Subdural false twins: concomitant appearance of subdural haematoma and spontaneous subdural empyema

Background

Chronic subdural haematomas are one of the most common types of intracranial post-traumatic collections and their incidence appears to be increasing in developed countries, in part due to the increasing life expectancy and prevalence of antiplatelet and anticoagulation therapy. The timing and cause of chronic subdural haematomas are often unclear and undetermined. Prognosis is favourable and treatment is usually simple and straightforward.

Conversely, subdural empyemas are relatively rare conditions, most often occurring after neurosurgical procedures, penetrating head injuries or otorhinogenic infections. On the other hand, spontaneous subdural empyemas are extremely rare with only a few reported cases. Furthermore, we could not find any report of a synchronous occurrence of a subdural chronic haematoma and a spontaneous subdural empyema.

We believe this is a curious and challenging case due to the unforeseen initial diagnosis, only possible at surgical inspection, that elicited doubts about the ideal course of action and need of a multidisciplinary approach to achieve the best clinical management.

Case presentation

The authors present the case of a 55-year-old man with a history of hypertension, type 2 diabetes mellitus, obesity, chronic alcoholism and smoking habits. He was brought to the emergency department (ED) due to right arm weakness for the past 3 days. He reported several episodes of syncope on coughing in the past month and was being investigated for possible carotid sinus hypersensitivity. His vital signs were stable, except for fever (39°C) and he had no consciousness impairment (Glasgow Coma Scale (GCS) 15). No other neurological changes were noted at physical examination; meningeal signs were absent and no focus of systemic or local infection was found after observation by the neurology and internal medicine departments.

Investigations

In the month preceding this acute presentation, a cranial CT scan had been done as part of the investigation of carotid sinus hypersensitivity, which was deemed as normal (figure 1).

A new CT scan was requested at the ED owing to the new neurological findings, revealing bilateral hypodense subdural collections with hyperdense areas suggestive of subdural membranes or blood clots (figure 2). Blood samples showed an elevation of C reactive protein (23 mg/dL) but no associated leucocytosis. Blood coagulation values were within normal range.

By this time, the neurosurgical department was confident that the subdural collections were the reason behind the new symptoms and signs of the patient and that they were compatible with chronic subdural haematomas.

Treatment

Given the dimensions and the development of neurological impairment, surgery was considered the primary treatment option. As with most chronic/subacute subdural haematomas, it was decided to use burr holes to evacuate the collections. No specific adjustments were made concerning the normal approach to this surgery. The patient was positioned in dorsal decubitus position, with head elevated 30° and centred in the midline.

The first two burr holes were made on the left frontal and parietal bones and, after opening of the dura mater, blood clots and a typical ‘motor oil’ chronic subdural collection were drained.

The next two burr holes were made on the right frontal and parietal bones. Although the same findings were expected on the right side, after opening the dural layer, a yellow, purulent liquid under pressure was drained and collected for microbiological analysis. The remaining of the procedure was uneventful and included macroscopic cleaning of both collections after repeated washing with conventional lukewarm saline solution. The recently expanded cerebral parenchyma was visualised through the burr holes on both sides. Bilateral subdural drainage systems were placed at the frontal burr holes before closure and gentamicin was applied to the subcutaneous tissue on the right side.

Postoperative CT scan (24 hours after the procedure) confirmed the drainage of both subdural collections, with clear improvement of mass effect (figure 3). In the first postoperative days, an improvement of motor function on the right arm was noticed. The patient was transferred to infectious diseases department, according to our institution’s protocol for spontaneous infections of the central nervous system, and empirical intravenous antibiotherapy was started using broad-spectrum antibiotics (ceftriaxone, vancomycin and metronidazole). On the fourth day, the microbiological analysis of the subdural empyema revealed the presence of Escherichia coli and therapeutic regimen was changed accordingly to piperacilin/tazobactam.

Despite good analytical evolution with reduction in the C reactive protein values (1.71 mg/dL), by the seventh day after surgery, a marked neurological deterioration was noted (the patient opened his eyes only on request, did not obey commands and was confused—GCS 12) and a new CT scan was performed showing a recurrence of the right subdural collection and associated generalised sulcus attenuation (figure 4).

The patient was, once again, brought to the operating room. This time, a small circular frontoparietal craniotomy was performed on the right side. A well-organised fibrotic capsule was identified in the subdural space circumscribing the subdural empyema. The same capsule was coagulated and removed, with copious washing of the subdural space. The drained subdural collection was once again sent to microbiological analysis.

A control CT scan was performed on the next day, showing no complications (figure 5).

The patient started a new cycle of intravenous antibiotherapy (ceftriaxone and metronidazol during 4 weeks) and remained in the infectious diseases ward until discharge. The new microbiological study was inconclusive.

No local or systemic infections (besides the subdural empyema) were detected during in-hospital stay (urine, blood and sputum cultures were negative).

The patient progressively recovered from his previous status (GCS 15 with no neurological deficits), with analytical improvement at discharge (C reactive protein=0.18 mg/dL without other relevant changes) and complete reabsorption of the residual subdural collection was confirmed by imaging (figure 6).

He was discharged 51 days after admission and underwent an additional 2 weeks of oral antibiotics at home (amoxicillin/clavulanic acid).

Outcome and follow-up

The patient was observed at 1 month, 6 months and 1 year after discharge by a neurosurgeon and an infectiologist. No complications were observed and the patient remained completely functional, with no limitations, returning to his normal activity.