An uncommon case showing three different pathologies on ^99mtechnetium-methylene diphosphonate bone scintigraphy

A 64-year-old female was referred to our department for a three phase ^99mtechnetium (^99mTc)-methylene diphosphonate bone scintigraphy (BS) for evaluation of skull base osteomyelitis. Co-morbidities included diabetes mellitus and renal failure. Planar BS was equivocal in showing mildly increased uptake on the skull base left side [Figure 1a, dotted arrow] which when corroborated with single photon emission computed tomography/computed tomography (SPECT/CT) revealed involvement of the left mastoid [Figure 1b–d, arrow] and petrous temporal thus confirming skull base osteomyelitis. SPECT/CT had an incremental value over planar imaging in evaluating the bones involved. Diffuse radiotracer uptake was also noted in bilateral lung fields [Figure 1a, thin arrows] along with another area of increased uptake in dorso (D12) - lumbar (L1) spine [Figure 1a, thick arrow]. Her serum urea was 74 mmol/l; serum creatinine - 2.4 mmol/l; serum calcium - 13 mg/dl; serum phosphate - 7.0 mg/dl and alkaline phosphatase - 247 IU/l, thus confirming lung uptake secondary to hypercalcemia of renal failure. The patient had a history of Pott's spine 2 years ago for which she had taken antitubercular treatment followed by pedicle screw fixation of D12-L1 vertebrae. So BS basically revealed all three aspects of disease pathology in the same scan.

Close

Figure 1 ^99mTechnetium-methylene diphosphonate bone scan planar (a) and Single photon emission tomography (SPECT) (b), computed tomography (CT) (c) and hybrid SPECT/CT (d) images. SPECT/CT showed an incremental value over planar imaging in diagnosis of skull base osteomyelitis (a, dotted arrow; b-d, arrow). Also diffuse radiotracer uptake was noted in bilateral lung fields (a, thin arrows) due to hypercalcaemia, along with another focal area of increased uptake in lower dorso (D12) - lumbar (L1) spine region (a, thick arrow) due to Pott's spine

Export to PPT

A positive uptake on a ^99mTc-MDP or gallium-67 scan is said to be diagnostic of skull base osteomyelitis in the appropriate clinical scenario.[1] SPECT/CT has been found to be useful for the diagnosis of skull base osteomyelitis.[2] Radioisotope scans are also useful for follow-up and treatment monitoring.[3] Lung is the most common site of metastatic calcification as relatively low carbon dioxide tension of the extra-cellular fluid surrounding the alveoli causes an alkaline environment that favors the deposition of calcium.[4] Metastatic calcium deposition has been reported in hyperparathyroidism, parathyroid carcinoma, chronic renal failure among other diseases associated with a calcium-phosphate ion-product >5 mmol²/l².[5] Extra-osseous calcium deposition has also been reported in kidney and stomach.[6] BS has emerged as an important tool in the diagnosis and management of Pott's spine[7] with sensitivity approaching 75%.[8] To our knowledge this is a unique case in literature showing three different findings from different etiologies in the same BS.