A clinical pharmacist’s involvement in the diagnosis and treatment of a case of brainstem abscess: a case report

Brainstem abscess is a rare, life-threatening intracranial pyogenic infection (accounting for < 1% of brain abscesses) with nonspecific clinical manifestations, posing great challenges to diagnosis and treatment. Optimal antibiotic selection requires comprehensive consideration of blood–brain barrier penetration, abscess wall permeability, pathogen susceptibility, and PK/PD properties. Timely management of adverse drug reactions is critical for improving prognosis. This case report describes the full-course conservative management of a brainstem abscess patient with clinical pharmacist participation, providing practical reference for similar rare cases. A 56-year-old Asian Han male was admitted on November 14, 2024, presenting with dizziness, partial right ptosis, and gait lateropulsion. Initial non-contrast cranial computed tomography (CT) findings were initially interpreted as acute ischemic stroke (right basal ganglia/brainstem infarctions), which represents a well-recognized diagnostic challenge for early-stage brainstem abscess on plain CT. On hospital day 2, infection-related coagulation dysfunction was noted, and head magnetic resonance imaging (MRI) with diffusion-weighted imaging (DWI) revealed a right midbrain ring-enhancing lesion with restricted diffusion, highly suggestive of abscess formation. The patient developed a fever (38.4 °C) on the same day. On hospital day 3, cerebrospinal fluid (CSF) findings, together with multiparametric MRI features, supported the diagnosis of encapsulated brainstem abscess; the pathogens remained unidentified without definitive microbiological confirmation. Over approximately 2 months, clinical pharmacists participated in multidisciplinary team (MDT) discussions and sequentially optimized the antibiotic regimen in response to clinical/radiological progression, antimicrobial pharmacokinetic considerations, and adverse drug reaction management: ceftriaxone → ceftriaxone + vancomycin → meropenem + vancomycin → meropenem + vancomycin + linezolid → ceftriaxone + linezolid. All key pharmacist recommendations were accepted by the treatment team. Probable drug‑associated thrombocytopenia (nadir platelet count: 63 × 10⁹/L) improved after regimen adjustments, with recovery occurring during continued linezolid therapy. The patient was discharged on day 58 (CSF IL-6: 19.62 pg/mL), and his platelet count normalized to 130 × 10 9 /L at the 14-day post‑discharge follow-up, with near‑complete radiological lesion resolution (tiny residual nodular enhancement) and no residual neurological deficits. Consistent with current evidence-based guidelines, empirical antimicrobial therapy with reliable blood–brain barrier penetration should be initiated promptly for critically ill patients with brainstem abscess and unidentified pathogens, with regimen selection individualized according to clinical context. Clinical pharmacists may contribute meaningfully to regimen optimization and safety monitoring of antibiotic-associated adverse events such as thrombocytopenia. Balancing antimicrobial efficacy and safety facilitates individualized optimization, providing valuable experience for the conservative management of rare brainstem abscess.