Craniotomy flap osteomyelitis: a diagnostic approach

Potential utility of bone scan in cranial bone flap osteomyelitis

OBJECTIVE

Currently, the diagnosis of bone flap osteomyelitis (BFO) remains a challenge for medical imaging. The present study aimed to identify predictive scintigraphic patterns of BFO.

METHODS

This retrospective study reviewed planar bone scan of patients with suspected BFO between 2010, and 2016. A total of 15 patients were included. Final diagnosis of BFO was obtained by histological and bacteriological documentation. Eight scintigraphic signs potentially helpful were reviewed and correlated with the final diagnosis individually or in combination through Fischer exact test.

RESULTS

Eight patients out of 15 (53.3%) were diagnosed with BFO. Radionuclide uptake inside the bone flap during blood-pool phase was predictive for BFO (p = 0.007) with 75.0% sensitivity 100% specificity, and 86.7% accuracy. In combination, radionuclide uptake inside the bone flap or a spreading wavefront between blood-pool and delayed phases was associated with BFO (p = 0.007). It did not improve diagnostic performance.

CONCLUSION

Using well-defined and reproducible scintigraphic signs, bone scan is helpful for the diagnosis of BFO.

Management of infections complicating the orbitocranial approaches: Report of two cases and review of literature

BACKGROUND

The orbitocranial approaches are now indispensible for treating lesions of the skull base, providing access to lesions in the anterior and middle cranial fossae, as well as the upper clivus and anterior brainstem. The management of infectious complications of the orbitocranial approaches, however, has evaded the literature.

CASE DESCRIPTION

We present two cases of patients who underwent orbitocranial approach whose clinical course was complicated by wound infection and osteomyelitis. One patient was treated with antibiotics and then had a custom implant placed for cranioplasty. The other case was managed with removal of bone and wire-mesh cranioplasty.

CONCLUSION

Management of orbitocraniotomy infections can be difficult due to the complex geometry of the flap and to cosmetic considerations. Once the infection involves the bone, the bone can be replaced after cleaning or discarded and a cranioplasty performed. Cranioplasty can be performed with wire-mesh or a custom implant made by computer-assisted modeling.

Compartmentalization of immune responses during Staphylococcus aureus cranial bone flap infection

Decompressive craniectomy is often required after head trauma, stroke, or cranial bleeding to control subsequent brain swelling and prevent death. The infection rate after cranial bone flap replacement ranges from 0.8% to 15%, with an alarming frequency caused by methicillin-resistant Staphylococcus aureus, which is problematic because of recalcitrance to antibiotic therapy. Herein we report the establishment of a novel mouse model of S. aureus cranial bone flap infection that mimics several aspects of human disease. Bacteria colonized bone flaps for up to 4 months after infection, as revealed by scanning electron microscopy and quantitative culture, demonstrating the chronicity of the model. Analysis of a human cranial bone flap with confirmed S. aureus infection by scanning electron microscopy revealed similar structural attributes as the mouse model, demonstrating that it closely parallels structural facets of human disease. Inflammatory indices were most pronounced within the subcutaneous galeal compartment compared with the underlying brain parenchyma. Specifically, neutrophil influx and chemokine expression (CXCL2 and CCL5) were markedly elevated in the galea, which demonstrated substantial edema on magnetic resonance images, whereas the underlying brain parenchyma exhibited minimal involvement. Evaluation of immune mechanisms required for bacterial containment and inflammation revealed critical roles for MyD88-dependent signaling and neutrophils. This novel mouse model of cranial bone flap infection can be used to identify key immunologic and therapeutic mechanisms relevant to persistent bone flap infection in humans.

Polymicrobial skull osteomyelitis: a rare complication of subdural hematoma evacuation

BACKGROUND

Osteomyelitis of the skull (SO) is a rare condition. The infection may complicate community-acquired sinusitis, otitis, or mastoiditis, in which case, the skull base is affected most commonly. The flora typically seen in these conditions, such as Streptococcus pneumoniae and Haemophilus influenzae, tends also to be responsible for the SO. Osteomyelitis also may follow neurosurgical procedures that breach the skull, in which case, the pathogens frequently are typical cutaneous flora such as Staphylococcus aureus or coagulase-negative staphylococci.

METHODS

A case report of post-neurosurgical SO and a review of the relevant English-language literature.

RESULTS

We report a delayed presentation of SO after craniotomy for the evacuation of a chronic subdural hematoma. Cranial tissue cultures grew Staphylococcus aureus, Corynebacterium spp., and Escherichia coli.

CONCLUSIONS

The isolation of Escherichia coli as an infecting organism in SO has been reported rarely and may reflect a unique pathogenesis.

Post-operative infections of osteoplastic compared with free bone flaps

A retrospective study was performed to evaluate the rate of infection in free and osteoplastic bone flaps after craniotomy. Two hundred and two craniotomies were performed in 98 cases of tumour, 35 cases of trauma and 69 cases of vascular disease. The overall incidence of infection was 6.4% (13 cases). The infectious agents were Staphylococcus aureus in four cases; Pneumococcus and gram-positive rods each in one case. In seven cases no infectious agent was identified. In 127 cases with free bone flaps eight (6.3%) were infected, and in 75 cases with osteoplastic bone flaps five (6.7%) were infected. One of five (20%) osteoplastic and four of eight (50%) free bone flaps had to be removed in order to accomplish healing, suggesting that an osteoplastic bone flap may be preserved more often in cases of infection.