Abstract A 63-year-old man with a history of chronic lympho- cytic leukemia and a prosthetic aortic valve was hospitalized because of a mastoiditis, complicated by meningitis and epileptic seizures. Two weeks later he developed a lesion in the right temporal lobe. A brain abscess was suspected. However, after treatment his clin- ical condition failed to improve. 99m Tc-Tetrofosmin brain SPECT was performed and revealed substantially increased tracer uptake. Due to the patient’s clinical deterioration, surgery was considered most appropriate. Histopathology established the diagnosis of glioblas- toma multiforme. This case suggests a note of caution in every case of a rapidly evolving space-occupying lesion independently of the patient’s previous history. Key words : SPECT ; imaging of ; infections CNS ; glioblastoma, brain abscess, 99m Tc-Tetrofosmin. Introduction The differential diagnosis of a brain lesion that shows a ring-like enhancement pattern on comput- ed tomography (CT) and magnetic resonance imag- ing (MRI) may be difficult and typically includes necrotic tumour and pyogenic brain abscess. A sys- tematic approach and assessment of the patient’s history may provide clues to narrow the differential. Discrimination between these two entities is of paramount importance, since they require com- pletely different therapeutic approaches and they carry diverse prognosis. Herewith we report on an unusual case of a rapidly evolving glioblastoma mimicking a brain abscess, in an immunocompro- mised patient. Case history A 63-year-old man was referred to our hospital complaining of nausea and gait disorder of two months duration. The patient had been diagnosed with and was treated for chronic lymphocytic leukemia the past 5 years ; he also had cardiac sur- gery to replace the aortic valve with a prosthesis 15 months earlier. Two months prior to his initial referral, he had an episode of mastoiditis on the left side, for which he was hospitalized and treated by myringotomy with tympanostomy and tube inser- tion. His condition was then complicated by menin- gitis and epileptic seizures, for which he underwent a CT scan. This demonstrated a normal brain parenchyma (Fig. 1A) ; it also supported the pres- ence of mastoiditis, demonstrating fluid-filled mid- dle ears and mastoids, as well as fluid accumulation in the frontal, ethmoidal, and maxillary sinuses. The patient received the proper antibiotic treatment, his condition improved and he was discharged twelve days later. Two weeks later he complained of right otalgia with otorrhea and acute otitis media was diagnosed. The neurological examination was unremarkable. A subsequent brain CT scan at that time revealed a space-occupying lesion 14 mm in diameter in the posterior part of the right temporal lobe (Fig. 1B). Considering his preceding history and the fact that on the CT scan the brain lesion appeared to develop in a fortnight, an abscess was the most likely diag- nosis. The patient was treated accordingly with intravenous antibiotics. However, after ten day’s hospitalization and treatment his clinical condition failed to improve. On a follow-up CT scan the brain lesion had increased in size, developed a peripheral ring-enhancing pattern following the administration of contrast medium, and was surrounded by edema (Fig. 1C). The clinical course and the radiographic aggrava- tion suggested the possibility of a brain tumor. In order to evaluate the metabolic status of the lesion, we decided to perform a brain scintigraphic study using the tumor-seeking radiopharmaceutical tech- netium-99m Tetrofosmin ( 99m Tc-TF). The single- photon emission computed tomographic (SPECT) study revealed substantially increased tracer uptake in a region spatially corresponding to the brain lesion on the last CT scan (Fig. 2). This finding denoted the presence of a lesion of strong metabol- ic activity, which was more compatible with the presence of a brain neoplasm. Due to the patient’s clinical deteriorating and in light of the aforementioned morphologic and Acta neurol. belg., 2008, 108, 24-26 Rapidly progressing glioblastoma resembling brain abscess in leukemia George A. ALEXIOU 1 , Spyridon TSIOURIS 2 , Athanasios P. KYRITSIS 3 , Konstantinos S. POLYZOIDIS 1 , Spyridon VOULGARIS 1 and Andreas D. FOTOPOULOS 2 1 Department of Neurosurgery, 2 Department of Nuclear Medicine, 3 Department of Neurology, University Hospital of Ioannina, Ioannina, Greece ————