Teaching Case

Patient admitted with headache, left side hemiparesis, protuberance on the scalp and low grade fever.

An 48 year old man was admitted in our hospital with headache and left side weakness. Clinical examination showed left side hemiparesis protuberance on the left scalp and low grade fever. A dual-phase spiral CT (fig 1) was performed before and after the injection of iodine contrast medium (100ml). An MRI (fig 2) was also performed and the diagnostic procedures were completed with a percutaneous biopsy of the scalp lesion (fig 3). Biopsy results showed Actinomyces israelii as the cause of infection. The patient was treated effectively with antibiotic therapy.

Actinomycosis is most commonly caused by the gram-positive, higher bacterium Actinomyces israelii but the bulk of evidence supports the concept that most actinomycotic infections are polymicrobial in nature. A. israelii is found in the normal flora of the oral cavity gastrointestinal tract, bronchii and female genital. Actinomycosis of the brain is rare but treatable cause of infection. It may cause brain abscess (67%), meningitis/meningoencephalitis (13%) or actinomycoma (7%)[1]. Subdural empyema and epidural empyema occur in 6% of the cases[1]. Its source might be hematogenous or through extension of oral cervicofacial disease. Diagnostic approach includes dual-phase helical CT and MRI imaging but definite diagnosis is made microbiologically after surgically acquired specimen is examined. As a result of the infrequent involvement of the CNS, the radiological features of this infection have been described in only a few cases. CT findings vary and and are not specific: hemispheric or periventricular location, pyocephalus, rim-enhancing and edema[2]. MRI findings are also not specific and depend on the location of the infection. In the case of a patient with an abscess [3] MRI showed a rim enhancing mass with a cystic component and edema. Treatment includes surgical treatment and prolonged antibiotic therapy [4].