Safety study of the Cochlear Nucleus 24 device with internal magnet in the 1.5 Tesla magnetic resonance imaging scanner
OBJECTIVES: To evaluate the effect of the 1.5 Tesla magnetic resonance imager (MRI) on the Cochlear Nucleus 24 Device without removing the internal magnet. To determine whether device fixation using a compression dressing could prevent internal magnet displacement in the MRI scanner and potentially obviate the need for surgical removal of the internal magnet. STUDY DESIGN: Prospective cadaveric study. METHODS: Four cadaver heads were implanted bilaterally with the Nucleus device with the internal magnet in place and placed into the 1.5 Tesla MRI scanner. The devices were then explanted after interaction with the MRI and evaluated for displacement of the internal magnet. Conditions tested include device fixation with a commercially available compression dressing and no fixation (worst-case scenario). Magnet strength was measured before and after each of the test conditions. RESULTS: Moderate to severe displacement of the magnet from the internal device occurred in 14 of 16 (87%) implants when no compression dressing was placed. Displacement occurred in 0 of 16 (0%) implants when the compression dressing was applied. No decrease in the strength of the implant magnet was found with the initial or subsequent MRI/implant interactions. CONCLUSIONS: Use of the 1.5 Tesla MRI on subjects with Cochlear Nucleus 24 implants did not result in any significant demagnetization of the internal magnet and did not cause displacement of the magnet when an external compression dressing was applied. Surgical removal of the internal magnet before scanning with the 1.5 Tesla MRI may not be necessary if a compression dressing is applied.
Indications for cerebrospinal fluid drainage and avoidance of complications
An understanding of normal CSF physiology is a prerequisite to treating problems such as CSF fistulae and pseudomeningoceles. CSF diversion techniques fall into two categories, external and internal. External lumbar drainage is useful when temporary CSF diversion is necessary (eg, in cases necessitating manipulation and retraction of the brain to gain access to deep lesions) and in treating otorrhea or rhinorrhea following traumatic or iatrogenic insults to the cranial base. Drawbacks include insertion discomfort and limited duration of therapy.LP and VP shunts came into widespread use in the 1970s, and both systems share risks of bowel perforation, obstruction, over drainage and wound-related complications. In addition, VP shunts add the risks of intracerebral hematoma and ventriculitis. New valve technology has made it possible to alter the volume drained, thus alleviating problems of over-and under drainage.
Supraorbital craniotomy for parasellar lesions. Technical note
The authors present a modification to a previously reported supraorbital craniotomy procedure that is smaller, simpler, safe, and cosmetically pleasing. Minimal brain retraction is used without compromising the surgical exposure of the orbital roof, floor of the anterior fossa, and the parasellar region to treat tumoral lesions that are located medial to the ipsilateral optic nerve as well as aneurysms of the anterior communicating artery.
Extradural anterior clinoidectomy. Technical note
The anterior clinoid process (ACP), located on the skull base, is a relatively small structure, although its removal provides enormous gain in facilitating the management of lesions--either tumors or aneurysms--in the paraclinoid region and upper basilar artery. The extensive surgical field gained contributes to safer exposure of the neurovascular elements in the vicinity while avoiding excessive and hazardous retraction of the brain. In this report the authors present a technically simpler avenue for performing an extradural anterior clinoidectomy after reviewing the anatomy of the ACP and its anatomical variations. Additionally, the original Dolenc procedure and its subseqtient derivatives are compared and contrasted to the authors' simpler and less laborious technique. Different clinical situations in which to use the procedure are described based on the authors' experience from 60 cases (40 aneurysm cases and 20 tumor cases) during a 4-year period.
Modified osteoplastic orbitozygomatic craniotomy. Technical note
The authors report on a surgical technique involving a one-piece osteoplastic bone flap, which incorporates the frontal, temporal, and lateral portions of the orbital rim as a technically simpler alternative to the standard orbitozygomatic (OZ) craniotomy. The orbital rim component extends just laterally from the supraorbital foramen/notch to the frontozygomatic suture. This craniotomy obviates the need for removing the zygoma and has evolved from the authors' experience in more than 200 patients with a variety of pathological lesions, both vascular and tumorous. The osteoplastic aspect of this technique was initially evaluated in 14 cadaveric sites in seven heads dissected prior to implementing this procedure clinically. The osteoplastic bone flap minimally obstructs the surgical view and provides all the advantages of a standard OZ craniotomy. Temporalis muscle atrophy leading to temporal hollowing is avoided, a bone union to the calvaria is improved, and the possibility of bone infection is decreased. The osteoplastic component of the technique adds to the improved long-term cosmesis and warrants active consideration in the art of neurosurgery.
Cochlear implant fixation using polypropylene mesh and titanium screws
HYPOTHESIS: Fixation of cochlear implants using prosthetic mesh is an improvement of the traditional fixation methods. STUDY DESIGN: A retrospective chart review was performed examining all adult and pediatric patients between 1998 and 2003 who underwent cochlear implantation using polypropylene mesh and titanium screws to fix the cochlear implant internal receiver. Patient age at implantation, postoperative infections, device failures, device migrations or extrusions, cerebrospinal fluid (CSF) leaks, flap complications, epidural hematoma data, and follow-up data were evaluated. RESULTS: Two hundred and eighty-five patients were identified who received cochlear implantation using the polypropylene mesh securing technique. There were five postoperative infections, two device failures, zero flap complications, zero device migrations or extrusions, zero cerebral spinal fluid leaks, and zero epidural hematomas. The two delayed device failures in this series were not related to fixation technique. CONCLUSIONS: We conclude that this technique is widely applicable, technically superior, and not associated with increased complications.
Hearing preservation with the transcrusal approach to the petroclival region
OBJECTIVE: We studied the hearing results and outcomes after transcrusal craniotomy. STUDY DESIGN: We conducted a retrospective review. SETTING: This study was conducted at a tertiary care hospital. PATIENTS: We studied 10 consecutive patients, including two men and eight women, who underwent transcrusal craniotomy for petroclival masses or tumors. INTERVENTION: The intervention consisted of therapeutic removal of petroclival meningioma. MAIN OUTCOME MEASURE: The main outcome measure of this study was hearing preservation as measured by standard audiogram. RESULTS: There were six meningiomas, one eighth nerve schwannoma, one fifth nerve schwannoma, one chordoma, and one midbasilar artery aneurysm. Postoperative hearing was measured according to the AAOHNS criteria. Complications and further therapies were recorded. Postoperative hearing was measured in eight. The cochlear nerve was severed in one patient. One was unavailable for follow up. Eight patients retained hearing at or near preoperative levels, seven with SRT within 10 dB and speech discrimination within 10% of preoperative levels. Four patients presented with trigeminal symptoms, one with third nerve palsy and two with facial weakness. Postoperative deficits included fourth, sixth, seventh, and eighth nerve palsies in three patients. Complications included one wound infection, two cerebrospinal fluid leak, and two cases of meningitis, both of which were sterile. There were secondary procedures in five patients-three radiosurgery, two shunts, one tracheotomy, and one g-tube. CONCLUSIONS: Transcrusal craniotomy is a safe and effective approach to the petroclival region. Excellent hearing results can be expected with this technique.
Extended middle fossa approach: quantitative analysis of petroclival exposure and surgical freedom as a function of successive temporal bone removal by using frameless stereotaxy
OBJECT: Conventional wisdom regarding skull base surgery says that more extensive bone removal equals greater exposure. Few researchers have quantitatively examined this assertion, however. In this study the authors used a frameless stereotactic system to measure quantitatively the area of petroclival exposure and surgical freedom for manipulation of instruments with successive steps of temporal bone removal. METHODS: With the aid of high-power magnification and a high-speed drill, 12 cadaveric specimens were dissected in four predetermined, successive bone removal steps: 1) removal of the Kawase triangle; 2) removal of the Glasscock triangle; 3) removal of the cochlea together with skeletonization of the anterior internal auditory canal; and 4) inferior displacement of the zygoma. Step 1 offered 62 +/- 43 mm2 of exposed petroclival area, with 84 +/- 69 mm2 of surgical freedom; Step 2, 61 +/- 22 and 76 +/- 58 mm2; Step 3, 128 +/- 47 and 109 +/- 87 mm2; and Step 4, 135 +/- 38 and 102 +/- 69 mm2, respectively. CONCLUSIONS: The middle fossa approach provided a means surgically to expose the petroclival area. When examined quantitatively by using a frameless stereotactic device, the authors determined that the removal of the cochlea and skeletonization of the anterior internal auditory canal (Step 3) provided the most significant increase in both exposure and surgical freedom. Removal of the zygoma improved neither exposure nor surgical freedom.
Choroid plexus papilloma of the third ventricle in the fetus. Case illustration [Case Report]
Microsurgery vs gamma knife radiosurgery for the treatment of vestibular schwannomas