Interdisciplinary management of skull base surgery

Skull base surgery remains one of the challenging areas in the field of cranio-maxillofacial surgery, otolaryngology and neurosurgery. Subsequent reconstruction of bone and soft tissue are an essential component to restore function and appearance after ablative surgery. Establishment of interdisciplinary tumor boards with presentation of the individual patient cases have become standard. Multiplanar reconstruction using MRI or CT imaging techniques combined with virtual 3D planning allow precise planning of the procedures. Intraoperative navigation helps for complete resection of malignant findings with safety margins; surgical approaches provide a good overview of the surgical site. Reconstruction using local flaps have a low complication rate with equally reliable results in reconstruction of small tissue defects. Free flap surgery makes reconstruction of large tissue defects possible. Alloplastic materials are alternatively used for reconstruction of bone defects. Based on selected patients, treatment algorithms and standard surgical procedures in extracerebral skull base surgery will be illustrated. Current techniques and new approaches will be discussed with emphasize on hard and soft tissue reconstruction.

Medication-related osteonecrosis of the mandible: an unusual presentation and treatment

A 71-year-old woman was referred to the clinic with extensive medication-related osteonecrosis of the jaw (MRONJ) involving the mandible. She had received 7 years of zoledronate therapy. On cone beam computed tomography, the MRONJ presented as a large sequestrum spanning from the left to the right condylar process, surrounded by thick sub-periosteal bone. The sequestrum was excised via an intraoral approach, leaving the newly formed sub-periosteal bone as a neo-mandible. The patient recovered well from the operation and was discharged 5 days after surgery. She healed completely without complications. This case report presents an alternative surgical treatment that may be considered if there is clinically stable sub-periosteal bone surrounding extensive MRONJ.

Osteopenia in the maxillofacial area: a study in sheep

Osteoporosis is a major public health problem worldwide. Its significance in the fields of traumatology and implantology of the maxillofacial area requires investigation. A large animal model was used to assess bone loss in the lumbar spine and mandible.

INTRODUCTION

Osteoporosis is a prevalent disease characterized by low bone mass and microarchitectural deterioration of bone tissue. Osteoporosis-related fractures represent a major public health burden. The presence and relevance of osteoporosis in the maxillofacial area remain controversial. Research in humans is limited by difficulties in finding large homogenous study groups and, due to ethical considerations, numerous animal models have been used in osteoporosis research. The aim of this study was to assess a sheep model of generalized osteopenia for changes in the maxillofacial area.

METHODS

Bone loss was induced in ten Merino sheep by ovariectomy, intramuscular administration of glucocorticoids, and a calcium-reduced diet. Five untreated animals served as controls. Bone mineral density (BMD) was assessed by dual-energy X-ray absorptiometry at the lumbar spine at baseline and after 1, 3, 6, 9, and 12 months. Lumbar and mandibular bone biopsies were obtained and analyzed with microcomputed tomography.

RESULTS

Lumbar BMD decreased progressively in the intervention group and was most significantly low after 6 months (p < 0.001). Lumbar trabecular bone showed a significant decrease in bone volume (BV)/tissue volume (TV; p < 0.05) in the inducted group. Significant changes were found in both analyzed mandibular regions for BV/TV (p < 0.05). Regional variations were found for other parameters in the mandible. The cortical width was substantially reduced in the intervention group (p < 0.001).

CONCLUSIONS

Microstructural changes occurring in sheep as a result of induction seem to have a generalized nature. This sheep model meets the criteria for further investigation in the maxillofacial area.

Navigation-guided resection with immediate functional reconstruction for high-grade malignant parotid tumour at skull base

The authors report a case of navigation-guided tumour ablation of a high-grade epithelial-myoepithelial carcinoma of the right parotid gland extending to the skull base. Immediate functional reconstruction of the mandible with a prosthetic temporomandibular joint and facial nerve was performed. Postoperative follow-up showed no evidence of local tumour recurrence or distant metastasis with satisfactory temporomandibular and facial nerve function.

Determination of the N=16 shell closure at the oxygen drip line

The neutron unbound ground state of (25)O (Z=8, N=17) was observed for the first time in a proton knockout reaction from a (26)F beam. A single resonance was found in the invariant mass spectrum corresponding to a neutron decay energy of 770_+20(-10) keV with a total width of 172(30) keV. The N=16 shell gap was established to be 4.86(13) MeV by the energy difference between the nu1s(1/2) and nu0d(3/2) orbitals. The neutron separation energies for (25)O agree with the calculations of the universal sd shell model interaction. This interaction incorrectly predicts an (26)O ground state that is bound to two-neutron decay by 1 MeV, leading to a discrepancy between the theoretical calculations and experiment as to the particle stability of (26)O. The observed decay width was found to be on the order of a factor of 2 larger than the calculated single-particle width using a Woods-Saxon potential.