**2. Clinical presentation**

Most patients present with trigeminal dysfunction in the opening of its clinical picture, more common being the decreased sensitivity in the ophthalmic divisions (V1), maxillary (V2), and mandibular (V3). The progressive decrease in sensitivity is compatible with the slow growth form of this type of tumor; one of its major concerns is the involvement of V1 segment, with consequent decreased corneal sensitivity and keratitis. Pain may also be a part of the clinical picture, mainly in the ganglionic subtype, having been found in more than 40% of patients 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 neurosurgical technique offers low morbidity and mortality for these tumors today.

#### **2.1. Preoperative preparation**

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**).

**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.

Most patients present with trigeminal dysfunction in the opening of its clinical picture, more common being the decreased sensitivity in the ophthalmic divisions (V1), maxillary (V2), and mandibular (V3). The progressive decrease in sensitivity is compatible with the slow growth form of this type of tumor; one of its major concerns is the involvement of V1 segment, with consequent decreased corneal sensitivity and keratitis. Pain may also be a part of the clinical picture, mainly in the ganglionic subtype, having been found in more than 40% of patients

**2. Clinical presentation**

74 Brain Tumors - An Update

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 nerve invasion, for preoperative documentation of hearing status.

#### **2.2. Intraoperative monitoring**

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.
