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|Year : 2015 | Volume
| Issue : 5 | Page : 656-658
Petroclival meningioma: Resisting the Siren’s song
Anil Nanda, Subhas Konar
Department of Neurosurgery, Louisiana State Health Sciences Center - Shreveport, Shreveport, USA
|Date of Web Publication||6-Oct-2015|
Department of Neurosurgery, Louisiana State Health Sciences Center - Shreveport, Shreveport
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Nanda A, Konar S. Petroclival meningioma: Resisting the Siren’s song. Neurol India 2015;63:656-8
When Odysseus on a journey home heard the sirens, he had his crew tie him up to the pole so that he would not be tempted by them and sail down the wrong path. Sometimes dealing with complex tumors in neurosurgery, one has to resist the siren's song and try to be conservative. There are very few cases in neurosurgery that cause as much anguish as petroclival meningiomas, although large acoustics, giant aneurysms, and brain stem cavernomas can be challenging as well.
The petroclival area is a complex anatomical area because of its proximity to the brain stem, basilar artery, multiple dural folds, and traversing cranial nerves. A good surgical outcome in petroclival meningioma depends not only on the proper selection of the surgical approach but also on microsurgical techniques including minimal retraction on the cerebellum or temporal lobe, maintenance of the arachnoidal plane, and avoidance of cross-over while dissecting the cranial nerves or veins.
Panigrahi et al., have performed a comprehensive prospective study of petroclival meningiomas. The authors have also proposed a grading system to help in the decision-making process for choosing a surgical procedure. They stratified 76 patients with petroclival meningiomas into a grading system based on transverse growth and showed that 77.6% of gross total resections (GTRs) of tumor had minimal complications. The authors considered the horizontal extension of tumor as a deciding factor for selecting the surgical approach. However, a tumor can extend vertically down to the foramen magnum or more anteriorly involving the cavernous sinus. In that context, the authors' grade system would not be completely practical. They also found in the subtotal resection group that the sagittal diameter was high and was also associated with fewer complications.
The growth pattern of petroclival meningiomas is not predictable and is usually manifested by progression in size and clinical deterioration. The selection of approach depends on preoperative hearing status, facial nerve function, location and extension of the tumor, brain stem edema, size of the tumor, patient's age, and surgeon's preference. There are three main approaches for petroclival meningioma surgery: Transpetrous (anterior/posterior/combined), retrosigmoid, and orbitozygomatic. Several modifications of these approaches have been described in the literature. The philosophy of choosing the appropriate corridor is to improve the patient's quality of life and the comfort of the surgeon. The technical pearls in petroclival meningioma surgery are proper delineation and protection of cranial nerves and avoidance of injury of the small perforators arising from the basilar artery. This is followed by debulking of the tumor in a piecemeal manner. Sometimes, a part of the capsule attached to pia of the brain stem, epineurium of the cranial nerves or adventitia of the arteries is left behind to prevent further morbidity and mortality. Intraoperative neuromonitoring is a necessary adjunct in those cases. The retrosigmoid approach is our personal workhorse for this tumor; the major drawback of this approach is the minimal exposure of the central part of the clivus as well as trochlear nerve injury in case of supratentorial extension. This approach can be staged with the subtemporal approach for anterior extension or the transcondylar approach for inferior extension. The transpetrosal approach is ideal for a tumor medial to IAC as well as for contralateral extension. The advantages of this corridor are the short operative distance to the clivus and the early devascularization of the tumor on the posterior petrous surface. The dominancy of transverse sinus or sigmoid sinus, location of the superior petrosal sinus, position of the jugular bulb, and the draining pattern of the vein of Labbe are important considerations in the transpetrous corridor. Deafferentation pain due to the manipulation of the trigeminal nerve is one of the morbidities after anterior petrosectomy. Cerebrospinal fluid leaks, injury to the facial nerve or loss of hearing are the complications encountered in posterior petrosectomy or combined petrosectomy. The orbitozygomatic approach is for a tumor with more anterior extension into the cavernous sinus and the involvement of the upper and the middle clivus. Radical resection can be achieved with this corridor. The disadvantage of this approach is the difficulty in accessing the posterior fossa dura below the upper clivus and Dorello's canal. Cranial neuropathy is unavoidable in this procedure owing to cavernous sinus exposure.
The predictors of the extent of resection are tumor size, adherence to or compression of the brain stem, infiltration or encasement of neurovascular structures, firm tumor consistency, brain stem pial invasion, and a history of radiotherapy or surgery. In our series, GTR was achieved in 28% of cases. In the literature, the range of GTR varies between 20% and 85%.
The devastating complication of petroclival meningioma surgery is brain stem dysfunction due to direct injury or vasospasm of the small perforators of the brain stem. The temporal lobe hemorrhagic venous infarction is another serious complication, particularly if it develops in the dominant hemisphere. The incidence of cranial nerve deficits varied between 28% and 76% in the literature, and in our series, we found that 44% of patients developed new-onset cranial nerve deficits. Careful drilling should be done near the posterior face of the petrous temporal bone inferolateral to posterior meatal lip to avoid injury to the endolymphatic sac.
Recurrence rates for published series have ranged from 0% to 42%. Factors positively influencing the recurrence are the extent of resection, malignant histology, involvement of the cavernous sinus, and tumor location. Stereotactic radiosurgery is an excellent option for a small tumor or asymptomatic tumor with progression on serial imaging. In a large tumor, safe resection followed by stereotactic radiosurgery has proven to be well tolerated and effective. Starke et al., published a multicenter study of radiosurgery on petroclival meningiomas and found that tumor volumes increased in 9% of the tumors, remained stable in 52%, and decreased in 39% at a mean follow-up of 71 months (range, 6–252 months).
Scenario 1: (Tumor was soft): A-45-year old nurse with a meningioma <3 cm in size in the petroclival regions decided to undergo surgery and had an excellent resection with no deficits [Figure 1].
|Figure 1: (a and b) Preoperative contrast (axial & coronal) images show a left sided petroclival meningioma (<3cm); c) Post operative contrast scan shows gross total resection|
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Scenario 2: (Tumor was firm): A 50-year-old woman with a giant petroclival meningioma underwent subtotal resection and had worsened cranial nerve functions. After extensive rehabilitation, she improved [Figure 2].
|Figure 2: a) Preoperative contrast axial MR scan shows a giant left sided petroclival meningioma; b) coronal image shows brain stem distortion; c) Postoperative contrast (axial) scan shows gross total resection|
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These are two different scenarios. The first one could have undergone radiosurgery, but the patient insisted on undergoing surgery.
In the end, petroclival meningiomas require technical finesse, patience, and perhaps a sense of humility in deciding when to stop and when to move on. This could not be expressed more elegantly than in the words of our master, Harvey Cushing, when he said
"When to take great risks; when to withdraw in the face of unexpected difficulties; whether to force an attempted enucleation of a pathologically favorable tumor to its completion with the prospect of an operative fatality, or to abandon the procedure short of completeness with the certainty that after months or years even greater risks may have to be faced at a subsequent session—all these take surgical judgement which is a matter of long experience."
| » References|| |
Panigrahi M, Vooturi S, Rao M, Kulkarni D. Novel classification for surgical approach of petroclival meningiomas: A single-surgeon experience. Neurol India 2015;63:718-22.
Xu F, Karampelas I, Megerian CA, Selman WR, Bambakidis NC. Petroclival meningiomas: An update on surgical approaches, decision making, and treatment results. Neurosurg Focus 2013;35:E 11.
Nanda A, Javalkar V, Banerjee AD. Petroclival meningiomas: Study on outcomes, complications and recurrence rates. J Neurosurg 2011;114:1268-77.
Starke R, Kano H, Ding D, Nakaji P, Barnett GH, Mathieu D, et al
. Stereotactic radiosurgery of petroclival meningiomas: A multicenter study. J Neurooncol 2014;119:169-76.
Little KM, Friedman AH, Sampson JH, Wanibuchi M, Fukushima T. Surgical management of petroclival meningiomas: Defining resection goals based on risk of neurological morbidity and tumor recurrence rates in 137 patients. Neurosurgery 2005;56:546-59.
[Figure 1], [Figure 2]