Petroclival tumor model—technical note and educational implications


Petroclival area lesions are rare, and their surgery is challenging due to the deep location and to the complex relationships between the tumor and the neurovascular structures. The objective is to present a petroclival tumor model simulating the distorted anatomy of a real petroclival lesion and propose its use to practice microsurgical removal while preserving neurovascular structures. Four embalmed cadaver heads were used in this study. An endoscopic endonasal transclival approach was used to access the dura in front of the trigeminal nerve; a pediatric Foley was inserted above the trigeminal nerve and was gradually inflated (one-balloon technique). If a larger tumor model was desired, an additional balloon was placed below the trigeminal nerve (two-balloon technique). A pre-mixed tumor polymer was injected into the petroclival space and allowed to harden to create an implanted tumor. A post-implant CT scan was done to evaluate the location and volume of the implanted artificial tumor. Tumors were subsequently excised via retrosigmoid and anterior petrosal approaches. Six petroclival tumors were successfully developed: three were small (9.41–10.36 ml) and three large (21.05–23.99 ml). During dissection, distorted anatomy created by the tumor model mimicked that of real surgery. We have established a petroclival tumor model with adjustable size which offers opportunities to study the distorted anatomy of the area and that is able to be used as a training tool to practice microsurgical removal of petroclival lesions. The practice dissection of this tumor model can be a bridge between a normal anatomic dissection and real surgery.

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Correspondence to Mario Ammirati.

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Jose Alberto Landeiro, Jose Orlando Junior, Rio de Janeiro, Brazil

Several lesions may arise in the petroclival region, and the most frequent is meningioma [1]. By definition, a “true” petroclival meningioma has its origin at the upper two thirds of the clivus medial to the fifth cranial nerve and has distinct clinical and outcome features [1, 6]. In the majority of cases, meningiomas are benign tumors (WHO grade I classification system) [2], and their slow-growing pattern allow them to reach large size before become apparent clinically [7].

The petroclival region contains important neurovascular structures that are frequently involved or displaced by tumor in a variable pattern. Usually, the third and fourth nerves are displaced upwardly, the sixth nerve is frequently surrounded by the tumor, and the basilar artery with its branches may be wrapped [1].

Petroclival meningioma has been described in the early to mid twentieth century as a relentlessly progressive tumor, with ultimately fatal outcomes [12, 13, 14]. In the past decade, Van Havenbergh et al. evaluated the natural history of 21 cases of petroclival meningiomas that were followed for a period of 4 to 10 yeas and found that 76 % of tumors grew radiographically and 50 % of the initially asymptomatic patients developed some kind of cranial nerve deficit [11]. Therefore, these tumors often need treatment [6].

Petroclival meningiomas are formidable surgical challenges attributable to their deep-seated location and proximity and adhesion to cranial nerves, major blood vessels, and the brainstem [3, 4]. Although advances in microsurgery and skull base techniques have been developed, the mortality rate ranges from 0 to 9 % and the incidence of permanent cranial nerve deficits has been shown to vary from 20.3 to 76 % in a number of series [5, 15]. Due to their often benign pathology and the risks associated with operating in this region, there has been much debate over the proper management of these tumors, and with the advent of radiosurgery, many have recommended subtotal removal and subsequent radiosurgery to avoid operative morbidity [7].

Although the use of stereotactic radiosurgery for intracranial meningiomas have been described extensively in the literature, there are few large reports over the treatment of posterior fossa meningiomas and fewer studies include long-term follow-up [8, 9, 10]. Starke et al. have described a large series of petroclival meningioma treated with gamma-knife stereotactic radiosurgery as an adjunct to microsurgery or a primary treatment modality and showed favorable outcomes, especially for smaller tumor, no previous radiation therapy and patients free of symptom [9]. Clival or petrous-based locations are predictive of an increased risk of new or worsening neurological deficit following gamma-knife radiosurgery [8]. Couldwell, Cole, and Al-Mefty have reported aggressive growth of skull base meningioma after failed radiosurgery, and careful extended (exceeding 10 years) follow-up evaluations must be undertaken for all patients after radiosurgery [16].

Almefty et al. have advocated the total resection as a primary goal for petroclival meningioma, if the circumstances allow it, and it was achievable in 76.4 % of their 64 cases and is facilitated by the use of appropriate skull base approaches, with good outcome and functional status. Radiosurgery was considered only for cases where the unresectable residual tumor regrows [6].

The preferred surgical approach for treatment of petroclival meningiomas is still controversial [5]. Bambakidis et al. have considered the retrosigmoid craniotomy as the workhorse surgical approach for most petroclival tumors of any size and reserved the combined transpetrosal approach for tumors that are medial to the internal auditory canal and extend to both middle and posterior cranial fossa [5]. Erkmen, Pravdenkova, and Al-Mefty have proposed an algorithm for selection of the skull base approach requiring careful examination of the preoperative MR imaging, hearing evaluation, and venous anatomy. They proposed the anterior petrosal approach for small petroclival lesions superior to the internal auditory canal; for larger tumors that extend below the internal auditory canal with intact or serviceable hearing, which should undergo a posterior petrosal approach; for large tumors with loss of hearing, which will benefit from the extended exposure provided by a complete petrosectomy; and for those tumors extending across the midline of the clivus or into the anterior cavernous sinus, which require a combined petrosal approach [3, 6].

The authors of this manuscript have showed a brilliant technique in creating similar conditions offered by a petroclival lesion. They describe in a detailed manner how to produce the tumor model simulating the relationship of it with adjacent structures. Although the petroclival meningiomas are the most frequent tumor in the petroclival region, they are rare, accounting for less than 0.15 % of intracranial tumors [1, 6]. Therefore, the laboratory practice of dissection in a tumor model is a formidable way to improve microsurgical skills and surgical outcomes, offering the opportunity to the Neurosurgeon to face and to become familiar with the anatomical distortion created by a petroclival tumor.


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Imad N. Kanaan, Riyadh, Kingdom of Saudi Arabia 

The best venue to teach clinical skills, sound judgment, and surgical dexterity to young neurosurgeons is the operating theater (laboratory of highest order) as correctly stated for the clinical ward by William Halstead. Taken into account the complexity of neurosurgical, otological skull-base interventions and patient’s safety, it is a prerequisite for training young neurosurgeons to have rehearsal for their surgical skills at alternative set-up prior to live surgical experience using modern facilities such as navigation system, surgical simulators or attending microsurgical courses, and cadaver dissection workshops using artificial models similar to the one described by Grananiello and validated by the authors. This should be eventually complemented by witness life surgery performed by the great masters in the field. The authors eloquently highlight some of the challenges to be considered such as mixture rate, time between injection and dissection, and proper preparation of the embalmment of the cadaveric head in order to optimise the use of this model. Tactile sensation and tissue feedback remain an issue to be taught at life surgery in their future training.

Atul Goel, Manu Kothari, Mumbai, India

Amongst all things non-clinical, dissection of human cadavers has been now and again viewed as needless, dispensable, and excusable. No wonder then that in advanced academic debates, dissection of a cadaver had been evaluated with points in favor and against. The votes against outnumber those for dissection largely on the grounds of time saved, no bother of cadaveric management, and so on. Even in the home ground of Henry Gray, dissection is on the “decline” (Utting and Willan, 1995) [6].

Be as it may, this presentation wishes to sing the song of the undeniable and overwhelming advantages, benefits, and the joys of cadaveric dissection. We are used to neglecting the seasons, the stars, the spring, sunset, and sunshine. So, what place can there be for such a dispensable exercise as dissection when a CD-ROM can unpeel the human body layer by layer, vessel by vessel, may be one day cell by cell? Our addiction to the computer screen has triumphed over the avoidable exercise of a dissection of “dead-body.” Our alienation from what is real and our fascination with what is a mere shadow play is complete.

The cadaver on dissection table is fully a human being, save that “prana” or “chaitanya (life)” is not permeating it. Otherwise, cell-to-cell and fiber-to-fiber, a live human being and a cadaver are structurally alike. It has been emphasized that dissection is the opportune moment at which students can be inculcated with the values of respect and compassion. A CD or an image (MRI or CT) feeds the eyes, but what of the hands, the touch receptors, the tension receptors, and so on? It cannot provide the dimensions or give the idea of the texture of the artery, the toughness of a tendon, or the resilience of fascia or cartilage. Nothing can replace the hands-on experience that dissection provides. It is only the direct contact with the cadaver that can impress upon the student’s mind the importance of being alive and robust.

Jean Ternel declared. “What is geography to history, anatomy is to medicine.” It described the theater to events. Any knowing of the human body, short of dissection, is to travel the world on a map and to eat the menu card. It is like learning to swim without entering into water. There is no escape for us from feeling, cutting, probing, and dissecting a human being that is lifeless but full of all other mysteries. Robert Boyle of Boyle’s law of gasses aphorized that the human body is a divine mansion in which God has come to stay for a while, and we must know the making and working of it. Dissection is trekking in the wilderness of the human universe. Let dissection be! All textbooks of anatomy, including Gray’s, and all imaging and computer techniques are accessory to dissection but should not, and cannot, ever replace it. We are the inheritors of privileges that have been passed on to us by Sushruta and Vesalius. Let us not fritter our treasures in the name of experience and modernization. Dissection is golden and all the rest is silvery. Once again, let dissection prevail in the learning of surgery.

It is heartening to see the contribution by Dr. Ammirati and his colleagues in designing an artificial tumor model. Although no model can simulate a lifelike situation, it is an attempt to enhance the scope of learning and practicing prior to actually performing on live humans. Anatomical understanding is the key for a surgeon [1-5]. If one can acquire the key, doors can open up. Through this note, I wish to congratulate Dr. Ammirati and his colleagues who have enhanced the scope of anatomical dissections and through their contribution stressed on the importance of preoperative planning and workouts before actually entering the arena of the “living.”


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Electronic supplementary material

Below is the link to the electronic supplementary material.

Endoscopic endonasal transclival approach to implant right artificial petroclival tumor (MPG 21750 kb)

Removal of a right artificial petroclival tumor using a retrosigmoid approach (MPG 22358 kb)

Video 1

Endoscopic endonasal transclival approach to implant right artificial petroclival tumor (MPG 21750 kb)

Video 2

Removal of a right artificial petroclival tumor using a retrosigmoid approach (MPG 22358 kb)

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Lee, J., Tailor, A., Lamki, T. et al. Petroclival tumor model—technical note and educational implications. Neurosurg Rev 39, 251–258 (2016).

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  • Artificial petroclival tumor
  • Balloon technique
  • Microsurgical dissection
  • Neurosurgical training
  • Tumor model