Minimally invasive carpal tunnel decompression using the KnifeLight: How I Do It.

BACKGROUND: Carpal tunnel decompression is commonly performed open or endoscopically. Carpal tunnel release using the KnifeLight instrument (Stryker, Kalamazoo, MI) is an alternative method established in 2000. METHOD: The instrument has a cutting blade placed between two blunt flat tips with an integrated light source which helps to locate the tool blade by transillumination through the tissues. The instrument is inserted into an opening made in the wrist crease and transverse carpal ligament and used to divide the ligament. CONCLUSION: This is a simple, efficient, and reproducible alternative for carpal tunnel decompression.

Use of intracranial and ocular thermography before and after arteriovenous malformation excision.

Excision of arteriovenous malformations (AVMs) is known to carry a risk of postoperative hemorrhage, postulated to be the result of normal perfusion pressure breakthrough. It is also possible that AVMs may cause a steal effect, reducing perfusion in nearby vessels. There is currently no simple method of visualizing the presence or absence of steal effect intraoperatively. We hypothesized that the infrared thermographic (heat sensitive) imaging of perilesional brain may be useful for detecting reduced perfusion due to steal. Moreover, we hypothesized that if steal effect was present, it could impact on ocular perfusion and thereby temperature. Our objective was, therefore, to investigate whether perilesional cortical and ocular temperature (OT) may be a marker of steal effect. We intraoperatively acquired conventional and thermal images of the surgical field and eyes bilaterally, pre- and post-excisions of a large left hemisphere AVM. We found OT asymmetry preoperatively, which was absent after the AVM was excised. Intraoperative thermal images showed an increase of perilesional temperature, although this could be confounded by generalized changes in cortical perfusion due to anesthetics or surgery.

Postoperative intracranial haemorrhage: a review.

Postoperative haemorrhage (POH) is one of the most serious complications of any cranial neurosurgical procedure and is associated with significant morbidity and mortality. The relative paucity of work investigating this postoperative complication prompted us to undertake a review of the literature, focussing on demographic, clinical, and surgical risk factors. A literature search was undertaken using Ovid MEDLINE (1950-2009) using keywords including craniectomy, craniotomy, neurosurgery, intracranial, reoperation, repeat craniotomy, postoperative, haemorrhage, haematoma, and bleeding. The rates of POH following intracranial procedures reported in the literature vary greatly, and meaningful comparison is difficult. We defined postoperative haemorrhage as that following craniotomy, which is clinically significant and requires surgical evacuation. Risk factors include pre-existing medical comorbidities including hypertension, coagulopathies and haematological abnormalities, intraoperative hypertension and blood loss, certain lesion pathologies including tumours, chronic subdural haematomas, and deficiencies in haemostasis. We conclude by providing recommendations for clinical practice based on the literature reviewed to aid clinicians in the detection and avoidance of POH.

The epidemiology of BCVI at a single state trauma centre.

BACKGROUND: Blunt carotid and vertebral artery injury (BCVI) is a relatively uncommon but potentially devastating injury. The aim of our study was to highlight the incidence, patterns, presentation and associations of BCVI at our institution. METHODS: Retrospective data between 1st January 2003 and 31st December 2006 was obtained from The Alfred Hospital's health information system, patient medical records and the Department of Neurosurgery's database. Injuries were graded using the Denver grading scale. RESULTS: 67 patients (0.64%) out of 10,417 minor and major trauma admissions, were diagnosed with BCVI. 33 (49%) sustained blunt carotid and 34 (51%) sustained blunt vertebral injuries. Motor vehicle accident (MVA) was the cause in 43 out of 67. 35% had associated head injury whilst 57% had concurrent cervical spine fractures. Odds ratio analysis showed that MVA victims with concomitant upper cervical spine injury were 22.9 times more likely to suffer BCVI than those without such risk factors. Approximately 50% of patients had a Glasgow coma score of 14 or less (GCS < or = 14). Grade 4 BCVI was most common. Stroke occurred in 22 (32%) and mortality in 14 (20%). CONCLUSION: BCVI although infrequent, is a serious injury. Our study suggests that MVA patients with cervical spine fractures especially of the upper C-spine are at much higher risk of BCVI than those without such injuries.

Virtual temporal bone: an interactive 3-dimensional learning aid for cranial base surgery.

OBJECTIVE: We have developed an interactive virtual model of the temporal bone for the training and teaching of cranial base surgery. METHODS: The virtual model was based on the tomographic data of the Visible Human Project. The male Visible Human's computed tomographic data were volumetrically reconstructed as virtual bone tissue, and the individual photographic slices provided the basis for segmentation of the middle and inner ear structures, cranial nerves, vessels, and brainstem. These structures were created by using outlining and tube editing tools, allowing structural modeling either directly on the basis of the photographic data or according to information from textbooks and cadaver dissections. For training and teaching, the virtual model was accessed in the previously described 3-dimensional workspaces of the Dextroscope or Dextrobeam (Volume Interactions Pte, Ltd., Singapore), whose interfaces enable volumetric exploration from any perspective and provide virtual tools for drilling and measuring. RESULTS: We have simulated several cranial base procedures including approaches via the floor of the middle fossa and the lateral petrous bone. The virtual model suitably illustrated the core facts of anatomic spatial relationships while simulating different stages of bone drilling along a variety of surgical corridors. The system was used for teaching during training courses to plan and discuss operative anatomy and strategies. CONCLUSION: The Virtual Temporal Bone and its surrounding 3-dimensional workspace provide an effective way to study the essential surgical anatomy of this complex region and to teach and train operative strategies, especially when used as an adjunct to cadaver dissections.

Surgical planning for microsurgical excision of cerebral arterio-venous malformations using virtual reality technology.

BACKGROUND: To evaluate the feasibility of surgical planning using a virtual reality platform workstation in the treatment of cerebral arterio-venous malformations (AVMs) METHODS: Patient-specific data of multiple imaging modalities were co-registered, fused and displayed as a 3D stereoscopic object on the Dextroscope, a virtual reality surgical planning platform. This system allows for manipulation of 3D data and for the user to evaluate and appreciate the angio-architecture of the nidus with regards to position and spatial relationships of critical feeders and draining veins. We evaluated the ability of the Dextroscope to influence surgical planning by providing a better understanding of the angio-architecture as well as its impact on the surgeon's pre- and intra-operative confidence and ability to tackle these lesions. FINDINGS: Twenty four patients were studied. The mean age was 29.65 years. Following pre-surgical planning on the Dextroscope, 23 patients underwent microsurgical resection after pre-surgical virtual reality planning, during which all had documented complete resection of the AVM. Planning on the virtual reality platform allowed for identification of critical feeders and draining vessels in all patients. The appreciation of the complex patient specific angio-architecture to establish a surgical plan was found to be invaluable in the conduct of the procedure and was found to enhance the surgeon's confidence significantly. CONCLUSION: Surgical planning of resection of an AVM with a virtual reality system allowed detailed and comprehensive analysis of 3D multi-modality imaging data and, in our experience, proved very helpful in establishing a good surgical strategy, enhancing intra-operative spatial orientation and increasing surgeon's confidence.

Minimally invasive carpal tunnel decompression using the KnifeLight.

OBJECTIVES: Carpal tunnel syndrome is a common condition causing hand pain, dysfunction, and paresthesia. Endoscopic carpal tunnel decompression offers many advantages compared with conventional open surgical decompression. However, it is equipment intensive and requires familiarity with endoscopic surgery. We review a minimally invasive technique to divide the flexor retinaculum by using a new instrument, the KnifeLight (Stryker, Kalamazoo, Michigan), which combines the advantages of the open and endoscopic methods, without the need for endoscopic set-up. METHODS: Between July 2003 and April 2005, 44 consecutive patients (26 women [59%] and 18 men [36%]), with clinical signs and symptoms, as well as electrodiagnostic findings consistent with carpal tunnel syndrome, who did not respond to non-surgical treatment, underwent the new procedure. All patients were asked about scar hypertrophy, scar tenderness, and pillar pain. The Michigan Hand Outcomes Questionnaire (MHQ) was used to determine overall hand function, activities of daily living, work performance, pain, aesthetics, and satisfaction with hand function. Other preoperative testing included grip strength and lateral pinch strength. Grip strength was measured using the Jamar hand dynamometer (Asimov Engineering Co., Los Angeles, CA); lateral key pinch was measured using the Jamar hydraulic pinch gauge. Postoperative evaluations were scheduled at 2 weeks, 3 months, and 6 months after the procedure. A small 10-mm incision was made in the wrist crease and a small opening was made at the transverse carpal ligament. The KnifeLight tool was inserted, and the ligament was incised completely. Follow-up evaluations with use of quantitative measurements of grip strength, pinch strength, and hand dexterity were performed at 2 weeks, 3 months, and 6 months after surgery. RESULTS: Fifty procedures were performed on 22 left hands (44%) and 28 right hands (56%). There were no complications related to the approach. All patients were able to use their hands immediately after the surgery. Scar tenderness and incisional pain were mild-to-moderate in the first 2 weeks, and these symptoms disappeared completely 6 months after surgery. Significant postoperative improvements in pain relief, patient satisfaction, hand function, daily activities, and work performance as assessed with the MHQ were noted at 3 and 6 months after surgery. Furthermore, significant improvement in patients' hand grip and pinch strength were observed 6 months after surgery. From a literature review, we found that the mean operation time of KnifeLight carpal tunnel release was the shortest compared with the conventional and endoscopic carpal tunnel release techniques. The median time needed for our patients to return to work was also the shortest among the different techniques. CONCLUSION: Excellent functional outcomes and satisfaction were achieved using the KnifeLight for carpal tunnel decompression. Our minimally invasive method offers a quick, easy, and effective alternative to conventional or endoscopic carpal tunnel decompression.

Neurosurgical management of intracranial aneurysms following unsuccessful or incomplete endovascular therapy.

The publication of the ISAT trial in 2002 has resulted in increasing numbers of patients with aneurysmal subarachnoid haemorrhage undergoing endovascular coiling, as first line treatment for aneurysm occlusion. During the first 2-year period post-ISAT, in which all suitable intracranial aneurysms were coiled first, we had to perform surgery in seven patients out of 54 who underwent initial coiling. The reasons for subsequent surgery were failed coiling, residual or recurrent aneurysm necks and delayed aneurysmal rebleeding despite coiling. We reviewed our surgical experience with the repair of these previously coiled aneurysms to identify unique technical difficulties. In particular, we found that an aneurysm height to neck ratio of less than 2:1 after coiling, and the use of stent-assisted coiling presented formidable challenges to direct clipping.

Gene transfer to dorsal root ganglia by intrathecal injection: effects on regeneration of peripheral nerves.

Gene delivery to sensory neurons of the dorsal root ganglion (DRG) offers the prospect of developing new clinical interventions against peripheral nerve diseases and disorders. Here we show that genes can be transferred to rat DRG through lumbar intrathecal injection of delivery vectors into the cerebrospinal fluid. Genes could be transferred to DRG using polyethylenimine (PEI)/DNA complexes, Lipofectamine 2000/DNA complexes, adeno-associated virus vectors, or baculovirus vectors. We also show that nerve growth factor cDNA, delivered through lumbar intrathecal injection of PEI complexes, was able to improve regeneration of transected rat sciatic nerves. These data demonstrate the viability of using an intrathecal gene delivery approach for treating peripheral neuropathies.

Peripheral nerve regeneration with sustained release of poly(phosphoester) microencapsulated nerve growth factor within nerve guide conduits.

Prolonged delivery of neurotrophic proteins to the target tissue is valuable in the treatment of various disorders of the nervous system. We have tested in this study whether sustained release of nerve growth factor (NGF) within nerve guide conduits (NGCs), a device used to repair injured nerves, would augment peripheral nerve regeneration. NGF-containing polymeric microspheres fabricated from a biodegradable poly(phosphoester) (PPE) polymer were loaded into silicone or PPE conduits to provide for prolonged, site-specific delivery of NGF. The conduits were used to bridge a 10 mm gap in a rat sciatic nerve model. Three months after implantation, morphological analysis revealed higher values of fiber diameter, fiber population and fiber density and lower G-ratio at the distal end of regenerated nerve cables collected from NGF microsphere-loaded silicone conduits, as compared with those from control conduits loaded with either saline alone, BSA microspheres, or NGF protein without microencapsulation. Beneficial effects on fiber diameter, G-ratio and fiber density were also observed in the permeable PPE NGCs. Thus, the results confirm a long-term promoting effect of exogenous NGF on morphological regeneration of peripheral nerves. The tissue-engineering approach reported in this study of incorporation of a microsphere protein release system into NGCs holds potential for improved functional recovery in patients whose injured nerves are reconstructed by entubulation.