99mTc-HMPAO-leukocyte scintigraphy for diagnosis and therapy monitoring of skull base osteomyelitis

Abstract

Objective: Skull base osteomyelitis (SBO) is a rare but life-threatening disease observed in elderly diabetic patients, with high risk of recurrence and difficult therapeutic management. The diagnosis is ascertained from a set of clinical, biological, and imaging findings. CT and MRI allow initial diagnosis, but are not accurate to affirm healing at the end of therapy. 99mTc-HMPAO-Leucocyte Scintigraphy (LS) is highly sensitive and specific for the detection of infection. The aim of this study was to evaluate LS i) for initial diagnosis, and ii) to confirm healing at the end of antibiotherapy in SBO.

Study design: We retrospectively reviewed from November 2011 to September 2015 all patients with confirmed SBO who underwent LS twice, at diagnosis and at the end of antibiotic therapy in our nuclear medicine department (n = 27).

Methods: Clinical, biological, CT, LS, and follow-up data were recorded in all patients. LS images (planar and tomographic performed 4 hours and 24 hours after intravenous injection of autologous Tc-99m-HMPAO-leucocytes) were visually assessed and quantified.

Results: At initial diagnosis, 25 of 27 patients had a positive LS. At the end of antibiotic therapy (3 ± 1 months duration), 26 of 27 patients had a negative LS. During subsequent follow-up (= or >6 months), the disease recurred in four patients including three with a negative postantibiotherapy LS scan.

Conclusion: In this retrospective study, LS was powerful for initial diagnostic of SBO and for healing assessment at the end of antibiotic therapy. We conclude it is a useful technique for therapeutic monitoring of SBO.

Level of evidence: 4.

Keywords: Skull base osteomyelitis; infection; recurrence; scintigraphy.

Figure 1

Typical imaging features of skull base osteomyelitis on MRI and Leukocyte Scintigraphy (SPECT/CT). MRI: T2 axial weighted‐sequences (A), T1 axial weighted‐sequences (B); LS: axial, coronal, sagittal CT (C), and fused SPECT/CT images (D). MRI shows an hypersignal on the T2 weighted‐sequence and an hyposignal on the T1 weighted‐sequence of the left part of the sphenoid, left part of the clivus and of the petrous part of the left temporal bone, and soft tissue infiltration in the left retropharyngeal and parapharyngeal spaces. CT enables localization of the tracer uptake and shows bony rarefaction of the clivus. SPECT/CT shows high uptake of the radiotracer in the left part of the clivus and in the petrous part of the left temporal bone.

Figure 2

Typical Leucocyte Scintigraphy (LS) scans before and after antibiotic therapy in a patient with no recurrence. A. Planar 4 and 24 hours anterior images before treatment; B. SPECT, CT and SPECT/CT axial 24 hours images before treatment; C. planar 4 and 24 hours anterior images after treatment; D. SPECT, CT and SPECT/CT axial 24 hours images after treatment. In September 2014, planar and SPECT/CT images showed high uptake of radiotracer on the tympanic part of the temporal bone and mandibular condyle. After two months of systemic antibiotherapy against pseudomonas aeruginosa, LS scan was normalized.

Figure 3

False‐negative post‐therapeutic LS: a case of recurrence 7 months after the end of the antibiotic treatment. A. June 2014, SPECT, CT and fused SPECT/CT axial slices: high radiotracer uptake in the right part of the clivus corresponding to bone osteolysis. B. August 2014, SPECT, CT and fused SPECT/CT axial slices: normalization 1 month after the end of adequate systemic therapy. C. January 2015, SPECT, CT and fused SPECT/CT axial slices: radiotracer uptake in the left part of the clivus and in the petrous part of the left temporal bone23. D. April 2015, SPECT, CT and fused SPECT/CT axial slices: normalization after 3 months of adequate systemic therapy against pseudomonas aeruginosa.