Frank M. Warren

Management of carotid 'blowout' with endovascular stent grafts.

Objectives/Hypothesis Since 1992, endovascular techniques for vascular occlusion and stenting have evolved significantly. Endovascular occlusion of the carotid artery has been used in the management of carotid “blowout.” Although it seems logical to expand this application to the use of arterial stents to repair rather than occlude the artery when cerebral cross‐circulation is inadequate, concerns remain regarding the placement of a foreign body in a contaminated field. The purpose of the present report is to describe our experience with endovascular stents for control of carotid hemorrhage.

Automatic segmentation of the facial nerve and chorda tympani in CT images using spatially dependent feature values

In cochlear implant surgery, an electrode array is permanently implanted in the cochlea to stimulate the auditory nerve and allow deaf people to hear. A minimally invasive surgical technique has recently been proposed-percutaneous cochlear access-in which a single hole is drilled from the skull surface to the cochlea. For the method to be feasible, a safe and effective drilling trajectory must be determined using a preoperative CT. Segmentation of the structures of the ear would improve trajectory planning safety and efficiency and enable the possibility of automated planning. Two important structures of the ear, the facial nerve and the chorda tympani, are difficult to segment with traditional methods because of their size (diameters as small as 1.0 and 0.3 mm, respectively), the lack of contrast with adjacent structures, and large interpatient variations. A multipart, model-based segmentation algorithm is presented in this article that accomplishes automatic segmentation of the facial nerve and chorda tympani. Segmentation results are presented for ten test ears and are compared to manually segmented surfaces. The results show that the maximum error in structure wall localization is approximately 2 voxels for the facial nerve and the chorda, demonstrating that the method the authors propose is robust and accurate.

Percutaneous cochlear access using bone-mounted, customized drill guides: demonstration of concept in vitro.

Hypothesis: Percutaneous cochlear access can be performed using bone-mounted drill guides that are custom made on the basis of preintervention computed tomographic scans. Background: We have previously demonstrated the ability to use image guidance based on fiducial markers to obtain percutaneous cochlear access in vitro. A simpler approach that has far less room for application error is to constrict the path of the drill to pass in a predetermined trajectory using a drill guide. Methods: Cadaveric temporal bone specimens (n = 8) were affixed with three bone-implanted fiducial markers. The temporal bone computed tomographic scans were obtained and used in planning a straight trajectory from the mastoid surface to the cochlea without violating the boundaries of the facial recess, namely, the chorda tympani, the incus buttress, and the facial nerve. These surgical plans were used to manufacture a customized drill guide by means of rapid prototyping (MicroTargeting Platform; FHC Inc.; Bowdoinham, ME, U.S.A.) that mounts onto anchor pins previously used to mount fiducial markers. The specimens then underwent traditional mastoidectomy with facial recess. The drill guide was mounted, and a 1-mm drill bit was passed through the guide across the mastoid and the facial recess. The course of the drill bit and its relationship to the boundaries of the facial recess were photographed and measured. Results: Eight cadaveric specimens were subjected to the study protocol. In seven of eight specimens, the drill bit trajectory was accurate; it passed from the lateral cortex to the lateral wall of the cochlea without compromise of any critical structures. In one specimen, the access to the middle ear was achieved, but the incus was hit by the drill. The average shortest distance ± standard deviation from the edge of the drill bit to the boundaries of the facial recess was 0.78 ± 0.56 mm (chorda tympani), 2.00 ± 1.06 mm (incus buttress), and 1.27 ± 0.54 mm (facial nerve). Conclusion: Our study demonstrates the ability to obtain percutaneous cochlear access in vitro using customized drill guides manufactured on the basis of preintervention radiographic studies.

Intraoperative Parathyroid Hormone Levels in Thyroid and Parathyroid Surgery

Objective To determine the utility of intraoperative parathyroid hormone measurement in predicting postoperative hypocalcemia after thyroid and parathyroid surgeries that places total parathyroid function at risk.

Robotic Surgery of the Infratemporal Fossa Utilizing Novel Suprahyoid Port

To develop a minimally invasive technique for robotic access to the infratemporal fossa and describe use of a novel suprahyoid port placement.

Apparent cochlear nerve aplasia: to implant or not to implant?

Objective: To describe the imaging findings and clinical outcomes of children with apparent cochlear nerve aplasia undergoing cochlear implantation. Study Design: Retrospective case review. Setting: Tertiary care center. Patients: Three patients with imaging findings consistent with absent cochlear nerve canal on diagnostic imaging and questionable audiometric responses on testing who underwent promontory stimulation and subsequent cochlear implantation. Intervention(s): Magnetic resonance imaging and computed tomography, audiologic assessment, and cochlear implantation. Main Outcome Measure(s): Audiologic performance after cochlear implantation. Results: Three patients were identified to have hearing loss on newborn hearing screening and underwent auditory brainstem response testing revealing absent brainstem responses. ASSR testing was inconclusive when performed. Imaging in all cases identified 1 ear with a small internal auditory canal with 2 nerves present, one of which seems to enter the vestibule in each case and the other is assumed to be the functioning facial nerve. There was a bony plate present over the entrance to the cochlea in 2 of the 3 patients. Over time, 2 of the families reported responses to auditory stimuli with amplification. Promontory stimulation testing showed reproducible responses to electrical stimuli in the ears in question. After cochlear implantation, all 3 patients have shown responses to auditory stimuli. Conclusion: The absence of a visible cochlear nerve or cochlear nerve canal on radiologic imaging does not preclude auditory innervation of the cochlea. Cochlear implantation can be a viable option for patients with apparent cochlear nerve aplasia who have undergone appropriate testing. Electronically evoked auditory brainstem response is critical in the evaluation of this patient group.

Perioperative parathyroid hormone levels in thyroid surgery: Preliminary report

Objectives/Hypothesis An immediate method of accurately predicting postoperative hypocalcemia after total thyroidectomy would allow for selective early discharge of patients at low risk. The objective of the study was to determine the utility of perioperative parathyroid hormone measurement in predicting postoperative hypocalcemia after a thyroid surgery that places total parathyroid function at risk.

Postoperative imaging of vestibular schwannomas

Objectives Assess the need for serial magnetic resonance imaging after vestibular schwannoma surgery. Study Design Retrospective case review. Subjects and Methods Study included all patients who underwent vestibular neuromas surgery over a five-year period from 1996 to 2000 at a single tertiary referral center. Analysis of tumor recurrence and correlation with enhancement types on postoperative imaging was performed. Results During the five-year period, 359 cerebellopontine angle tumors were removed. The 299 patients had MRI imaging at one and five years for analysis and a five-year follow-up examination. Of these patients, 284 were found to have no enhancement at both one and five years. Linear enhancement was seen in ten patients but did not enlarge in any patient. Nodular enhancement of the internal auditory canal was observed in three patients. Two patients with nodular enhancement had tumor recurrence. Conclusions Complete vestibular schwannoma resection has a low recurrence rate. Initial imaging should be performed at one year. Only patients with enhancement, subtotal resections, or neurofibromatosis type II need serial imaging.

Management of brain herniation and cerebrospinal fluid leak in revision chronic ear surgery.

Objectives/Hypothesis: Brain herniation and cerebrospinal fluid (CSF) leakage into the middle ear and mastoid are rare but described complications of chronic ear disease. This paper will discuss the presentation and management of brain herniation and/or CSF leak encountered in revision chronic ear surgery.

Congenital cholesteatoma of the mastoid temporal bone.

Objective: Congenital mastoid cholesteatomas are rare lesions of the temporal bone. The clinical presentation of these lesions is variable, making them difficult to identify preoperatively. We evaluated our series of mastoid congenital cholesteatomas (CCs) in an effort to better define the clinical presentation, imaging characteristics, and surgical challenges specific to this lesion.