Successful frameless radiosurgery for glossopharyngeal neuralgia — Case report

Abstract

Idiopathic glossopharyngeal neuralgia (GPN) is a rare disorder of the ninth cranial nerve characterized by severe paroxysmal pain affecting the ear, tongue and throat. Frame-based radiosurgery (SRS) has been shown to be an effective option. We report the first successful pain alleviation by frameless SRS in a GPN patient that failed both medical and surgical interventions.

Introduction

Idiopathic glossopharyngeal neuralgia (GPN) is a craniofacial pain disorder of the ninth cranial nerve characterized by extreme paroxysmal pain affecting the ipsilateral side of ear, tongue, and throat.^1,2,3 These attacks of severe pain tend to be associated with triggering events such as gentle touch or movements of the jaw. GPN can also be associated with hemodynamic instability, leading to arrhythmias, hypotension, syncope, and cardiac arrest.^3,4 GPN is often misdiagnosed for idiopathic trigeminal neuralgia (TGN) due their similarity of symptoms and TGN’s higher incidence (28.9 cases for TGN versus 0.4 cases for GPN per 100,000 person-years).⁵

Like TGN, pharmacological management is generally the initial treatment for GPN. For drug refractory GPN patients, microvascular decompression (MVD) surgery is effective, with 80% complete pain relief rate but 10% lower cranial nerve complication rate.^6,7 Recently, frame-based Gamma Knife (GK) radiosurgery (SRS) has been utilized successfully in GPN patients.^8,9,10

In this report, we describe the very first case of a patient with idiopathic GPN successfully treated with frameless SRS. Patient’s informed consent was obtained in accordance with local and institutional laws and regulations.

Case Report

A 54-year-old Caucasian female nurse midwife developed progressively worsening severe “piercing” right facial pain involving ear, throat and jaw region that could be triggered by light touch, yawning or chewing over a 4-year duration. Eventually, each pain attack “lasted for 4 to 5 days straight” and she could not perform her daily job. At first, she was diagnosed with atypical TGN and treated with multiple pain medications, including Neurontin, Tegretol and Nortriptyline. She tolerated the pain medications poorly and received little pain relief. She then underwent MVD surgery. During the surgery, the right CN V was normal appearing, but the right CN IX/X/XI complex had granular tissue and an abutting vessel. Therefore, the right CN IX/X/XI complex was instead decompressed. The patient’s severe right ear pain resolved postoperatively despite the development of dysphagia for 3 weeks. Unfortunately, her severe right ear pain recurred 92 days after MVD.

Under the renewed diagnosis of right GPN, she was referred to Radiation Oncology for frameless SRS. Before SRS, she underwent a thin-slice, volumetric three-dimensional spoiled gradient (3D-SPGR) and a 3D-Fast Imaging Employing Steady-state Acquisition (FIESTA) magnetic resonance imaging (MRI) studies for target delineation. She then was immobilized by a thermoplastic facemask (BrainLAB facemask) and simulated with CT localizer utilizing a CT scan with 1.25-mm sequential axial slices. Her imaging data were imported to the treatment planning station, fused and planned using the iPlan® RT computer software (BrainLAB AG, Feldkirchen, Germany). The SRS plan was designed to deliver 80 Gy isocentric maximum dose to the glossopharyngeal nerve at the level of the glossopharyngeal meatus of the jugular foramen (Figure 1), via 4 mm cone utilizing 7 non-coplanar arcs at 6 couch positions similar to TGN SRS scheme.^9,10,11

Figure 1.

Axial (A-C) and coronal(B-D) images of the radiosurgery dose plan.

A-B Fiesta sequence MR images. C-D Computed tomography (CT) images. The radiosurgery targets the glossopharyngeal nerve at the level of the glossopharyngeal meatus of the jugular foramen. The dose plan shows 40 Gy (yellow) and 12 Gy (green) isodose lines. The isocentric maximum dose is 80 Gy.

At SRS, the patient was positioned in the facemask and treated by a dedicated Novalis Tx SRS system (BrainLab AG, Munich, Germany; Varian Medical Systems, Palo Alto, CA), equipped with the ExacTrac X-ray system and 6-degree of freedom robotic couch. Six-dimensional shifts were conducted for initial setup at couch zero degree, and for intra-fraction shifts at 6 different couch positions. The targeting tolerances were set as 0.5 mm for translational lengths and 0.5 degrees for rotational angles. In our analysis of frameless SRS utilizing similar treatment plan for TGN, 97% of the intra-fraction shifts were within 0.7 mm in translational directions and 0.6 degrees along rotational axes.^11,12 At dose rate of 1000 MU, the total treatment time was within 45 minutes.

The patient tolerated the frameless SRS well. She reported significant pain relief within 2 weeks from SRS. At 3months, the patient reported some pain but adequately controlled with medications. At 2 years, the patient reported pain-free without need for medications and had no facial weakness, numbness or any neurological deficit.

Discussion

Frame-based SRS has become an excellent option for GPN patients who have failed medical management or MVD surgery.^8,9,10 In a multi-institutional study of 22 patients, 13 patients (59%) had initial complete pain relief at a median of 12 days , 3 patients (14%) had partial pain relief and 6 patients (27%) had no pain relief.⁹ However, 7 of 16 patients with initial pain relief developed pain recurrence at a median of 20 months.⁹ The study reports no apparent adverse effects of 80 Gy SRS targeting at the level of the glossopharyngeal meatus.⁹

In frame-based SRS, mounting the rigid headframe to the patient causes pain, swelling, and risks for bleeding, infection and scarring at pin sites. In contrast, frameless SRS is non-invasive and allows imaging, treatment planning and delivery to be performed at different times, which is beneficial to both patients and clinicians.^11,12 For our patient with drug refractory GPN, MVD provided only a short-lived pain relief. In contrast, frameless SRS completely alleviated her pain for a long duration of 2 year. She has been able to perform her regular work without interruption from the severe facial pain she previously had.

Conclusion

In conclusion, our case supports frameless SRS as an equally potent treatment procedure to frame-based SRS for GPN patients in a manner that provides improved patient comfort and flexibility for treatment delivery.