Serdar Erdine MD, FIPP Medical Faculty of Istanbul University, Istanbul Pain Center, Istanbul, Turkey Trigeminal neuralgia is one of the most severe chronic pain syndromes of the face. Pharmacologic management with anticonvulsants is the first-line treatment, however, during the chronic course of the disease these drugs may not be efficient or with intolerable side effects. The most frequently used percutaneous procedures include radiofrequency (RF) thermocoagulation, retrogasserian glycerol injection, and percutaneous balloon compression. All procedures cause injury to trigeminal rootlets: RF by thermal, glycerol by chemical, and balloon compression by mechanical injury. All procedues have potential complications that should be avoided by meticulous attention. The ganglion lies within the cranium in an area called Meckel’s cave, close to the apex of the petrous part of the temporal bone. The ganglion is shaped like a crescent moon and in the vicinity of the internal carotid artery, trochlear, and optic nerves. The posterior border of the ganglion includes the dura of Meckel’s cave and cerebrospinal fluid (CSF). Anteriorly, the ganglion gives off three branches intracranially: ophthalmic, maxillary and mandibular somatotropically located. The ophthalmic branch is dorsal, the maxillary branch is intermediate, and the mandibular branch is located ventrally. Ophthalmic and maxillary branches are sensory, whereas the mandibular branch is partly motor. These nerves and their branches provide the cutaneous and dermatomal innervation of the head and face (Figures 15.1 and 15.2) [1–4]. Figure 15.1 3D-computed tomography scan of the trigeminal ganglion and its branches. (Source: Courtesy of S. Erdine.) Figure 15.2 3D-computed tomography scan showing the various foramina at the base of the skull. (Source: Courtesy of S. Erdine.) Three main techniques are RF thermocoagulation, retrogasserian glycerol injection, and percutaneous balloon compression and these will be described in this chapter. The patient is placed in a supine position on the table in neutral position. In cases where visualizing the foramen ovale in neutral position is difficult, the head may be hyperextended (Figure 15.3). Figure 15.3 Patient in supine position. All three procedures depend on the Hartel technique estimating the location of the foramen ovale on the three landmarks on the patient’s face; point below the midpupil, point 3 cm anterior to the external auditory meatus along the inferior border of the zygoma, and point lying 2.5–3 cm lateral to the oral commissure which is the entrance point of the electrode or needle. The skin for needle entry is at the angle of the mouth inline with the pupil when looking at the front of the face and the midpoint of the zygomatic arch when looking from the side of the face (Figure 15.4a,b). Figure 15.4 3D-computed tomography scan in the AP view identifying the point of entry from the upper molar tooth. (a) The needle needs to be toward the middle of the ipsilateral orbit (red arrow). (b) 3D-computed tomography lateral scan identifying the point of entry at the mandibular notch (red dot) [4]. (Source: Courtesy of S. Erdine.) All trigeminal nerve-lesioning techniques are performed with initial needle entry through the foramen ovale. The foramen ovale may be visualized by approaching it in a submental view of the fluoroscope. When the foramen ovale is clearly visible, the needle is advanced through it, parallel to the axis of the C-arm in a “submental view”. The electrode is directed to the lateral edge of the foramen ovale for the mandibular branch, to the middle for the maxillary branch, and medially for the ophthalmic branch (Figure 15.5a–c). Then, the C-arm is turned to lateral position, avoiding advancing the needle too deeply, which could cause it to penetrate the cerebral cortex or the brainstem (Figure 15.6a,b). Figures 15.5 (a–c) Entrance through the foramen ovale in submental view. Figures 15.6 (a) and (b) Placement of the needle in lateral view. After confirming the position of the needle, an aspiration test is mandatory when the needle enters the foramen ovale to avoid entering into the cerebrospinal fluid (CSF) or a blood vessel. If blood is aspirated, the position of the needle should be changed slightly and aspirated again. If blood is still aspirated, the procedure is terminated. If the needle penetrates deeper than required, it can enter the dura mater in Meckel’s cave. If that happens, one may see CSF during aspiration. Aspiration of CSF does not interfere with RF thermocoagulation. However, it could interfere with injection of therapeutic agents with high viscosity, such as contrast material or glycerol or phenol in glycerine; the injected solution is likely to spread to the brainstem, causing nausea and vomiting and other neurologic side effects. Improper positioning of the needle is diagnosable if both the lateral and PA fluoroscopic view are used to prevent the needle entering through the other foramina-like infraorbital fissure, the foramen lacerum or the jugular foramen. In order to place the tip of the electrode precisely at the desired portion of the trigeminal ganglion or its branches, test stimulation is required. The patient should be awake to respond to the stimulation at this stage. Stimulating the region at 2 Hz, with 0.1–1.5 V settings, the contraction of the mandible is observable as the mandibular branch of the trigeminal nerve has motor fibers. Next, look for paresthesia at the desired branch with stimulating at 50–100 Hz at a 0.1–1.5 V setting. Generally, patients feel paresthesia at the 0.5 V setting. When the electrode is confirmed to be in place for RF, then proceed with the thermocoagulation lesioning with lesioning at 70°C for 60 seconds. If more than one branch of the trigeminal nerve is affected, several lesions by repositioning the electrode on this nerve may be performed but not more than three times. For glycerol injection, the needle is advanced until free flow of the CSF is obtained. If blood is aspirated instead of CSF, the needle is withdrawn and advanced again slightly in another direction. After observing the free flow of clear CSF by gravity alone, the patient is placed in a semi-sitting position, with the neck flexed and fixed in that position. Under the lateral fluoroscopic view, 0.1–0.5 ml contrast solution (iohexol) is injected visualizing this solution filling the cistern. If this is not observed, the needle is repositioned. When the cistern is seen to be appropriately filled, allow some time for the solution to saturate in the region. After this period, the contrast solution flows out with gravity, without aspiration. When this is seen to be satisfactory, 0.5 ml of 50% glycerol into the cistern, keep the patient in the semi-sitting position for the next 2 hours. For balloon compression, a 14-G 10 cm needle is directed toward the foramen ovale. Next, a Fogarty catheter (4 French) is introduced and the tip is advanced through the needle in the foramen ovale in the lateral view. The balloon of the Fogarty catheter is inflated by injecting 1 ml of contrast material (iohexol). In the lateral fluoroscopic view, the balloon should resemble a pear. The balloon stays inflated for 60 seconds to 6 minutes although there is no consensus about the duration of this period. After completing the desired time for inflation, the contrast solution is aspirated and the balloon is deflated and the catheter, together with the needle as one unit, is withdrawn (Figure 15.7a–d). Figure 15.7 (a)14-G needle in submental view. (b) Needle position in lateral view, advancing. (c) The Fogarty catheter through the needle, balloon compresssion view with dye within the baloon. (d) The Fogarty catheter inflated. Complications related with the procedures may be classified as:
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Complications of Percutaneous Trigeminal Ganglion Procedures
Introduction
Anatomy
Indications
Contraindications
Technique
Complications During the Procedures for the Treatment of Trigeminal Neuralgia
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