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NCT02687386

**Chapter 3**

**Provisional chapter**

**Trigeminal Schwannomas**

**Trigeminal Schwannomas**

Leandro César Tângari Pereira, Eduardo Quaggio, Fred Bernardes Filho and George Peter Stevens

DOI: 10.5772/intechopen.74115

Trigeminal schwannomas (TS) are rare entities occurring in various trigeminal nerve locations and present a peak incidence between the fourth and fifth decades of life, being more common in women. Patients usually present with symptoms of trigeminal nerve dysfunction. Depending on the tumor's topography, various approaches might be used to obtain its gross total resection. Trigeminal schwannoma's classification, nuances of the approaches, pathology, postoperative care, and outcomes are revised as follows. In conclusion, anatomical knowledge and the disease's comprehension are essential when dealing with such lesions, and despite their rarity, we must be obstinately committed to the surgical technique and devoted to the patient's functional postoperative outcome.

Schwannomas are benign tumors originating from Schwann cells, which form the myelin sheath around cranial and peripheral nerves. When occurring in various trigeminal nerve locations, these tumors account for 0.1–0.4% of all intracranial tumors and 1–8% of intracranial neurinomas [1, 2]. There is no doubt that vestibular schwannomas represent the vast majority of brain schwannomas, but other unusual topographies can be seen, in descending order, in the following cranial nerves: glossopharyngeal, vagus, facial, accessory, hypoglossal, oculomotor, trochlear, and abducent [3–5]. The trigeminal schwannomas (TS) present a peak incidence between the fourth and fifth decades of life, being more common in women. Since their

**Keywords:** schwannoma, Schwann cells, trigeminal nerve, cranial nerves

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

Eduardo Quaggio, Fred Bernardes Filho and

Breno Nery, Marcelo Nery Silva, Rodrigo Antônio Fernandes Costa,

George Peter Stevens

**Abstract**

**1. Introduction**

Breno Nery, Marcelo Nery Silva, Rodrigo Antônio Fernandes Costa, Leandro César Tângari Pereira,

http://dx.doi.org/10.5772/intechopen.74115

#### **Trigeminal Schwannomas Trigeminal Schwannomas**

Breno Nery, Marcelo Nery Silva, Rodrigo Antônio Fernandes Costa, Leandro César Tângari Pereira, Eduardo Quaggio, Fred Bernardes Filho and George Peter Stevens Breno Nery, Marcelo Nery Silva, Rodrigo Antônio Fernandes Costa, Leandro César Tângari Pereira, Eduardo Quaggio, Fred Bernardes Filho and George Peter Stevens

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.74115

#### **Abstract**

Trigeminal schwannomas (TS) are rare entities occurring in various trigeminal nerve locations and present a peak incidence between the fourth and fifth decades of life, being more common in women. Patients usually present with symptoms of trigeminal nerve dysfunction. Depending on the tumor's topography, various approaches might be used to obtain its gross total resection. Trigeminal schwannoma's classification, nuances of the approaches, pathology, postoperative care, and outcomes are revised as follows. In conclusion, anatomical knowledge and the disease's comprehension are essential when dealing with such lesions, and despite their rarity, we must be obstinately committed to the surgical technique and devoted to the patient's functional postoperative outcome.

DOI: 10.5772/intechopen.74115

**Keywords:** schwannoma, Schwann cells, trigeminal nerve, cranial nerves

#### **1. Introduction**

Schwannomas are benign tumors originating from Schwann cells, which form the myelin sheath around cranial and peripheral nerves. When occurring in various trigeminal nerve locations, these tumors account for 0.1–0.4% of all intracranial tumors and 1–8% of intracranial neurinomas [1, 2]. There is no doubt that vestibular schwannomas represent the vast majority of brain schwannomas, but other unusual topographies can be seen, in descending order, in the following cranial nerves: glossopharyngeal, vagus, facial, accessory, hypoglossal, oculomotor, trochlear, and abducent [3–5]. The trigeminal schwannomas (TS) present a peak incidence between the fourth and fifth decades of life, being more common in women. Since their

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

in the initial series of Day and Fukushima [7]. Wanibuchi et al. published a series with 105 patients operated on with trigeminal neurinomas, and the most frequent preoperative clinical picture was facial hypoesthesia, present in more than 65% of the patients. Facial pain was found in approximately 23% of the cases, followed by diplopia related to paresis of the abducent nerve, headache, and ataxia/vertigo as symptoms in 17, 14, and 10%, respectively [8]. Pain with longer duration, without a specific trigger, and associated with low response to carbamazepine therapy or other anticonvulsant medications may occur, characterizing atypical facial pain and always raising the hypothesis of a secondary cause for trigeminal neuralgia. Compression of intracranial nerves that travel through the cavernous sinus can determine clinical diplopia (due to the compression of III, IV, and VI cranial nerves), *tic douloureux* (V compression), exophthalmos (due to the invasion of the orbit), and decrease of auditory acuity or facial mimic by compression of the VII/VIII complex in the posterior fossa. Patients with small and oligosymptomatic tumors can be clinical and imaging followed with intervals between 6 and 12 months. If there is worsening of symptoms, the revaluation must be anticipated, due to a small possibility of malignant tumor of the trigeminal nerve. Patients who are symptomatic or do not respond to drug therapy should be promptly operated, and good

Trigeminal Schwannomas

75

http://dx.doi.org/10.5772/intechopen.74115

neurosurgical technique offers low morbidity and mortality for these tumors today.

nerve invasion, for preoperative documentation of hearing status.

Detailed clinical examination and imaging study with MRI with and without contrast constitute the primary evaluation to define tumor extension and neurovascular relationship of the tumor. Computed tomography (CT) helps in assessing bone involvement, and digital angiography should be performed in cases of suspected engulfment of the internal carotid arteries (ICA) during growth through the middle fossa or of the vertebral artery (VA) in case of growth of the tumor lesion into the posterior fossa. The audiogram may be necessary in the preoperative evaluation in cases with the presence of hearing loss, or suspected vestibulocochlear

Monitoring through somatosensory-evoked potential (SEP) and motor-evoked potential (MEP) is mandatory in this surgery. In case of tumor extension to the posterior fossa and compression of the brainstem/cranial nerves, brainstem auditory-evoked potential is also part of the armamentarium needed during surgery, reducing the possibility of injury to the intracranial nerves.

The choice of the ideal approach for the surgical treatment of trigeminal schwannomas depends essentially on the location of the tumors of this region. Tumors originating in Gasserian's ganglion or whose major component is found in the cavernous sinus (Type A) may benefit from temporal craniotomy associated or not with zygomatic osteotomy for anterolateral interdural access (Dolenc's approach) [9] or frontotemporal craniotomy for temporopolar extradural resection [7]. Tumors originating from the root of the fifth cranial nerve (Type B) can be approached via simple suboccipital craniotomy and retrosigmoid approach [10]. Combined accesses may

**2.1. Preoperative preparation**

**2.2. Intraoperative monitoring**

**3. Approaches**

**Figure 1.** Jefferson's classification revised by day and Fukushima. Type A: tumors of the middle fossa in the interdural space; type B: tumors of the posterior fossa in the subdural space; type C: dumbbell-shaped tumors (afflicting both middle and posterior fossae); and type D: TS which may arise from any extracranial division of the trigeminal nerve.

location directly affects the surgical approach, several classification systems were proposed for trigeminal schwannomas. The first classification scheme was proposed by Jefferson [6] and modified by Day and Fukushima who classified the TS according to their anatomical location and apparent origin of the trigeminal nerve in their classical paper [7]. According to those authors, TS can grow in one, two, or all three of the following compartments: subdural compartment (pontocerebellar angle), interdural compartment (lateral wall of the cavernous sinus and Meckel's cavity), and extradural or extracranial compartment (orbit, pterygopalatine fossa, and infratemporal fossa). Advances in imaging modalities and the ability to accurately diagnose these lesions in nuclear magnetic resonance imaging (MRI) allow us to easily demonstrate these extension patterns for the posterior, middle, and infratemporal fossae. In this classification system, tumors can therefore be divided into four groups: type A: tumors of the middle fossa in the interdural space; type B: tumors of the posterior fossa in the subdural space; type C: dumbbell-shaped tumors (afflicting both middle and posterior fossae); and type D: TS which may arise from any extracranial division of the trigeminal nerve (**Figure 1**).
