Cranial Osteomyelitis Secondary to Myiasis: Case Report

Abstract

A 48-year-old male patient was admitted to an emergency care unit with a history of gunshot wound and traumatic brain injury. He underwent neurosurgical debridement, with removal of fractured bone fragments in the left frontal region, drainage of the underlying brain contusion, and dural plastic surgery. He showed clinical improvement, underwent autologous cranioplasty approximately 4 weeks after the hospital admission, and was discharged for neurological outpatient follow-up. After 6 months, he returned to the hospital with signs of dehiscence of the surgical wound in the left frontal region, with the presence of larvae at the site, compatible with the diagnosis of cranial myiasis. He underwent two debridements of the surgical site to remove visible larvae on the bone flap, which also showed signs of infectious involvement, confirming the diagnosis of osteomyelitis. A wide left frontal craniectomy was also performed, with removal of the infected cranial bone. The culture of surgical material showed the presence of the bacterium Klebsiella aerogenes. Ivermectin and broad-spectrum antibiotic therapy were prescribed. The patient showed good progress and was discharged from the hospital. Myiasis is caused by the fly Dermatobia hominis, whose eggs are laid in open wounds, where their larvae feed on tissues and body fluids. It is usually a self-limiting condition with low morbidity, except in the presence of cranial osteomyelitis, a rare complication that can lead to amaurosis, sepsis, and death. Therefore, rigorous removal of the larvae, extensive surgical debridement, craniectomy, and prolonged antibiotic therapy are the main therapeutic strategies.

Resumo

Um paciente do sexo masculino, de 48 anos de idade, foi admitido em unidade de pronto atendimento terciário, com histórico de agressão física por projétil de arma de fogo e traumatismo cranioencefálico. Foi submetido a desbridamento neurocirúrgico, com remoção de fragmentos ósseos fraturados na região frontal esquerda, drenagem da contusão cerebral subjacente e cirurgia plástica dural. Apresentou melhora clínica, realizou cranioplastia autóloga cerca de 4 semanas após a admissão hospitalar e recebeu alta para seguimento neurológico ambulatorial. Após 6 meses, retornou ao hospital, com sinais de deiscência da ferida operatória na região frontal esquerda, com a presença de larvas no local, compatível com o diagnóstico de miíase craniana. Foi submetido a dois desbridamentos do sítio cirúrgico, para remoção de larvas visíveis no retalho ósseo, que também apresentava sinais de envolvimento infeccioso, confirmando o diagnóstico de osteomielite. Foi realizada, também, ampla craniectomia frontal esquerda, com remoção do osso craniano infectado. A cultura do material cirúrgico evidenciou a presença da bactéria Klebsiella aerogenes, sendo prescritos ivermectina e antibioticoterapia de largo espectro. O paciente apresentou boa evolução e recebeu alta hospitalar. A miíase é causada pela mosca Dermatobia hominis, cujos ovos são depositados em feridas abertas e suas larvas se alimentam de tecidos e fluidos corporais. Normalmente, é um quadro autolimitado e com baixa morbidade, exceto na presença de osteomielite craniana, complicação rara, mas que pode levar a amaurose, sepse e óbito. Assim, a remoção rigorosa das larvas, o amplo desbridamento cirúrgico, a craniectomia e a antibioticoterapia por tempo prolongado são as principais estratégias terapêuticas.

Keywords

skull - myiasis - osteomyelitis

Palavras-chave

crânio - miíase - osteomielite

Introduction

Myiasis can be defined as the infestation of vertebrate animals or humans by the deposition of dipteran larvae eggs on intact or damaged skin, and it can be classified according to the affected body area.[1] [2] [3] The most common type is cutaneous myiasis, which includes the furuncular, migratory, and wound subdivisions.[1] [4] In South and Central America, the primary etiological agent is flies of the Dermatobia hominis species, typically found in hot and humid regions.[1] [2] [4]

Myiasis is a pathological condition generally associated with poor socioeconomic conditions[4] [5] and factors such as nutritional imbalance, immunosuppression, diabetes mellitus, renal and hepatic insufficiency, high radiation exposure, Paget's disease, chronic hypoxia, osteoporosis, mental illnesses, prolonged hospitalization, and the excessive use of alcohol, illicit drugs, and tobacco.[6] [7] [8] It may also occur in individuals who have traveled to endemic regions, in which case it is referred to as traveler's myiasis.[2] [3] [9]

The symptoms of myiasis are variable: the furuncular subtype is characterized by frequently pruritic and painful lesions with a central opening through which the larva breathes and expels its secretory waste. In migratory myiasis, the movement of larvae beneath the skin can be observed, leading to “serpiginous tracks”. The wound subtype occurs when larvae infest open wounds, causing increased tissue damage and promoting secondary infections, which result in pain, foul-smelling discharge, and visible larvae. All clinical presentations can cause systemic symptoms such as itching, fever, and malaise.[1] [3]

Myiasis in the craniocervical region often leads to bone destruction, as larvae invade both necrotic and healthy tissue, resulting in extensive damage. This invasive nature can facilitate the spread of infection to the bone, leading to osteomyelitis.[10] [11]

Cranial osteomyelitis is a rare complication of myiasis, reported in the scientific literature almost exclusively in case studies. Thus, there are still no studies with robust population data that accurately quantify the incidence and prevalence of this outcome. On the other hand, it is relatively common in tropical and subtropical countries, such as in Latin America and Sub-Saharan Africa, though it is underreported.[12] According to a national study, “cases of myiasis in Brazil are commonly reported in the literature”.[13] “Poor basic sanitation conditions and taxonomic difficulty, as well as the lack of case reporting, hinder the acquisition of more concrete epidemiological data to identify the actual prevalence of this disease.”[13]

Moreover, the cranial presentation of osteomyelitis also lacks incidence and prevalence data, both nationally and globally. However, in Brazil, it is known that there were 183,975 hospitalizations for osteomyelitis in the SUS between 2009 and 2019, of which 38.88% were in the Southeast region.[14]

Case Report

A 48-year-old male patient, homeless, with a history of alcohol and illicit drug abuse, was admitted to a tertiary hospital emergency unit with altered consciousness following physical assault and severe traumatic brain injury caused by a firearm projectile. Upon admission, his Glasgow Coma Scale score was 11, with no focal deficits. A cranial computed tomography (CT) scan revealed a depressed fracture of the frontal bone and an underlying left cerebral contusion.

The patient was taken to the operating room for neurosurgical debridement, which involved the removal of fractured bone fragments in the left frontal region, drainage of the cerebral contusion, and dural repair using pericranium. He received intensive clinical support and showed good postoperative progress.

20 days after surgery, the patient underwent autologous cranioplasty and was discharged without neurological deficits for outpatient follow-up. Then, 6 months later, the patient returned to the hospital lucid and oriented, but with dehiscence of the surgical wound in the left frontal region and presence of larvae at the site, consistent with a diagnosis of cranial myiasis ([Fig. 1] [2] [3]).

Fig. 1 Clinical aspect of the surgical wound. Clinical evaluation of the dehiscent surgical wound in the left frontal region reveals exposed bone, necrotic tissue patches, and visible larvae, all indicative of active wound myiasis. The diagnosis of osteomyelitis is corroborated by macroscopic signs of infection in the exposed bone, such as darkened discoloration and an irregular surface. Management involved extensive surgical debridement, craniectomy, and administration of broad-spectrum antibiotics.

Fig. 2 Cranial CT scan demonstrating bone rarefaction and irregular hypodense areas suggestive of cranial osteomyelitis and an ongoing infectious process. There are also regions of bone lysis and discontinuity in the outer table of the left frontal bone. Additionally, hypodense areas containing air bubbles are present, indicating active infection and possible cutaneous-cranial communication. These findings are consistent with cranial osteomyelitis secondary to myiasis—a rare complication.

Fig. 3 Axial noncontrast CT in bone window scan of the head revealing a depressed fracture of the left frontal bone with irregular and demineralized bony margins. There is associated soft-tissue disruption and subcutaneous emphysema. These findings are consistent with cranial osteomyelitis secondary to myiasis, with bone destruction and scalp involvement resulting from extensive parasitic infestation.

The patient underwent a new surgical procedure, during which pediculosis of the scalp and scabies upon exposure were identified. Extensive bilateral frontotemporoparietal trichotomy was required, followed by thorough cleansing of the skin using an iodinated antiseptic. It was necessary to enlarge the margins of the previous surgical wound and explore the scalp. Numerous larvae were manually removed from the subgaleal, subperiosteal, and intramuscular spaces of the temporal muscle. The frontal bone on the left side was found to be fractured, depressed, and demineralized, showing signs of infectious involvement, which lead to its removal. Multiple larvae were also found in the epidural space and were manually extracted. Despite this, the dura mater remained intact and showed no signs of violation. The entire surgical field was rigorously irrigated with 0.9% saline solution and iodinated antiseptic. The dura mater was anchored to the bone, and the scalp was closed in layers, with proper approximation of wound edges.

Culture of the surgical material revealed secondary bacterial infection by Klebsiella aerogenes, part of the Citrobacter, Enterobacter, Serratia, and Providencia (CESP) group as Enterobacteriaceae with inducible beta-lactamase production. Broad-spectrum antibiotic therapy (ciprofloxacin) was initiated for 6 weeks. The patient was discharged for outpatient follow-up and planning for heterologous cranioplasty within 6 months. He also took ivermectin.

Discussion

The infestation of myiasis occurs through the adult female of D. hominis, which is hematophagous and lays its eggs on the skin of vertebrates while feeding. The increase in temperature causes the eggs to hatch, and the larvae lodge in the hair follicle, at the bite site, or penetrate directly into the host's skin.[1] [2] [3] [15] Over 4 to 18 weeks, the larvae grow, feeding on the host's tissues and body fluids, penetrating deeper into the skin and forming a cavity with a central pore for respiration.[1] [2] [3] [15] When mature, the larvae emerge from the wound and fall to the ground, developing into the pupal stage.[2]

Myiasis is a prevalent condition among homeless individuals with poor hygiene, the elderly, bedridden patients, mentally impaired individuals, alcoholics, and drug users,[4] [5] as well as travelers.[2] [3] [9] Diagnosis is performed through a detailed clinical examination and attention to the patient's travel history.[1] [16]

The treatment for myiasis consists of the complete removal of the larvae without damaging them, to avoid foreign body reactions in the host's organism.[15] Conventional methods for this extraction include surgical excision and “suffocation” of the larva by occluding the cavity's opening with substances like mineral oil and liquid paraffin, which lead to the larva's asphyxiation and subsequent exit through the central pore.[2] [9] [15] Treatment with ivermectin may be used as an adjunctive alternative, especially when ocular and oral involvement is present.[1] [3] [10]

Human myiasis generally has a good prognosis. Its main complication is secondary bacterial infection, which is rare because larvae produce bactericidal substances.[1] [3] [16] Due to their invasive nature, larvae may also cause extensive tissue necrosis, with exposure of the underlying bone. This exposure, combined with the presence of necrotic tissue, creates a favorable environment for secondary bacterial colonization. If the primary infection site is not treated quickly and effectively, deeper structures will be affected.[17]

In the described case, the patient presented with cranial osteomyelitis caused by K. aerogenes. It is an inflammation with bone destruction caused by infectious agents such as bacteria and fungi. Inflammatory factors and leukocytes themselves contribute to tissue necrosis, but the compression of bone vascular channels by the inflammatory process can also lead to bone ischemia.[18] Additionally, protein-calorie malnutrition, alcoholism, use of illicit drugs, and smoking are considered risk factors for cranial osteomyelitis.[8] The most common etiological agents are Staphylococcus aureus, coagulase-positive Staphylococcus epidermidis, Serratia marcescens, and anaerobic Streptococcus.[18] [19] Simple radiography and CT of the skull may reveal areas of bone rarefaction with a lytic aspect.[3] [19] However, cranial magnetic resonance imaging is considered the gold standard diagnostic test for this condition.[8]

This clinical case illustrates a rare complication of myiasis: cranial osteomyelitis. Myiasis is usually a self-limiting condition with low morbidity, except in the presence of this secondary condition. In such cases, strict larva removal, extensive surgical debridement, including the removal of cranial bone affected by infection, and prolonged treatment for 4 to 6 weeks with broad-spectrum antibiotics should be performed. Myiasis is associated with low socioeconomic conditions, malnutrition, chronic use of alcohol and illicit drugs, smoking, and the lack of social and financial support among low-income populations.

In light of the above, medical guidance is essential in the management of cranial myiasis, particularly among vulnerable populations such as those experiencing homelessness, who often face significant barriers to accessing healthcare and maintaining adequate hygiene. In such cases, the involvement of social services is equally critical to provide continuous support, ensure minimum standards of care, facilitate social reintegration, and prevent recurrence. The integrated action between healthcare and social assistance services reinforces an intersectoral and humanized response, which is indispensable for addressing the complexity and recurrence associated with this condition.

Conflict of Interests

The authors have no conflict of interests to declare.

Acknowledgements

The authors would like to thank Fundação Educacional Lucas Machado (FELUMA), Fundação Hospitalar do Estado de Minas Gerais (FHEMIG), and the Research and Extension Department of Faculdade de Ciências Médicas de Minas Gerais (CMMG) for institutional and technical support in the preparation of the present article.

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Publication History

Received: 09 January 2025

Accepted: 09 September 2025

Article published online:
29 December 2025