ISCA is a rare entity, even rarer when it is associated with a brain abscess. Our review of the literature suggests that ISCA mainly involves the cervical cord [1,2,3, 5,6,7,8]. An ISCA typically presents with progressive back pain with fever followed by neurological deficits, and it can also present with acute neurological deficits similar to episodes of transverse myelitis [3, 6]. The specific symptoms are location-dependent and rapidly progressive [8]. But sometimes the clinical manifestations may progress insidiously [9].The mechanisms of infection include hematogenous dissemination, contiguous spread from adjacent infection or infected dermal sinus, direct penetrating trauma, or septic emboli [10]. Many organisms can cause intramedullary abscesses, including Mycobacterium tuberculosis in the developing world and gram-positive cocci in the developed world [3]. In terms of clinical manifestations, the patient presented to our hospital complaining of head and neck pain and numbness in both lower extremities for 7 days. There was no fever at the time of admission, and a fever ≥ 38.0℃ occurred after admission. The blood culture was streptococcus anginosus. Streptococcus anginosus group bacteria are gram-positive organisms that are part of the oral and gastrointestinal microbiome [11]. They are common pathogens in ISCA. Str. viridans was seen in 25% of all streptococcal ISCA and is a common pathogen in subacute bacterial endocarditis [2]. Subacute infective endocarditis progresses insidiously, with no fever in the early stage. Therefore, patients with no fever in the early stage should also be alert to infective endocarditis.
Contrast-enhanced MRI is the method of choice when intramedullary or brain abscesses are suspected [3, 12]. Typical MRI features of intramedullary and brain abscesses are hypointensity on T1WI, the increased signal on T2WI and peripheral contrast enhancement with gadolinium [6, 13]. The hyperintensity on T2-weighted images gradually subsided as the infection resolved after treatment [14]. The images of our patients were similar to typical images. After treatment, the hyperintensity range on T2WI was reduced. It is worth mentioning that our case suffered from nausea and vomiting during hospitalization. Computer tomography showed an intracerebral hemorrhage at the location of the left occipital brain abscess. At present, cerebral hemorrhage caused by brain abscess is related to many influencing factors, but the pathogenesis is not very clear. The authors support the idea that a strong inflammatory response destroys fragile new blood vessels, leading to vascular rupture and secondary cerebral hemorrhage [15].
For treatment and prognosis, a reasonable empiric regimen in an immunocompetent patient without recent instrumentation would be vancomycin, ceftriaxone, and metronidazole. This regimen can cover gram-positive bacteria (including methicillin-resistant Staphylococcus aureus), gram-negative bacteria and anaerobes [16]. Our patient was given ceftriaxone combined with linezolid based on blood culture susceptibility results. Both of them not only have excellent anti-streptococcal activity, but also have the characteristics of strong tissue penetration and the ability to cross the blood–brain barrier, which can achieve higher cerebrospinal fluid concentration [3, 7]. The optimal duration of treatment has not been established. Patients should be followed closely with serial neurological examinations and MRIs. Mortality has recently declined due to imaging techniques and antibiotic use but remains at 4%. Neurological sequelae occur in 60% of surviving patients [4]. Patients with persistent bacteremia and a combined brain and spinal cord abscess should be treated with surgery, but in patients with hemorrhagic stroke, surgery should be delayed for at least 4 weeks and reimaging should be performed before surgery [17, 18]. At the follow-up 1 month later, our patient's symptoms and imaging findings were improved but left lower extremity numbness remained. The patient is advised to see a cardiovascular surgeon for surgical evaluation.
In conclusion, although ISCA is a rare entity, we need to increase awareness and vigilance of ISCA. Early diagnosis and rapid use of broad-spectrum antibiotics are the keys to halting disease progression and reducing mortality. When the patient's symptoms, signs or imaging suggest an ISCA, regardless of whether there are symptoms such as fever and headache, blood culture, spinal cord, head MRI and echocardiography should be completed early to identify whether the patient is complicated with bacteremia and brain abscess, and then identify whether the cause is infective endocarditis.
