A 59-year-old man with an unremarkable medical history presented with an acute state of confusion, fever and two episodes of generalized tonic-clonic seizures on that day. On admission, the patient was febrile (tympanic temperature of 38.1 C), his blood pressure was 137/79 mm Hg with a pulse rate of 103 beats/min, his respiratory rate was 16/min, and his oxygen saturation was 98% at room air. There were no murmurs or other abnormalities on cardiac auscultation, and examination of the respiratory system, the abdomen and anogenital region was normal. The neurological examination revealed psychomotor inhibition and left homonymous hemianopsia, without any motor abnormalities or other neurological deficits.
There were no abnormalities found on the laboratory studies (hemoglobin 15.23 g/dl, white blood cell count 8.70 x 103/mul, C-reactive protein 0.5 mg/dl, erythrocyte sedimentation rate 11 mm/h), including negative results on the immunological study, seronegative status for HIV and negative serological tumor markers.
A brain magnetic resonance imaging (MRI) scan revealed a single, large, right, frontoparietal lesion. Cerebrospinal fluid analysis showed no abnormalities, including negative results for DNA of HSV 1 and 2, Mycobacterium tuberculosis, toxoplasmosis, and JC virus. A repeated brain MRI scan showed a worsening of the lesion, and the hypothesis of brain abscess was strongly considered (fig. 1). Treatment with ceftriaxone (2 g i.v. every 12 h) combined with metronidazole (500 mg i.v. every 6 h) and dexamethasone (5 mg i.v. every 8 h) was started. Seizures were controlled with levetiracetam (500 mg p.o. every 12 h). There was no evidence of paroxysmal activity on the electroencephalogram, and contrast-enhanced computed tomography of the chest, abdomen and pelvis resulted negative. Blood and urine cultures were obtained before starting antibiotic therapy, also with negative results. Endocarditis was ruled out by a normal transesophageal echocardiogram.
After 4 weeks of antibiotic therapy, although the neurological exam was normal, the patient again became febrile and symptomatic, complaining of a severe headache that evolved for 4 days, throbbing in nature and precipitated by Valsalva maneuver. Another brain MRI was performed, with evidence of further worsening of the lesion (fig. 2).
Given the lack of evidence of a resolution of the lesion and the persistence of neurological symptoms, surgical drainage was performed with isolation of S. lugdunensis. The antibiogram of the isolated microorganism disclosed susceptibility to trimethoprim-sulfamethoxazole, methicillin, gentamicin, and erythromycin. Transesophageal echocardiogram and blood cultures were then repeated, again with negative results.
Treatment with trimethoprim-sulfamethoxazole (5 mg/kg p.o. every 6 h) was performed during 12 weeks with a good response. There was also a favorable imaging response, with brain MRI undertaken a month after starting this therapy revealing almost complete resolution of the brain abscess (fig. 3). After 6 months of follow-up, the patient remains asymptomatic, and his neurological exploration is unremarkable.