Sonographic reference values of cranial nerve size: A systematic review and meta-analysis.

INTRODUCTION/AIMS: Ultrasonography of the cranial nerves has recently gained attention for assessment of inflammatory, compressive, or degenerative neuropathies. However, sonographic reference values of cranial nerves have received less attention than those of peripheral nerves. In this systematic review and meta-analysis we aimed to provide current evidence of sonographic reference values for cranial nerve size. METHODS: By searching Medline (via PubMed), Scopus, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), and Web of Science, we conducted a systematic review and meta-analysis of studies that reported ultrasound measurements of the facial, spinal accessory, and hypoglossal nerves in healthy adults. We included studies that reported either the sonographic cross-sectional area (CSA) or the nerve diameter; the included nerves were subgrouped according to the site of nerve measurement. RESULTS: Fourteen studies with a total of 661 participants and 1437 ultrasound nerve measurements met the inclusion criteria. The anatomical sites for each nerve were combined to provide single-nerve mean measurements. We found an overall mean nerve diameter of 0.80 mm for the facial nerve, 0.63 mm for the spinal accessory nerve, and 1.82 mm2 for hypoglossal nerve CSA. DISCUSSION: This meta-analysis provides reference values for the diameter and cross-sectional area of the facial, spinal accessory, and hypoglossal nerves at different sites, which can be used as guidance in clinical practice to detect pathological changes in cranial nerve size in cranial neuropathies. We recommend further validation in large-scale studies as well as standardization of the scanning protocols.

Ultrasound Shear Wave Elastography of the Tongue during Selective Hypoglossal Nerve Stimulation in Patients with Obstructive Sleep Apnea Syndrome.

Currently, there is no established technique to directly measure extrinsic tongue muscle activation during selective hypoglossal stimulation therapy (sHNS) in patients with obstructive sleep apnea syndrome (OSAS) in a simple, non-invasive clinical setting. Ultrasound shear-wave elastography (US-SWE) enables quantitative measurement of tissue stiffness. We investigated whether US-SWE is able to detect changes in muscle stiffness of the tongue during sHNS. Patients with OSAS treated with sHNS were prospectively enrolled. A standardized US-SWE protocol was used to selectively measure tissue stiffness of the geniohyoid muscle (GH) and genioglossus (GG) muscles on the side of stimulator implantation (sGH, sGG) and on the contralateral side (nGH, nGG) without and with sHNS. Eighteen patients were included (median age = 62 years, interquartile range: 56-65, 83.3% male). Median shear-wave velocity (SWV) increased during contraction with each patient's clinically prescribed therapeutic regimen in the sGH (+19%, p = 0.020) and sGG (+81%, p < 0.001) and decreased during contraction in the nGH (-8%, p = 0.107) and nGG (-8%, p = 0.396). Differences in SWV during contraction were significant only on the side of stimulation (sGG +81%, sGH +19%). SWE measurements had excellent reliability as reflected by a Cronbach α value ≥0.9 for all target muscles pre- and post-contraction and an item-total correlation ≥0.5. US-SWE allows reliable measurement of SWV as an indicator of muscle stiffness of extrinsic tongue muscles. This non-invasive method provides new possibilities to distinguish and characterize responders from non-responders in hypoglossal stimulation therapy. Compared with the regular visual assessment of tongue movement, US-SWE of individual muscle groups provides a new non-invasive imaging tool in patients with OSAS.

Ultrasound Localization and Percutaneous Electrical Stimulation of the Hypoglossal Nerve and Ansa Cervicalis.

OBJECTIVE: Hypoglossal nerve stimulation for obstructive sleep apnea (OSA) can be effective for appropriately selected patients, but current patient selection criteria are complex and still result in a proportion of nonresponders. Ansa cervicalis stimulation of the infrahyoid cervical strap muscles has recently been proposed as a new form of respiratory neurostimulation (RNS) therapy for OSA treatment. We hypothesized that percutaneous stimulation of both nerves in humans with temporary electrodes would make testing of the physiologic response to different RNS strategies possible. STUDY DESIGN: Nonrandomized acute physiology study. SETTING: Tertiary care hospital. METHODS: Fifteen participants with OSA underwent ultrasonography and placement of percutaneous electrodes proximal to the medial division of the hypoglossal nerve and the branch of the ansa cervicalis innervating the sternothyroid muscle (ACST). Procedural success was documented in each participant, as were any failures or procedural complication. RESULTS: The hypoglossal nerve was successfully localized in 15 of 15 (100%) participants and successfully stimulated in 13 of 15 (86.7%). The ACST was successfully localized in 15 of 15 (100%) participants and successfully stimulated in 14 of 15 (93.3%). Stimulation failure of the hypoglossal nerve was due to suboptimal electrode placement in 1 participant and electrode displacement in the other 2 cases. No complications occurred. CONCLUSIONS: The hypoglossal nerve and ACST can be safely stimulated via percutaneous electrode placement. Larger trials of percutaneous stimulation may help to identify responders to different RNS therapies for OSA with temporary or permanent percutaneous electrodes. Techniques for electrode design, nerve localization, and electrode placement are described.

Hypoglossal Nerve Lesions: The Role of a 3D IR-Prepped Fast SPGR High-Resolution 3T MRI Sequence.

BACKGROUND AND PURPOSE: To assess a 3D high-resolution IR-prepped fast SPGR high-resolution MRI sequence for evaluating hypoglossal nerve lesions. METHODS: The clinical data of 8 patients with hypoglossal nerve lesions admitted from December 2011 to February 2016 were retrospectively analyzed. MRI included contrast-enhanced conventional sequences and a 3D IR-prepped fast SPGR high-resolution T1-weighted (BRAVO) MRI sequence at 3T. RESULTS: Eight patients had hypoglossal lesions detected by MRI. Conventional enhanced scanning could not clearly display the hypoglossal nerve and canal, while the enhanced 3D high-resolution sequence could. In addition, multiple planar reconstruction clearly displayed the hypoglossal nerve, hypoglossal canal, and lesions in multiple planes. CONCLUSIONS: Compared with conventional MRI, we show superior results from an advanced sequence to improve image quality in characterizing hypoglossal nerve lesions.

The intracanalicular segment of the hypoglossal nerve: An anatomical study using magnetic resonance imaging.

Few studies have documented the morphology of the intracanalicular segment of the hypoglossal nerve (CSHN). Therefore, the aim of this study was to characterize the CSHN using magnetic resonance imaging (MRI). In total, 95 patients underwent thin-sliced, contrast MRI. The axial and coronal images were used for analysis. The CSHNs were bilaterally identified in 97% and 94% of the 95 patients on the axial and serial coronal images, respectively. On axial images, length of the hypoglossal canal was measured as 8.2 ±â€¯1.66 mm on the right and 8.4 ±â€¯1.71 mm on the left. The CSHN was delineated as a slightly tortuous, linear structure with variable length. The CSHN course in the hypoglossal canal could be classified into the ventral, central, and ventrodorsal types, with the ventral type most predominant and found in 65% on the right side and 43% on the left. The angle formed by the CSHN and perpendicular line was highly variable. On serial coronal images, the CSHN course in the hypoglossal canal was also variable and could be found in the any part of the canal. The CSHN is a distinct structure characterized by morphological variability, which can influence the type of hypoglossal neuropathy arising from the CSHN.

Incidence and outcomes of radiation-induced late cranial neuropathy in 10-year survivors of head and neck cancer.

OBJECTIVES: To characterize the late cranial neuropathy among 10-year survivors of head and neck cancer treatment. MATERIALS AND METHODS: We retrospectively evaluated patients treated with curative-intent radiation for HNC between 1990 and 2005 at a single institution with systematic multidisciplinary follow-up ≥ 10 years. New findings of CNP were considered radiation-induced when examination, imaging and/or biopsy did not demonstrate a structural or malignant cause. Cox proportional hazards modeling was used for univariable analysis (UVA) and multivariable analysis (MVA) for time to CNP after completion of radiation. RESULTS: We identified 112 patients with no evidence of disease and follow-up ≥ 10 years (median 12.2). Sixteen (14%) patients developed at least one CNP. The median time to CNP was 7.7 years (range 0.6-10.6 years). Most common was CN XII deficit in eight patients (7%), followed by CN X deficit in seven patients (6%). Others included CN V deficit in three, and CN XI deficit in two. Eight of the thirteen patients with a CN X and/or CN XII deficit required a permanent gastrostomy tube. On UVA, site of primary disease, post-radiation neck dissection, chemotherapy, and radiation dose were significantly associated with increased risk of CNP. CONCLUSION: Iatrogenic CNP may develop years after head and neck cancer treatment and often leads to swallowing dysfunction. Long-term follow up is essential for these patients receiving head and neck radiation.

Transvenous coil embolization with intra-operative cone beam CT assistance in the treatment of hypoglossal canal dural arteriovenous fistulae.

BACKGROUND: Hypoglossal canal dural arteriovenous fistulae (HC-dAVF) are a rare subtype of skull base fistulae involving the anterior condylar confluence or anterior condular vein within the hypoglossal canal. Transvenous coil embolization is a preferred treatment strategy, however delineation of fistula angio-architecture during workup and localization of microcatheter tip during embolization remain challenging on planar DSA. For this reason, our group have utilized intra-operative cone beam CT (CBCT) and selective cone beam CT angiography (sCBCTA) as adjuncts to planar DSA during workup and treatment. The purpose of this article is to present our experience in the treatment of HC-dAVF using transvenous coil embolization (TVCE) with cone beam CT assistance, describing our technique as well as presenting our angiographic and clinical outcomes. METHODS: Ten patients with symptomatic HC-dAVF were treated using TVCE with intra-operative cone beam CT assistance. Prospectively collected data regarding clinical and angiographic results and complication rates was recorded and reviewed. RESULTS: Complication-free fistula occlusion was achieved in our entire patient cohort. The dominant symptom of pulsatile tinnitus resolved in all 10 patients. CONCLUSIONS: This study demonstrates that TVCE with CBCT assistance is a highly effective treatment option for HC-dAVF, achieving complication-free fistula occlusion in our entire patient cohort. We have found low-dose sCBCTA and CBCT to be an extremely useful adjunct to planar DSA imaging during both workup and treatment of these rare fistulae.

Changes in the Morphology of Hypoglossal Motor Neurons in the Brainstem of Developing Rats.

The autonomic brainstem generates breathing rhythm by integrating inputs from chemosensors and mechanosensors in the viscera and coordinating descending outputs from higher structures in the central nervous system. Hypoglossal motoneurons (XII MNs) receive inputs from respiratory premotor neurons, important for maintaining airway patency. Previous studies in rodents report significant changes in breathing control during the first 3 weeks of life, with a sensitive period at 10 to 13 days postbirth (P10-P13) characterized by pronounced changes in neurotransmitters, excitation-inhibition balance, and breathing physiology. However, age-dependent morphological changes of XII MNs during the first 3 weeks postbirth and especially this sensitive period are under-studied. Here, we comprehensively characterize and quantify the early morphological changes in rat XII MNs. We hypothesized that morphological changes in XII MNs correspond to the functionally defined sensitive period observed at postnatal day 10-13 (P10-P13). To test this hypothesis, we used an innovative contemporary statistical approach to analyze Golgi-Cox stained XII MNs at nine postnatal ages between P1 and P21. Our findings reveal two subpopulations of XII MNs, which are dependent on age and morphological features. Soma size increased approximately 40% from P1 to P21, without changing shape. However, dendritic arborization increased in extent/distance and complexity. Dendritic branching of developing neurons significantly increased from P1 through P13, with the greatest increase at P10-P13 based on the Sholl method. Our detailed characterization of XII MN morphological development establishes a foundation for the study and elucidation of morphological changes caused by maternal and perinatal conditions. Anat Rec, 302:869-892, 2019. © 2018 Wiley Periodicals, Inc.

An analysis of the anatomic route of the hypoglossal nerve within the hypoglossal canal using dynamic computed tomography angiography in patients with anterior condylar arteriovenous fistulas.

OBJECTIVE: The venous outlet of anterior condylar arteriovenous fistulas (AC-AVFs) often empties into the anterior condylar vein (ACV). Hypoglossal nerve palsy is one of the major complications after transvenous embolization (TVE) for the AC-AVF within the hypoglossal canal. However, no studies have investigated the route of the hypoglossal nerve within the hypoglossal canal in AC-AVF. The aim of the current study is to retrospectively verify the anatomical route of the hypoglossal nerve within its canal using dynamic computed tomography angiography (CTA) in order to facilitate the safe TVE for AC-AVF. PATIENTS AND METHODS: We included five patients with AC-AVF from 2011 to 2017. Dynamic CTA was performed on all patients. When the ACV was well-visualized by dynamic CTA, the hypoglossal nerve could be recognized as a less-intense structure within the surrounding enhanced vasculatures and the nerve route within the canal was analyzed. We also analyzed the location of the fistulas by digital subtraction angiography and cone-beam computed tomography. RESULTS: In all five patients, the filling defect of the hypoglossal nerve ran through the most caudal portion of the hypoglossal canal. The fistulous pouches were located in the hypoglossal canal in three cases, and in the jugular tubercle venous complex in two cases. In all three cases with AC-AVF in the hypoglossal canal, the fistulous pouches were located in the superior wall of the hypoglossal canal, which means superior to the ACV. We performed TVE in four patients and none developed post-therapeutic hypoglossal nerve palsy. CONCLUSION: In the current study, dynamic CTA is useful for detecting the hypoglossal nerve within the hypoglossal canal. The hypoglossal nerve usually ran the bottom of its canal and the fistulous pouches were usually located at the superior aspect of the canal opposite side to the hypoglossal nerve. Accordingly, the selective embolization within the fistulous pouch located in the superior aspect of the ACV including jugular tubercle venous complex can reduce the risk of hypoglossal nerve palsy.

Surgical Pitfalls in Carotid Endarterectomy: A New Step-By-Step Approach.

Carotid endarterectomy (CEA) is a surgical intervention that may prevent stroke in asymptomatic and symptomatic patients. Our aim was to examine the microsurgical anatomy of carotid artery and other related neurovascular structures to summarize the CEA that is currently applied in ideal conditions. The upper necks of 2 adult cadavers (4 sides) were dissected using ×3 to ×40 magnification. The common carotid artery, external carotid artery (ECA), and internal carotid artery were exposed and examined. The surgical steps of CEA were described using 3-D cadaveric photos and computed tomography angiographic pictures obtained with help of OsiriX imaging software program. Segregating certain neurovascular and muscular structures in the course of CEA significantly increased the exposure. The division of facial vein allowed for internal jugular vein to be mobilized more laterally and dividing the posterior belly of digastric muscle resulted in an additional dorsal exposure of almost 2 cm. Isolating the ansa cervicalis that pulls hypoglossal nerve inferiorly allowed hypoglossal nerve to be released safely medially. The locations of the ECA branches alter depending on their anatomical variations. The hypoglossal nerve, glossopharyngeal nerve, and accessory nerve pierce the fascia of the upper part of the carotid sheath and they are vulnerable to injury because of their distinct courses along the surgical route. Surgical exposure in CEA requires meticulous dissection and detailed knowledge of microsurgical anatomy of the neck region to avoid neurovascular injuries and to determine the necessary surgical maneuvers in cases with neurovascular variations.

[Occipital condyle syndrome as the first symptom of a metastatic hepatocellular carcinoma. Two case reports]. / Sindrome del condilo occipital como primera manifestacion de un carcinoma hepatocelular metastasico. Presentacion de dos casos.

INTRODUCTION: Occipital condyle syndrome consists of the presence of unilateral occipital headache exacerbated by moving the head and is accompanied by paralysis of the ipsilateral hypoglossal nerve. One of its causes is infiltration of the base of the skull by bone metastases, especially those affecting the hypoglossal nerve due to infiltration as it passes through the osseous canal. CASE REPORTS: We report two clinical cases of occipital condyle syndrome secondary to metastatic hepatocarcinoma. The first is that of a 52-year-old male with liver cirrhosis secondary to liver pathology caused by hepatitis C virus with occipital condyle syndrome as the presenting symptom in disseminated hepatocarcinoma. The second case is that of a 56-year-old male after recurrence of hepatocarcinoma following a liver transplant, despite not fulfilling the Milan criteria. CONCLUSION: Occipital condyle syndrome is an alarm symptom and requires a thorough study by means of imaging tests, since it may be the first symptom of an undetected hepatocarcinoma.

TITLE: Sindrome del condilo occipital como primera manifestacion de un carcinoma hepatocelular metastasico. Presentacion de dos casos.Introduccion. El sindrome del condilo occipital consiste en la presencia de cefalea occipital unilateral que empeora con los movimientos cefalicos y se acompaña de paralisis del XII par ipsilateral. La infiltracion de la base del craneo por metastasis oseas se encuentra entre sus etiologias, especialmente las que afectan por infiltracion al nervio hipogloso en su paso a traves del canal oseo. Casos clinicos. Se presentan dos casos clinicos de sindrome del condilo occipital secundario a un hepatocarcinoma metastasico. El primero, un varon de 52 años con cirrosis hepatica secundaria a hepatopatia por virus de la hepatitis C, con sindrome del condilo occipital como sintoma inicial en un hepatocarcinoma diseminado; y el segundo, un varon de 56 años, tras recidiva de un hepatocarcinoma despues de un trasplante hepatico, a pesar de no cumplir los criterios de Milan. Conclusion. El sindrome del condilo occipital es un sintoma de alarma y requiere realizar un estudio completo mediante pruebas de imagen, puesto que puede ser la primera manifestacion de un hepatocarcinoma oculto.

[Hypoglossal canal dural arteriovenous fistulas treated with transvenous embolization:report of two cases and literature review].

Two cases of hypoglossal canal dural arteriovenous fistulas (HCDAVF) were reported. The clinical manifestation, radiological features, treatment and prognosis were reviewed. Both cases presented chemosis and pulsatile tinnitus. 3D-time-of-flight (TOF) magnetic resonance angiography (MRA) demonstrated abnormal high signal in hypoglossal canal. Cerebral digital subtraction angiography (DSA) showed that these HCDAVFs were supplied by multiple intracranial and extracranial arteries, and fistulas were located in hypoglossal canal. Fistulas were blocked by coils and Onyx-18 through transvenous approach, and the angiography after the embolism showed complete occlusion of fistula. No adverse events after treatment and no recurrence during the follow up were observed.

Nerve cuff electrode using embedded magnets and its application to hypoglossal nerve stimulation.

OBJECTIVE: A novel nerve cuff electrode with embedded magnets was fabricated and developed. In this study, a pair of magnets was fully embedded and encapsulated in a liquid crystal polymer (LCP) substrate to utilize magnetic force in order to replace the conventional installing techniques of cuff electrodes. In vitro and in vivo experiments were conducted to evaluate the feasibility of the magnet-embedded nerve cuff electrode (MENCE). Lastly, several issues pertaining to the MENCE such as the cuff-to-nerve diameter ratio, the force of the magnets, and possible concerns were discussed in the discussion section. APPROACH: Electrochemical impedance spectrum and cyclic voltammetry assessments were conducted to measure the impedance and charge storage capacity of the cathodal phase (CSCc). The MENCE was installed onto the hypoglossal nerve (HN) of a rabbit and the movement of the genioglossus was recorded through C-arm fluoroscopy while the HN was stimulated by a pulsed current. MAIN RESULTS: The measured impedance was 0.638 âˆ  -67.8° kΩ at 1 kHz and 5.27 âˆ  -82.1° kΩ at 100 Hz. The average values of access resistance and cut-off frequency were 0.145 kΩ and 3.98 kHz, respectively. The CSCc of the electrode was measured as 1.69 mC cm-2 at the scan rate of 1 mV s-1. The movement of the genioglossus contraction was observed under a pulsed current with an amplitude level of 0.106 mA, a rate of 0.635 kHz, and a duration of 0.375 ms applied through the MENCE. SIGNIFICANCE: A few methods to close and secure cuff electrodes have been researched, but they are associated with several drawbacks. To overcome these, we used magnetic force as a closing method of the cuff electrode. The MENCE can be precisely installed on a target nerve without any surgical techniques such as suturing or molding. Furthermore, it is convenient to remove the installed MENCE because it requires little force to detach one magnet from the other, enabling repeatable installation and removal. We anticipate that the MENCE will become a very useful tool given its unique properties as a cuff electrode for neural engineering.

Isolated Unilateral Tongue Atrophy: A Possible Late Complication of Juxta Cephalic Radiation Therapy.

BACKGROUND Isolated unilateral hypoglossal nerve injury is extremely rare. It may be caused by radiation therapy targeting neoplasms of the cephalic region. CASE REPORT A 51-year-old man with synovial sarcoma of the left upper arm status post extensive radiation therapy in 1980 presented in late 2014 with gradual onset of speech difficulty and difficulty moving his tongue for a couple of weeks. Neurological examination revealed isolated left-sided unilateral tongue atrophy. Postradiation residual extensive cicatrix with erythema over the whole left upper extremity extending to the neck on the affected side was noticed. On head magnetic resonance imaging (MRI) before and after administration of gadolinium, he was found to have asymmetrically fatty striations, atrophy, and fibrosis in the left tongue consistent with radiation toxicity. The patient's tongue weakness persisted without improvement. CONCLUSIONS The diagnosis of unilateral hypoglossal nerve injury is usually difficult. Detailed neurological examinations and thorough investigations including head MRI are very helpful. Previous exposure to radiation therapy is a potential cause of hypoglossal nerve injury. To our knowledge, this is the first case report that presents isolated unilateral tongue atrophy as a late complication of juxta cephalic radiation therapy.

Ultrasound of the Hypoglossal Nerve in the Neck: Visualization and Initial Clinical Experience with Patients.

BACKGROUND AND PURPOSE: The hypoglossal nerve, providing motor innervation for the tongue, can be affected in many diseases of the neck and skull base, leading to dysarthria, dysphagia, and ultimately atrophy of the tongue. We determined the feasibility of direct visualization of the hypoglossal nerve in the neck with ultrasound, testing this technique on healthy volunteers and evaluating it in clinical practice. MATERIALS AND METHODS: The study consisted of 4 parts: first, ultrasound-guided perineural ink injections along the course of the hypoglossal nerve at 24 sides of 12 fresh, nonembalmed cadaver necks. Subsequently, the specimens were dissected to confirm the correct identification of the nerve. The second part was examination of healthy volunteers with ultrasound and measurement of cross-sectional areas for generating reference data. The third part was scanning of healthy volunteers by 2 resident physicians with little and intermediate experience in ultrasound. Fourth was examination with ultrasound of patients with motor symptoms of the tongue. RESULTS: The hypoglossal nerve was correctly identified bilaterally in all cadaveric specimens (24/24) and all volunteers (33/33). The cross-sectional area ranged from 1.9 to 2.1 mm(2). The resident physicians were able to locate the nerve in 19 of 22 cases, demonstrating that locating the nerve is reproducible and feasible even with intermediate experience in ultrasound. Finally, alterations of the hypoglossal nerve in disease states could be depicted. CONCLUSIONS: Direct, reliable, and reproducible visualization of the extracranial hypoglossal nerve with ultrasound is feasible.

[Motor nerves of the face. Surgical and radiologic anatomy of facial paralysis and their surgical repair]. / L'innervation motrice de la face. Anatomie chirurgicale et radiologique des paralysies faciales et de leur réparation chirurgicale.

Motor innervation of the face depends on the facial nerve for the mobility of the face, on the mandibular nerve, third branch of the trigeminal nerve, which gives the motor innervation of the masticator muscles, and the hypoglossal nerve for the tongue. In case of facial paralysis, the most common palliative surgical techniques are the lengthening temporalis myoplasty (the temporal is innervated by the mandibular nerve) and the hypoglossal-facial anastomosis. The aim of this work is to describe the surgical anatomy of these three nerves and the radiologic anatomy of the facial nerve inside the temporal bone. Then the facial nerve penetrates inside the parotid gland giving a plexus. Four branches of the facial nerve leave the parotid gland: they are called temporal, zygomatic, buccal and marginal which give innervation to the cutaneous muscles of the face. Mandibular nerve gives three branches to the temporal muscles: the anterior, intermediate and posterior deep temporal nerves which penetrate inside the deep aspect of the temporal muscle in front of the infratemporal line. The hypoglossal nerve is only the motor nerve to the tongue. The ansa cervicalis, which is coming from the superficial cervical plexus and joins the hypoglossal nerve in the submandibular area is giving the motor innervation to subhyoid muscles and to the geniohyoid muscle.

ANATOMICAL STUDY OF CRANIAL NERVE EMERGENCE AND SKULL FORAMINA IN THE HORSE USING MAGNETIC RESONANCE IMAGING AND COMPUTED TOMOGRAPHY.

For accurate interpretation of magnetic resonance (MR) images of the equine brain, knowledge of the normal cross-sectional anatomy of the brain and associated structures (such as the cranial nerves) is essential. The purpose of this prospective cadaver study was to describe and compare MRI and computed tomography (CT) anatomy of cranial nerves' origins and associated skull foramina in a sample of five horses. All horses were presented for euthanasia for reasons unrelated to the head. Heads were collected posteuthanasia and T2-weighted MR images were obtained in the transverse, sagittal, and dorsal planes. Thin-slice MR sequences were also acquired using transverse 3D-CISS sequences that allowed mutliplanar reformatting. Transverse thin-slice CT images were acquired and multiplanar reformatting was used to create comparative images. Magnetic resonance imaging consistently allowed visualization of cranial nerves II, V, VII, VIII, and XII in all horses. The cranial nerves III, IV, and VI were identifiable as a group despite difficulties in identification of individual nerves. The group of cranial nerves IX, X, and XI were identified in 4/5 horses although the region where they exited the skull was identified in all cases. The course of nerves II and V could be followed on several slices and the main divisions of cranial nerve V could be distinguished in all cases. In conclusion, CT allowed clear visualization of the skull foramina and occasionally the nerves themselves, facilitating identification of the nerves for comparison with MRI images.

Hypoglossal canal invasion by glomus jugulare tumors: clinico-radiological correlation.

The aim of this retrospective study is to assess the rate at which glomus jugulare tumors invade the hypoglossal canal (HC) and to correlate computed tomography (CT) and magnetic resonance imaging (MRI) findings with the clinical evidence of cranial nerve (CN) XII dysfunction. CT and MRI imaging modalities of 31 patients were blindly reviewed by an attending neuroradiologist. Imaging studies identified involvement in 22 tumors (22/31, 71.0%). Thirteen of 22 patients (59.1%) had clinically evident CN XII symptoms. Accuracy rate was 76.7% (23/30) for MRI and 78.6% (11/14) for CT. MRI showed 100% sensitivity but had only 59% specificity and the specificity for CT was 66.7%. When radiologists elucidate HC involvement, it may alter the surgical approach and may lead to more focused/accurate clinical evaluation of tongue function.