A case of tophaceous pseudogout (i.e., calcium pyrophosphate dihydrate (CPPD) crystal deposition disease) in the temporomandibular joint (TMJ), extending to the base of the skull, is reported. A 38-year-old man was referred to the hospital with mild pain in the right chin and tip of the tongue. Panoramic radiography showed a large calcified mass around the right TMJ. Computed tomography imaging revealed a large, granular, calcified mass surrounding the right condylar head and extending to the base of the skull. The mass was clinically and radiographically suspected to be a pseudogout lesion. A biopsy specimen was collected under general anaesthesia to confirm the diagnosis. On histology, the mass was found to contain deposits of numerous rod-shaped and rhomboid crystals, which suggested tophaceous pseudogout. The deposits were identified as CPPD crystal deposition, based on analysis by X-ray diffraction and Fourier transform infrared spectroscopy. These two crystallography methods were useful in confirming the diagnosis of CPPD crystal deposition disease in the TMJ.
McCarty et al. first identified calcium pyrophosphate dihydrate (CPPD) crystals rather than sodium urate crystals in the synovial fluid of patients who had gout-like symptoms; they termed the condition ‘pseudogout’. The term ‘tophaceous pseudogout’ has recently been used to describe lesions that have massive or tumoural CPPD crystal deposition. This variant is one of the rarest forms of CPPD deposition disease; however, it is important because it shares a histological and clinical resemblance to cartilaginous tumours.
A case of tophaceous pseudogout in the temporomandibular joint (TMJ) extending to the base of the skull is presented herein. Images of tophaceous pseudogout obtained through X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) are also presented.
A 38-year-old man was admitted to the hospital for the diagnosis and treatment of mild pain in the right chin and tip of the tongue. He had first noticed mild pain in the right chin 2 months before admission, and had undergone root canal treatment of his right lower second molar at a neighbouring dentist. However, the pain in the area did not subside and he was admitted to hospital.
The patient’s medical history included hyperlipidemia, gout, diabetes, and hypertension. These conditions were all well controlled with medication. It was noted that he had been involved in sumo wrestling since he was 16 years old. He was a high school teacher and coach of the sumo club. As part of his role as a sumo coach, he always received the students’ tackles (i.e., ukemi (‘passiveness’)) on the right half of his body, including his right chin.
Clinical examination showed an obvious pre-auricular swelling on the right side, which was tender to the touch. His intrinsic mouth opening was limited to 38 mm. However, he did not have any symptoms that affected his day-to-day function and quality of life.
Computed tomography (CT) scans revealed a calcified mass around the right TMJ, but it was not continuous with the mandibular condyle ( Fig. 1 A ). The calcified mass was pressing on the temporal bone, and erosive bone resorption had occurred at the base of the skull ( Fig. 1 B). The CT views of the right TMJ showed limited opening positions due to the right condylar opaque mass. In addition, the calcified mass around the mandibular condyle gained mobility and changed shape on translating the joint from the open to the closed position ( Fig. 1 C). A pseudogout crystal mass was suspected on the basis of these CT views. However, it was not possible to completely confirm that the lesion was not a tumour.
Because the lesion extended to the base of the skull, the case was discussed with neurosurgical specialists. As a result of the discussion, a biopsy of the mass was performed under general anaesthesia to confirm the diagnosis. An intraoral incision was created on the mucosal membrane at the anterior margin of the mandibular ramus. The periosteum of the lateral surface of the mandibular ramus towards the coronoid process was detached. After reaching the mandibular notch, a significant amount of intracapsular calcareous material, which appeared chalky or ‘grist-like’, was identified between the coronoid process and the articular process ( Fig. 2 A ). The biopsy samples were gently removed from the inside of the mass using a sharp surgical spoon ( Fig. 2 B).
One-half of the biopsy specimen was immersed in 10% formalin solution and used for the pathological examination. This examination of the specimen revealed that the mass contained numerous deposits of rod-shaped or rhomboid crystals. The background of the crystals was cellular fibrous tissue and foreign body-type giant cells ( Fig. 2 C). These views suggested CPPD crystal deposition.
For the differential diagnosis, the remaining half of the specimen was examined by XRD and FT-IR spectroscopy using the potassium bromide (KBr) disc method. The XRD profile was recorded using a D8 Advance diffractometer (Bruker AXS, Karlsruhe, Germany) operated at 40 kV–40 mA acceleration using copper–potassium alpha (Cu Kα) radiation. The patterns obtained by XRD showed that nearly all peaks corresponded to those of CPPD (JCPDS-ICDD-PDF#00-041-0488), although some peaks with an unknown pattern were also observed ( Fig. 3 A ). The FT-IR spectrum was recorded on an FT/IR-6700 spectrometer (JASCO, Tokyo, Japan) at a resolution of 4 cm −1 . The FT-IR spectrum of calcium pyrophosphate tetrahydrate (CPPT) crystals has been reported previously, and it was found to be similar to the FT-IR spectrum obtained in this study ( Fig. 3 B). In brief, the following were recorded: the O P O bending vibrations at 509 cm −1 and 568 cm −1 ; P O stretching vibrations at 923 cm −1 , 990 cm −1 , 1037 cm −1 , and 1089 cm −1 ; O H plane bending vibration at 1659 cm −1 ; and broad peak around 3300 cm −1 due to the absorption of water. These data provided further support for the histological diagnosis of CPPD deposition disease, including tophaceous pseudogout.
After the diagnosis was confirmed, the treatment plan was discussed with the neurosurgeons. The patient was not experiencing any disruption to his daily function or everyday life as a result of the lesion, aside from the mild pain in the joint. Furthermore, the lesion was not neoplastic. Based on the situation and the clinical and pathological findings, the neurosurgeons advised against resection, because severe neurological dysfunction could result. The patient ultimately did not wish to have the mass resected. He continued to coach sumo wrestling, but decided that he should not receive student tackles to the right chin in the future. Three years after the first visit, the mass showed virtually no change in size.
CPPD crystal deposition occurs in a generalized or local pattern. Generalized CPPD crystal deposition is often associated with medical conditions, such as hyperparathyroidism, chronic gout, renal failure, hypomagnesemia, and hypophosphatemia. In this case report, the patient had gout, but the condition was controlled with medication. This finding suggests that CPPD crystal deposition may occur, even if gout is well controlled. Local CPPD crystal deposition occurs secondary to trauma and results in tissue degeneration or necrosis. The present patient had been participating in sumo wrestling for a long time and always received tackles to the right cheek. It is possible that there is an association between the patient’s history of participating in this sport and the force exerted on the right cheek and his development of tophaceous pseudogout in the TMJ.
The term ‘tophaceous pseudogout’ has also been used to describe lesions that have massive or tumoural CPPD crystal deposition. Tophaceous pseudogout more frequently occurs in the large joints such as the knees, hips, wrists, and pubic symphysis. However, it can also affect the small joints, including the TMJ. Tophaceous pseudogout in the TMJ shares clinical and radiographic features with neoplastic disorders, most frequently pain, swelling, and limited opening of the mouth. However, a wide range of clinical symptoms has also been reported, such as facial pain, otalgia, trismus, delayed healing, pre-auricular tenderness and swelling, and joint destruction. In these cases, clinicians usually consider neoplasms as a differential diagnosis. Potential diagnostic possibilities include fibrous dysplasia, synovial chondromatosis, osteochondroma, chondroblastoma, and chondrosarcoma.
In this patient, CT scans revealed a large calcified mass around the right TMJ, but the mass had no continuity with the mandibular condyle or other neighbouring bones. In addition, it gained mobility and changed shape on translating the joint from the open to the closed position. These views suggested that the calcified mass was not fibrous dysplasia. Synovial chondromatosis was also ruled out because it is characterized by the formation of small, multiple, metaplastic nodules of cartilage that are generally within the joint space. It is difficult to differentiate tophaceous pseudogout from malignant tumours such as osteochondroma, chondroblastoma, and chondrosarcoma. The calcifications are usually in these tumours, although the calcifications are generally heterogeneous in CT scans. Furthermore, the contour of the tumour is relatively unclear. These characteristics are different from those seen in the case presented here; therefore, tophaceous pseudogout was suspected. However, the radiographic features of tophaceous pseudogout of the TMJ are non-specific, and it was not possible to completely rule out other diseases. Therefore, a biopsy was performed to make a definitive diagnosis. Abdelsayed et al. reported that they could not make a definitive diagnosis by fine-needle aspiration ; therefore, an open biopsy was planned.
Pathological diagnosis of the specimen revealed that the mass contained numerous deposits of rod-shaped or rhomboid crystals, suggesting tophaceous pseudogout. In 1981, Martel et al. stated that evidence of CPPD crystals using a polarizing microscope and chemical analysis was necessary for a diagnosis of CPPD deposition disease. Many cases of CPPD deposition disease have been diagnosed using electron probe microanalysis. Electron probe microanalysis can detect the ratio of calcium and phosphorus components in a specimen; however, this method cannot identify the crystal structure. On the other hand, the use of methods such as XRD and FT-IR allows the identification of the crystal structure and element. Therefore, XRD and FT-IR were chosen for use in this patient, which led to a definitive diagnosis.
X-ray diffraction is most widely used to identify unknown crystalline materials such as minerals and inorganic compounds. Electron clouds surrounding an atom in a crystal structure tend to diffract X-rays. Therefore, XRD measurement gives XRD patterns consisting of the intensity and diffraction angle. The XRD pattern obtained can be identified by checking the powder diffraction files (PDF) of the International Center for Diffraction Data (ICDD; Newtown Square, PA, USA). For most patients, the identification of the XRD pattern obtained is performed using the function of ‘peak search’ in the application installed in the PC attached to the XRD machine.
FT-IR spectroscopy is used to obtain the infrared absorption spectrum of the specimen. Some infrared radiation is absorbed by the specimen, whereas some radiation passes through. As a result, the spectrum represents the molecular absorption. When hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ) is measured by FT-IR, molecular absorption such as P O bending and stretching vibration are detected in the resulting spectrum.
The treatment of CPPD crystal deposition in the TMJ varies according to the extent of the clinical findings and the patient’s symptoms. Painful but non-expansile cases of CPPD deposition may be treated by non-surgical approach using non-steroidal anti-inflammatory medication or by conservative arthrotomy. On the other hand, surgical excision is the main treatment for tophaceous pseudogout lesions. After the excision of the mass, symptoms were relieved and the patient’s ability to open his mouth increased. Surgical excision remains the best therapeutic option for the management of tophaceous pseudogout. However, in this patient, the CPPD crystal deposition was substantial, and the mass was pressing on the temporal bone and extended to the base of the skull. Surgical excision of the mass may have resulted in severe neurological dysfunction. The patient decided not to undergo surgery. Furthermore, he continued to coach sumo, but decided not to receive any tackles to the right chin in future. Three years after the first visit, the size of the mass showed almost no change.