Functional Deficits of Cranial Nerves in Patients with Jugular Foramen Lesions

Lower cranial neuropathies are a leading presenting symptom in patients with tumors involving the jugular foramen. The purpose of this study is to assess acute and chronic functional deficits along with neurologic findings in 31 patients who underwent resection of a tumor involving the jugular foramen. Preoperative nerve dysfunction made intraoperative preservation unlikely, while postoperative lower cranial nerve dysfunction was found to be transient in many patients. Compensation of permanent dysfunction was usually excellent.     

The Jugular Dural Fold—A Helpful Skull Base Landmark to the Cranial Nerves

During a retrosigmoid (or combined retrolabyrinthine-retrosigmoid) approach to the posterior fossa for vestibular neurectomy or removal of small acoustic neuromas, a white dural fold is a consistent landmark to cranial nerves VII through XII. This fold of dura appears as a white linear structure extending from the foramen magnum across the sigmoid sinus, attaching to the posterior aspect of the temporal bone, anterior to the vestibular aqueduct. The name “jugular dural fold” is suggested for this landmark. The jugular dural fold overlies the junction of the sigmoid sinus and the jugular foramen. As measured in formalin-fixed cadaver heads, the overall length of the jugular dural fold is 20.8 mm (± 2.9 mm). The cochleovestibular nerve lies 9.9 mm (± 1.5 mm) anterior to the superior aspect of the jugular dural fold, the glossopharyngeal nerve lies 9.5 mm (± 1.6 mm) anterior to the midpoint of the jugular dural fold, and the operculum of the vestibular aqueduct lies 6.6 mm (± 0.7 mm) posterior to the jugular dural fold. Intraoperative measurements in patients undergoing combined retrolabyrinthine-retrosigmoid vestibular neurectomy show an overall length of the jugular dural fold of 16.3 mm (± 1.9 mm). The cochleovestibular nerve lies 8.6 mm (± 1.3 mm) anterior to the superior aspect of the jugular dural fold, the glossopharyngeal nerve lies 8.6 mm (± 1.3 mm) anterior to the midpoint of the jugular dural fold, and the operculum lies 7.5 mm (± 0.8 mm) posterior to the jugular dural fold. The jugular dural fold can be used as a reliable landmark for rapidly locating cranial nerves in the posterior fossa.     

Management of Zone III Missile Injuries Involving the Carotid Artery and Cranial Nerves

Carotid and cranial nerve injuries from zone III (high cervical/cranial base) missile injuries are rare and difficult to treat. We have treated five patients with such injuries. We present our management scheme, and compare it to the management of the same injuries in other reports. Five consecutive zone III missile injuries presented to our institution. Trauma assessment by the trauma team, followed by detailed neurological assessment and radiographs (angiogram and computed tomography) were obtained on admission. All patients presented with dysphagia and carotid artery injury with good collateral flow, documented by angiogram. Two patients had facial nerve injury, one had trigeminal nerve injury, one patient presented with tongue weakness, and one patient suffered conductive hearing loss. No patient had evidence of stroke clinically or radiographically. Carotid artery injury was managed with bypass (3 of 5) or ligation (2 of 5). Cranial nerve injuries were documented and treated aggressively with surgery if needed. All patients were discharged to home. Patients presenting with zone III missile injuries should receive an expeditious neurological exam and four-vessel angiogram after initial trauma survey and resuscitation. Bypass of the injured portion of carotid artery is a valid treatment in the hemodynamically stable patient. The unstable patient should undergo ligation to stop hemorrhage and protect against immediate risk for stroke, with the option to bypass later. Cranial nerve injuries should be pursued and aggressively treated to minimize morbidity and prevent mortality.     

Management of Zone III Missile Injuries Involving the Carotid Artery and Cranial Nerves

Carotid and cranial nerve injuries from zone III (high cervical/cranial base) missile injuries are rare and difficult to treat. We have treated five patients with such injuries. We present our management scheme, and compare it to the management of the same injuries in other reports. Five consecutive zone III missile injuries presented to our institution. Trauma assessment by the trauma team, followed by detailed neurological assessment and radiographs (angiogram and computed tomography) were obtained on admission. All patients presented with dysphagia and carotid artery injury with good collateral flow, documented by angiogram. Two patients had facial nerve injury, one had trigeminal nerve injury, one patient presented with tongue weakness, and one patient suffered conductive hearing loss. No patient had evidence of stroke clinically or radiographically. Carotid artery injury was managed with bypass (3 of 5) or ligation (2 of 5). Cranial nerve injuries were documented and treated aggressively with surgery if needed. All patients were discharged to home. Patients presenting with zone III missile injuries should receive an expeditious neurological exam and four-vessel angiogram after initial trauma survey and resuscitation. Bypass of the injured portion of carotid artery is a valid treatment in the hemodynamically stable patient. The unstable patient should undergo ligation to stop hemorrhage and protect against immediate risk for stroke, with the option to bypass later. Cranial nerve injuries should be pursued and aggressively treated to minimize morbidity and prevent mortality.     

Value of Free-Run Electromyographic Monitoring of Lower Cranial Nerves in Endoscopic Endonasal Approach to Skull Base Surgeries

Objective The main objective of this study was to evaluate the value of free-run electromyography (f-EMG) monitoring of cranial nerves (CNs) VII, IX, X, XI, and XII in skull base surgeries performed using endoscopic endonasal approach (EEA) to reduce iatrogenic CN deficits.Design We retrospectively identified 73 patients out of 990 patients who had EEA in our institution who had at least one CN monitored. In each CN group, we classified patients who had significant (SG) f-EMG activity as group I and those who did not as group II.Results We monitored a total of 342 CNs. A total of 62 nerves had SG f-EMG activity including CN VII = 18, CN IX = 16, CN X = 13, CN XI = 5, and CN XII = 10. No nerve deficit was found in the nerves that had significant activity during procedure. A total of five nerve deficits including (CN IX = 1, CN X = 2, CN XII = 2) were observed in the group that did not display SG f-EMG activity during surgery.Conclusions f-EMG seems highly sensitive to surgical manipulations and in locating CNs. It seems to have limited value in predicting postoperative neurological deficits. Future studies to evaluate the EMG of lower CNs during EEA procedures need to be done with both f-EMG and triggered EMG.     

Skull Base Meningiomas and Cranial Nerves Contrast Using Sodium Fluorescein: A New Application of an Old Tool

Objective The identification of cranial nerves is one of the most challenging goals in the dissection of skull base meningiomas. The authors present an application of sodium fluorescein (SF) in skull base meningiomas with the purpose of improving the identification of cranial nerves. Design A prospective study within-subjects design. Setting Hospital Ernesto Dornelles, Porto Alegre, Brazil. Participants Patients with skull base meningiomas. Main Outcomes Measures Cranial nerve identification. Results The group of nine meningiomas was composed of one cavernous sinus, three petroclival, one tuberculum sellae, two sphenoid wing, one olfactory groove, and one temporal floor meningioma. The SF enhancement in all tumors was strong, and the contrast with cranial nerves clearly evident. There were one definite olfactory nerve deficit, one transient abducens deficit, and one definite hemiparesis. All lesions were resected (Simpson grades 1 and 2). The analysis of the difference of the delta SF wavelength between the meningiomas and cranial nerve contrast was performed by the Wilcoxon signed rank test and showed p = 0.011. Conclusions The contrast between the enhanced meningiomas and cranial nerves was evident and assisted in the visualization and microsurgical dissection of these structures. The anatomical preservation of these structures was improved using the contrast.     

Virtual Cisternoscopy: 3D MRI Models of the Cerebellopontine Angle for Lesions Related to the Cranial Nerves

This study was conducted to show that high-resolution magnetic resonance imaging (MRI) can aid in the neurosurgical approach to lesions affecting the cranial nerves (CNs) in the cerebellopontine angle (CPA). Three patients with symptomatology related to CNs VII and VIII underwent MRI examinations performed on a 1.5-Tesla Siemens MR scanner. As part of these routine examinations, the imaging technique of constructive interference in the steady state (CISS) was used to collect a volume of data through the brainstem and internal auditory canals. This high-resolution technique acquires a three-dimensional (3D) volume of data at 0.7-mm intervals. Parameters included TR 12.3/TE 5.9, number of acquisitions of 2, a matrix of 230 x 512, bandwidth of 130 Hz per pixel, and time of 8:40. Data were transferred to a commercially available GE workstation and reconstructed into a 3D surface-rendered model. This interactive method allows the model to be visualized from any angle, including that of a standard skull base approach of suboccipital craniotomy for access to the CPA cistern. The images shown include the CPA cistern as seen from the suboccipital surgical approach. CNs V, VII, and VIII can easily be seen in relation to the pons and petrous face. The relationship between the CNs and acoustic neuromas and skull base tumors can be evaluated. Vascular structures, which are often seen in relation to CNs VII and VIII, can be viewed in a 3D format to determine the need for microvascular decompression. Direct intraoperative photographs taken through the operating microscope confirmed the anatomic accuracy of the 3D models. Imaging used for interactive neurosurgical planning must demonstrate a high degree of anatomic detail. Virtual cisternoscopy using CISS MRI technique can achieve the required resolution. Reconstruction algorithms to create surface rendering can generate images with similar 3D anatomic detail to that seen during neurosurgical approaches to the CPA cistern.     

Value of Intraoperative Brainstem Auditory Evoked Potential Monitoring in Reducing the Auditory Morbidity Associated with Microvascular Decompression of Cranial Nerves

The present study was performed to determine whether the intraoperative monitoring of brainstem auditory evoked potentials (BAEPs) during microvascular decompression operations is effective in preventing profound hearing loss or deafness in the ipsilateral ear. The authors retrospectively compared the auditory morbidity of posterior fossa microvascular decompression surgery for the treatment of tic douloureux and hemifacial spasm before and after the introduction of routine intraoperative BAEP monitoring in 1984. Each patient underwent a similar procedure performed by the same surgeon. The two patient groups were comparable with regard to age, sex, and indications for surgery, Auditory morbidity did not decline with the increasing experience of the surgeon prior to 1984; 10 (6.6%) of 152 primary operations (151 patients) in which monitoring was not performed were followed by a profound ipsilateral hearing loss or deafness. In the monitored group, none of 109 operations (104 patients) caused profound hearing loss or deafness. This significant decline in auditory morbidity is attributed by the authors to the use of intraoperative BAEP monitoring, which allows the surgeon to alter the operation in response to degradations in the wave patterns. Based on our experience and that of others, we believe that intraoperative BAEP monitoring is of value in reducing the auditory morbidity of posterior fossa microvascular decompression surgery.     

Cranial and orbital epidermoid tumours.

This paper reports on 14 cases of cranial and orbital epidermoid tumours, of which 2 epicranial, 4 extradural intracranial, 4 fronto-orbital-sinusal, 2 orbital and 2 orbito-nasal cases. Referring to these cases and data published in the specialised literature, the authors show that this type of tumour is more frequent in males, and is generally of embryologic but very rarely of mechanical origin. The main symptom is tumefaction in cranial tumours and exophthalmos in orbital tumours. There is very rarely association with a space-occupying process (tumour, cerebral abscess). Evolution is slow and progressive; the only treatment is surgical. After total ablation there were no recurrences and the postoperative course was very satisfactory.     

Cranial nerve injuring during carotid endarterectomy.

Injury to the greater auricular, hypoglossal and superior laryngeal nerves during carotid endarterectomy is preventable. A knowledge of regional anatomy and the mechanisms of such injury allows prevention of this complication. Unilateral individual nerve injury is generally well tolerated, but bilateral or combined nerve injuries can pose a serious threat to life. Minor modifications in technique aid greatly in avoiding nerve injury.     

Cranial deformation in craniosynostosis. A new explanation.

Skull growth after premature fusion of a single suture was described by Virchow in 1851. He observed that growth was restricted in a plane perpendicular to a fused suture. However, he failed to predict the compensatory growth patterns that produce many of the deformities recognized as features of individual craniosynostosis syndromes. The deformities resulting from premature closure of a coronal, sagittal, metopic, or lambdoid suture can be predicted by the following observations: (1) cranial vault bones that are prematurely fused act as a single bone plate with decreased growth potential; (2) asymmetrical bone deposition occurs mainly at perimeter sutures, with increased bone deposition directed away from the bone plate; (3) sutures adjacent to the stenotic suture compensate in growth more than those sutures not contiguous with the closed suture; and (4) enhanced bone deposition occurs along both sides of a nonperimeter suture that is a continuation of the prematurely closed suture. These four rules were derived by critically examining the clinical deformities observed with each form of craniosynostosis. These rules assume that cranial sutures have the capacity to compensate by depositing bone asymmetrically along their edges. Unequal growth patterns have been demonstrated in the frontonasal suture of rabbits by Selman and Sarnat. In addition, unequal bone deposition has also been demonstrated along the parieto-interparietal suture in albino rats by Baer. Human studies to determine if asymmetrical bone deposition actively occurs along cranial vault sutures in response to a stenotic suture have not been performed, however. It is also unclear whether these four guidelines apply to cranial base abnormalities observed with craniosynostosis. As new radiologic techniques develop to define the configuration of the skull in intricate detail, a skull pattern of growth explaining the pathogenesis of all deformities created by premature fusion of a cranial vault suture may become apparent.