ISCA is a rare central nervous system infection. The case discussed here is a unique instance of a patient diagnosed with both ISCA and a brain abscess caused by K. pneumoniae, an extremely unusual combination. In imaging, it’s vital to distinguish ISCA from tuberculosis infection. Differentiating between ISCA, brain abscess, and tuberculosis abscess is crucial in imaging assessments. Contrast-enhanced MRI is the preferred method when suspecting intramedullary or brain abscesses[5, 6], showing low T1-weighted signal and high T2-weighted signal. Post-contrast, a distinct annular enhancement with a complete, smooth, and uniform abscess wall is observed[7]. Including DWI and SWI in the evaluation can be particularly useful. Abscesses exhibit high signal intensity on DWI with corresponding low ADC values, indicating restricted water diffusion due to inflammatory cell viscosity within the pus[8, 9]. Brain abscesses often display a smooth, low-signal ring on SWI, forming two concentric rings, known as the "double ring sign"[10]. Remarkably, our case exhibits all these imaging characteristics, significantly enhancing the diagnostic accuracy.
Mechanisms of ISCA infection encompass hematogenous dissemination, contiguous spread from adjacent infection or infected dermal sinus, trauma, or septic emboli[11]. Hematogenous spread is the primary pathogenesis among adults[12], involving septic emboli from extraspinal sources like urogenital sepsis, infective endocarditis, and pneumonia [13, 14]. In this case, blood cultures were negative, and cardiac ultrasound, abdominal ultrasound, and urinary system ultrasound did not reveal any other apparent sources of infection. The patient displayed pneumonia, and both sputum and pus cultures indicated K. pneumoniae infection. Therefore, absence of evident direct infection invasion, like vertebral destruction, points to likely hematogenous infection.
Pinpointing the infection source was challenging. While K. pneumoniae frequently triggers hospital-acquired infections, particularly urinary tract infections, pneumonia, and bacteremia[3], but community-acquired cases are rare[4]. Immunocompromised and malignancy-afflicted individuals are more susceptible. Our patient’s history ruled out post-trauma or post-operative infection. However, a chest CT revealed signs of pulmonary infection. Notably, the patient had a history of pulmonary tuberculosis and compromised immunity. Cerebrospinal fluid NGS analysis, pus culture and Sputum culture all confirmed K. pneumoniae infection, suggesting the infection spread from the lungs to the central nervous system through the bloodstream.
Evidence-based medicine advocates combining neurosurgery (like craniotomy, biopsy, or stereotactic drainage) with extended antibiotic therapy (4–8 weeks, considering brain abscess size, bacteria, and operability) led by neurologists[15]. Guidelines recommend surgery for brain abscesses over 2.5 cm or in herniation risk cases. Following spinal abscess surgery, the patient's headaches and left limb weakness improved. Though the brain abscess lacked surgery, worsening right limb weakness during antibiotic treatment prompted another surgery for relief. This case emphasizes timely surgical intervention's pivotal role in effective treatment.
In summary, we firstly presented a case of ISCA and brain abscess caused by K. pneumoniae. The diagnosis was established through DWI and CSF NGS. The patient underwent surgical intervention and experienced a significant improvement in clinical symptoms. Our report underscores the importance of early, accurate diagnosis and timely surgical intervention.