Stray Bone Dust Finds Its Way Into the Brain After Routine Surgery, Triggering Rare Sterile Meningitis

In a striking reminder that even routine neurosurgical procedures can take unexpected turns, physicians have reported a rare complication in which tiny particles of autologous bone dust—material taken from the patient’s own skull and routinely used to seal surgical openings—migrated deep into the brain’s fluid-filled ventricles after endoscopic third ventriculostomy, a minimally invasive operation for the neurological disorder known as normal pressure hydrocephalus. The migrated particles were associated with a sterile inflammatory reaction of the meninges called chemical meningitis, and the case, described in the open-access journal Heliyon, offers neurosurgeons worldwide a cautionary lesson about postoperative cerebrospinal fluid dynamics and the choice of materials used to close burr-holes.

Normal pressure hydrocephalus, first characterized by Hakim and Adams in 1965, is a potentially reversible condition that classically produces three symptoms: a distinctive walking disturbance, cognitive decline, and urinary incontinence. Its underlying mechanisms remain only partly understood, but prevailing hypotheses point to impaired absorption of cerebrospinal fluid at the arachnoid granulations, disturbed pulsatile flow of the fluid through the brain’s cavities, and changes in ventricular compliance. Because these features overlap with other disorders of aging, diagnosis can be difficult, and neuroimaging markers such as ventriculomegaly with disproportionately enlarged subarachnoid spaces—known as the DESH pattern—help clinicians build diagnostic confidence.

The patient at the center of the report was a 75-year-old man who arrived with months of progressively worsening gait, difficulty initiating walking, and intermittent urinary incontinence. Neurological examination revealed a short-stepped, broad-based gait and mild frontal release signs, but no focal deficits. Brain computed tomography demonstrated ventriculomegaly with an Evans index of 0.32, alongside imaging features consistent with DESH, including enlarged Sylvian fissures with relative narrowing of the high-convexity sulci. Critically, the man improved significantly after a high-volume cerebrospinal fluid tap test, a diagnostic maneuver in which fluid is withdrawn and the patient’s response is observed. Together, these findings established a diagnosis of probable normal pressure hydrocephalus and supported surgical intervention.

The surgical team chose endoscopic third ventriculostomy, or ETV, a procedure in which a small perforation is created in the floor of the third ventricle to allow cerebrospinal fluid to bypass an obstruction and circulate more freely. ETV is increasingly favored in selected patients because it avoids permanent shunt hardware and its long-term complications. In this case, the operation itself was uneventful. At closure, the surgeons applied autologous bone dust—fine particles of bone collected during the drilling of the burr-hole—over the opening and gently compacted it. Bone wax and fibrin sealant were then applied superficially to reinforce the closure and reduce the risk of postoperative fluid leakage. An immediate postoperative CT scan showed only mild pneumocephalus, air within the cranial cavity, and no other abnormalities, and the patient was discharged in good condition with improved gait and continence.

Trouble emerged on the fourth day after surgery, when the man returned with a low-grade fever of 38 degrees Celsius and a serous discharge from his right frontal wound. Because fever in the early postoperative period after neurosurgery raises concern for central nervous system infection, the team performed a lumbar puncture to obtain cerebrospinal fluid for diagnostic evaluation; the opening pressure was normal. Importantly, the authors note, fever and an inflammatory cerebrospinal fluid profile were already present before the lumbar puncture was performed, a detail that complicates any attempt to assign causation. Within 24 hours of the puncture, however, the patient’s fever climbed to 39 degrees Celsius and he developed mild confusion, prompting a repeat brain CT scan.

That scan revealed the unexpected: new hyperdense particulate material within the frontal horn of the right lateral ventricle, adjacent to the trajectory of the previous frontal burr-hole. The material appeared as irregular, non-layering hyperdense foci scattered across the anterior portion of the frontal horn, without forming a dependent fluid level, a pattern suggesting particulate content rather than hemorrhage. Although quantitative density measurements were unavailable, the discrete, irregular appearance and the continuity with the burr-hole trajectory were considered more consistent with bone material than with blood or calcification. Notably, this finding was entirely absent on the immediate postoperative scan, supporting interval migration of the material into the ventricular system between the two imaging studies.

Cerebrospinal fluid analysis from the lumbar puncture painted a picture characteristic of chemical meningitis, a sterile inflammatory reaction triggered by irritants introduced into the fluid spaces of the nervous system. The fluid contained 32 white blood cells per microliter, predominantly lymphocytes, with elevated protein at 105 milligrams per deciliter, normal glucose of 68 milligrams per deciliter against a serum level of 102, negative Gram stain and culture, and negative polymerase chain reaction testing for a panel of common pathogens including Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae, herpes simplex virus types 1 and 2, varicella-zoster virus, and enteroviruses. These findings were most compatible with a sterile inflammatory process, with irritation from the intraventricular bone dust considered the most likely cause.

Management reflected the diagnostic uncertainty inherent in any postoperative fever. The patient initially received empiric intravenous antibiotics—vancomycin and ceftriaxone—to cover possible bacterial meningitis, but these were discontinued after 72 hours when cultures remained negative, PCR results came back clean, no neutrophilic predominance was seen, and the patient improved rapidly on corticosteroids. He was given dexamethasone, 8 milligrams intravenously every 8 hours, followed by a gradual taper through oral dosing, along with intravenous fluids and antipyretics. Over the following days the fever resolved and his mental status normalized. He was discharged in good condition after one week, and at six-month follow-up he had a normal gait, no urinary symptoms, no signs of infection, and stable imaging without further complications. No repeat lumbar puncture was performed, because his rapid and complete clinical recovery strongly supported a non-infectious cause.

The authors place their observation within a sparse but intriguing literature. Reports of bone fragment migration after cranial procedures are exceedingly rare. Kafadar and colleagues described postoperative migration of autologous bone fragments into the ventricular cavity after intraventricular neuroendoscopy, attributing the mechanism to pressure gradients created during healing or variations in cerebrospinal fluid flow, while Turhan and Erşahin reported bone particles migrating into the third ventricle after ETV, where they risked incorporation into the ventricular system and obstruction. Previous studies of burr-hole reconstruction materials have found that autologous bone dust, because of its particulate nature and tendency toward resorption or incomplete integration, may lack structural stability under changing pressure conditions. What distinguishes the present case, the authors argue, is the clinical presentation: rather than acute hydrocephalus, stoma obstruction, or the need for endoscopic removal, the patient developed fever and confusion with cerebrospinal fluid findings of a sterile inflammatory process that resolved with corticosteroids alone, suggesting that intraventricular bone dust can produce not only mechanical complications but also clinically significant chemical meningitis.

The proposed mechanism rests on the physics of cerebrospinal fluid. Lumbar puncture reduces spinal fluid pressure and can transiently induce intracranial hypotension, potentially creating pressure gradients that destabilize materials placed near cranial entry sites. The authors hypothesize that such alterations may have drawn the loosely compacted bone dust inward through the burr-hole closure and into the ventricle. They are careful, however, to label this mechanism speculative: no direct intracranial pressure monitoring was performed, the material was never retrieved for histopathological confirmation, and because no CT was obtained immediately before the lumbar puncture, the precise timing of the migration could not be determined. Alternative explanations—including incomplete mechanical stability of the closure independent of the puncture, natural postoperative fluctuations in fluid dynamics, or gradual inward displacement of loosely packed particles—cannot be excluded, and the phenomenon is likely multifactorial rather than attributable to a single cause.

From the case, the authors distill practical recommendations for neurosurgeons. Lumbar puncture should be performed only when absolutely necessary in the early period after ETV, given the risk of generating sudden pressure gradients across a fresh, incompletely integrated burr-hole closure. When postoperative pressure fluctuations are anticipated, alternatives to bone dust—such as bone cement, titanium mesh, or collagen-based matrices, which provide stronger or more flexible sealing—may be preferable. Finally, clinicians should maintain a high index of suspicion for chemical meningitis, distinguishing it from bacterial infection through careful cerebrospinal fluid analysis, since recognizing sterile findings allows early tapering of antibiotics and prevents unnecessarily prolonged antimicrobial therapy.

The authors acknowledge the limitations inherent in a single-case report: generalizability is limited, the relationship between lumbar puncture and migration remains hypothetical, and the identity of the intraventricular material rests solely on CT appearance and its anatomical relationship to the burr-hole, without quantitative attenuation measurements or pathological confirmation. Nevertheless, given the high frequency of ETV procedures worldwide and the routine nature of lumbar puncture in postoperative neurological assessment, the report expands the literature in a way the authors believe has not been highlighted before, connecting postoperative lumbar puncture, bone dust migration, and chemical meningitis in a single narrative. Awareness of this rare but plausible chain of events, they conclude, may help clinicians time diagnostic procedures more cautiously, choose more stable closure materials, and recognize sterile inflammation promptly—lessons that could spare future patients the fever, confusion, and anxiety that followed this otherwise successful operation.

Subject of Research: Intraventricular migration of autologous bone dust and chemical meningitis following endoscopic third ventriculostomy

Article Title: When bone dust goes astray: Intraventricular migration and chemical meningitis after ETV — A case report

Article References: Moznebiisfahani, M., & Askariardehjani, N. (2026). When bone dust goes astray: Intraventricular migration and chemical meningitis after ETV — A case report. Heliyon, 12(15), Article e45435. https://doi.org/10.1016/j.heliyon.2026.e45435

Image Credits: AI Generated

DOI: 10.1016/j.heliyon.2026.e45435

Keywords: endoscopic third ventriculostomy, normal pressure hydrocephalus, chemical meningitis, bone dust migration, lumbar puncture, cerebrospinal fluid dynamics, burr-hole closure, neurosurgery complications, intraventricular particulate material, corticosteroid treatment, case report, Heliyon