MR imaging at 3.0 tesla of glossopharyngeal neuralgia by neurovascular compression

Transcription

1 MR imaging at 3.0 tesla of glossopharyngeal neuralgia by neurovascular compression Poster No.: C-1281 Congress: ECR 2011 Type: Scientific Exhibit Authors: M. Nishihara 1, T. Noguchi 1, H. Irie 1, K. Sasaguri 1, M. Kawashima 2, Keywords: DOI: T. Matsushima 2, S. Kudo 1 ; 1 Saga/JP, 2 Saga City/JP MR-Angiography, MR, Neuroradiology peripheral nerve, Neuroradiology brain /ecr2011/C-1281 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 15

2 Purpose Background Purpose Glossopharyngeal neuralgia (GPN) is a rare disease that produces a severe attack of facial or pharyngeal pain and can be caused by neurovascular compression. Medical treatment with agents such as carbamazepine remains the first choice in patients with GPN. Microvascular decompression (MVD) surgery can be performed for GPN patients who have an unsatisfactory response to medications or suffer from side effects of the drugs [1,2]. Head MRI is important to diagnose the neurovascular compression and to exclude other organic causes. The root entry zone (REZ) has been identified as the contact point causing GPN. However, detailed imaging findings of GPN with neurovascular compression have not been fully assessed so far. In this study, we retrospectively evaluated the findings of preoperative 3.0- tesla (3.0-T) magnetic resonance imaging (MRI) to clarify the usefulness of MRI in analyzing GPN with neurovascular compression. Methods and Materials Patients -We performed 3.0-T MRI for 7 GPN patients with typical symptoms (2 male and 5 female; age range, years; mean age, 56.6 years) from February 2007 to July 2010 #Fig. 1#. Page 2 of 15

3 Fig.: Patients' list References: M. Nishihara; Radiology, Saga University, Saga, JAPAN Imaging technique -MRI was performed on 3.0-T scanners (MAGNETOM Trio, A Tim, 3.0-T clinical MRI unit, Siemens, Erlangen, Germany). -In addition to routine imaging studies, three-dimensional constructive interference in steady state (3D-CISS) and three-dimensional time-of-flight magnetic resonance angiography (3D-TOF MRA) were performed in all 7 patients, and T2-reversed image (T2R) MRI was performed in five of 7 patients. -The imaging parameters were as follows: 3D-CISS: TR/TE, / ; flip angle, 48 ; matrix size, ; slice thickness, mm 3D-T2R: TR/TE, 1300/106; flip angle, 120 ; matrix size, ; slice thickness, 0.6 mm 3D-TOF MRA: TR/TE, 22/3.1; flip angle, 18 ; matrix size, ; slice thickness, mm Image analysis - MR images were analyzed visually for the following imaging findings by two radiologists in consensus fashion: Page 3 of 15

4 1. Image assessment 1-1. Identification of offending vessels on 3D-TOF MRA Offending vessel defined as the vessel which contacted with a glossopharyngeal nerve Identification of contact points of a glossopharyngeal nerve where the offending vessels are attached on 3D-CISS and 3D-T2R based on the following criteria by reference to De Ridder's reports [3]: <1.1 mm: REZ (root entry zone; central nerve system segment) #1.1 mm: PNS (peripheral nerve system) segment 1-3. The presence or absence of a shift of the glossopharyngeal nerve at the contact points 1-4. The presence or absence of deformation of the brain stem at the origin of the glossopharyngeal nerve on the affected side Deformation of the brain stem defined as that there was a difference between right and left side and a depression by the vessel in affected side. 2. Comparison of the imaging findings with the operative findings - the offending vessels 3. Comparison of the demonstrating ability between 3D-CISS and 3D-T2R based on the following criteria; 3-1. The degree of demonstrating the glossopharyngeal nerve in the cistern Grade 1: The whole glossopharyngeal nerve is visible in the cistern Grade 2: The glossopharyngeal nerve is partially visible Grade 3: The glossopharyngeal nerve is not visible 3-2. The Contrast of the glossopharyngeal nerve with the offending artery at the contact point Grade 1: The nerve can be differentiated from the offending vessel Grade 2: It is somewhat possible to differentiate the nerve from the offending vessel Grade 3: It is impossible to differentiate the nerve from the offending vessel Page 4 of 15

5 Images for this section: Fig. 1: Patients' list Page 5 of 15

6 Results 1. Image assessment #Fig. 4# on page Identification of offending vessels on 3D-TOF MRA All offending vessels were arteries: 5 were posterior inferior cerebellar arteries (PICAs), 1 was a vertebral artery (VA)+PICA and 1 was the common trunk of the anterior inferior cerebellar artery (AICA) and PICA. On 3D-CISS and 3D-T2R, offending vessels coursed at the supraolivary fossette in all cases Identification contact points of a glossopharyngeal nerve where the offending vessels are attached on 3D-CISS and 3D-T2R The contact points were the REZ of the glossopharyngeal nerve in 3 patients and the PNS segment in 4 patients Presence or absence of a shift of the glossopharyngeal nerve at the contact point In 6 of 7 cases, the shift of the glossopharyngeal nerve at the contact point was found in MRI Presence or absence of deformation of the brain stem at the origin of the glossopharyngeal nerve on the affected side Deformation of the brain stem at the origin of the glossopharyngeal nerve on the affected side was found in 4 of 7 cases on MRI. 2. Comparison of the offending artery in imaging findings with the operative findings#fig. 4# on page 9 MVD was performed in 6 of our 7 patients. MRI findings were consistent with surgical findings in 5 cases. The offending vessels in the other patient were not only the PICA, which was identified on MRI, but also the small branch from the AICA, which was not identified on MRI. Page 6 of 15

7 3. Evaluation of the demonstrating ability between 3D-CISS and 3D-T2R (Fig. 5) on page 10 - Five out of 7 patients were examined with both 3D-CISS and 3D-T2R Degree of demonstrating the glossopharyngeal nerve in the cistern Grades 1, 2 and 3 of demonstrating the glossopharyngeal nerve in the cistern were achieved in 4, 1 and 0 patients in 3D-CISS and 3, 2 and 0 patients in 3D-T2R, respectively Contrast the glossopharyngeal nerve with the offending artery at the contact point Grades 1, 2 and 3 of the contrast the glossopharyngeal nerve with the offending artery at the contact point were achieved in 3, 2 and 0 patients in 3D-CISS and 4, 1 and 0 patients in 3D-T2R, respectively. Images for this section: Page 7 of 15

8 Fig. 1: MRI study of patient 1. (a) 3D-CISS and (b) 3D-T2R Axial view. The left glossopharyngeal nerve appears to be in contact with the PICA at the REZ, and is shifted by the PICA (red arrow). No deformation of the brain stem at the origin of the glossopharyngeal nerve on the affected side was found. 3D-TOF-MRA post-processed with VR lateral view (c) and MIP algorithm frontal view (d). A prominent vascular loop (yellow arrow) is seen. The grade of demonstrating the glossopharyngeal nerve in the cistern is 1 for both 3D-CISS and 3D-T2R. The grade of the contrast between the glossopharyngeal nerve and the offending artery at the contact point was 1 for both 3D- CISS and 3D-T2R. Page 8 of 15

9 Fig. 2: MRI study of patient 5. (a) 3D-CISS and (b) 3D-T2R Axial view. The left glossopharyngeal nerve appears to be in contact with the PICA at the REZ, and is shifted by the PICA (red arrow). Deformation of the brain stem at the origin of the glossopharyngeal nerve on the affected side was found. (c) 3D-TOF-MRA postprocessed with MIP algorithm lateral view. A prominent vascular loop (yellow arrow) is seen. The grade of demonstrating the glossopharyngeal nerve in the cistern is 1 for both 3D-CISS and 3D-T2R. The grade of the contrast between the glossopharyngeal nerve and the offending artery at the contact point was 2 for 3D-CISS and 1 for 3D-T2R. It is our opinion that the 3D-T2R image was clearer when the contact point was near the brain stem. Fig. 3: MRI study of patient 6. (a) 3D-CISS and (b) 3D-T2R Axial view. The left glossopharyngeal nerve appears to be in contact with the PICA in the PNS, and no shift by the PICA was identified (red arrow). No deformation of the brain stem at the origin of the glossopharyngeal nerve on the affected side was found. (c) 3D-TOF-MRA postprocessed with MIP algorithm lateral view. A prominent vascular loop (yellow arrow) can be seen. The grade of demonstrating the glossopharyngeal nerve in the cistern was 2 for both 3D-CISS and 3D-T2R. The grade of the contrast between the glossopharyngeal nerve and the offending artery at the contact point was 1 for both 3D-CISS and 3D-T2R. Page 9 of 15

10 Fig. 4: Image assessment - results * The distance from the brain stem to the contact point (mm) ** The evaluation of the contact point *** Did the glossopharyngeal nerve shift at the contact point? **** Was there deformation of the brain stem at the origin of the glossopharyngeal nerve on the affected side? Fig. 5: the evaluation of the demonstrating ability between 3D-CISS and 3D-T2R * The degree of demonstrating the glossopharyngeal nerve in the cistern ** The degree of contrast between the glossopharyngeal nerve and the offending artery at the contact point Page 10 of 15

11 Conclusion Discussion In previous reports [2, 4, 5], the offending vessels were the PICA, the AICA, VA, veins, or the combination of those vessels. The PICA is the most frequently reported offending vessel. Among our cases, the offending vessels were the PICA (Figs. 1-3) as the most frequent, the VA+PICA (one case), and the common trunk of the AICA and PICA (one case). The previous reports [3-7] suggested that an attachment area was the REZ or the rootlet of glossopharyngeal nerve on MRI. However, to our knowledge, we could not find the report which clearly expressed that PNS was responsible for GPN. Axons of cranial nerves are covered by a myelin membrane composed of two histological cell types, oligodendrocytes and Schwann cells. Oligodendrocytes are found dominantly in a central zone, that is, the REZ, and Schwann cells are found in a peripheral zone as part of the PNS. A recent study reported that the was structurally more fragile than PNS because REZ was composed of sparse connective tissues. For this reason, the nerve compression in the REZ was more common than that in the PNS as a manifestation of GPN. Although the proximal fragile zone varies in each of the cranial nerves, its distance from the glossopharyngeal nerve has been reported to be about 1.1 mm [1], which is much shorter than the distance from any other cranial nerves. This might be why GPN occurs less frequently than the other neurovascular compression syndromes such as trigeminal neuralgia or hemifacial spasm. In the present study, however, there were 3 of 6 cases (50%) who had PNS compression instead of REZ attachment as seen on MRI and obtained a pain relief after neurovascular decompression surgery. In the contrary to the previous reports [1], this result suggested that GPN might occur by compression in the not-fragile zone as well as the fragile zone. Or, if the hypothesis should be speculated in relation to the fragile zone, it might be possible that the peripheral compression indirectly pull the fragile zone along the nerve root and adversely affect the REZ segment. However, further assessment would be needed to confirm this hypothesis. In this study, 6 of 7 cases (86%) demonstrated the shift of glossopharyngeal nerve at the contact point. While previous reports suggested that this finding was important as one of diagnosing findings on MRI[6, 7], its frequency has been unknown yet. In addition, the deformations of the brain stem were found in 4 of 7 cases (57%). The compression of the brain stem by the tortuous arteries or branches might indicate not the direct cause but predictor of neurovascular compression. However, further examination should be performed for this hypothesis. Page 11 of 15

12 3D-CISS was reported to be useful in detecting nerves and other structures [6,7]. 3D-T2R MR images were found to be especially useful for elucidating extraaxial structures such as the trigeminal nerve [8]. We can demonstrate the glossopharyngeal nerve in the cistern in both 3D-CISS and 3D- T2R images, with almost no difference between the two modalities in demonstrating the contact point. However, it seemed to be demonstrated more clearly on 3D-T2R when the contact point was near the brain stem (Fig.1, 2). It would be important to understand each of MR sequence imaging characteristics for the preoperative estimation of GPN. Conclusion In GPN patients, the offending arteries were mainly PICAs. Our series revealed that the PICA could come into contact with not only the REZ but also the PNS segment of the glossopharyngeal nerve in GPN patients. There was no difference between 3D-CISS and 3D-T2R in demonstrating the contact point. It might be useful to know the imaging findings as well as MR sequence imaging characteristics for the preoperative estimation of GPN. Images for this section: Page 12 of 15

13 Fig. 1: MRI study of patient 1. (a) 3D-CISS and (b) 3D-T2R Axial view. The left glossopharyngeal nerve appears to be in contact with the PICA at the REZ, and is shifted by the PICA (red arrow). No deformation of the brain stem at the origin of the glossopharyngeal nerve on the affected side was found. 3D-TOF-MRA post-processed with VR lateral view (c) and MIP algorithm frontal view (d). A prominent vascular loop (yellow arrow) is seen. The grade of demonstrating the glossopharyngeal nerve in the cistern is 1 for both 3D-CISS and 3D-T2R. The grade of the contrast between the glossopharyngeal nerve and the offending artery at the contact point was 1 for both 3D- CISS and 3D-T2R. Page 13 of 15

14 Fig. 2: MRI study of patient 5. (a) 3D-CISS and (b) 3D-T2R Axial view. The left glossopharyngeal nerve appears to be in contact with the PICA at the REZ, and is shifted by the PICA (red arrow). Deformation of the brain stem at the origin of the glossopharyngeal nerve on the affected side was found. (c) 3D-TOF-MRA postprocessed with MIP algorithm lateral view. A prominent vascular loop (yellow arrow) is seen. The grade of demonstrating the glossopharyngeal nerve in the cistern is 1 for both 3D-CISS and 3D-T2R. The grade of the contrast between the glossopharyngeal nerve and the offending artery at the contact point was 2 for 3D-CISS and 1 for 3D-T2R. It is our opinion that the 3D-T2R image was clearer when the contact point was near the brain stem. Fig. 3: MRI study of patient 6. (a) 3D-CISS and (b) 3D-T2R Axial view. The left glossopharyngeal nerve appears to be in contact with the PICA in the PNS, and no shift by the PICA was identified (red arrow). No deformation of the brain stem at the origin of the glossopharyngeal nerve on the affected side was found. (c) 3D-TOF-MRA postprocessed with MIP algorithm lateral view. A prominent vascular loop (yellow arrow) can be seen. The grade of demonstrating the glossopharyngeal nerve in the cistern was 2 for both 3D-CISS and 3D-T2R. The grade of the contrast between the glossopharyngeal nerve and the offending artery at the contact point was 1 for both 3D-CISS and 3D-T2R. Page 14 of 15

15 References 1. Matsushima T, et.al: Surgical Treatment of Glossopharyngeal Neuralgia as Vascular Compression Syndrome via Transcondylar Fossa (Supracondylar Transjugular Tubercle) Approach, Acta Neurochir (Wien) 142: , Kawashima M, et al: Microvascular decompression for glossopharyngeal neuralgia through the transcondylar fossa (supracondylar transjugular tubercle) approach, Neurosurgery 66: , De Ridder, et al: Is the root entry/exit zone important in microvascular compression syndromes?, Neurosurgery 51: , Sampson JH, et al: Microvascular decompression for glossopharyngeal neuralgia: long-term effectiveness and complication avoidance. Neurosurgery 54: , Wakiya K, et al: Results of Microvascular Decompression in 16 Cases Glossopharyngeal Neuralgia [in Japanese]. Neurol Med Chir (Tokyo) 29: Karibe H, et al: Preoperative visualization of microvascular compression of cranial nerve IX using constructive interference in steady state magnetic resonance imaging in glossopharyngeal neuralgia Journal of Clinical Neuroscience 11: , Hiwatashi A, et al: MRI of Glossopharyngeal Neuralgia Caused by Neurovascular Compression, AJR 191: , Fujii Y, et al: High-resolution T2-reversed magnetic resonance imaging on a high magnetic field system, Technical note, J Neurosurg. 89: 492-5, 1998 Personal Information Page 15 of 15