Subdural empyema and its correlation with subdural hematomas a local experience and literature review

ABSTRACT

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Subdural empyemas, both are infrequent –whether if they appear spontaneously or arise as a complication in the evolution of a subdural hematoma (SH) –. There are just a few publications in the literature1 about this topic. This work is aimed to review 15 cases of patients who were operated at the “Hospital de Urgencia de la Asistencia Pública” (HUAP) within a period of 15 years. In general, these patients have a good evolution, if a timely treatment is applied and it is dormant in its presentation, and diagnosis could even be made during the intraoperative stage. No evolution differences were reported when these patients were operated by means of a craniectomy or a craniotomy (plate) 2, as well as no differences were found when treated with/with no drainage. As a general consensus, both must be treated with antibiotics therapy to last for -at least- three to four weeks, in order to control the focus of infection2. None of the reviewed cases required reintervention.

Key words: Subdural Empyema, Subdural Hematoma

INTRODUCTION

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Both, chronic and subacute subdural hematomas (SH) are a pathological entity usually reported in neurosurgical clinical practice. Onset of a subdural empyema, –whether spontaneous or as a complication in the evolution of these hematomas– are infrequent, but there are just a few clinical picture studies in medical literature1. Most of these studies focus on identifying the pathogen agent involved. In general, most of them do not encompass more than just a few cases in each publication. So far, there is no good definition about what the most adequate surgical procedure for treating this pathology is. It is possible to use a craniectomy (enlarged drill) approach, as well as a craniotomy (plate) 2 approach. No description has been made if it is adequate to manage them with or with no drainage. Likewise, there is no consensus about the time to keep them covered with an antibiotics therapy.
In this work a set of 15 cases of patients operated at the “Hospital de Urgencia Asistencia Pública de Santiago” (HUAP) with this type of subdural empyemas were retrospectively reviewed, both if spontaneous or as a complication of subdural hematomas. The search was made within a period of 15 years. The type of surgery used, the use of drainage, antibiotics therapy duration and the resulting evolution in these patients were analyzed.

MATERIALS AND METHODS

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All cases of subdural empyemas –diagnosed and operated at the HUAP– during a period of 15 years were reviewed, including those related with subacute/chronic SH, and those with spontaneous onset (with no prior surgery). All cases related with acute SH and severe cranial trauma (as we consider these are a pathologically different entity) were not included in this review. Those cases of empyemas related with adjacent acute infectious processes, as an origin focus, such as otitis, mastoiditis and sinusitis, which can cause infections due to proximity, with epicortical purulent secretion, but not related with presence of subdural collections, were not included, either. According to these criteria, 15 cases were found. All relevant clinical records and operation protocols obtained from the Record Program of Operating Room Protocols of the HUAP were reviewed. From all the records reviewed, only one could not be properly reviewed, as the folder was in very poor conditions. The results obtained were tabulated in an Excel spreadsheet, with information such as age, sex, prior surgery, type of surgery performed, use of drainage, type of germ obtained in the cultures and duration of the antibiotics therapy, among others aspects, as well as the time elapsed between the SH removal surgery, and the empyema onset, if applicable.

RESULTS

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Since January 2004 till June 2019 15 subdural empyemas were operated at the HUAP. Apart from these cases, during this same period 85 operations dealing with acute SH and 139 dealing with Chronic SH were reported. The percentage of subdural empyemas operated was 6.27 % of the whole amount of patients. Empyemas reported as surgical complication, after removal of a prior SH, were 4.5% of all cases. From all these empyemas, five of 15 (33%) did not have a prior surgery and the diagnosis was intraoperative. The other 10 patients left were previously operated due to subdural hematomas (only two of them had more than one subdural hematoma operation) with further infections. In all these empyemas, operated as chronic-type or subacute subdural empyemas, a subdural capsule was found and the empyema was a subdural collection. From all patients operated of subdural empyema, most of them were male patients, 73% (11 of 15 patients). Female patients were a smaller number, 27% (four of 15 patients). Their ages ranged from 20 to 97 years old, with a higher tendency in patients older than 60 years old (median of 62 years old and average of 56 years old) (Graph 1). Graph 1(distribution per age and sex) For those empyemas having a prior SH surgery, the time elapsed between the initial surgery and empyema onset was 36.1 days, as an average (ranging between 19 and 97 days). An intraoperative diagnosis was made in seven patients, this is 47% of all cases. Two of the patients had a diagnosis via imagery (TAC with contrast) (Figure 1), this is 13% of all cases. Five patients were diagnosed due to clinical suspicion, that is 33% of all cases, (three patients with operative wound infection, one patient with fever and one patient with CSF fistula). In one case, no diagnosis could be determined, as we did not have the information of the clinical record, only the operative protocol was available. The germ isolated in the cultures dealt with: eight cases with staphylococcus aureus; one case with Eschericchia coli; one case with Klebsiella pneumoniae, associated to proteus mirabilis; one case with streptococcus anginosus, associated to streptococcus constellatus; and one case with streptococcus gordonii. Staphylococcus aureus was the germ with the highest incidence, as identified pathogen. Among the other three cases, in two of them, the cultures were negative; in one case, we did not have clinical record information. The antibiotic medication used was very varied. Vancomycin was used only in four patients; Vancomycin associated with Ceftriaxone was used in two patients; Vancomycin associated with Meropenem was used in three patients; Imipenem was used only in one patient; Ceftriaxone associated to Metronidazol was used in two patients; Ceftriaxone associated to Ciprofloxacin was used in one patient. The antibiotic program was managed, according to the antibiogram and according to the direction given by the infectious diseases specialist. The duration of the antibiotic treatment was 32.7 days, as an average, ranging between 21 to 56 days (three to 8 weeks). Most of the cases were treated for more than four weeks. Regarding the surgical technique used, 10 patients were operated by means of craniectomy (enlarged drill) and five of them, by means of craniotomy (plate). Only in seven of them, a subdural drainage was inserted. No outcome differences have been found among patients operated by means of craniectomy and those operated by means of craniotomy. No differences were found among those who were treated with drainage and those with no drainage. Regarding neurological examination, the Objective Glasgow Admittance score, ranged between 10 to 15, with an average of 13. Eight of the patients were admitted due to hemiparesis; five of them had no focal neurological deficit; in two of them, no data were found about their admittance conditions. From a clinical standpoint, among the 15 patients checked, six of them had fever when admitted; five of them had migraine; and four of them had convulsions. In three of them migraine and fever were associated (Graph 2). Graph 2 (Distribution as per Clinical Manifestations) Among of the nine patients from whom we could get an admittance haemograma, only four of them had objetivable leukocytosis. It is also important to report there was no need to reoperate none of the patients who were treated due to empyema. When discharged, most patients had a Glasgow Scale ranging between 14 to 15, with recovery of their paresis. Only one patient was discharged with a Glasgow score of 13.

Discussion

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Regarding the review made on 15 empyemas found during the period, we could infer that the highest percentages were found in elderly males. This does not match findings from other published works, dealing with subdural empyemas, but encompassing all the causes, where the tendency is to find this in rather young male patients,^{3, 4}. Likewise, the clinical picture of the empyemas published involving all the causes, had a much higher severity compared with the subdural empyemas found at the HUAP, whose symptoms were rather dormant and with little clinic associated. Among the symptoms found, only fever and migraine provided hints that the patients could have a possible infectious etiology; except for those patients who had an operative wound infection and CSF fistula, which –from the beginning– led us to the potential finding that collections were empyemas. Most laboratory tests did not provide any hint about the infectious etiology of the collection. One point to highlight is that half of the empyemas (47%) were misleading –at their initial stage– as we thought these were chronic-type subdural collections, given the few symptoms thereof. The diagnosis was finally made during the intraoperative stage, when hematic fluid with pus was found (Figure 2). This review also highlights that a third of the empyemas did not have any prior surgery. The origin of the infectious focus could not be identified in these patients. Regarding imagery diagnosis, at the HUAP we can only perform Brain CT. It is an excellent tool to identify collections, but it does not allow to clearly differentiate the infectious condition thereof, because even if it is performed with a contrast medium, the capsule of the hematomas may have some uptake. After reviewing the literature, the most useful tool for making the differential diagnosis is NMR with a diffusion sequence, which clearly restricts, in case of empyemas^{5, 2}. Regarding the infectious etiology, the germs identified in our review match those found in the empyemas, secondary to surgical interventions. Staphylococcus aureus is the germ with the highest incidence^{6, 7}. In our review, the onset period of empyemas –when these were secondary to removing a previous SH– was up to three months, after the surgery. This was not reported in the reviewed literature that described an average period of one month after surgery. However, such data was found in other publications. Therefore, the onset of this type of complication, related with a prior removal surgery of a subdural (Figure 3), must be considered a long latency in its appearance in patients. The antibiotic therapy used did not allow to state a treatment program for this pathology, as it must match the antibiogram obtained. This is clearly evidenced in the various antibiotic programs used. On the contrary, the treatment period to be agreed cannot be shorter than three weeks. In most reviews, an adequate period is more than four weeks². It is important to highlight that in this review the type of germ was objectified in 86% of all cases, in contrast to literature findings, that ranged only between 54 to 81%¹. Regarding the surgical technique, it is important to highlight that in our series no differences were reported between the outcome obtained with a craniectomy, against that of a craniotomy. There are no differences either, between using/not using drainage. Literature findings are variable. Some works prefer the use of craniotomy², and others prefer to use a craniectomy⁸. Regarding the foregoing, the advantages of using craniectomy is to execute a more enclosed technique, it involves less bleeding, it has no risk of osteomyelitis, it may be easily repeated, it is less risky in elderly patients and has a shorter surgical time¹. On the contrary, the advantage of using craniotomy is to have a better exposure, better exploration, but with a higher rate of associated complications, such as hemorrhages edema and osteomyelitis. Regarding the foregoing, a proper use of craniotomy would be for those cases with presence of septums inside the collection¹. Some works mentioned the relapse would be lower when performing craniotomy⁷, however in our review no such differences were found. Another very important point to highlight is that none of the patients –in our series– who were operated required an additional intervention. No evident correlation was reported in those patients who had more than one intervention of their subdural hematomas and the appearance of empyemas in this series. The reviewed literature reports that a possible etiology for empyemas onset is a vascularized capsule, acting as a vessel for germs². Notwithstanding the foregoing, there are obviously various etiological possibilities to discuss, such as the distance between the drainage outlet and the surgery spot, their residence time, the concomitant infectious states, basal conditions of the patient and highlighting the operative wound infection, as well as cerebrospinal fluid leakage. In general, in this type of empyemas, it is clear that its severity is much lower than in those cases when this complication is produced by an adjacent focus of infection, such as otitis, sinusitis and mastoiditis. Likewise, patients have a very good neurological recovery when being timely treated two. Most patients reviewed in this series were discharged with a Glasgow Scale ranging between 14 to 15, with recovery of the initial neurological focality, if any.

CONCLUSIONS

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In the analysis made, we could find that chronic-type or subacute empyemas, secondary to subdural collections, are not as severe as those related with adjacent focus of infection which arise with little symptomatology, and whose diagnosis –in many cases– is related with the intraoperative procedure. No differences were found in the outcome with the various surgical techniques that could be used. It is not essential to be managed with or with no drainage. Patient´s evolution had –in most cases–an excellent recovery, with a good clinical condition when discharged, and with a regression of their initial neurological picture. It is clear that this type of infectious conditions require an antibiotic treatment, for not less than three weeks. Ideally, it should be prescribed for more than four weeks, in order to get proper control of the focus of infection. Another point to be highlighted in this review is that, for this type of empyemas, there is no need of reintervention. In order to properly solve this, it is only necessary to devise an adequate treatment, with the initial drainage of the collection and with a proper antibiotic therapy. It is also high suspicious when this type of complication, when there is an infection of operative wound, fever and leakage of cerebrospinal fluid thereof. Future reviews may be necessary to better define if there is an advantage among the various surgical techniques, as that was not evident in this paper.

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