Custom implant design for large cranial defects.

PURPOSE: The aim of this work was to introduce a computer-aided design (CAD) tool that enables the design of large skull defect (>100 [Formula: see text]) implants. Functional and aesthetically correct custom implants are extremely important for patients with large cranial defects. For these cases, preoperative fabrication of implants is recommended to avoid problems of donor site morbidity, sufficiency of donor material and quality. Finally, crafting the correct shape is a non-trivial task increasingly complicated by defect size. METHODS: We present a CAD tool to design such implants for the neurocranium. A combination of geometric morphometrics and radial basis functions, namely thin-plate splines, allows semiautomatic implant generation. The method uses symmetry and the best fitting shape to estimate missing data directly within the radiologic volume data. In addition, this approach delivers correct implant fitting via a boundary fitting approach. RESULTS: This method generates a smooth implant surface, free of sharp edges that follows the main contours of the boundary, enabling accurate implant placement in the defect site intraoperatively. The present approach is evaluated and compared to existing methods. A mean error of 89.29 % (72.64-100 %) missing landmarks with an error less or equal to 1 mm was obtained. CONCLUSION: In conclusion, the results show that our CAD tool can generate patient-specific implants with high accuracy.

Integration of multimodality imaging and surgical navigation in the management of patients with refractory epilepsy. A pilot study using a new minimally invasive reference and head-fixation system.

OBJECTIVE: To review the experience with a new system (VBH system) for minimally invasive frameless stereotactic guidance, acting as a common platform to provide multimodal image integration and surgical navigation in a consecutive series of 25 patients who underwent surgery for drug-resistant seizures. METHODS: The usefulness of the VBH system for integrating all images to produce one dataset and for intraoperative instrument guidance and navigation was judged semiquantitatively in a three-tiered scale (+, ++, +++). Seizure outcome was classified according to Engel. RESULTS: The presurgical evaluation extended over 21.2 months (mean). A total of 141 registrations of images were performed (mean 5.6 per patient, range: 2 to 16). In 19 (76%) of 25 patients structural data fused with functional data were used for the presurgical workup. Six patients proceeded directly to navigated resection. Nineteen patients (76%) underwent invasive recording, of whom 13 underwent resective surgery. In seven patients (28%) the combination of multimodal image fusion and intra-operative stereotactic guidance was judged "essential" (+++) to remove the epileptogenic zone. Integration of all images to form one dataset was "essential" (+++) for decision making in 15 and "helpful" (++) in 4 patients (overall 76% of patients). Intraoperative use of frameless neuronavigation was "essential" (+++) in ten and "helpful" (++) in all remaining patients. Eighty percent of the patients achieved satisfactory seizure outcome after 1 year. CONCLUSION: The VBH system is a safe and effective non-invasive tool for repetitive imaging, multimodal image fusion and frameless stereotactic surgical navigation in candidates for epilepsy surgery.

Flexibility of head positioning and head fixation provided by a novel system for non-invasive maxillary fixation and frameless stereotaxy: technical note.

OBJECTIVE: The aim of this study was to demonstrate the flexibility in patient positioning and head fixation provided by a newly developed, minimally invasive upper jaw fixation device in combination with standard navigation software. TECHNIQUE: The Vogele-Bale-Hohner (VBH) headholder and the Stereotactic Intervention and Planning Laboratory (SIP-Lab) Innsbruck reference frame, were applied in epilepsy surgery requiring stereotactic guidance. The system can be adapted to various positioning and instrument guidance requirements. Instrument holders can be fixed either to a base plate or directly to the mouthpiece. When used together with a head clamp and a stabilizing arm, there are no restrictions on patient positioning. When used with the non-invasive headholder, only the supine position is well-suited for use with the described guidance instrumentation. The system can also be used with the head placed on the horseshoe headholder without altering navigation support. CONCLUSION: The VBH mouthpiece combined with an external registration frame is a flexible tool that permits patient positioning and neuronavigation with the head either fixed with a head clamp, or restrained non-invasively with a headholder, or not fixed at all. This might be advantageous within the context of epilepsy surgery.

Outcome of adult patients with temporal lobe tumours and medically refractory focal epilepsy.

BACKGROUND: Tumours are a well-recognized cause of medically intractable epilepsies. Tumours represent the primary pathology in 10%-30% of patients undergoing surgical treatment for chronic epilepsy. This study examines the surgical and epileptological outcome of adults with temporal lobe tumoural epilepsy treated within a comprehensive epilepsy surgery programme. METHODS: Between 1999 and 2004, 99 consecutive patients have been operated for intractable temporal lobe epilepsy (TLE). Among these, 14 adult patients exhibited temporal lobe neoplasms associated with TLE. Every patient underwent a comprehensive presurgical evaluation including video-EEG monitoring, MRI, interictal PET scan, ictal SPECT and neuropsychological testing. Surgical strategies were determined in an interdisciplinary seizure conference and tailored to the findings of the presurgical evaluation. All patients were available for follow up at regular intervals after 3, 6, 12 months and yearly thereafter. Epileptological outcome was classified according to Engel [10] and the ILAE (International League Against Epilepsy)/systems [33]. FINDINGS: The surgical procedures performed were temporal lobe resection in 3 patients, extended lesionectomy in 4 and extended lesionectomy with resection of the temporomesial structures in 7. One patient with an astrocytoma grade III underwent a second and third operation for recurrent disease. Histological results: Astrocytoma 5 patients, ganglioglioma/gangliocytoma 5, oligodendroglioma 2, ependymoma 1 and dysembryoplastic neuroepithelial tumour (DNET) 1. Postoperative follow-up was performed after 12-74 months (mean 31). The outcome according to the Engel classification indicated class IA in 9 patients, class IC in 3, and 1 each in classes IIIA and IVA. Epileptological outcome according to the ILAE classification indicated class 1 (12 patients) and class 4 (2 patients). Surgical mortality was zero and mild permanent neurological deficits due to surgery were seen in 2 patients. Postoperatively 3 patients showed a homonymous quadrantanopia. CONCLUSIONS: Patients with drug resistant epilepsy and temporal lobe tumours should undergo evaluation in dedicated epilepsy surgery programmes.