Introduction Aneurysmal bone cysts (ABCs) are expansive and destructive lesions positive for osteoclast markers, resembling benign giant cell tumors (GCTs). Treatment options include surgical resection, curettage and cavity filling, embolization, injection of fibrosing agents, or radiotherapy. Particularly in children and adolescents with spinal ABCs, these options may be unsatisfactory, and innovative forms of treatment are needed. Denosumab is a human monoclonal antibody that inhibits osteoclast function by blocking the cytokine receptor activator of the nuclear factor-kappa B ligand. Satisfactory results with denosumab in treating GCTs and immunohistochemical similarities suggest that it may also have positive effects on ABCs. Methods and ResultsThis report is the first description of the therapeutic use of denosumab in two patients with spinal ABCs. Two boys (aged 8 and 11) had recurrent ABCs at C5 after surgery with intralesional tumor resection. Treatment options were discussed by the interdisciplinary tumor board. Arterial embolization was attempted, but failed due to an absence of appropriate afferent arteries. After the families had received extensive information and provided written consent, denosumab therapy was initiated as an individualized treatment, despite the absence as yet of scientific evidence. After the start of denosumab therapy, both patients recovered from pain and neurologic symptoms significantly and are now in a healthy condition with no severe side effects. Magnetic resonance imaging check-ups after 2 or 4 months of denosumab treatment, respectively, showed tumor regression in both patients. Discussion Longer follow-up and clinical studies are warranted to establish the value of denosumab in the treatment of ABCs.

Introduction Klippel-Feil syndrome (KFS) is considered a rare developmental disorder characterized by mono-or multisegmental fusion of the cervical vertebrae which is frequently associated with diverse non-osseous, e.g. neural, visceral, cardiopulmonary and genitourinary development anomalies. Anterior cervical meningomyelocele (MMC) in KFS has only been described in two previous patients, both with non-surgical treatment. Clnical presentation We present the case of a 26-year-old female suffering from KFS, presenting with progressive bilateral C6 paraesthesias, C7 and C8 motor weakness and myelopathy. Radiological imaging revealed incomplete osseous fusion of the vertebrae C2-Th1. The spinal cord was displaced ventro-caudally through a large anterior MMC, apparently fixed at the dorsal oesophagus, severely stretching the cervical nerve roots. Surgery was indicated due to progression of the symptoms and was performed through a combined partial sternotomy and ventral anterolateral cervical approach. Intraoperatively, both division of oesophago-dural adhesions and intradural untethering of adhesions of the myelon with caudal parts of the cele were performed. Evoked somatosensory potentials improved immediately and 6-day postoperative MRI revealed a nearly complete reposition of the spinal cord in its physiological position. Genetic sequence analyses ruled out mutation of the growth and differentiation factor 6 (GDF6). Apart from slight intermittent paraesthesia, symptoms resolved almost completely within weeks after operation. Both radiological and neurological improvement remained stable at 16 months of follow-up. Conclusion KFS with anterior cervical MMC is rarely seen and may require surgery in case of clincial signs of nerve root compression or myelopathy. Osseous decompression, untethering and adhesiolysis under electrophysiological monitoring can provide sufficient radiological and clinical improvement.

Purpose Cervical spondylotic myelopathy is a multifactorial disease that is directly correlated by the degree of spinal stenosis. Surgery remains the best therapy. A posterior approach is often recommended in patients with multilevel dorsal cervical compression. Aim of the present experimental study was to evaluate the feasibility of a fullendoscopic arcocristectomy in a cadaver study. Methods We performed full-endoscopic arcocristectomy on ten formalin-fixed human cervical specimens. Before and after decompression we obtained high-resolution computerized tomography (CT) data to evaluate the diameter of the cervical spinal canal. Results Overall, surgery was possible on 55 segments in ten cadaver specimens. A mean increase of 4.1 mm (±1.2 mm) in the sagittal diameter of the cervical spinal canal could be achieved (p \ 0.05, t test). Conclusions The full-endoscopic arcrocristectomy is feasible and achieves a sufficient decompression. This minimal invasive technique protects most of the dorsal structures and therefore probably preserves biomechanical functions, which has to be proven in future studies.

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Preoperative marking of spinal level or peripheral nerve pathologies with a flexible hooked-wire needle marking system is feasible and appears to be safe and useful for neurosurgical spinal and peripheral procedures.