A microanatomical map of the structures hidden in the middle fossa based on the facial nerve hiatus: measurements and their variability.

The aim of this study was to investigate the relationships/variations between the facial nerve hiatus (FNH) and middle cranial fossa neuro-vascular structures. Twenty CT-scanned middle cranial fossae of fresh adult cadavers were used; the greater superficial petrosal nerves, and critical neuro-vascular structures were identified. Using the FNH as a reference point, a neuronavigation system was used to measure the distance between each structure and the FNH. The coefficient of variation (CV) was used to quantify the degree of variation among each distance. The mean distances and standard deviations between the various landmarks and the FNH, and the associated CV were analyzed. Furthermore, a microanatomical map of the structures hidden in the middle fossa based on the greater superficial petrosal nerve was generated. The most reliable relationships of the FNH were with the internal auditory canal (CV = 14.59), and with the vertical portion of the intrapetrous internal carotid artery (CV = 15.54). Our data demonstrate that the FNH can be used as anatomical landmark to plot the position of several hidden neurovascular structures when performing a middle-fossa skull base approach. However, the pattern and the variation of these structures had to be recognized.

Effect of registration mode on neuronavigation precision: an exploration of the role of random error.

The aim of this paper is to analyze the variations in registration accuracy for computer-assisted surgical navigation using three different modes of registration, in order to explore the behavior of random error, and to highlight the precision of neuronavigation as a concept distinct from accuracy. The operational accuracy of three different registration modes (bone fiducials, scalp adhesive fiducials and an auto-registration mask) was evaluated in a total of 20 fresh cadaveric heads. The precision of the neuronavigation system was then assessed by evaluating the variation in the accuracy measurements associated with each registration mode. The coefficient of variation was employed to quantify the degree of variation in the attained accuracy using the following formula: Coefficient of variation = standard deviation/mean * 100. For external targets, the precision of the neuronavigation system was greatest with mask registration (43.75 and 51.41 for anterior and posterior external targets, respectively) and lowest with bone registration (65.30 and 67.17 for anterior and posterior external targets, respectively). For internal targets, the precision of the neuronavigation system was greatest with bone registration (47.69 and 42.6 for anterior and posterior internal targets, respectively) and lowest with mask registration (62.9 and 58.67 for anterior and posterior internal targets, respectively). The precision (reproducibility) of the neuronavigation system is another important quantity besides accuracy that characterizes the performance of the system. Understanding both of these quantities for a given registration mode enhances the use of a neuronavigation system in neurosurgery.

Jugular foramen paragangliomas: management, outcome and avoidance of complications in a series of 75 cases.

Jugular foramen paragangliomas are rare skull base tumours posing multiple complex diagnostic and management problems. We did a study to evaluate surgical technique, outcome and complications in 75 cases of tumours treated by multidisciplinary approach (i.e. combined neurosurgery, neuroradiology, ear, nose and throat surgery and intensive care unit team). Retrospective study on 75 consecutive patients with jugular foramen paragangliomas treated surgically from 1989 to 2005. Preoperative balloon occlusion test was performed in all patients as well as embolization (100%). A combined limited infratemporal and juxtacondylar approach was used in all patients. Gross total resection was achieved in 59 patients (78.7%). The most common complication was represented by lower cranial nerve deficits in five patients (6.6%), which was only temporary in three. Postoperative facial nerve weakness occurred in five cases (6.6%) and resolved in three of them. The remaining two patients underwent facial nerve reconstruction by hypoglossal/facial nerve anastomosis. Four patients (5.3%) had a postoperative cerebrospinal fluid leak, which was successfully treated by lumbar drainage. Two patients (2.7%) died because of complications related to surgical injury of lower cranial nerves: one patient developed aspiration pneumonia and septicemia and the second one developed a large cervico-bulbar hematoma that led to severe respiratory distress and ultimately global cerebral hypoxia. Paragangliomas are rare and complex skull base lesions that may be managed with low morbidity and mortality if a multidisciplinary approach is considered. Facial and lower cranial nerve postoperative deficits can be limited.

Decompressive craniectomy and early cranioplasty for the management of severe head injury: a prospective multicenter study on 147 patients.

OBJECTIVE: In emergency care of patients with severe blunt head injury, uncontrollable high intracranial pressure is one of major causes of morbidity and mortality. The purpose of this study was to evaluate the efficacy of aggressive surgical treatment in managing uncontrollable elevated intracranial pressure coupled with early skull reconstruction. METHODS: This was a prospective study on a series of 147 consecutive patients, managed according to the same protocol by five different neurosurgical units, for severe head injuries (Glasgow coma scale score ≤8/15 and high intracranial pressure >25 mm Hg) during a five-year period. All patients received a wide decompressive craniectomy and duroplasty in the acute phase, and a cranioplasty was also performed within 12 weeks (median 6 weeks, range 4-12 weeks). RESULTS: The emergency decompressive surgery was performed within 28 hours (median 16 hours, range 6-28 hours) after sustaining the head injury. The median preoperative Glasgow coma scale score was 6/15 (range 3-8/15). At a mean follow-up of 26 months (range 14-74 months) 14 patients were lost to long-term follow-up, leaving only 133 patients available for the study. The outcome was favorable in 89 (67%, Glasgow outcome score 4 or 5), it was not favorable in 25 (19%, Glasgow outcome score 2 and 3), and 19 patients (14%) died. A younger age (<50 years) and earlier operation (within 9 hours from trauma) had a significant effect on positive outcomes (P < 0.0001 and P < 0.03, respectively). CONCLUSIONS: A prompt aggressive surgery, including a wide decompressive craniectomy coupled with early cranioplasty, could be an effective treatment method to improve the outcome after a severe closed head injury reducing, perhaps, many of the complications related to decompressive craniectomy.

Accuracy validation in a cadaver model of cranial neuronavigation using a surface autoregistration mask.

BACKGROUND: Image guidance systems are widely used in neurosurgical practice. OBJECTIVE: To compare the operational accuracy of a neuronavigation system when registration was accomplished with a commercially available surface-based autoregistration system vs other fiducial-based registrations. METHODS: We evaluated the operational accuracy of different registration methods in 20 cadaveric heads. Every specimen was prepared with 10 titanium microscrews functioning as external/internal targets and as bone fiducials. Six scalp fiducials were also affixed to each specimen that was registered with bone, scalp fiducials, and the autoregistration mask. The coordinates of all the target points were measured, first manually on the screen of the navigation system and then by touching the head of the implanted screw on the specimen. The difference between the real and virtual coordinates was calculated. RESULTS: Means of the differences for external anterior targets were 1.96, 3.12, and 3.20 mm and 1.95, 3.24, and 3.19 mm for external posterior targets for the bone fiducials, adhesive fiducials, and autoregistration mask, respectively. Means of the differences for internal anterior targets were 2.60, 3.65, and 2.16 mm and 2.91, 3.83, and 2.41 mm for internal posterior targets for the bone fiducials, adhesive fiducials, and autoregistration mask, respectively. CONCLUSION: Bone fiducial registration is associated with a statistically greater operational accuracy than scalp adhesive fiducials and the autoregistration mask in reaching anterior and posterior external targets (P < .001). Registration accomplished with the autoregistration mask is associated with a statistically greater operational accuracy in reaching internal targets than adhesive fiducials registration (P < .001) or bone fiducials registration (P < .05 and P < .01 for anterior and posterior targets, respectively).

Quantitative and qualitative analysis of the working area obtained by endoscope and microscope in various approaches to the anterior communicating artery complex using computed tomography-based frameless stereotaxy: a cadaver study.

OBJECTIVE: Surgical treatment of aneurysms of the anterior communicating artery complex is challenging, owing to its intricate vascular anatomy. Endoscopy is a recently rediscovered neurosurgical technique that could lend itself well to overcoming some of the vascular visualization challenges associated with this procedure. The purpose of this study was to quantify and compare the working area afforded by the microscope and the endoscope to the anterior communicating artery complex in different surgical approaches and using image guidance. METHODS: We performed a total of 9 dissections, including mini-supraorbital, pterional, and orbitozygomatic approaches bilaterally in 5 whole, fresh cadaver heads. We used computed tomography-based image guidance for intraoperative navigation as well as for quantitative measurements. We estimated the working area of the anterior communicating artery complex region, using both a rigid endoscope (4.0 mm in diameter and 18 cm long with 0- and 30-degree lenses) and an operating microscope. Operability was qualitatively assessed by the senior authors. RESULTS: In microscopic exposure, the orbitozygomatic approach provided the greatest working area (204.5 +/- 33.9 mm2), as compared with the mini-supraorbital approach (114.8 +/- 26.9 mm2) and pterional approach (170 +/- 20.4 mm2; P < 0.05). Evaluation of the endoscopic working area showed that the supraorbital approach, using both 0- and 30-degree endoscopes, provided a working area greater than that of a conventional pterional approach (P < 0.05) and comparable to that of an orbitozygomatic approach (P > 0.05). CONCLUSION: In our model, use of the endoscope, in an assistive manner to microscopic surgery, provided a working area advantage without loss of microneurosurgical techniques of dissection or of depth perception in the surgical field. This advantage was most prominent when smaller craniotomies were used.

Multilevel oblique corpectomy without fusion in managing cervical myelopathy: long-term outcome and stability evaluation in 268 patients.

OBJECT: The multilevel oblique corpectomy (MOC) allows widening of the spinal canal and foramen trough via an anterolateral access to the cervical spine with control of the vertebral artery and does not require vertebral stabilization or fusion. In the present study, the authors' goal was to demonstrate the long-term efficacy and safety of MOC in the treatment of selected cases of spondylotic myelopathy. METHODS: The authors conducted a prospective study in a series of 268 patients who underwent MOC for cervical spondylotic myelopathy over a 14-year period. Preoperative and postoperative neurological functioning were evaluated with the modified Japanese Orthopaedic Association scale. Spinal stability was assessed in all patients on serial plain and dynamic cervical radiographs at the last follow-up. The degree of canal expansion after MOC was also measured using the spinal canal/vertebral body ratio, and directly by measuring the diameter of osseous canal on pre- and postoperative CT scans and high-resolution MR images. RESULTS: At a mean follow-up of 96 months, clinical improvement was recorded in 86.6% of patients with a global recovery rate of 87.6%, clinical stability in 8%, and worsening in 5%. Long-term spinal stability was demonstrated in 98% of patients. CONCLUSIONS: Multilevel oblique corpectomy was demonstrated to be a safe procedure that provided good results in terms of improved functional status and long-term spinal stability.