Can Ophthalmologic Examination Predict Abducens Nerve Recovery After Endoscopic Skull Base Surgery?

OBJECTIVES: While abducens nerve palsy (ANP) is a known risk in the setting of some endoscopic endonasal skull base surgery (ESBS), frequency and prognosis of post-operative palsy remain unknown. Our goals were to determine the frequency and prognosis of ANP after high-risk ESBS, and identify factors associated with recovery. METHODS: Retrospective case series of all patients with pathology at highest risk for abducens nerve injury (pituitary adenoma, chordoma, meningioma, chondrosarcoma, cholesterol granuloma) generated a list of patients with abducens nerve palsy after ESBS performed from 2011-2016. A validated ophthalmologic clinical grading scale measuring lateral rectus duction from 0 to -5 (full motion to inability to reach midline) was measured at multiple time points to assess recovery of ANP. RESULTS: Of 655 patients who underwent ESBS with increased risk of abducens injury, 40 (6.1%) post-operative palsies were identified and 39 patients with dedicated examination at multiple time points were included in subsequent analysis. Complete resolution was noted in 25 patients (64%) within 12 months. While 19 of 23 (83%) with a partial palsy had complete resolution, only six of 16 (38%) with a complete palsy resolved entirely (P = .005; Fisher's exact test). All six patients with delayed onset of palsy resolved (P = .070; Fisher's exact test). Meningioma and chordoma had higher rates of both temporary and permanent post-operative ANP (P < .0001; Fisher's exact). CONCLUSIONS: The frequency of post-operative ANP following ESBS is low, even in high-risk tumors. While only a minority of complete abducens nerve palsies recover, patients with partial or delayed palsy post-operatively are likely to recover function without intervention. LEVEL OF EVIDENCE: IV Laryngoscope, 131:513-517, 2021.

Anatomía radiológica de la base de cráneo y los nervios craneales parte 2: Nervios craneales / Skull base and cranial nerves radiologic anatomy part 2: Cranial nerves

Resumen: La anatomía de la base del cráneo es compleja. Numerosas estructuras neurovasculares vitales pasan a través de múltiples canales y agujeros ubicados en la base del cráneo. Con el avance de la tomografía computarizada (TC) y la resonancia magnética (RM), es posible la localización cada vez más precisa de lesiones y la evaluación de su relación con las estructuras neurovasculares adyacentes. El trayecto de los nervios craneales sigue un recorrido conocido y se transmiten a la cara y cuello por los forámenes de base de cráneo. La tomografía computada y la resonancia magnética son complementarias entre sí y, a menudo, se usan juntas para demostrar la extensión total de la enfermedad. La segunda parte de esta revisión se centra en el estudio radiológico de los nervios craneales.

Abstract: The skull base anatomy is complex. Many vital neurovascular structures course through the skull base canals and foramina. With the advancement of CT and MRI, the localization of lesions has become more precise as their relationship with adjacent neurovascular structures. There is a known course of the cranial nerves as well as their skull base exiting foramina to the head and neck. CT and MRI are complimentary modalities and are often used together to map the full extent of disease. The second article in this review focus on the radiologic study of the cranial nerves.

High-dose conformal proton therapy for clinical perineural invasion in cutaneous head and neck cancer.

Non-melanomatous skin cancer (NMSC) is the most common malignancy worldwide. Perineural invasion (PNI) is an uncommon (<5%), high-risk feature observed with NMSC more commonly seen in those with squamous cell carcinoma. One-third of these patients will have clinical PNI, which refers to tumor cell invasion extensive enough to cause clinically detectable deficits of the involved nerve. Uncontrolled disease within the skull base can be debilitating and, if not eradicated, fatal. The primary management options including radiotherapy with or without surgery, with local control rates exceeding 50%. Given the overwhelming influence of local control on disease control and survival, dose escalation and complication mitigation through hyperfractionated and high-dose conformal skull-base proton therapy are strategies to improving the therapeutic window in patients with cutaneous head and neck cancer with clinical PNI.

Recurrent abducens nerve palsy and hypophosphatasia syndrome.

A 47-year-old woman presented with six episodes of horizontal binocular double vision over a 2-year period. CT imaging was significant for extensive dural calcification in the spine and calcification of the skull base, likely involving Dorello's canal. Biochemical testing revealed a persistently low alkaline phosphatase level. Recurrent nerve palsy may possibly be induced by mechanical compression of the sixth cranial nerve in Dorello's canal from calcification due to hypophosphatasia syndrome.

Anatomía radiológica de la base de cráneo y los nervios craneales parte 1: generalidades y base de cráneo / Skull base and cranial nerves radiologic anatomy part 1: basics and skull base

La anatomía de la base del cráneo es compleja. Numerosas estructuras neurovasculares vitales pasan a través de múltiples canales y formámenes de la base del cráneo. Con el avance de la tomografía computarizada (TC) y la resonancia magnética (RM) es posible la localización cada vez más precisa de lesiones y la evaluación de su relación con las estructuras neurovasculares adyacentes. El trayecto de los nervios craneales sigue un recorrido conocido y se transmiten a la cara y cuello a través de los forámenes de base de cráneo. La TC y la RM son complementarias entre sí y, a menudo, se usan en conjunto para demostrar la extensión completa de la enfermedad. La primera parte de esta revisión se centra en generalidades del estudio radiológico y anatomía de base de cráneo.

The skull base anatomy is complex. Many vital neurovascular structures course through the skull base canals and foramina. With the routine use of CT and MRI, the localization of lesions has become more precise as well as their relationship with adjacent neurovascular structures. There is a known anatomical course of the cranial nerves and their skull base s they course through the foramina towards the head and neck. CT and MRI are complimentary modalities and are often used together to map the full extent of disease. The first part of this review article series focus on the radiologic approach to disease and the skull base anatomy.

Lateral skull base chondroblastoma resected with facial nerve posterior transposition.

INTRODUCTION: Chondroblastoma is a rare tumor that can involve the temporal bone. Because it is a benign tumor, functional surgery must be proposed. We report a case of a patient with a massive chondroblastoma operated on with preservation of the facial nerve, and description of the surgical technique. CASE PRESENTATION: A 37-year-old man presented with a 9-month history of a growing left pre-auricular mass and hearing loss. Neuroimaging showed an osteolytic mass invading the temporal bone and temporomandibular joint. Excision was performed via a transpetrosal and transcochlear approach with posterior transposition of the facial nerve. EMG monitoring was effective in preventing facial palsy. Four years later, no sign of recurrence was observed. DISCUSSION: Chondroblastoma is a locally aggressive tumor, especially when located in the petrous bone and temporomandibular joint. The suggested treatment is a complete excision.

Dosimetric Analysis of Neural and Vascular Structures in Skull Base Tumors Treated with Stereotactic Radiosurgery.

Objective To examine the relationship between the prescribed target dose and the dose to healthy neurovascular structures in patients with vestibular schwannomas treated with stereotactic radiosurgery (SRS). Study Design Case series with chart review. Setting SRS center from 2011 to 2013. Subjects Twenty patients with vestibular schwannomas treated at the center from 2011 to 2013. Methods Twenty patients with vestibular schwannomas were included. The average radiation dose delivered to healthy neurovascular structures (eg, carotid artery, basilar artery, facial nerve, trigeminal nerve, and cochlea) was analyzed. Results Twenty patients with vestibular schwannomas who were treated with fused computed tomography/magnetic resonance imaging-guided SRS were included in the study. The prescribed dose ranged from 10.58 to 17.40 Gy over 1 to 3 hypofractions to cover 95% of the target tumor volume. The mean dose to the carotid artery was 5.66 Gy (95% confidence interval [CI], 4.53-6.80 Gy), anterior inferior cerebellar artery was 8.70 Gy (95% CI, 4.54-12.86 Gy), intratemporal facial nerve was 3.76 Gy (95% CI, 3.04-4.08 Gy), trigeminal nerve was 5.21 Gy (95% CI, 3.31-7.11 Gy), and the cochlea was 8.70 Gy (95% CI, 7.81-9.59 Gy). Conclusions SRS for certain vestibular schwannomas can expose the anterior inferior cerebellar artery (AICA) and carotid artery to radiation doses that can potentially initiate atherosclerotic processes. The higher doses to the AICA and carotid artery correlated with increasing tumor volume. The dose delivered to other structures such as the cochlea and intratemporal facial nerve appears to be lower and much less likely to cause immediate complications when shielded.

Base of Skull Blocks for Open Reduction and Internal Fixation of Faciomaxillary Fractures.

INTRODUCTION: Faciomaxillary fractures (FMF) occur in a significant proportion of trauma patients. Nearly all polytrauma patients and even those with isolated FMF are managed under general anesthesia for definitive management. We propose the use of regional nerve blocks as a safe and effective means for open reduction and fixation of isolated FMF. AIM AND OBJECTIVES: The aim is to evaluate the feasibility, effectiveness and safety of base of skull maxillomandibular and distal trigeminal nerve blocks in the management of FMF. MATERIALS AND METHODS: Ten young adults with fractures of the zygoma, mandible and Le Fort I/II injuries were included in the study. Patients with associated craniocervical and abdominothoracic injuries were excluded. RESULTS: The patients' ages ranged from 21 to 40 years, with a mean time of onset of anesthesia being 5 to 12 minutes and total duration of 105 to 220 minutes. Supplementary block for patchy anesthesia was needed in three. All underwent unhindered surgery without complication. CONCLUSION: Base of skull maxillary-mandibular and distal trigeminal blocks are an effective and efficient alternative to general anesthesia for the open reduction and internal fixation of FMF.

Efficacy of the greater occipital nerve block in recurrent migraine type headaches.

AIMS: We aimed to evaluate six months of results following repeated GON blocks. METHODS: We evaluated the results from GON block performed on 60 patients. Briefly, we applied a standard 2 mL of 0.5% Bupivacaine GON blockage once a week for 4 weeks. We recorded the Visual Analog Scale (VAS) scores, the number of migraine attacks and the Migraine Disability Assessment Questionnaire (MIDAS) scores. The study subjects were not allowed to use medication for prophylaxis, and Ibuprofen (400 mg, 1200 mg at maximum) was prescribed for any migraine attacks. RESULTS: The initial mean number of attacks per month before starting treatment was 8.33+2.31. After treatment, the initial MIDAS mean was found to be 2.82 per month; this declined to 1.47 in 3rd, and was 1.50 in the 6th month. The individual month values were found to be significant, and were listed respectively as, 1st month: 3.95+2.52, 2nd month: 3.23+1.82, 3rd month: 2.60+1.90, 4th month: 2.68+2.10, 5th month: 2.58+1.90 and 6th month: 2.58+1.90. The mean VAS scores were recorded as follows for each month: 6.28±1.24, 3.13±0.97, 2.55±1.19, 2.35±1.26, 2.38±1.20 and 2.48±1.30, respectively. This difference was noted to be statistically significant. No difference regarding the efficacy of the treatment was determined when the results were compared across age groups. CONCLUSION: We assume that GON blockage with 2 mL of 0.5% Bupivacaine can be a supportive treatment in migraine treatment, with no serious adverse effects reported.

The role of cranial and thoracic electromyography within diagnostic criteria for amyotrophic lateral sclerosis.

INTRODUCTION: The contribution of cranial and thoracic region electromyography (EMG) to diagnostic criteria for amyotrophic lateral sclerosis (ALS) has not been evaluated. METHODS: Clinical and EMG data from each craniospinal region were retrospectively assessed in 470 patients; 214 had ALS. Changes to diagnostic classification in Awaji-Shima and revised El Escorial criteria after withdrawal of cranial/thoracic EMG data were ascertained. RESULTS: Sensitivity for lower motor neuron involvement in ALS was highest in the cervical/lumbar regions; specificity was highest in cranial/thoracic regions. Cranial EMG contributed to definite/probable Awaji-Shima categorization in 1.4% of patients. Thoracic EMG made no contribution. For revised El Escorial criteria, cranial and thoracic data reclassified 1% and 5% of patients, respectively. CONCLUSION: Cranial EMG data make small contributions to both criteria, whereas thoracic data contribute only to the revised El Escorial criteria. However, cranial and thoracic region abnormalities are specific in ALS. Consideration should be given to allowing greater diagnostic contribution from thoracic EMG. Muscle Nerve 54: 378-385, 2016.

Identification of the posterior deep temporal nerve groove and canal, and its relationship to basicranial angle.

The posterior deep temporal nerve (PDTN) groove accommodates the posterior deep temporal nerve and is infrequently described. This area is important for some clinical procedures including mandibular nerve blockade. This study assesses the prevalence and morphological variations of the PDTN groove in a single population, investigating its relationship with basicranial angle to assess predictive value for the existence of this feature. The infratemporal regions of 101 contemporary Sinhalese Sri Lankan skulls were examined bilaterally and ordinally scored for PDTN groove morphology (six point scale); 11 random skulls were radiographed and basicranial angles measured. Descriptive statistics and significance testing (P < 0.05) were used for analysis, including symmetry (Wilcoxon matched-pairs signed rank test), sex differences (Mann and Whitney U test), and between basicranial angle and PDTN morphology (Pearson's product-moment correlation coefficient). Ninety skulls (44 males) were included for analysis (180 sides). PDTN groove morphology on individual sides ranged from non-existent (20.6%) to partial (5.6%) and complete canals (1.1%); 93.3% of skulls had a PDTN groove or canal. Skulls exhibited bilateral symmetry (P = 0.12) and males had significantly deeper PDTN grooves or canals (P = 0.018). Basicranial flexion correlated strongly with PDTN groove or canal prevalence (P = 0.0028). Sri Lankan skulls have a high prevalence of PDTN grooves and also canals, a feature not previously described. Prevalence was related significantly to sex but not symmetry, and PDTN grooves and canals correlated significantly with basicranial angle. Knowledge of this morphology is important for some clinical procedures, anthropological assessment, and as a location for PDTN entrapment.

The origin of the auriculotemporal nerve and its relationship to the middle meningeal artery.

Knowledge of the anatomy of the auriculotemporal nerve (ATN) and middle meningeal artery (MMA) in the infratemporal fossa is necessary for assisting concise medical diagnosis and intervention. Current textbook descriptions describe a relationship between these structures that is not reported in previous studies. In addition, no previous studies have reported on symmetry or ethnicity affecting the relationship between these structures. This study aims to provide information on the relationship between the ATN and the meningeal artery in a specific ethnic group to further our understanding of normal morphology in this region. The infratemporal fossae of 19 Caucasian cadaveric heads were dissected bilaterally and the relationship between the ATN and MMA scrutinised. Twenty-five samples were included for analysis, including 6 bilateral (12 sides, 8 female) and 13 unilateral (9 female) specimens. Nerve root contributions to the ATN from the mandibular and inferior alveolar nerve included 8 specimens with 1 root, 12 with 2, 5 with 3, and 1 with 4. Three of six bilaterally dissected specimens had asymmetrical numbers of nerve roots. Two specimens were found with a 'button hole' arrangement of the ATN; these did not enclose the MMA. Variation was found both between and within specimens in relation to the relationship between the ATN and MMA. None of the specimens examined demonstrated a morphology that was consistent with common anatomical texts. Findings suggest modern texts require revision in order to accurately describe the relationship between these structures.

[Perioperative management of skull base tumor surgery].

In this chapter, vital points in perioperative management of skull base tumor (SBT) surgery are described. Not only surgical techniques and devices but also peri-operative management have been greatly improved in a relatively short period of time, resulting in many additional indications for more complex procedures. Anesthesiologists have therefore assumed more responsibility for the perioperative management of patients. We begin with an introduction of newly developed surgical approaches and a review of major perioperative complications for each approach. Next we describe intraoperative electrophysiological monitoring (IOEM) methods for neuronal protection. Neuronal damage can be caused by maneuvers for obtaining better views of surgical fields, such as compression of juxtaposed tissues and clamping of major arteries. Thus, IOEM should be used for not only structures in the surgical field but also surrounding structures that are exposed to risk of damage. Finally, we describe intraoperative anesthetic management and postoperative intensive care. Some of the methods that were once considered to be neuroprotective have been denied by results of recent studies. Anesthesiologists should therefore update their knowledge of perioperative management for SBT surgery to promote patient safety.

Anastomoses between lower cranial and upper cervical nerves: a comprehensive review with potential significance during skull base and neck operations, part I: trigeminal, facial, and vestibulocochlear nerves.

Descriptions of the anatomy of the neural communications among the cranial nerves and their branches is lacking in the literature. Knowledge of the possible neural interconnections found among these nerves may prove useful to surgeons who operate in these regions to avoid inadvertent traction or transection. We review the literature regarding the anatomy, function, and clinical implications of the complex neural networks formed by interconnections among the lower cranial and upper cervical nerves. A review of germane anatomic and clinical literature was performed. The review is organized in two parts. Part I concerns the anastomoses between the trigeminal, facial, and vestibulocochlear nerves or their branches with any other nerve trunk or branch in the vicinity. Part II concerns the anastomoses among the glossopharyngeal, vagus, accessory and hypoglossal nerves and their branches or among these nerves and the first four cervical spinal nerves; the contribution of the autonomic nervous system to these neural plexuses is also briefly reviewed. Part I is presented in this article. An extensive anastomotic network exists among the lower cranial nerves. Knowledge of such neural intercommunications is important in diagnosing and treating patients with pathology of the skull base.

A comprehensive review with potential significance during skull base and neck operations, Part II: glossopharyngeal, vagus, accessory, and hypoglossal nerves and cervical spinal nerves 1-4.

Knowledge of the possible neural interconnections found between the lower cranial and upper cervical nerves may prove useful to surgeons who operate on the skull base and upper neck regions in order to avoid inadvertent traction or transection. We review the literature regarding the anatomy, function, and clinical implications of the complex neural networks formed by interconnections between the lower cranial and upper cervical nerves. A review of germane anatomic and clinical literature was performed. The review is organized into two parts. Part I discusses the anastomoses between the trigeminal, facial, and vestibulocochlear nerves or their branches and other nerve trunks or branches in the vicinity. Part II deals with the anastomoses between the glossopharyngeal, vagus, accessory and hypoglossal nerves and their branches or between these nerves and the first four cervical spinal nerves; the contribution of the autonomic nervous system to these neural plexuses is also briefly reviewed. Part II is presented in this article. Extensive and variable neural anastomoses exist between the lower cranial nerves and between the upper cervical nerves in such a way that these nerves with their extra-axial communications can be collectively considered a plexus.

Ossification of the petrosphenoidal ligament: unusual variation with the potential for abducens nerve entrapment in Dorello's canal at the skull base.

Variable bony anatomy at the skull base may result in compression or entrapment of exiting cranial nerves. The authors present an unusual variation of bilateral ossification of the roof of Dorello's canal and review the germane literature. Clinicians might consider ossification of the petrosphenoidal ligament (also called Gruber's ligament) in patients with unexplained cases of abducens nerve palsy.

Microsurgical anatomy of the infratemporal fossa.

The objective of this study is to clearly and precisely describe the topography and contents of the infratemporal fossa. Ten formalin-fixed, adult cadaveric specimens were studied. Twenty infratemporal fossa were dissected and examined using micro-operative techniques with magnifications of 3-40×. Information was obtained about the inter-relationships of the contents of the infratemporal fossa. The infratemporal fossa lies at the boundary of the head and neck, and the intracranial cavity. It is surrounded by the maxillary sinus anteriorly, the mandible laterally, the pterygoid process anteromedially, and the parapharyngeal space posteromedially. It contains the maxillary artery and its branches, the pterygoid muscles, the mandibular nerve, and the pterygoid venous plexus. The course and the anatomic variation of the maxillary artery and the branches of the mandibular nerve were demonstrated. The three-dimensional (3D) relationships between the important bony landmarks and the neurovascular bundles of the infratemporal fossa were also shown. The skull base anatomy of the infratemporal fossa is complex, requiring neurosurgeons and head and neck surgeons to have a precise knowledge of 3D details of the topography and contents of the region. A detailed 3D anatomic knowledge is mandatory to manage benign or malignant lesions involving the infratemporal fossa without significant postoperative complications.

[Treatment outcome of patients with cranial base lesions of unknown etiology: focusing on infectious cases with multiple cranial nerve disorders].

Involvement of cranial nerves caused by cranial base lesions manifests diverse symptoms according to the localization of lesions. These localization-related symptoms are classified into syndromes such as orbital apex syndrome, cavernous sinus syndrome, and jugular foramen syndrome. Since the lesions may have various etiologies including infection, inflammation and tumor, etiological diagnosis should be performed simultaneously if possible. However, previous reports have described poor and/or fatal outcome following inappropriate treatment mainly due to difficulties in making a definitive pathological diagnosis. Nineteen patients with multiple cranial nerve involvement caused by skull base lesions were enrolled over the past 12 years. The patients were divided into an "infectious" group (n=11) and a "noninfectious" group (n=8) based on the final diagnosis. Chi-square analysis was conducted to examine the sensitivity and specificity of various factors including patient characteristics, clinical course and treatment response in infectious and noninfectious groups. Consequently, we identified some patients with good outcome irrespective of infectious or noninfectious etiology, even though a pathological diagnosis was not reached before the initial treatment. These patients with good outcome consistently received antifungal therapy in the early stage if infectious etiologies were suspected. We recommend conducting diagnostic therapy with antifungal drugs in patients with skull base lesions of unknown origin although infection cannot be excluded, when a pathological diagnosis is difficult due to various patient conditions.

The trochlear nerve: microanatomic and endoscopic study.

The purpose of the present study was to analyze the relationships of the trochlear nerve with the surrounding structures through both endoscopic and microscopic perspectives. The aim was to assess the anatomy of the nerve and to carry out a thorough description of its entire course. A comprehensive anatomically and clinically oriented classification of its different segments is proposed. Forty human cadaveric fixed heads (20 specimens) were used for the dissection. The arterial and venous systems were injected with red and blue colored latex, respectively, in the transcranial dissection. For illustrative purposes, the arterial vessels were injected alone in endoscopic endonasal procedures. A CT scan was carried out on every head. Median supracerebellar infratentorial, subtemporal, fronto-temporo-orbito-zygomatic, and endoscopic endonasal transsphenoidal approaches were performed to expose the entire pathway of the nerve. A navigation system was used during the dissection process to perform the measurements and postoperatively to reconstruct, using dedicated software, a three-dimensional model of the different segments of the nerve. The trochlear nerve was divided into five segments: cisternal, tentorial, cavernous, fissural, and orbital. Detailed and comprehensive examination of the basic anatomical relationships through the view of transcranial, endoscope-assisted, and pure endoscopic endonasal approaches was achieved. As a result of a thorough study of its intra- and extradural pathways, an anatomic-, surgically, and clinically based classification of the trochlear nerve is proposed. Precise knowledge of the involved surgical anatomy is essential to safely access the supracerebellar region, middle fossa, parasellar area, and orbit.

Eyebrow craniotomy for anterior skull base lesions: how I do it.

BACKGROUND: The eyebrow craniotomy is a less invasive alternative approach for accessing anterior skull base lesions, compared to traditional and more extensive exposures. We give a stepwise description of this minimally invasive technique with discussion on the indications, limitations and key aspects of perioperative management. METHODS: Positioning of the head and planning the surgical corridor are dictated by the nature, site and size of the target lesion. The eyebrow incision should spare the medial and posterolateral neural structures. Microsurgical strategy is based on opening up the basal cisterns and respecting the distorted neurovascular anatomy. Selective use of brain retractor and angulation of the operative microscope enable the surgeon to make use of the "keyhole effect" for accessing a larger target. Perioperative measures are in part dictated by the nature of the pathology, involvement of the optic apparatus and changes to pituitary function. CONCLUSION: The eyebrow craniotomy may be safely used as a minimally invasive approach for a variety of anterior skull base lesions. There is an operative learning curve and some types of pathologies are easier to approach by this technique than others. KEY POINTS: • The eyebrow craniotomy is an alternative less invasive approach for accessing anterior skull base lesions • Positioning of the head and planning the surgical corridor are dictated by the nature, site and size of the target lesion • Microsurgical strategy is based on opening up the basal cisterns and respecting the distorted neurovascular anatomy. • Selective use of brain retractor and angulation of the operative microscope enable the surgeon to make use of the "keyhole effect" for accessing a larger target • Perioperative measures are in part dictated by the nature of the pathology, involvement of the optic apparatus and changes to pituitary function. • There is an operative learning curve and some types of pathologies are easier to approach by this technique than others.