Conventionally, the first choice of treatment for brain abscess beyond 2.5 cm in diameter would be surgical method [16, 1]. However, there was once a patient with brain abscess diameter over 2.5 cm was reluctant to be treated with surgical method, and he had accepted conservative medical treatment in our center. To our surprise, the clinical symptoms of fever, headache, and visual field defect relieved soon after several days of medicine therapy, and abscess lesions, edema around abscess decreased obviously in MRI too. Which interested us to find out whether brain abscess beyond 2.5 cm must be treated with surgical method? Which patients with brain abscess over 2.5 cm could be treated with medicine only?
In our study, in the 18 cases of conservative treatment patients, the maximal abscess diameter of 11 was beyond 2.5 cm, and the largest one was about 4.2 cm far beyond 2.5 cm, the mean size of abscess in conservative group was 2.85 ± 0.98 cm. Our date showed that even if the abscess was bigger than 2.5 cm, medicine alone could get a good response in some cases. In fact, medicine is the basis for the treatment of brain abscess, even with the surgical therapy, patients also need a long time of medicine treatment to go. With the development of better antibiotics, more and more brain abscess patients showed good response to the medicine treatment in modern times [5, 23, 13].
The most common causative pathogens of most brain abscesses are gram positive (streptococci and staphylococci) and anaerobic bacteria . In one week of trial medical treatment, we used meropenem, vancomycin and sometimes plus metronidazole as the first choice of antibiotics combination which were broad-spectrum and might cover all the likely pathogens with good ability penetrating through blood-brain barrier and into abscess cavity .
In fact, in this group of patients, almost everyone had responded to the first week of trial medicine therapy. Abscess sizes, GCS, KPS, mental status (MMSE), and the degree of edema around the abscess are important factors to judge the clinical status for the brain abscess [1, 7, 11, 12, 18]. After a week of trial medical treatment, almost every patient got an improvement in clinical status, but there were different changes in these factors between the two groups. Conservative group got a more obvious decline in abscess sizes (Fig. 3), more obvious improvement in MMSE scores (Fig. 5), KPS scores and GCS scores (Fig. 6) than that in surgical group. However, no obvious differences about the extent of GCS and KPS scores improvement between the two groups were observed, while MMSE scores improvement and abscess sizes decline were much more obvious in conservative group than that in surgical group after trial medical treatment, which implied that conservative group was more sensitive to the medical therapy than the surgical group.
Compared to these factors, although both groups got a little decline in edema indexes, but the edema indexes before and after medical therapy were not obvious different between the two groups in our study. Maybe the edema around the abscess and the abscess size decreased in a certain ratio.
About all the changes of factors during one week of trial medical treatment, logistic regression analysis showed that the consecutive variation of MMSE scores and brain abscess sizes were highly correlated with the final choice of treatment methods for the brain abscess patients (p = 0.027; p = 0.019), and might be two of the most predictive crucial factors related the choice of treatment methods.
Nevertheless, surgical group had a more severe clinical condition on admission, while after surgical treatment, the surgical group recovered more quick than the conservative group (Fig. 8), which was in consistent with convention views. But for the patients who are not reluctant to accept surgical treatment, maybe the trial medicine therapy would be a good choice.