Dormant Fungus Hid Inside a Brain Surgery Wound for Two Years Before Striking

Doctors in Xi’an, China, have documented an extraordinary case of fungal stealth: a common yeast species, Candida parapsilosis, apparently lay dormant inside a patient’s brain for two full years after routine neurosurgery before finally announcing itself. The report, published in the British Journal of Biomedical Science, describes the first known instance of this particular fungus establishing a chronic intracranial infection following burr-hole drainage for a chronic subdural hematoma, one of the most frequently performed operations in neurosurgery. The case is a striking reminder that the human skull can harbor quiet infections that mimic entirely different diseases, and that the tissue surgeons remove during operations can hold the decisive diagnostic clue.

The patient was a 66-year-old man with hypertension and schizophrenia who had undergone bilateral burr-hole drainage at another hospital two years earlier to treat chronic subdural hematomas, collections of old blood that accumulate slowly between the dura mater and the brain surface, typically in older adults after minor head trauma. Burr-hole drainage is favored because it is minimally invasive and generally safe: surgeons drill a small opening in the skull, evacuate the liquid hematoma, and often leave a temporary drain. In this patient, drainage had been limited, the drain was removed after 48 hours, the wound healed well, and he was discharged without fever or any obvious complication. On the surface, the operation appeared to be a success.

Over the following two years, however, the man experienced recurrent, progressively worsening headaches, along with involuntary tongue protrusion and shaking of his limbs. His body temperature remained normal throughout, a detail that would later prove diagnostically misleading. Ten days before admission, he suffered a generalized tonic-clonic seizure that resolved spontaneously after roughly two minutes. Imaging performed on arrival revealed bilateral frontotemporoparietal hematomas of inhomogeneous density, including hyperdense areas and a significant mass effect on the brain. Those hyperdense regions suggested that the chronic hematomas had organized, meaning the liquid blood had transformed into a thick, fibrous, scar-like structure, a known but troublesome evolution of subdural collections.

Because organized hematomas cannot be drained through a burr hole, the surgical team concluded that conservative management or repeat drainage would fail to relieve the brain compression. After confirming that the patient had normal serum immunoglobulin levels and no immunosuppressive history, they performed a bilateral craniotomy to evacuate the hematomas. What they found in the operating room was unusual: the hematoma membrane had become abnormally thickened and organized, reaching approximately one centimeter at its thickest point, with a leathery, tough consistency. The cavity contained a small amount of yellowish fluid and abundant organized material with a distinctive sandy appearance. Recognizing that these findings deviated from a typical chronic subdural hematoma, the surgeons sent the membrane and its contents for pathological examination, a decision that would ultimately crack the case.

The patient was transferred to intensive care with a low-grade fever and lethargy, and empirical antibiotics were started. Five days after surgery, histopathological examination of the resected membrane revealed fibrous connective tissue with hyaline degeneration, hemosiderin deposition from old blood, and structures suggestive of fungal hyphae on hematoxylin and eosin staining. Specialized fungal stains, including Grocott’s methenamine silver and periodic acid-Schiff, could not be performed due to technical constraints at the treating institution, but the suspicious findings were enough to trigger a multidisciplinary team meeting. A lumbar puncture followed, revealing cerebrospinal fluid with a markedly elevated nucleated cell count dominated by polymorphonuclear cells, and a serum (1→3)-β-D-glucan test, which detects a cell wall component shared by many pathogenic fungi, came back positive. Empirical antifungal therapy with voriconazole was initiated, and a lumbar drain was placed for continuous cerebrospinal fluid drainage to limit fungal spread within the now widely opened subdural cavity.

Definitive identification came from the laboratory. Cerebrospinal fluid was inoculated onto Sabouraud dextrose agar and incubated at 35 degrees Celsius; after 48 hours, creamy-white, smooth, glistening colonies appeared, and Gram staining revealed ovoid budding yeast-like cells. Matrix-assisted laser desorption ionization-time of flight mass spectrometry, a technique that identifies microbes by the mass fingerprint of their proteins, identified the isolate as Candida parapsilosis with 99.9 percent confidence. Fungal spores were also visible on direct microscopic examination of the cerebrospinal fluid sediment. To rule out contamination and hematogenous spread, the team applied rigorous controls: sterile saline served as a negative control in all fungal cultures, three serial blood culture sets incubated for 14 days were all negative, and only isolates recovered from at least two independent specimens were accepted as true pathogens. Once the identification was confirmed, therapy was switched to targeted fluconazole at 400 milligrams daily.

The recovery was not smooth. The hospitalization was complicated by intestinal obstruction, pneumonia, and bacteremia, all managed successfully with supportive care and targeted antibiotics. A follow-up CT scan on postoperative day 40 showed near-complete absorption of the subdural fluid collection and good re-expansion of the brain. After completing eight weeks of antifungal therapy, the patient was discharged with only mild residual involuntary tongue protrusion, free of headaches and limb shaking. At three months after discharge, he remained asymptomatic, with no clinical or radiological evidence of recurrent infection.

The two-year latency period is the most scientifically provocative element of the case. The authors propose a multifactorial model to explain it. The most likely source is iatrogenic contamination during the original burr-hole drainage, since surgery is the most common route by which fungi enter the central nervous system, gaining access via the patient’s skin, the surgeon’s gloves, or contaminated instruments. Candida parapsilosis is a commensal of human skin with a well-characterized ability to form biofilms on plastic surfaces, which makes it a notorious cause of device-associated infections even when a drain is in place for only 48 hours. Biofilm fragments or colonized fungi can persist after device removal and serve as a reservoir for late-onset infection. The organized hematoma cavity itself may then function as an immune-privileged niche: relatively enclosed, hypoxic, iron-rich, and physically sequestered by a membrane up to a centimeter thick, it suppresses local immunity and shields the fungus from both host defenses and circulating antifungal drugs. This model neatly accounts for the patient’s two asymptomatic years, his persistently normal temperature, and his negative blood cultures.

The case also exposes a dangerous diagnostic blind spot. Chronic fungal infections of the central nervous system account for less than five percent of all central nervous system infections, but retrospective reviews of post-neurosurgical Candida infections report mortality rates exceeding 30 percent, with diagnostic delays being common. The insidious presentation here, progressive headache, a movement disorder, and a single seizure without fever, closely mimicked simple recurrence and organization of the original hematoma, and preoperative imaging could not distinguish a sterile organized hematoma from an infected one. The authors argue that atypical intraoperative findings, such as an abnormally thickened or leathery membrane, should prompt immediate submission of tissue for pathological and microbiological study. They also note that cerebrospinal fluid testing for (1→3)-β-D-glucan offers a rapid screening tool for preemptive diagnosis of iatrogenic fungal infections. Treatment, they emphasize, rarely succeeds with drugs alone: surgical resection of infected membranes and removal of contaminated material are essential, while fluconazole, which achieves cerebrospinal fluid concentrations of roughly 70 to 80 percent of serum levels, remains the drug of choice for fluconazole-susceptible C. parapsilosis. The team acknowledges the limitations inherent in a single case report: the exact route of infection could not be determined, antifungal susceptibility testing was not possible due to low specimen volume, and long-term follow-up will be needed to watch for late recurrence. Still, the message for surgeons and microbiologists alike is clear: when an old surgical site behaves strangely, the pathology laboratory may hold the answer that imaging cannot.

Subject of Research: A delayed intracranial Candida parapsilosis infection diagnosed two years after burr-hole drainage for chronic subdural hematoma

Article Title: Intracranial Candida parapsilosis infection occurring 2 years after burr-hole drainage for chronic subdural hematoma: a case report

Article References: Li, J., Lin, S., Liu, W., Li, P., & Luo, L. (2026). Intracranial Candida parapsilosis infection occurring 2 years after burr-hole drainage for chronic subdural hematoma: a case report. British Journal of Biomedical Science, 83, Article 16761. https://doi.org/10.3389/bjbs.2026.16761

Image Credits: AI Generated

DOI: 10.3389/bjbs.2026.16761

Keywords: Candida parapsilosis, chronic subdural hematoma, burr-hole drainage, fungal infection, neurosurgery, biofilm, cerebrospinal fluid, MALDI-TOF, voriconazole, fluconazole, case report, iatrogenic infection