A rare case of ruptured anterior cerebral artery infected aneurysm with angioinvasion secondary to disseminated Nocardia otitidiscaviarum: A case report and literature review

Abstract

Background: The cases of ruptured infected aneurysms secondary to disseminated nocardiosis are exceptionally rare. Therefore, there is no guideline for investigation or optimal treatment.

Case description: A 51-year-old man with immunocompromised status was first presented with pneumonia and cerebral infarction, where the infected aneurysm was ruptured thereafter. Intraoperative findings revealed left anterior cerebral artery thrombosis and occlusion with evidence of angioinvasion along with pus discharge which was later identified with Nocardia otitidiscaviarum. Our case was the first to report on the angioinvasive nature of cerebral nocardiosis, which occurs concurrently with a ruptured infected aneurysm and an unusual presentation that made the diagnosis and treatment challenging.

Conclusion: Cerebral nocardiosis may cause ruptured infected aneurysms in patients with risk factors, especially for immunocompromised hosts. Furthermore, Nocardia can present with severe cerebral manifestation due to angioinvasion causing cerebral infarction accompanied by a ruptured infected aneurysm.

Keywords: Anterior cerebral artery aneurysm; Case report; Cerebral nocardiosis; Infected aneurysm; Nocardia.

Figure 1:

Preoperative computed tomography (CT) scan of the brain. (a) Cerebral infarction was noted at bilateral anterior cerebral artery (ACA) territory which is more prominent on the right side (arrowheads). (b) Small intracerebral hemorrhage was noted in the right frontal region (arrowheads). CT angiography (CTA) (c) showing distal A2 segment aneurysm (white arrow). (d) Three-dimensional CTA showing left distal A2 segment aneurysm (white arrow). (e) Repeated CT scan of the brain showing expanded hematoma at the bilateral frontal region with intraventricular hemorrhage.

Figure 2:

Intraoperative findings. (a) Pus and infected slough were noted along the bilateral frontal cortex, which is prominent on the right side (arrowheads). (b) Pus was identified in the right subdural space consistent with subdural empyema (arrow). After interhemispheric dissection, (c) thrombosis the in left distal ACA was noted at A2 to A3 segment (white arrowheads). (d) The left ACA was whitish in color and covered with slough (black arrowheads) in contrast to the right ACA (asterisk). (e) Flow was not detected in left distal ACA using intraoperative micro-Doppler ultrasound since it was thrombosed. (f) Aneurysm was identified at the left A2 segment (asterisk) with pus along proximal ACA wall (arrow). (g) Clips were applied at both proximal and distal to the aneurysm in an attempt to trap the aneurysm. (h) Pus was also noted in the left subdural space and Sylvian cistern (arrow).

Figure 3:

Microscopic findings from brain pus and thrombus in an. (a) Gram stain showing Gram-positive branching filament with prominent polymorphonuclear leukocytes in the background (×1000). (b) Modified acid-fast staining of the same specimen showing a positive result (×1000). Macroscopic growth of the Nocardia from brain pus and thrombus in an aneurysm. (c) Chalky white colonies were identified in the Lowenstein-Jensen medium. (d) Colonies’ growth was evident in chocolate media after 3 days.

Figure 4:

Postoperative CT scan of the brain. (a) New infarction was evident at the right internal capsule and right thalamus, including the left thalamus (arrowheads). (b) Infarction was also noted at the right midbrain (white arrow). (c) Sagittal view showing the applied clips at proximal and distal to an aneurysm (arrow).