Novel classification for surgical approach of petroclival meningiomas: A single-surgeon experience
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.166551
Source of Support: None, Conflict of Interest: None
Background: Management of petroclival meningiomas (PCMs) is a surgeons' challenge. Planning the surgical approach and extent of excision play a vital role. The current study discusses a novel grading system that may help to choose the surgical approach.
Keywords: Novel classification; outcome; petroclival meningiomas; radiosurgery; sagittal diameter
Approximately one-fourth of all intracranial tumors are meningiomas. Nearly 10% of all meningiomas are reported in the posterior fossa, and 5–10% of the posterior fossa meningiomas arise from the petroclival region., Petroclival meningiomas (PCMs) typically have dural attachment located medial to the skull base foramina from the 5th to 11th cranial nerves thus, making their excision a surgeon's challenge. Though benign and slow growing, PCMs grow relentlessly before apparent clinical sequele or functional deterioration occur. The clinical presentation include headache, cerebellar signs, and cranial nerve paresis in a majority of these patients., However, patients with small to moderate volume meningiomas of the skull base present with few to no symptoms. As the tumors grows, it displaces the brain stem posteriorly and to the contralateral side resulting in further functional deterioration; therefore, surgical resection of the meningioma provides the only chance of cure.
The close proximity of PCMs to the brain stem, cranial nerves and vascular structures is responsible for the difficulties encountered in their complete surgical resection. Complex surgical approaches are necessary for patients with large PCMs. The earliest published series on surgical management of large PCMs have reported a high morbidity and mortality in these patients making perioperative care a challenge.,, However, the advent of newer diagnostic procedures and modern neurosurgical techniques in skull base surgery over the last 3 decades have reduced the mortality during surgical excision of these lesions to 1–3%; and, more than 75% patients return to independent living 1-year after undergoing surgery.,, Despite these advances, controversy surrounds the management of small (≤3 cm) and moderate sized PCMs. Furthermore, with recent advances in magnetic resonance imaging, early detection of small-to-moderate volume PCMs has become more common.
Sekhar et al., have reported that pre- and peri-operative factors influence the occurence of clinical dysfunction following surgery in patients with PCMs. A permanent postoperative functional deterioration was noted in patients with a difficult dissection, especially when the tumor retained its blood supply from the basilar artery, and when a previous incomplete tumor resection had been performed. Therefore, an appropriate surgical approach may perhaps determine the functional outcome. Seifert et al., concluded that the size of tumor and its extent influence the surgical approach chosen. However, in the existing literature reporting various surgical approaches, ranging from the conventional to the transpetrosal and microsurgical approaches (with considerable literature reported from India by Goel and Muzumdar),,, there is no consensus regarding the most appropriate surgical approach. The petrosal approaches are associated with cerebrospinal fluid (CSF) leak, seventh cranial nerve palsy, and hearing defect. The labyrinthine approach is time consuming and can precipitate hearing loss and facial nerve injury.
Radiosurgery (RS) is used in the volume control of PCMs not amenable to complete resection and in PCMs in high-risk locations. In recent years, many series have reported good results in tumors treated by RS; however, majority of these series compare the outcome of small tumors treated by RS to that of large tumors treated by surgical approaches. At 3 years, the failure rates following RS are 4–13%,, with the long-term results of RS indicating tumor control in 97% and symptom control in 94% of the patients at 10 years. Despite the advantages of RS, if feasible, gross total resection (GTR) is desirable. However, in patients where GTR is not possible, subtotal resection (STR) and functional preservation of hearing and facial nerve followed by RS to the remnant PCM is suggested.,
Appropriate grading of the PCM based upon its preoperative radiological evaluation may perhaps determine the most suitable surgical approach and ensure their safe maximal resection. Furthermore, this may also help in preoperatively formulating a multidisciplinary approach involving various management strategies and hence, help in minimizing treatment related mortality and in improving the functional outcome. The current study proposes a novel grading system of PCMs and evaluates its role in the surgical management of PCMs.
The study was a nonrandomized, prospective study conducted between January 2006 and January 2013. Seventy-six patients with PCMs, who were operated by the senior author (MP) were followed-up for at least 6 months postoperatively. The study was conducted at two tertiary referral centers, Krishna Institute of Medical Sciences and Nizam's Institute of Medical Sciences, India. Informed consent was obtained from all the study participants.
Preoperatively, all patients underwent a detailed clinical and neurological evaluation, following which computed tomography (CT) and magnetic resonance imaging (MRI) of the brain, and pure tone audiometry were also done.
Based on the extension of dural attachment of PCMs in the posterior fossa [Figure 1], we formulated a grading system and the surgical approach to resect these lesions [Table 1]. Grade 1 tumors were those that were seen extending around the ipsilateral internal auditory meatus (IAC). Grade 2 tumors were those in which dural attachment extended from ipsilateral IAC to the ipsilateral petrous apex. In Grade 3 tumors, the dural attachment extended from the ipsilateral IAC to the contralateral petrous apex. In Grade 4 tumors, dural attachment extended from the ipsilateral IAC to the contralateral IAC. Grade 5 tumors were those Grade 3 or Grade 4 tumors that had an additional dural attachment extending up to the jugular tubercle. [Figure 2] is a representation of tumors of various grades. [Table 1] summarizes the surgical approaches adopted.
Postoperatively, all the patients enrolled were followed-up for a minimum of 6 months. At 3 months and 6 months post surgery, the patients underwent a CT or MRI of the brain along with a thorough neurological evaluation.
Of the 76 patients, 39 (51.3%) were women, and 2 patients were below 20 years of age. Forty patients were aged between 21 and 40 years, and 26 patients between 41–59 years. The remaining 8 patients were aged 60 years and above. The mean age was 39.74 ± 13.38 years (range 16–77 years).There were 30 cases of Grade 1, 39 cases of Grade 2, 4 cases of Grade 3, 2 cases of Grade 4, and 1 case of Grade 5 tumor. [Table 2] summarizes the characteristics of the study population.
Complete excision was achieved in 59 patients (77.6%) and subtotal excision in 17 cases (22.4%). In the subtotal excision group, most patients underwent more than 90% excision. Among patients who underwent a STR (n = 17), the mean sagittal diameter of the tumor was significantly greater than the axial diameter (4.6 ± 0.9 vs. 3.4 ± 1.3; P = 0.01) and coronal diameter (4.6 ± 0.9 vs. 3.8 ± 1.4; P < 0.01) [Figure 3].
Morbidity and mortality
In the entire group, the complication rate was 34.2%. The most frequent complication was CSF leak reported in 10 (13.1%) patients, followed by new cranial nerve deficits in 7 (9.2%) patients, of which increased House-Brackmann facial nerve grade was the most common. Four cases who had a lower cranial nerve palsy preoperatively, and 2 cases who developed it postoperatively, underwent a percutaneous endoscopic gastrostomy, for feeding and to prevent aspiration. While 2 patients developed hemiparesis, operative site hematoma was observed in 2 patients where subsequent re-exploration and hematoma evacuation was done. Two patients died (1 patient post re-exploration and other due to venous infarct involving the brainstem).
There were no significant differences between the two groups (those with or without complications) for the number of male patients (56.0% vs. 34.6%; P = 0.09) and age (38.5 ± 13.4 years vs. 42.0 ± 13.2 years; P = 0.28). The differences between patients who had complications and those who did not, are summarized in [Table 3]. On correlation analysis with the incidence of complications, whereas sagittal diameter of the tumor showed a trend towards a negative correlation of r = −0.42; P = 0.09, coronal diameter (r = −0.20; P = 0.44), and axial diameter (r = −0.10; P = 0.67) did not show a significant correlation.
According to the histopathology, 73 patients had World Health Organization Grade 1 tumor, 2 patients had Grade 2 tumor, and 1 patient had Grade 3 tumor. During the course of the tumor management, 24 patients received adjuvant radiation therapy. Of these, 14 patients underwent Gamma Knife stereotactic RS. The mean follow-up period was 6 years. A detailed follow-up information of tumor progression was available in 62 patients. Of these, six developed tumor progression. Two of them developed tumor progression 4 years after surgery and the other four, at 6 years. In all the 6 patients with tumor progression, STR was performed. 94% patients had a progression free survival at 3 years and 85% at 4 years using the retrosigmoid approach.
The current study uses a novel grading system for PCMs and reports prospectively the outcome in 76 patients who underwent excision. Total excision was achieved in 77.6% of the patients. Our study shows that grading of PCMs based on the extent of their dural attachment in the transverse plane helps to choose an appropriate surgical approach and hence, in minimizing complications.
The indications for surgical treatment of PCMs are documented growth, development of neurological symptoms, and the patient's characteristics. The preferred surgical approach is still controversial and depends on the age of the patient, findings on evaluation of preoperative hearing and facial nerve function, and the surgeon's preference., The most commonly used surgical approaches include the orbitozygomatic, transpetrosal (anterior, posterior, and combined), and retrosigmoid approaches. Tumor location in relation to the IAC, the involvement of one or both cranial fossae, and preoperative cranial nerve functional status determine the optimal surgical strategy. Therefore, the best approach should provide the greatest exposure as well as better resection at minimal risk. Reports on gross total removal range from 20% to 85%, mostly depending on the surgical approach, as well as the size and extent of the tumor. GTR is mostly achieved in the petrosal approaches but with the inherent risk of traction injury and cranial nerve morbidity.
Large PCMs have an unclear natural history. Moreover, large tumors are often selected for definitive treatment due to their propensity for rapid growth or the development of neurological symptoms., Similarly, most of the cases in the current study were in Grades 1 and 2 and therefore, the most invasive petrosal approaches were perhaps not needed. Surgical management of PCMs has progressively moved away from the transpetrosal approach toward a conventional retrosigmoid approach, particularly for lesions that extend lateral to the IAC. In the current study, we have achieved total removal of the meningiomas in nearly 80% patients by using the retrosigmoid, presigmoid or a combination of both approaches based on our proposed tumor grading system.
Importantly, through our proposed grading system, we achieved higher GTR rates with lower incidence of complications. Where studies conducted previously have reported newer deficits of cranial nerves in nearly 40% of the patients,, in the current study, less than 10% of the patients had postsurgical cranial nerve deficits. However, the incidence of CSF leak in the current study is similar to that reported by Roberti et al.,, Tumor recurrence rates might be influenced by less extensive resection, results showing a malignant histology, and cavernous sinus involvement. As recommended by previous reports, in our series, patients with STR underwent RS and none of them developed progression of the tumor during the available follow up period. Interestingly, amongst patients who underwent STR, the sagittal diameter of the tumor was higher than the axial or coronal diameter, Further research is needed to evaluate the impact of planning the extent of excision based on the sagittal diameter of the tumor.
PCMs are extremely challenging to treat surgically, and the best approach should provide maximum exposure with minimal morbidity. Our proposed grading offers a high percentage of GTR at lower rates of complications and may be helpful in planning the approach for surgical excision of PCMs. The role of sagittal diameter in planning the extent of excision needs further research.
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Conflicts of interest
There are no conflicts of interest.
[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3]