Remarkable reduction or disappearance of retroodontoid pseudotumors after occipitocervical fusion

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1 J Neurosurg Spine 5: , 2006 Remarkable reduction or disappearance of retroodontoid pseudotumors after occipitocervical fusion Report of three cases IKUKO YAMAGUCHI, M.D., SEI SHIBUYA, M.D., PH.D., NOBUO ARIMA, M.D., PH.D., SHIRO OKA, M.D., YOSHIAKI KANDA, M.D., AND TETSUJI YAMAMOTO, M.D., PH.D. Department of Orthopaedic Surgery, Kagawa University School of Medicine, Kagawa, Japan Retroodontoid or periodontoid pseudotumor unassociated with rheumatoid arthritis or hemodialysis is clinically rare. The authors report three cases of retroodontoid pseudotumor that they treated surgically. All patients exhibited myelopathy of the upper cervical spinal cord. Plain radiography depicted atlantoaxial instability in two of the three patients. Spinal cord compression caused by a mass lesion in all patients was clearly demonstrated on magnetic resonance images. In two patients, the mass lesion was not limited to the retroodontoid region and expanded continuously to the cranial base. Posterior laminectomy of the atlas and occipitocervical fusion were performed. After surgery, the pseudotumor disappeared in two cases and was clearly reduced in one case, and neurological symptoms also improved. Retroodontoid pseudotumor is a lesion for which symptomatic improvement can be expected with posterior decompression and fusion, even without direct tumor excision. KEY WORDS pseudotumor upper cervical spine occipitocervical fusion N ONNEOPLASTIC mass lesions adjacent to the odontoid process of the axis are known to be associated with rheumatoid arthritis 4,8 and hemodialysis. 5,11 Recently, mass lesions around the axis unassociated with underlying disease have also been reported. 2,13 We report three cases of retroodontoid pseudotumor around the odontoid process of the axis, in which marked reduction or disappearance of pseudotumor was observed following surgical decompression and fusion without direct tumor excision. Case Reports Abbreviations used in this paper: ADI = atlas dens interval; CRP = C-reactive protein; JOA = Japanese Orthopaedic Association; MR = magnetic resonance; WBC = white blood cell. Case 1 History and Examination. This 58-year-old woman presented with gait disturbance and upper-extremity functional disturbance. Approximately 15 months before admission to our institution, the patient began experiencing numbness in her right index finger. During the subsequent 12 months, the numbness progressed to gait disturbance and upper-extremity functional disturbance. She visited a local hospital and underwent MR imaging, which revealed a tumorlike mass posterior to the odontoid process. She was then admitted to our institution for evaluation and treatment. At admission, deep tendon reflexes exhibited rightdominant augmentation below the biceps tendon reflex. Pathological reflexes were present in both the upper and lower extremities. Muscle strength was decreased in a right-dominant manner. Sensory testing revealed decreased temperature sensation on the left side and reduced deep sensation on the right, together with a Brown Séquard syndrome type sensory impairment. Blood testing revealed the following: absence of the rheumatoid factor, a CRP level of 0.4 mg/dl, and a WBC count of 5100 cells/dl, with no evidence of inflammatory reaction. The JOA score for cervical myelopathy was 10 (maximum score 17). Lateral radiography of the cervical spine during flexion revealed an ADI of 7 mm in flexion and 2 mm in extension, and atlantoaxial instability of 5 mm (Fig. 1A and B). Preoperative MR imaging demonstrated marked compression of the spinal cord due to a mass in the retroodontoid region. On subsequent MR imaging, the tumor was seen as a low-intensity area on T 1 -weighted images, a mixture of low- and high-intensity on T 2 -weighted images, with absence of contrast enhancement in the center but partial enhancement of the surrounding capsulelike structure after Gd administration (Fig. 1C E). The mass was diagnosed clinically as a retroodontoid pseudotumor. 156 J. Neurosurg: Spine / Volume 5 / August, 2006

2 Reduction or disappearance of retroodontoid pseudotumor FIG. 1. Case 1. A and B: Preoperative lateral radiographs of cervical vertebrae obtained during flexion (A) and extension (B), showing atlantoaxial instability of 5 mm at the ADI. C E: Preoperative sagittal MR images of the upper cervical spine. A T 1 -weighted image showing the retroodontoid pseudotumor as a low-intensity region almost isointense with the spinal cord (C). A T 2 -weighted image revealing a mixture of low and high intensity (D). A Gd-enhanced image depicting no contrast enhancement in the interior, although some enhancement of the surrounding capsulelike structure is observed (E). F and G: Postoperative images. A lateral radiograph (F) and a T 1 -weighted sagittal MR image (G) of the cervical spine obtained 12 years after surgery demonstrating no recurrence of the retroodontoid pseudotumor and continued spinal cord decompression. Operation. After completion of a posterior C-1 laminectomy, occiput C3 fusion was performed using a Luque rod (Tanaka Medical Co., Tokyo, Japan) and an Atlas Cable system (Medtronic Sofamor Danek, Memphis, TN) (Fig. 1F). Postoperative Course. Gradual improvement in the patient s neurological symptoms was observed between 1 and 10 months after surgery. The JOA score improved from 10 before surgery to 14 at 10 months after surgery. Long-term postoperative follow-up examination revealed marked regression of the retroodontoid pseudotumor at 18 months, disappearance of the tumor at 3 years, no recurrence of retroodontoid pseudotumor and maintenance of good spinal cord decompression at 12 years (Fig. 1G), and preservation of neurological function. At the last followup visit, the patient s JOA score was 14, with a recovery rate (postoperative score versus preoperative score) of 57.1% calculated using the formula proposed by Hirabayashi. 7 Case 2 History and Examination. This 68-year-old man presented with gait disturbance and lower-extremity obtundation. Three and one-half years before presentation, the patient had sustained an injury to the occipital region, resulting in numbness in the lower extremities and gait disturbance. Computed tomography scanning of the brain was performed, and no abnormality was detected. Because the patient s activities of daily living were only slightly impaired, no further treatment was sought at that time. Seven months before presentation, however, the patient s unstable sensation during walking gradually worsened. On admission, bilateral scapulohumeral reflexes 12 were observed and deep tendon reflexes were augmented globally below the biceps tendon reflex. The Hoffmann reflex (a pathological reflex of the fingers) was present bilaterally, and there was ankle clonus on both sides. The patient displayed a spastic gait. Muscle strength was decreased in a left-dominant manner. Sensory tests showed mild hypesthesia from the lateral side of the forearm to the thumb and index finger in the left upper extremity, and marked hypesthesia globally in the left lower extremity. Blood sampling revealed the following: absence of rheumatoid factor, a CRP level of mg/dl, and a WBC count of 5600 cells/dl, with no evidence of inflammatory reaction. The JOA score was 11. Lateral radiography of the cervical spine revealed an ADI of 4 mm in flexion and 2 mm in extension, and atlantoaxial instability of 2 mm (Fig. 2A and B). Preoperative MR imaging demonstrated that the retroodontoid pseudotumor located posterior to the axis extended upward to the cranial base and greatly compressed the spinal cord. The retroodontoid pseudotumor appeared as a low-intensity lesion on T 1 -weighted images, and as a mixed-intensity area on T 2 -weighted images; it had a double-layer structure with a clear border internally. After Gd administration, MR imaging did not reveal any contrast enhancement in the interior, although some enhancement of the surrounding capsulelike structure was observed (Fig. 2C E). J. Neurosurg: Spine / Volume 5 / August,

3 I. Yamaguchi, et al. FIG. 2. Case 2. A and B: Preoperative lateral radiographs of the cervical spine obtained during flexion (A) and extension (B), showing atlantoaxial instability of 2 mm at the ADI. C E: Preoperative sagittal MR images of the upper cervical spine. The retroodontoid pseudotumor extends continuously from the posterior region of the axis to the cranial base, greatly compressing the spinal cord. A T 1 -weighted image depicting a low-intensity region almost isointense with the spinal cord (C). A T 2 -weighted image revealing a low-intensity region (D). A Gd-enhanced image depicts no contrast enhancement in the interior, although some enhancement of the surrounding capsulelike structure is observed (E). The arrow denotes the deep layer and the arrowhead the superficial layer of the pseudotumor. F and G: Postoperative lateral radiograph of the cervical spine (F) and a T 1 -weighted sagittal MR image of the upper cervical spine obtained 10 months after surgery (G). At 20 months after surgery, the retroodontoid pseudotumor has almost disappeared. Operation. After completion of a posterior C-1 laminectomy, occiput C4 fusion was performed using a Luque rod and the Atlas Cable system. Because lateral radiographs obtained during flexion extension revealed instability between C-3 and C-4, fusion was extended to C-4 (Fig. 2F). Postoperative Course. At 4 months after posterior fusion, the retroodontoid pseudotumor was almost undetectable (Fig. 2G). At 20 months after surgery, the JOA score was 13 and the recovery rate was 33.3%. The slightly lower recovery rate was thought to be due to the long delay of 3 years from the onset of neurological symptoms to surgery and the great degree of obtundation in the left lower extremity, resulting in unsatisfactory improvement in the perception score. Case 3 History and Examination. This 75-year-old man presented with impaired upper-extremity function. Ten months before presentation at our institution, the patient had experienced the onset of left finger numbness followed by impairment of fine motion of the left hand. Nine months after onset, he visited a local hospital. Cervical disease symptoms were suspected, and MR imaging revealed a tumorlike lesion in the retroodontoid region. He was referred to our institution. On admission, deep tendon reflexes were augmented bilaterally in the upper and lower extremities (left dominant), and the augmentation of biceps tendon and patella tendon reflexes was especially marked. The Hoffmann reflex was present on the left side but not on the right side. There was no ankle clonus and no Babinski reflex in the lower extremities. Spastic gait was evident. Decreased muscle strength was observed in the upper extremities (left dominant) and manual muscle testing showed Grade 3/4 strength from the deltoid muscle downward. Sensory testing demonstrated hypesthesia in all fingers of the left hand, and from the left lower leg to the foot. Blood testing revealed the following: absence of rheumatoid factor, a CRP level of 0.1 mg/dl, and a WBC count of 4200 cells/dl, with no evidence of inflammatory reaction. The patient s JOA score was 11. Lateral radiography of the cervical spine during forward backward flexion revealed no atlantoaxial instability (Fig. 3A and B). Preoperative MR imaging demonstrated that the retroodontoid pseudotumor extended continuously from the posterior part of the axis up to the cranial 158 J. Neurosurg: Spine / Volume 5 / August, 2006

4 Reduction or disappearance of retroodontoid pseudotumor FIG. 3. Case 3 A and B: Preoperative lateral radiographs of the cervical spine obtained during flexion (A) and extension (B), depicting no atlantoaxial instability. C E: Preoperative sagittal MR images of the upper cervical spine. A T 1 - weighted image showing the retroodontoid pseudotumor as a low-intensity region almost isointense with the spinal cord (C). A T 2 -weighted image showing a mixture of low and high intensity (D). A Gd-enhanced image demonstrating no contrast enhancement in the interior, although some enhancement of the surrounding capsulelike structure is observed (E). The arrow denotes the deep layer and the arrowhead the superficial layer of the pseudotumor. F and G: Postoperative lateral radiograph of the cervical spine (F) and T 1 -weighted sagittal MR image of the cervical vertebrae (G) 6 months after surgery. Despite the fact that this pseudotumor was the largest of the three cases and compression was marked, tendency toward tumor regression is observed 6 months after posterior fusion. base, and greatly compressed the spinal cord. On MR imaging, the retroodontoid pseudotumor appeared as a region of low intensity that was almost isointense with the spinal cord on T 1 -weighted images, and an area of mixed low and high intensity on T 2 -weighted images, with a double-layer structure as in Case 2. After administration of Gd, MR imaging revealed no enhancement in the interior, although some enhancement of the surrounding capsulelike structure was observed (Fig. 3C E). Operation. As in the previous two cases, we performed a posterior C-1 laminectomy followed by occiput C3 fusion using a Luque rod and the Atlas Cable system (Fig. 3F). Postoperative Course. Although this patient had the largest tumor and the most marked spinal cord compression, a tendency toward tumor regression was observed 6 months after posterior fusion (Fig. 3G). Fourteen months after surgery, the patient s JOA score was 15 and the recovery rate was 66.6%, with a good postoperative outcome. Discussion Myelopathy caused by pseudotumor requiring surgical treatment, including cases of anterior subluxation of the atlantoaxial spine, spondylosis symptoms, and pseudoarthosis following fracture of the odontoid process, has been reported by Sze, 13 Crockard, 2 Lansen, 10 respectively, and their colleagues. Regarding MR imaging findings, Sze, et al., 13 reported that the retroodontoid pseudotumor appears as a low-intensity area on both T 1 - and T 2 -weighted images. Magnetic resonance imaging findings for retroodontoid pseudotumor in our three cases included an area of low intensity, almost isointense with the spinal cord, on T 1 -weighted MR images; a region of low intensity or a mixture of low and high intensity on T 2 -weighted images; and no contrast enhancement of the interior on images after Gd administration. Because none of the three patients had a history of dialysis, fracture of the odontoid process, or rheumatoid arthritis, and none exhibited hematological or biochemical abnormalities, the lesions were diagnosed as retroodontoid pseudotumor arising from the posterior side of the odontoid process. 2,6 Because of a lack of histological evidence, the present cases represent a diagnosis of exclusion. These cases are sometimes called seronegative rheumatoid arthritis. Conflicting histopathological findings for retroodontoid pseudotumor have been reported. Retroodontoid pseudotumor has been described as inflammatory granulomatous J. Neurosurg: Spine / Volume 5 / August,

5 I. Yamaguchi, et al. tissue that forms as a result of chronic atlantoaxial subluxation 13 as well as degenerative fibrochondral-like tissue with no inflammatory findings. 2,15 The reason for the fibrochondral tissue formation has been proposed to be as follows: atlantoaxial instability exerts stress on the cruciate ligament of the atlas, resulting in a partial tear, and a portion of the lesion becomes hypertrophic forming a pseudotumor. 15 The different histological presentations of retroodontoid pseudotumor may suggest different pathological origins within this entity. Anatomically, the cruciate ligament of the atlas passes through the foramen magnum and continues up to the cranial base, and a ligament is present between the odontoid process and the cranial base (clivus). This ligament has two components: a deep layer consisting of the upper longitudinal band of the cruciate, and a superficial layer consisting of the tectorial membrane continuous with the posterior longitudinal ligament. In Cases 2 and 3, MR imaging depicted a pseudotumor with a double-layer structure extending as far as the cranial base, consistent with the aforementioned ligament structure. Although the imaging findings are not conclusive, this lesion structure suggests that the lesion is due not only to atlantoaxial instability but also to atlantooccipital instability. Surgical treatment for retroodontoid pseudotumor can be broadly classified into two modalities: direct extirpation of the pseudotumor 2,13 and posterior decompression and fusion aimed at tumor regression, without pseudotumor excision. 1,6 Excision of the pseudotumor has an advantage in that histopathological examination of the surgical sample can be performed. The disadvantage of this method, however, lies in the risk of neurological damage caused by surgical procedures when using a posterior transdural approach. For excision of a pseudotumor via an anterior approach, the conventional transoral route has been associated with complicated postoperative management, risk of infection, and the need for strict external fixation due to the unstable bone graft. In addition, delayed extubation due to palatal dehiscence, delayed pharyngeal hemorrhage, and glossal edema were reported in a small number of cases. 9 Nevertheless, a safer and less invasive method of lesion excision through the transoral approach has been reported recently with the aid of neuronavigation. 14 Considering the risks, we chose to perform posterior decompression via a C-1 laminectomy followed by occipitocervical fusion with instrumentation. Grob, et al., 3 also used occipitocervical fusion to treat a deformity of the cervical spine caused by rheumatoid arthritis and achieved reduction or resolution of rheumatoid pannus of the posterior odontoid process. On the other hand, regarding the extent of posterior fusion Chatani, et al., 1 reported that atlantoaxial fusion may be indicated for a small pseudotumor with mild spinal cord compression. As illustrated by the present cases, however, the pseudotumor may extend from the posterior side of the odontoid process up to the cranial base. In these cases, instead of atlantoaxial fusion, fusion between the occipital bone and upper cervical spine is recommended. References 1. Chatani K, Nakajima S, Sakamoto A, Nishioka M, Kou K: [Cervical myelopathy associated with pseudotumor of retroodontoid space: two cases.] Bessatsu Seikeigeka 29: , 1996 (Jpn) 2. Crockard HA, Sett P, Geddes JF, Stevens JM, Kendall BE, Pringle JA: Damaged ligaments at the craniocervical junction presenting as an extradural tumour: a differential diagnosis in the elderly. J Neurol Neurosurg Psychiatry 54: , Grob D, Schutz U, Plotz G: Occipitocervical fusion in patients with rheumatoid arthritis. Clin Orthop Relat Res 366:46 53, Grob D, Wursch D, Grauer W, Sturzenegger J, Dvorak J: Atlantoaxial fusion and retrodental pannus in rheumatoid arthritis. Spine 22: , Hatakeyama A, Fujinaga H, Togo T, Tamura T, Ozawa K, Shoji T, et al: Remarkable improvement of activity by CAPD in a hemodialysis patient with a pseudotumor of the craniocervical junction. Adv Perit Dial 8: , Isono M, Ishii K, Kamida T, Fujiki M, Goda M, Kobayashi H: Retro-odontoid soft tissue mass associated with atlantoaxial subluxation in an elderly patient: a case report. Surg Neurol 55: , Japanese Orthopaedics Association: Scoring system for cervical myelopathy. Nippon Seikeigeka Gakkai Zasshi 68: , Kenez J, Turoczy L, Barsi P, Veres R: Retro-odontoid ghost pseudotumors in atlanto-axial instability caused by rheumatoid arthritis. Neuroradiology 35: , Kingdom TT, Nockels RP, Kaplan MJ: Transoral-transpharyngeal approach to the craniocervical junction. Otolaryngol Head Neck Surg 113: , Lansen TA, Kasoff SS, Tenner MS: Occipitocervical fusion for reduction of traumatic periodontoid hypertrophic cicatrix. Case report. J Neurosurg 73: , Rousselin B, Helenon O, Zingraff J, Delons S, Drueke T, Bardin T, Moreau JF: Pseudotumor of the craniocervical junction during long-term hemodialysis. Arthritis Rheum 33: , Shimizu T, Shimada H, Shirakura K. Scapulohumeral reflex (Shimizu). Its clinical significance and testing maneuver. Spine 18: , Sze G, Brant-Zawadzki MN, Wilson CR, Norman D, Newton TH: Pseudotumor of the craniovertebral junction associated with chronic subluxation: MR imaging studies. Radiology 161: , Vougioukas VI, Hubbe U, Schipper J, Spetzger U: Navigated transoral approach to the cranial base and the craniocervical junction: technical note. Neurosurgery 52: , Yoshida M, Tamaki T, Kawakami M, Natsumi K, Minamide A, Hashizume H: [Retro-Odontoid pseudotumor associated with chronic atlanto-axial instability: Pathogenesis and surgical treatment.] Rinshou Seikeigeka 30: , 1995 (Jpn) Manuscript received October 17, Accepted in final form May 8, Address reprint requests to: Sei Shibuya, M.D., Ph.D., Department of Orthopaedic Surgery, Kagawa University School of Medicine, Ikenobe, Miki-cho, Kagawa , Japan. shibuya@kms.ac.jp. 160 J. Neurosurg: Spine / Volume 5 / August, 2006