|
Ali EM, Al Shyal GR, Abu El Fotoh Shehab AE. Surgical management of cerebellopontine angle tumors. Sci J Al-Azhar Med Fac Girls 2020;4:34-41
|How to cite this URL:|
Ali EM, Al Shyal GR, Abu El Fotoh Shehab AE. Surgical management of cerebellopontine angle tumors. Sci J Al-Azhar Med Fac Girls [serial online] 2020 [cited 2020 Sep 28];4:34-41. Available from: http://www.sjamf.eg.net/text.asp?2020/4/1/34/282859
| Introduction|| |
The cerebellopontine angle (CPA) is a wedge-shaped cisternal space within the posterior fossa bounded by the petrous temporal bone laterally, the cerebellum and brainstem medially, and the lower cranial nerves (CN IX, X, and XI) inferiorly . The CPA is the most affected site of tumor formation within the posterior fossa and the location of ∼5–10% of all intracranial tumors .
Even though there is a high prevalence of tumors within the CPA, surgical management in this region remains a major obstacle owing to the critical neurovascular structures passing the CPA, crossing the surgical access, and this may lead to some complications ,,,,.
From a historical background, the earliest surgical procedures within the CPA led to high rates of death, despite those surgeons were typically operating on deeply large tumors ,.
Factors such as pathology, tumor size and location, extent of resection, and preoperative cranial (CN) function have been implicated in long-term outcome . Important management considerations in this site comprise the preservation of the facial and vestibulocochlear nerves function, as tumors in this site often adhere to these nerves .
The current study was conducted to evaluate the various clinical and radiological modalities that are used for diagnosis of CPA tumors and planning of their surgeries. Additionally, it aimed to compare the various surgical strategies that have been used for excision of CPA tumors, along with the assessment of cerebrospinal fluid (CSF) diversion role in CPA surgery, and to study the complications of CPA surgeries and the best strategy to avoid these complications.
| Patients and methods|| |
The current study was carried out in the Department of Neurosurgery, Al-Zahraa University Hospital, Faculty of Medicine for Girls, Al-Azhar University, Cairo, Egypt, throughout the period between October 2017 and October 2019. Each patient singed an informed consent prior to any surgical interevention. Twenty patients were managed surgically after approval of the ethical committee of our institute.
All patients were subjected to detailed history and clinical evaluation. Radiological assessment was done using MRI and computed tomography (CT) brain with contrast and thin cuts on the posterior fossa and CT angiography. Patients with clinically proved cranial nerve affection were subjected to constructive interference in steady state to reveal the relationship between the tumor and cranial nerves. Additionally, PET-scan was done for patients who had indefinite diagnosis based on conventional MRI. All patients were assessed for papilledema by fundus examination.
Two approaches were used for excision of our CPA cases.
Each patient was placed in a lateral position or park-bench position with his/her head turned toward the opposite side of the tumor and fixed by Mayfield framework (Integra Life Sciences Corp., Cincinnati, Ohio, USA). Lazy ‘S’-shaped scalp incision of ∼8–10 cm was made behind the ear. The incision was long enough to allow an ideal craniectomy for facilitating retraction of the cerebellum.
To get the largest exposure for the convenience of surgery, the mastoid air cells were opened, and the sigmoid sinus was partially or totally exposed according to the size and anteromedial extension of the tumor. Sealing air cells with bone wax helped to avoid postoperative leakage of CSF. The dura was incised in a C-shape fashion, and the cerebellar hemisphere was gently retracted to expose and open the cerebello-medullary cistern. The CSF was released in a great degree to ensure maximum brain relaxation.
We do not use fixed brain retractors. Instead, we do dynamic retraction with suction and bipolar forceps. Occasionally, we use handheld brain spatula for momentary retraction. The tumors were debulked in a piecemeal fashion under an operative microscope. Coagulation of the tumor tissues fruited bloodless resection. After good homeostasis, watertight closure of the dura and Frazer (Safety) Burr hole were done.
Middle fossa approach
On the lateral position, a 4×4 cm temporal craniotomy was performed. The zygomatic arch was resected and fixed postoperatively by miniplates. The dura was bluntly dissected from the middle fossa floor to reach the petrous ridge. Then, we open the dura and cut the tentorium with minimal retraction of the temporal lobe.
Ventriculoperitoneal shunt surgery
Five patients were subjected to preoperative ventriculoperitoneal shunt owing to hydrocephalic changes.
Immediate postoperative clinical assessment was implemented to reveal the intense complications of the surgery. Within a year from surgery, patients were re-evaluated to assess the improvement of the facial nerve and trigeminal nerve function to detect the effect of the surgery on those function. All patients were followed up for at least 6 months, whereas complete clinical assessment was conducted every 2, 6, and (for some patients) 12 months to reveal the potential improvement of the clinical manifestations or the evident adverse events. The surgical specimens were processed to confirm the diagnosis of tumor histopathologically, whereby patients with unclear histopathological diagnosis were subjected to immunohistochemistry to identify the pathological subtypes and malignant grades. Postoperative CT scan and MRI were performed throughout the follow-up period. The presence of residual tumor was recorded on postoperative MRI.
| Results|| |
Patient demographic and clinical characteristics are shown in [Table 1].
|Table 1 Clinical presentation of patients with cerebellopontine angle tumors|
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Cranial nerves affections other than eighth nerves are shown in [Table 2].
|Table 2 Cranial nerves affection among patients with cerebellopontine angle tumors|
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Preoperative pure tone audiometry revealed that 16 (80%) patients had hearing affection; six patients had severe Sensory Neural Hearing Loss (SNHL), five and four patients experienced moderate and mild SNHL, respectively, and one patient had mild to moderate SNHL. However, four (20%) patients showed normal hearing function.
Surgical approaches and outcome
Preoperatively, five (25%) patients were subjected to V-P shunt surgery as a result of hydrocephalic changes. The retrosigmoid approach was performed in 18 (90%) patients, whereas two (10%) patients were subjected to the middle fossa approach. Furthermore, we did total tumor resection for 14 (70%) patients, whereas subtotal resection was done in six (30%) patients.
There were seven (35%) cases with preoperative hydrocephalic changes, and six (85.7%) patients had experienced significant clinical improvement of their symptoms along with a significant reduction of the ventricular size after surgery. Five of them were subjected to preoperative V-P shunt surgery, and one patient improved by excision of tumor without shunting of CSF.
Based on the history and clinical evaluation, seven (87.5%), nine (69.2%), and eight (66.6%) patients revealed significant improvement of the tinnitus, headache, and vertigo symptoms, respectively. Additionally, eight (88.8%) patients showed noticeable improvement of ataxia symptoms.
Based on the postoperative pure tone audiometry, three (18.7%) patients experienced significant improvement of their hearing function after the surgery. However, one (6.25%) patient experienced deterioration of the hearing function. With cranial nerve assessment, postoperative facial weakness showed improvement in five (83.3%) patients out of six patients, whereas eight (72.7%) patients experienced significant improvement of facial pain after the surgery. Subsequent to that, the manifestations of lower cranial nerve affection were improved in three (100%) patients after the surgery.
Regarding the postoperative complications, two (10%) patients had experienced transient facial weakness that improved within 6 months after surgery and four (20%) patients had transient cerebellar ataxia owing to traction on cerebellar that improved within 2 weeks after surgery. Additionally, one (5%) patient had experienced aphasia. Subsequently, three (15%) patients experienced hematoma at the tumor bed postoperatively, two patient developed left-side hemiplegia, one patient experienced CSF leakage and meningitis, and one patient experienced local wound infection. Regarding mortality, four (20%) patients died within 2 weeks after surgery owing to one of the following causes: acute hydrocephalus, intraoperative herniation of the brain, meningitis, and hematoma at the tumor bed.
A 50-year-old female patient complained of right-side facial pain (trigeminal neuralgia). She is neither diabetes nor hypertension. On examination, the patient had manifestations of trigeminal hypothesia around the angle of mouth of the right side. The audiogram revealed normal hearing function. The radiological evaluation revealed right premeatal CPA meningioma and was subjected to retrosigmoid approach ([Figure 1],[Figure 2],[Figure 3],[Figure 4]).
|Figure 1 Preoperative MRI brain with contrast. T1WI axial view showing premeatal CPA meningioma. CPA, cerebellopontine angle.|
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|Figure 2 Postoperative MRI brain with contrast axial T1 showing total excision of the tumor.|
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|Figure 4 Microscopic specimen of the tumor showed meningothelial and fibrous meningioma grade 1.|
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A 50-year-old female patient presented with a history of mild facial pain and numbness in the right side of the face and tinnitus with decreased hearing of the right ear. The patient was hypertensive with morbid obesity. The audiogram revealed mild right SNHL. The radiological evaluation showed right CPA vetibular schwanoma. Total excision was done via retrosigmoid approach ([Figure 5],[Figure 6],[Figure 7]).
|Figure 5 MRI brain T1 axial view with contrast showing right vestibular schwannoma.|
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|Figure 6 Postoperative MRI brain axial T1 with contrast showing total excision of the tumor.|
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|Figure 7 Histopathological examination of the case showed vestibular schwannoma.|
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| Discussion|| |
Vestibular schwannomas comprise 70–90% of all mass lesions within the CPA space. After vestibular schwannomas, the next two most common lesions found within the CPA are meningiomas (5–10%) and epidermoid cysts (3%) ,.
Although most of the CPA tumors are benign, the complex anatomy and important neurovascular structures traversing this space makes the management of these tumors a surgical challenge to the neurosurgeon who would like to operate in this space .
Although full of challenges, surgical resection remains the main strategy to cope with this disease at the present. Considering the slow growth of the tumor and the possible complications secondary to intraoperative insult and damage to vital anatomical structures, such as the cranial nerves, the decision on the necessity of complete surgical resection remains critical .
In the present study, most patients experienced headache (65%), tinnitus (40%), and hearing loss (60%), whereas 45% of the patients experienced gait disturbance and cerebellar ataxia. In comparison, Memari et al.  found that hearing loss was the most presenting symptom (85%) of CPA tumors, whereas 50% of the patients experienced headache and 53% experienced cerebellar signs.
The manifestations of cranial nerve affection were elucidated in most of the patients with facial pain (55%) and facial weakness (30%). In addition, 15% of the patients experienced lower cranial nerve affection. On the contrary, Memari et al. , reported a close percentage (53%) of facial nerve affection among patients with CPA tumor; however, they found a comparatively smaller percentage (6%) of lower cranial nerve affection symptoms.
Retrosigmoid approach was implemented for 18 (90%) participants, whereas two (10%) patients were subjected to the middle fossa approach. Ten patients had vestibular schwannoma, whereas six, three, and one patient experienced meningioma, epidermoid, and paraganglioma, respectively. Subsequent to that, 14 participants were subordinated to total tumor excision, whereas six patients were subjected to subtotal tumor excision.
Preoperatively, V-P shunt surgery was done for five (25%) patients as a result of hydrocephalic changes. Accordingly, five (25%) patients experienced significant clinical improvement of their symptoms along with a significant reduction of the ICP which evident radiologically. V-P shunt enhanced considerably the outcomes of patients with CPA tumors. In comparison with our results, Memari et al.  illustrated that preoperative V-P shunt was required in 24% of patients. The incidence of preoperative shunt was as high as 66% in the study reported by Ramamurthi . In the study published by Jain and colleagues 8.5% of patients required V-P shunt.
In the current study, we accomplished total tumor excision in 70% of our patients, whereas subtotal resection was done in 30% of them. Complete tumor excision was done by Joarder and his colleagues at 2005 in 32% of patients. However, Jain et al.  reported complete tumor excision in 96.5% of patients.
Patients experienced considerable improvement of the manifestations of increased intracranial tension, particularly those subordinated to V-P shunt preoperatively. Subsequent to that, patients revealed dramatic improvement of the tinnitus, headache, vertigo, ataxia, and unsteadiness of gait after the surgery. These results bring to light that retrosigmoid or middle fossa approaches improved dramatically the short-term and long-term functional outcomes of CPA tumors.
In accordance with the current study, Memari et al. , reported that 47 (94%) patients had tinnitus preoperatively; which decreased to 21% postoperatively. Thirty (60%) patients experienced vertigo/disequilibrium, which decreased to 11% postoperatively.
In our study, patients with cranial nerves affection symptoms such as facial pain (trigeminal neuralgia) preoperatively experienced marked improvement by 72.7%, whereas 83.3% of the patients experienced improvement of the facial weakness. These results were concomitant with those reported in the literature, where approximately two-thirds of patients with large tumors experienced some permanent facial weakness following surgery .
On the contrary, Memari et al. , reported a progression of the facial weakness. In particular, 32 (64%) patients had grade 1 or 2 in House-Brakman score at 1 year postoperative, whereas 26% had a score of 3 or 4, and 8% had a score of 5 or 6.
Regarding postoperative complications, transient facial weakness was evident among two (10%) patients, whereas three (15%) patients experienced hematoma at the tumor bed. Subsequent to that, left-side hemiplegia was evident among two (10%) patients followed by CSF leakage (5%), local wound infection (5%), and meningitis (5%).
In comparison with our results, Nonaka et al.  reported that the main neurological complication was facial palsy, which was observed in 14% of cases. Other neurological complications included disequilibrium (6.3%), facial numbness (2.2%), and lower CN deficit (0.5%).
Cerebellar dysfunction secondary to cerebellar injury intraoperatively is a well-documented potential complication of the retrosigmoid approach and may partially be attributed to excessive cerebellar retraction intraoperatively . In our study, a large proportion of the patients (20%) experienced transient cerebellar ataxia, which improved within 2 weeks after surgery.
CSF leak is a common encountered complication of CPA surgery via the retrosigmoid approach. A CSF leak rate of 5% was identified in this study, which was comparable to published rates with the standard retrosigmoid approach, with an average rate of 6–18.7%. Careful obliteration of mastoid air cells is essential to eliminate potential routes for postoperative CSF leak .Similarly, the rates of infection in association with retrosigmoid approach are comparable to or less than previous reports within the literature. The rate of postoperative wound infection encountered in this study was 5%. In a study done by Joarder et al. , they found that the rate of postoperative wound infection was 4%.
On review of the literature, postoperative wound infection rates of up to 6.7% have been reported for acoustic neuroma microsurgery with a rate of ∼3.7% for the traditional, standard retrosigmoid/suboccipital approach. The use of autologous material in reconstruction may assist in the prevention of postoperative wound infection . Additionally, within this series one patient experienced meningitis following the retrosigmoid approach. This is similar to previous reports in the literature of 3.8–7.3% with the retrosigmoid approach .
The rate of death was considerably high in our study, where 20% of the patients died after the surgery as a sequence of acute hydrocephalus, intraoperative brain herniation, meningitis, and hematoma in tumor bed. This result was relatively high when compared with other studies. For instance, He et al.  reported one death owing to aspiration pneumonia, which might be the result of functional deterioration of either CN IX, CN X, or CN XII. Similar to that, Memari et al.  reported that there was one death in their series (2%), which was owing to intracranial hemorrhage.
Despite the evidence summarized in the current investigation, several limitations may hinder its conclusion: the relatively small sample size and the relatively short follow-up period, which may hinder our capability to follow up the patients for long time to appreciate the long-term outcomes of the surgery.
| Conclusion|| |
CPA tumors are challenging lesions to be treated surgically, which requires a high level of surgical experience. Retrosigmoid and middle fossa approaches accomplished significant outcome among patients with CPA tumors, counterpart hearing symptoms, bulbar affection, facial weakness, and cerebellar manifestations. Preoperative V-P shunt procedure improved noticeably the manifestations of increased intracranial tension.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
[Table 1], [Table 2]