Retrodental mass in rheumatoid arthritis.

STUDY DESIGN: A retrospective investigation of the retrodental mass secondary to rheumatoid arthritis (RA). OBJECTIVE: To propose a new classification of the retrodental mass in RA, and to evaluate their resorption processes and surgical procedures. SUMMARY OF BACKGROUND DATA: The retrodental mass secondary to RA has long been recognized as pannus formation. It is also known that pannus will disappear or radically reduce after stabilization of the atlantoaxial segment. The past reports, however, leave unanswered the following question; are there other types of mass with significantly different degeneration processes from the pannus? The need for anterior transoral decompression is still controversial. METHODS: Eleven patients with retrodental masses in RA were retrospectively analyzed. They underwent posterior fusion without decompression for atlantoaxial subluxation and occipitocervical fusion with decompressive laminectomy of the atlas for vertical subluxation. All patients had neurological, radiologic, and magnetic resonance imaging (MRI) evaluations both before and after surgery. MRI study was performed preoperatively and at 1-month interval after surgery until the mass had disappeared or stopped further reduction. RESULTS: This study identified 3 distinctive types in the rheumatoid retrodental mass on MRI. Type 1 displayed high intensity on T2 and low intensity on T1-weighted MRI or the pattern specific to pannus. Type 2 was identified with low intensity on T2-weighted MRI or pattern specific to pseudotumor. Type 3 displayed a combination of high and low intensity on T2-weighted images or indication that the mass was the mixture of pannus and pseudotumor. All the masses of types 1 and 3 disappeared within 1 month of surgery. The process in type 2 was found a few months slower. In all 11 cases, myelopathy improved postoperatively to the status before the emergence of the symptom. CONCLUSIONS: This article recognized 3 distinctive types of the retrodental mass in RA; type 1 (pannus), type 2 (pseudotumor), type 3 (mixed). It further concludes in all types of the retrodental mass associated with atlantoaxial subluxation secondary to RA, posterior fusion without decompression can achieve improvement of the myelopathy. In type 2 associated with vertical subluxation, on balance between calculable benefits and high risks of anterior transoral decompression, the authors prefer to opt for occipitocervical fusion with decompressive laminectomy of the atlas.

Synovial sarcoma of the cauda equina.

Primary synovial sarcoma originating from the cauda equina is extremely rare. Only one case, involving an 11-year-old girl, has been reported. The authors describe the case of a 23-year-old woman with a primary synovial sarcoma of the cauda equina. The patient visited a local hospital and described a 2-month history of low-back pain. She was referred to the authors' hospital for further evaluation. On physical examination, she had a straight-leg raising result of 70° bilaterally. Motor examination revealed Grade 4/5 strength in the bilateral extensor hallux longus muscles. There was normal sensation to light touch and vibration in the lower extremities. Sagittal Gd-enhanced T1-weighted MR imaging demonstrated an intradural, extramedullary, and uniformly enhancing mass that extended from L-3 to L-4. The mass was totally resected and adjuvant local radiation therapy was administered. Reverse transcriptase polymerase chain reaction (RT-PCR) of a paraffin-embedded tissue sample revealed SYT-SSX fusion transcripts, and the diagnosis of synovial sarcoma was confirmed. Five and a half years after surgery, the patient is free of local recurrence and metastatic disease. The RT-PCR detection of SYT-SSX fusion transcripts played a key role in establishing the diagnosis of synovial sarcoma of the cauda equina. Complete resection of the mass with adjuvant local radiation therapy proved to be effective.

Magnetic resonance imaging evaluation of patients with idiopathic scoliosis: a prospective study of four hundred seventy-two outpatients.

STUDY DESIGN: A prospective study of magnetic resonance imaging findings in outpatients with idiopathic scoliosis. OBJECTIVE: The purpose of this study was to determine the prevalence of neural axis abnormalities in outpatients with scoliosis and to analyze the characteristics of patients who had such abnormalities. SUMMARY OF BACKGROUND DATA: In previous studies, neural axis abnormalities were found in 2.9% to 37% of patients with idiopathic scoliosis. The current guidelines for MRI screening in scoliosis are valuable, and the proposed indications for performing MRI in the literature include early onset, atypical curvature, double thoracic curve (King type-5), rapid progression, male gender, and abnormal neurologic findings. METHODS: A total of 472 outpatients with a primary diagnosis of idiopathic scoliosis were examined for neural axis abnormalities by magnetic resonance imaging. Logistic regression was used to determine significant predictors of neural axis abnormalities on MRI. RESULTS: The incidence of neural axis abnormalities on MRI was 3.8% (18 of 472 patients). Among the 18 patients, 6 had a Chiari I malformation alone, 10 had a Chiari I malformation combined with syringomyelia, and 2 had a syringomyelia without Chiari I malformation. Male gender, patients younger than 11 years old, and abnormal superficial abdominal reflexes were significantly associated with the detection of neural axis abnormalities on MRI. CONCLUSION: We recommend routine use of MRI in male patients, younger than 11 years old, and abnormal superficial abdominal reflexes. Even if a patient has no specific indications for MRI, we recommend its routine use in preoperative planning.