Abstract
Infectious intracranial aneurysms are rare and most commonly associated with infective endocarditis. When infective endocarditis is not evident, and patients have common vascular risk factors such as hypertension, lobar hemorrhage may be misclassified as primary hypertensive intracerebral hemorrhage, and infectious intracranial aneurysms may be overlooked. We report a case in which a perihematomal isodense lesion on computed tomography prompted vascular evaluation and led to the diagnosis of a ruptured distal cortical presumed infectious aneurysm during treatment for pyogenic spondylodiscitis.
A 77-year-old woman with hypertension was hospitalized under orthopedic care for severe low back pain and treated with intravenous antibiotics. Lumbar imaging confirmed spondylodiscitis at L3/4. On hospital day 37, computed tomography revealed a left parietal subcortical hemorrhage with an approximately 12-mm isodense perihematomal lesion that was partially enhanced on contrast-enhanced computed tomography, prompting transfer to the neurosurgery department. She was neurologically intact except for higher cortical dysfunction. Cerebral angiography demonstrated a small aneurysm in a distal cortical branch. Craniotomy with aneurysm resection and hematoma evacuation was performed. Histopathology showed inflammatory cell infiltration consistent with infectious vasculitis; cultures were negative, likely due to prior antibiotic exposure. Transthoracic echocardiography showed no valvular vegetation.
This case highlights that a subtle perihematomal computed tomography lesion should prompt vascular imaging to exclude treatable secondary causes such as infectious intracranial aneurysm, even in patients with hypertension without evidence of infective endocarditis.
Introduction
Infectious intracranial aneurysms (IIAs) are rare but potentially devastating lesions that frequently rupture and cause intracranial hemorrhage.1,2) They are most commonly associated with infective endocarditis (IE); therefore, when IE is not evident and patients have common vascular risk factors such as hypertension, lobar hemorrhage may be prematurely attributed to primary hypertensive intracerebral hemorrhage, and vascular evaluation may be omitted.1-3) We report a case of a ruptured distal cortical IIA occurring during treatment for pyogenic spondylodiscitis in a patient without echocardiographic evidence of valvular vegetation. Rather than the occurrence of IIA during spondylodiscitis treatment per se, the central message of this report is that a subtle perihematomal isodense lesion on computed tomography (CT) served as the critical diagnostic clue that prompted cerebral angiography and led to definitive surgical treatment—a diagnostic pathway that, to our knowledge, has not been explicitly described in this clinical context.
Case Presentation
A 77-year-old woman with hypertension and dyslipidemia (treated with olmesartan, amlodipine, and atorvastatin) developed severe low back pain 1 day before admission and became unable to stand. She was transported to our hospital and admitted. She was initially treated for presumed urinary tract infection with intravenous cefazolin on hospital day (HD) 1-7, which was changed to cefmetazole on HD 8; intravenous antibiotic therapy was continued until HD 14. On admission, inflammatory markers were elevated (white blood cell [WBC] 10,400/μL; C-reactive protein [CRP] 10.02 mg/dL), with a transient peak on HD 4 (CRP 18.22 mg/dL), and then gradually improved under antibiotic therapy (CRP 1.69 mg/dL on HD 15 and 1.29 mg/dL on HD 33), ultimately normalizing by HD 73 (WBC 6,000/μL; CRP 0.18 mg/dL). Serial lumbar radiographs showed no findings suggestive of infection on HD 1 or HD 13 (Figure 1A, B); however, bony destruction of the superior endplate of L4 became evident on HD 23 (Figure 1C). Blood cultures obtained on HD 11 and HD 25 were negative. On HD 25, lumbar magnetic resonance imaging demonstrated endplate destruction across the L3/4 intervertebral disc, with inflammatory signal changes on short T1 inversion recovery image, consistent with pyogenic spondylodiscitis (Figure 1D, E). Throughout this period, the patient remained under the care of the orthopedic surgery department for the management of pyogenic spondylodiscitis. On HD 36, she developed difficulty using her mobile phone and became restless. Non-contrast head CT obtained on HD 37 revealed a left parietal subcortical (lobar) hemorrhage with a thin acute subdural hematoma along the left convexity (Figure 2A), prompting immediate transfer to the neurosurgery department. She was alert and had no motor weakness; however, she exhibited right-left disorientation, finger agnosia, and acalculia. Importantly, CT demonstrated an approximately 12-mm isodense mass-like lesion on the cortical side of the hematoma (Figure 2A, B), which was partially enhanced on contrast-enhanced CT (Figure 2C), raising suspicion of an underlying vascular lesion; however, the aneurysm itself was not definitively visualized on contrast-enhanced CT and was first confirmed by catheter cerebral angiography, which revealed a small fusiform aneurysm arising from a distal cortical branch of the posterior parietal artery corresponding to the lesion (Figure 2D, E).
Given suspicion of a ruptured aneurysmal lesion, craniotomy was performed for aneurysm resection and complete hematoma evacuation. Preoperative simulation and angiographic reconstruction clearly delineated the aneurysm and its parent artery (Figure 3A, B). Intraoperatively, after evacuation of a thin acute subdural hematoma, a portion of the intracerebral hematoma was seen extruding from the parietal cortical surface; the parent artery was identified anterior to the hematoma and dissected (Figure 3C, D). After temporary clipping and distal dissection, the aneurysmal lesion embedded in inflammatory granulation tissue was identified and completely resected (Figure 3E). Histopathology demonstrated vascular components with marked mixed inflammatory cell infiltration and inflammatory granulation tissue (Figure 3F). No microorganisms were identified histologically, and intraoperative bacterial cultures were negative. Considering the infectious background, distal cortical aneurysm on angiography, operative findings, and inflammatory pathology, the lesion was diagnosed as a presumed ruptured IIA, supported clinically and pathologically. Transthoracic echocardiography showed no valvular vegetation and no evidence of heart failure. Postoperatively, right-left disorientation and finger agnosia improved, whereas acalculia persisted. She was transferred to a rehabilitation ward on HD 60. Long-term oral minocycline was administered, and the pyogenic spondylodiscitis became quiescent. She was discharged home on HD 210.
Discussion
IIAs are rare, accounting for 2.6% to 6% of intracranial aneurysms in autopsy series, and carry a high risk of rupture and neurological morbidity.1) They are most commonly associated with IE, yet IIAs can arise from any bacteremic state that seeds the arterial wall via septic emboli or vasa vasorum inflammation, leading to transmural vessel wall destruction and pseudoaneurysm formation.2) When IE is not evident and patients have common vascular risk factors such as hypertension, IIA is frequently not considered, and lobar hemorrhage may be misattributed to primary hypertensive intracerebral hemorrhage, with vascular evaluation omitted. The present case, in which an IIA ruptured during antibiotic treatment for pyogenic spondylodiscitis without echocardiographic evidence of IE, illustrates this diagnostic pitfall and raises an important question about the threshold for vascular imaging in patients with active systemic infection who develop intracranial hemorrhage.
The central diagnostic contribution of this case is the identification on CT of a perihematomal isodense, partially enhancing lesion that triggered proactive cerebral angiography. Lobar hemorrhage in older patients with hypertension is most commonly attributed to hypertension or cerebral amyloid angiopathy; however, the 2022 American Heart Association/American Stroke Association (AHA/ASA) guideline recommends catheter intra-arterial digital subtraction angiography (DSA) as the gold standard when an underlying macrovascular cause is suspected, particularly in patients with lobar hemorrhage and atypical imaging features such as an adjacent abnormal structure or unusual hematoma configuration.4) In our patient, the approximately 12-mm isodense cortical-side lesion with partial contrast enhancement on CT was the critical finding that prevented premature attribution to a hypertensive etiology. To our knowledge, a perihematomal isodense or partially enhancing lesion has not been previously described as an explicit diagnostic clue prompting angiographic workup for ruptured IIA; prior reports of IIA presenting as intracerebral hemorrhage during treatment for a spinal or paraspinal infection have generally reached the diagnosis through autopsy, incidental imaging, or delayed recognition of concurrent endocarditis rather than through a specific perihematomal CT sign.5) This finding therefore appears to be rare or underrecognized, and we propose that it represents a clinically actionable imaging clue that should be specifically sought when interpreting CT in patients with lobar or subcortical hemorrhage occurring during active systemic infection. Cerebral angiography demonstrated a small fusiform aneurysm of the distal posterior parietal artery, consistent with the predilection of IIAs for distal cortical branches reported in large series.3) Surgical resection confirmed the diagnosis: histopathology demonstrated marked perivascular mixed inflammatory cell infiltration and inflammatory granulation tissue, supporting infectious vasculitis as the underlying mechanism. It deserves emphasis that small distal IIAs may be occult on CT angiography (CTA) or magnetic resonance angiography owing to their size and distal location; DSA should therefore be performed when non-invasive imaging is inconclusive in the appropriate clinical setting. In the present case, the aneurysm was not definitively identified on the initial contrast-enhanced CT, which showed only partial enhancement of the perihematomal lesion; the diagnosis was first established by catheter DSA. On retrospective review of the contrast-enhanced CT angiography dataset obtained for preoperative surgical planning, the aneurysm could, in fact, be delineated (Figure 3A), indicating that the lesion was present but not prospectively recognized on the original CT angiogram. This sequence underscores that even when CTA data technically contain the aneurysm, a high index of suspicion driven by a subtle perihematomal CT finding—rather than CTA interpretation alone—was required to prompt the angiographic workup that ultimately secured the diagnosis.1,2,6,7)
The absence of positive microbiological data warrants comment but does not invalidate the diagnosis. Both blood culture sets were drawn after antibiotic initiation, substantially reducing sensitivity; culture-negative IIA following antibiotic exposure is well recognized.8) Intraoperative cultures were similarly negative, and no microorganisms were identified histologically, findings likely attributable to the same mechanism. The sensitivity of blood cultures in pyogenic spondylodiscitis is reported to be 40%-60% even without prior antibiotic exposure, and pre-treatment sampling is therefore strongly recommended.9,10) In such circumstances, diagnosis should rely on an integrated clinicopathological assessment rather than microbiological confirmation alone. In the present case, the histopathological finding of dense perivascular inflammatory cell infiltration and inflammatory granulation tissue, the fusiform morphology and distal cortical location on angiography, and the clinical context of active systemic infection are each individually consistent with IIA and collectively support the presumptive diagnosis.
The pathogenic relationship between pyogenic spondylodiscitis and the intracranial aneurysm merits brief comment, while acknowledging important limitations in our data. Pyogenic spondylodiscitis is almost exclusively hematogenous in origin, and IIAs can arise from any bacteremic state through septic embolization to the vasa vasorum, with subsequent transmural inflammation and arterial wall destruction, independent of cardiac valvular disease.2,3,9,10) In the present case, blood cultures were obtained only after antibiotic exposure, and a culture-negative course does not exclude a prior bacteremic episode. An unrecognized or transient bacteremia may have served as a shared pathogenic event that concurrently seeded both the lumbar disc space and the distal cortical arterial wall. We avoid stronger causal claims given the absence of microbiological confirmation.2,3,11) IIAs without IE are characterized by a broader spectrum of predisposing conditions than classically recognized, underscoring that the pathogenesis extends beyond the cardiac embolic route.2,3)
Coexistent IE has been reported in up to one-third of patients with pyogenic spondylodiscitis, and bacterial cerebral aneurysm rupture has been described as the event that first reveals underlying IE in this setting.12,13) In the present case, transthoracic echocardiography showed no valvular vegetation or evidence of heart failure, making overt IE unlikely. However, transesophageal echocardiography was not performed, and occult or partially treated IE cannot be completely excluded; this represents a limitation of the present case. Regardless of this uncertainty, the broader clinical implication stands: in any patient with active systemic infection who develops lobar or subcortical hemorrhage, IIA should be actively considered even in the absence of established IE. When non-contrast CT demonstrates an isodense or partially enhancing perihematomal lesion—a finding that may be overlooked during routine stroke assessment—proactive vascular imaging, including DSA, is warranted. Conversely, the absence of such a CT lesion should not by itself be taken to exclude IIA, since small aneurysms may not produce a visible correlate. This case also illustrates that higher cortical dysfunction without motor deficit, as observed in our patient, may represent the initial neurological manifestation of IIA rupture in the parietal cortex and may be misinterpreted as delirium in the setting of systemic infection; prompt neuroimaging in this context is therefore essential.
The rationale for selecting open surgical resection over endovascular treatment or conservative antibiotic therapy alone merits brief comment. Endovascular parent artery occlusion is often favored for IIAs because of their typically fragile, fusiform morphology, which is poorly suited to coil embolization or stent-assisted techniques; however, in the present case, the aneurysm was already ruptured and located on a small, surgically accessible distal cortical branch, and a sizable evacuable lobar hematoma was present. Craniotomy therefore offered the combined advantages of immediate hemostasis, hematoma evacuation to relieve mass effect, and direct histopathological confirmation of the diagnosis in a single procedure—advantages not readily achieved with endovascular occlusion alone. Conservative management with antibiotics alone was not considered appropriate given that the aneurysm had already ruptured and posed an ongoing risk of rebleeding. This decision-making aligns with general management principles for ruptured IIAs, in which surgical resection is preferred when the aneurysm is distally located, technically accessible, and associated with a hematoma requiring evacuation, whereas endovascular or medical management may be favored for proximal, surgically inaccessible, or unruptured lesions.6,7)
Conclusion
Ruptured presumed IIA should be considered a secondary cause of lobar/subcortical hemorrhage, even in hypertensive patients without echocardiographic evidence of IE, including those undergoing treatment for pyogenic spondylodiscitis. An isodense or partially enhancing lesion adjacent to the hematoma on CT is an important diagnostic clue that should prompt proactive vascular imaging, including DSA, to avoid misclassification as primary hypertensive hemorrhage. When a patient with active systemic infection develops new focal or higher cortical symptoms, prompt neuroimaging and a low threshold for vascular evaluation are warranted, as early diagnosis enables definitive surgical or endovascular treatment.
Conflicts of Interest
All authors have no conflict of interest.
Ethics Statement
Written informed consent for publication of this case report and accompanying images was obtained from the patient. The institutional ethics committee determined that formal ethical approval was not required because this was a retrospective anonymized case report.
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