|LETTER TO EDITOR
|Year : 2016 | Volume
| Issue : 4 | Page : 313-315
Incidental finding of technetium-99m methylene diphosphonate uptake in acute cerebral infarct
Jayanta Das, Soumendranath Ray
Tata Medical Center, Kolkata, West Bengal, India
|Date of Web Publication||19-Sep-2016|
Tata Medical Center, Kolkata, West Bengal
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Das J, Ray S. Incidental finding of technetium-99m methylene diphosphonate uptake in acute cerebral infarct. Indian J Nucl Med 2016;31:313-5
|How to cite this URL:|
Das J, Ray S. Incidental finding of technetium-99m methylene diphosphonate uptake in acute cerebral infarct. Indian J Nucl Med [serial online] 2016 [cited 2019 Jul 23];31:313-5. Available from: http://www.ijnm.in/text.asp?2016/31/4/313/190802
Technetium-99m methylene diphosphonate (99m Tc-MDP) whole body skeletal survey is commonly performed in various primary malignancies for metastatic workup. Extraosseous radiotracer uptake in the whole-body bone scan is seen infrequently. Patterns of such unusual uptake help in the diagnosis of nonmalignant pathology at times, which influence the disease management significantly. We report such a case of acute cerebral infarct picked up in 99m Tc-MDP bone scan with anatomical localization by single photon emission tomography-computed tomography (SPECT-CT). The diagnosis was later confirmed by diffusion-weighted magnetic resonance imaging. Diagnosis and timely intervention saved the patient from long-term neurological sequelae.
A 65-year-old female presented with bloody nipple discharge and an ill-defined retro-areolar lump in the left breast. Biopsy confirmed ductal carcinoma in situ (DCIS), and Hadfield's operation was performed. Histopathology revealed positive resection margin for DCIS. Reoperation was planned for cavity shaving.99m Tc-MDP whole body bone scan was performed as a part of staging workup. In addition, SPECT-CT of the head was performed.
The delayed planner images of the whole body bone scan showed abnormally increased radiotracer concentration with moderate intensity over the right hemicranium, more conspicuous in the posterior view and right lateral spot view of the skull [Figure 1]. No other evidence of abnormal radiotracer uptake suggestive of osteoblastic metastasis was seen. SPECT-CT scan of the skull showed the abnormal uptake in the right cerebral hemisphere associated with subtle hypodensity in the parietooccipital region of the right cerebral hemisphere [Figure 2]. The corresponding MRI images showed T2 hyperintensity with restricted diffusion in the MRI [Figure 3]. The overall features were consistent with acute infarct involving the right cerebral hemisphere at the junction of the right middle cerebral and right posterior cerebral artery territory. On clinical correlation, the patient revealed history of recent onset weakness of the left lower limb.
|Figure 1: Technetium-99m methylene diphosphonate bone scan: Posterior planer image (a) and spot view of the lateral skull (b) show focal uptake of radiotracer in right hemicranium|
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|Figure 2: Single photon emission tomography-computed tomography scan of brain showed the abnormal uptake in right cerebral hemisphere associated with subtle hypo density in the parieto-occipital region of the right cerebral hemisphere suggestive of acute infarct|
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|Figure 3: Axial T2-weighted (a), diffusion-weighted imaging (b) and apparent diffusion coefficient (c) images of magnetic resonance imaging of the brain shows acute infarct of the right parietal lobe|
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The repeat operation for DCIS was deferred and the patient was referred to neurology department for management of the acute infarct.
99m Tc-MDP is an excellent radiopharmaceutical for bone scan. It attaches to the surface of the hydroxyapatite crystal of the bone by chemisorption.99m Tc-MDP bone scan is performed to detect skeletal metastasis. Occasionally, extraosseous tracer uptake is also noticed in various organs.
Immediately after intravenous injection, approximately 75% of the injected dose of 99m Tc-MDP redistribute into the extracellular fluid space of various organs. The initial uptake in normal tissues is directly related to blood flow and vascularity. Apart from tissue perfusion, sympathetic tone and capillary permeability are also responsible.
After 3 h of 99m Tc-MDP injection, the radiotracer concentration in tissue is directly proportional to their calcium content and thus highest in bone. A similar correlation between calcium and diphosphonate retention is also present in extraosseous pathological tissue.
Acute cerebral infarct causes cell membrane damage and rapid intracellular calcium influx. Released calcium precipitates in mitochondria. On the other hand, protein denaturation takes place as a consequence of tissue hypoxia. Deposition of calcium also takes place in denatured protein.
Increased tracer uptake in the brain is also seen in other conditions with blood-brain barrier disruption such as primary neoplasm, metastases, or inflammation. Extraosseous uptake of radiotracer is seen in hematomas, meningiomas, metastases, and dural calcifications.
SPECT-CT provides incremental information when planner images are equivocal. It can be used as a problem-solving tool for appropriate anatomical localization of the increased radiotracer uptake, for example, extraosseous radiotracer uptake in acute right cerebral infarct in this case.
In appropriate clinical setting, acute cerebral infarct should be considered in the differential diagnosis of intracranial extraosseous 99m Tc-MDP uptake in the whole body bone scan. It causes 99m Tc-MDP retention in delayed images because of rapid intracellular calcium influx as a consequence of cell membrane damage and protein denaturation. In selected cases, SPECT-CT may be used as a problem-solving tool.
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Conflicts of interest
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[Figure 1], [Figure 2], [Figure 3]