Magnetic Resonance Imaging Findings in Patients With Duane Retraction Syndrome.

BACKGROUND: Duane retraction syndrome (DRS) is known to relate to the absence of the abducens nucleus, with abnormal innervation of the lateral rectus (LR) muscle by branchesof the oculomotor nerve (CN III). The purposes of this study were to investigate the morphological characteristics of the oculomotor nerve (CN III), the abducens nerve (CN VI), and the extraocular muscles in patients with clinically diagnosed Duane retraction syndrome (DRS) using MRI. In addition, we assessed the association between ocular motility, horizontal rectus muscle volumes, and CN III/VI in patients with Duane retraction syndrome (DRS). METHODS: The study comprised 20 orthotropic control subjects (40 eyes) and 42 patients with Duane syndrome (48 eyes), including 20 patients with DRS Type I (24 eyes), 5 patients with DRS Type II (6 eyes), and 17 patients with DRS Type III (18 eyes). Three-dimensional (3D) T1/2 images of the brainstem and orbit were obtained to visualize the cranial nerves, especially the abducens (VI) and oculomotor (III) nerves, as well as extraocular muscles. RESULTS: Based on the clinical classification, among 42 patients, MRI showed that the abducens nerves (CN VI) on the affected side were absent in 24 of 24 eyes (100%; 20 patients) with Type I DRS and in 16 of 18 eyes (88%; 16 patients) with Type III DRS. However, CN VI was observed in 6 of 6 eyes (100%; 5 patients) with Type II DRS and in 2 of 18 eyes (11%) with Type III DRS. CN III was observed in all patients. The oculomotor nerves on the affected side were thicker than those on the nonaffected contralateral side in DRS Type I ( P < 0.05) and Type III ( P < 0.05), but not in DRS Type II. Smaller LR and larger MR volumes were shown in the affected eye than that in the nonaffected eye in DRS Types I and III. Based on the presence or absence of CN VI, there was a tendency for thicker oculomotor nerves in the affected eye than in the nonaffected eye in the absence groups ( P < 0.05). However, no significant difference was found in the present group. In the CN VI absence groups, similar results were found in the affected eyes than in the nonaffected eyes as in DRS Types I and III. In addition, the presence of CN VI was correlated with better abduction ( P = 0.008). The LR and MR volumes have positive correlations with the oculomotor nerve diameter in the affected eye. However, there was no correlation between the range of adduction/abduction and the LR/MR ratio in patients with or without an abducens nerve. CONCLUSIONS: Different types of DRS have different characteristic appearances of CN VI and CN III on MRI. Horizontal rectus muscles have morphological changes to adapt to dysinnervation of CN VI and aberrant innervation of CN III. Thus, these neuroimaging findings may provide a new diagnostic criterion for the classification of DRS, improving the comprehension of the physiopathogenics of this disease.

Location of the abducens nerve stretched by a tortuous vertebrobasilar artery in trigeminal neuralgia.

BACKGROUND: Trigeminal neuralgia (TGN) caused by the vertebrobasilar artery (VBA) is uncommon. The abducens nerve root is frequently dislocated by a tortuous VBA near the trigeminal nerve root. This unusual location of the root is not well known. This study aimed to investigate the location of the stretched abducens nerve root. METHODS: The objective is 26 patients with VBA-related TGN who underwent microvascular decompression (MVD). We retrospectively investigated the course of the abducens nerve root with magnetic resonance imaging (MRI) with three-dimensional (3D) imaging and surgical findings. The displacement of the abducens nerve root on the affected side was compared to the contralateral side. RESULTS: The abducens nerve root was distorted by a tortuous VBA (46.2%) or the anterior inferior cerebellar artery (53.8%). The average length of the cisternal segment was stretched to 23.4 mm versus 12.4 mm on the contralateral side. The peak point of the elevated abducens nerve root was mostly located rostro-medial (65.4%) or caudo-medial (34.6%) to the neurovascular compression site of the trigeminal nerve with a mean distance of 9.1 mm. Contact with the trigeminal nerve root was observed in 7 patients (26.9%). Three-dimensional imaging was consistent with the surgical findings and useful in predicting the location of the abducens nerve root. No abducens nerve palsy was noted in our series. CONCLUSIONS: The abducens nerve root is located near the trigeminal nerve root in VBA-related TGN. Preoperative understanding of the unusual course of the abducens nerve root contributes to avoiding accidental nerve injury during MVD.

Magnetic resonance imaging features of COVID-19-related cranial nerve lesions.

The complete features of the neurological complications of coronavirus disease 2019 (COVID-19) still need to be elucidated, including associated cranial nerve involvement. In the present study we describe cranial nerve lesions seen in magnetic resonance imaging (MRI) of six cases of confirmed COVID-19, involving the olfactory bulb, optic nerve, abducens nerve, and facial nerve. Cranial nerve involvement was associated with COVID-19, but whether by direct viral invasion or autoimmunity needs to be clarified. The development of neurological symptoms after initial respiratory symptoms and the absence of the virus in the cerebrospinal fluid (CSF) suggest the possibility of autoimmunity.

Aberrant Abducent Nerve During Microvascular Decompression for Trigeminal Neuralgiass.

BACKGROUND: Microvascular decompression (MVD) is a commonly performed procedure to treat trigeminal neuralgia and hemifacial spasm. Knowledge of the variable anatomy of the cerebellopontine angle is crucial to avoid injury to cranial nerves. CASE DESCRIPTION: A 76-year-old lady with right V1 (ophthalmic division of the trigeminal nerve) and V2 (maxillary division of the trigeminal nerve) trigeminal neuralgia, refractory to medical treatment, underwent elective MVD. Intraoperatively, a distorted course of the cisternal component of the abducent nerve was noticed, caused by an ectatic anterior inferior cerebellar artery. Careful mobilization of the offending vessel to decompress the trigeminal nerve was carried out; however, abducent nerve decompression was not attempted since its function was not compromised. Facial pain resolved postoperatively without new diplopia. CONCLUSIONS: Careful review of imaging before surgery is recommended in order to preempt such unusual anatomic variations.

Idiopathic third and sixth cranial nerve neuritis.

PURPOSE: To present cases with idiopathic third and sixth cranial nerve neuritis. STUDY DESIGN: Retrospective observational study METHODS: The results of high resolution pre- and post- cranial nerve magnetic resonance images (MRI) with three-dimensional sequences for visualizing cranial nerves in patients with third, fourth, and sixth cranial nerve palsies who were treated at the Neuro-ophthalmology Department of Samsung Medical Center were reviewed. Patients with cranial nerve enhancement confirmed by experienced radiologists were identified. The medical records of these patients were reviewed, and their demographics, clinical presentations, laboratory results, and clinical outcomes were analyzed. RESULTS: Of 265 patients with third, fourth, and sixth cranial nerve palsy, 60 were identified by high resolution MRI as having enhancement of the corresponding cranial nerve. Among these, 17 patients with infiltrative, granulomatous, or tumorous lesions were excluded. In addition, 28 patients with identifiable causes of cranial nerve palsy, such as Miller-fisher syndrome, virus infection, or radiation-induced neuropathy, as well as patients with vasculopathic risk factors, were also excluded. Ultimately, a total of 15 patients with idiopathic third and sixth cranial nerve neuritis were included in this study. The mean age of these patients was 43 ± 15 years. Eight patients had sixth cranial nerve palsy, six third cranial nerve palsy (two partial and four complete), and one patient with complete third and sixth cranial nerve palsy. Nine patients received steroid treatment. Eleven patients recovered fully within a period ranging from a few days to one year. Two patients were much improved up to 1 month after initial presentation, but were then ultimately lost to follow-up. Another patient was lost to follow-up after the initial work-up. The other patient lost to follow-up had partially recovered during the first 6 months. CONCLUSIONS: We present patients with idiopathic third and sixth cranial nerve neuritis. They tended to respond well to steroid treatment and to have good prognoses. In order to better understand the long-term prognosis of cranial nerve neuritis and possible association with other neurologic disorders, a larger scale and longer-term study is needed.

Abducens Nerve Schwannoma: A Case Report and Literature Review.

BACKGROUND: Abducens nerve function seldom shows complete recovery after removal of abducens nerve schwannoma. No cases with unclear course of the abducens nerve during surgery have been reported to achieve complete recovery of nerve function. CASE DESCRIPTION: We report the case of a 44-year-old woman who presented with occasional dysgeusia without abducens nerve paresis. Magnetic resonance imaging showed a solid tumor about 2 cm in diameter at the left cerebellopontine cistern. Cranial nerves except the abducens nerve appeared intact. The tumor was removed via suboccipital craniotomy. The abducens nerve was totally invisible on the surface of the tumor throughout the procedure. Only short segments of abducens nerve were identifiable at around Dorello's canal and the root exit zone. The tumor was resected by subcapsular dissection, and part of the tumor capsule was preserved as a scaffold for nerve generation, although whether any abducens nerve was included remained uncertain. Histopathologic examination confirmed World Health Organization grade I schwannoma. Postoperatively, the patient presented with complete left abducens nerve paresis and diplopia, but abducens nerve function began to improve 3 months later and had completely recovered within 16 months after surgery. CONCLUSIONS: This represents the first description of abducens nerve schwannoma in which the course of the abducens nerve was intraoperatively unclear but complete recovery was achieved. In such cases, intentional subcapsular dissection may potentiate functional recovery.

Möbius syndrome: clinico-radiologic correlation.

PURPOSE: Möbius syndrome is characterized by abducens and facial nerve palsy. However, the presence/absence of corresponding cranial nerves on MRI was not fully evaluated. The purpose of this study was to investigate the mechanism of Möbius syndrome by associating the presence of abducens and facial nerves on MR imagings with clinical features. METHODS: We retrospectively reviewed the medical records and MR imagings of nine patients with Möbius syndrome between January 2004 and October 2015. The presence/absence of abducens and facial nerves on MR imaging, as well as corresponding neuro-ophthalmologic clinical features, was investigated. RESULTS: Facial palsy was bilateral in six and unilateral in three patients. Abduction was limited bilaterally in five and unilaterally in four patients. The degrees of facial palsy and abduction limitation were variable, and asymmetric even in the bilateral cases. MR imaging documented bilateral absence of the abducens and facial nerves in six, absence of unilateral facial nerve and bilateral abducens nerves in one, and absence of facial and abducens nerves unilaterally on the same side in another. Both abducens and facial nerves were visualized bilaterally only in the one remaining patient. CONCLUSIONS: The absence of abducens and facial nerves on MR imaging was mostly correlated with the findings of facial palsy and abduction limitation in patients with Möbius syndrome. MR imaging aids in diagnosis of Möbius syndrome by documenting the absence or presence of abducens and facial nerves.

Estudio clínico, citogenético, molecular y de imagen de los pacientes con síndrome de Moebius del Hospital General 'Dr Manuel Gea González', Ciudad de México / Clinical, cytogenetic, molecular and image study of patients with Mobius syndrome at the General Hospital 'Dr Manuel Gea González', Mexico city

Introducción y Objetivo. El síndrome de Moebius es un trastorno congénito poco frecuente con prevalencia menor del 0.05%, caracterizado por parálisis facial congénita asociada a ausencia de abducción de los ojos por alteraciones del VI y VII nervios craneales, ya sea simétrica o asimétrica. La etiopatogenia cuenta con diferentes hipótesis: genética, vascular y teratógena. Existen pocos reportes en la literatura, y en especial en la latinoamericana, que describan las características clínicas y genéticas de estos pacientes. El presente estudio es el resultado del desarrollo de un equipo multidisciplinario en nuestro centro hospitalario para la descripción del espectro completo de la patología y así poder ofrecer los mejores tratamientos para cada uno de nuestros pacientes. Material y Método. Analizamos 115 pacientes con diagnóstico de síndrome de Moebius en sus 3 presentaciones: Moebius clásico, Moebius incompleto o Moebiuslike. Todos fueron sometidos a exploración física completa por un equipo multidisciplinario formado por ortopedistas, oftalmólogos, otorrinolaringólogos, ortodoncistas, neurólogos, pediatras, genetistas y cirujanos plásticos. Realizamos cariotipos a todos los pacientes para identificar anormalidades estructurales cromosómicas y enviamos muestras al Instituto Nacional de Medicina Genómica (INMeGen) para análisis molecular de cada paciente e identificación de posibles genes involucrados. Resultados. Un total de 52 pacientes (45%) fueron varones y 63 (55%) mujeres. Las manifestaciones clínicas fueron parálisis facial unilateral o bilateral con involucro de la abducción de los ojos en el 100%, asociada con estrabismo en el 62.6%, pie equino varo en el 46.1%, sindactilia simple 15.7%, paladar hendido 17.4%, micrognatia 17.4%, y síndrome de Poland 9.6%, entre otras manifestaciones. El análisis citogenético reportó 114 cariotipos de características estructurales normales y 1 solo caso de translocación recíproca balanceada entre el cromosoma 4 y 10. Dieciséis casos se asociaron a consumo materno de misoprostol en el primer trimestre del embarazo. El análisis molecular no se pudo concretar debido a falta de recursos materiales del INMeGen. Conclusiones. Hasta la fecha, y hasta donde hemos podido comprobar, esta es la cohorte de pacientes con síndrome de Moebius más grande reportada a nivel mundial en un solo centro hospitalario. La variabilidad de las presentaciones clínicas justifica el manejo por un equipo multidisciplinario tanto para el paciente como para los familiares. Este estudio abre las puertas para un campo de investigación mayor que nos pueda llevar a entender mejor la fisiopatología, intentar estableces causalidad y por lo tanto poder ofrecer mejores tratamientos, integrales y reproducibles (AU)

Background and Objective. Möbius syndrome is a rare congenital disease characterized by facial paralysis associated with an absence of abduction of the eyes for abnormalities in VI and VII cranial nerves. The pathogenesis has different hypothesis that include genetic, vascular and teratogenic causes. There are few reports in the literature and especially in Latin America to describe the clinical and genetic characteristics of these patients. The current study is the result of a multidisciplinary team developed in our center to describe the wide spectrum of the disease and offer the best treatment options to each of our patients. Methods. We analyzed 115 patients with the diagnosis of Möbius syndrome in its 3 presentations. All patients underwent a complete clinical examination by a multidisciplinary team formed by orthopedist, ophthalmologist, otolaryngologist, orthodontist, neurologist, plastic surgeon, pediatrician and geneticist. They underwent CTG banded karyotype to identify structural chromosome abnormalities. Results. Fifty two patients (45%) patients were male and 63 (55%) female. Clinical manifestations were found with unilateral or bilateral facial paralysis with VI nerve involvement in 100% of patients, associated with strabismus in 62.6%, 46.1% clubfoot, simple syndactyly 15.7%, 17.4% cleft palate, micrognathia 17.4%, Poland syndrome 9.6%, among others. Cytogenetic analysis showed normal karyotype in 114 patients and a reciprocal translocation between chromosome 4 and 10 in 1 patient. Sixteen cases of reported intake of misoprostol during the first trimester. Conclusions. As far as we know, this study is the largest global cohort reported in a single hospital of patients with Möbius syndrome. Variability of the clinical presentation justifies the management of these patients is a multidisciplinary team. This study opens the door for new studies that allow us to understand the pathophysiology of this disease and its response to different treatments (AU)

Imaging of Cranial Nerves III, IV, VI in Congenital Cranial Dysinnervation Disorders.

Congenital cranial dysinnervation disorders are a group of diseases caused by abnormal development of cranial nerve nuclei or their axonal connections, resulting in aberrant innervation of the ocular and facial musculature. Its diagnosis could be facilitated by the development of high resolution thin-section magnetic resonance imaging. The purpose of this review is to describe the method to visualize cranial nerves III, IV, and VI and to present the imaging findings of congenital cranial dysinnervation disorders including congenital oculomotor nerve palsy, congenital trochlear nerve palsy, Duane retraction syndrome, Möbius syndrome, congenital fibrosis of the extraocular muscles, synergistic divergence, and synergistic convergence.

Abducens nerve palsy due to inferior petrosal sinus thrombosis.

Isolated unilateral abducens nerve palsy is usually due to ischemia, trauma or neoplasm. Dorello's canal is the space between the petrous apex and superolateral portion of the clivus, bound superiorly by Gruber's ligament. The abducens nerve travels with inferior petrosal sinus (IPS) though the Dorello's canal before entering the cavernous sinus. A 31-year-old man presented with neck pain, and binocular horizontal diplopia, worse looking towards left and at distance. He had a history of intravenous drug abuse but no history of hypertension or diabetes. On examination, he had complete left 6th nerve palsy with normal fundi, pupils, and other cranial nerves. Methicillin-resistant Staphylococcus aureus bacteremia was detected with naïve tricuspid valve endocarditis and multiple septic emboli to lungs with infarcts. His cerebrospinal fluid was normal. MRI of the brain was normal. MRV of head and neck showed thrombosis of the left internal jugular vein, left sigmoid sinus and left inferior petrosal sinus with normal cavernous sinus and no evidence of mastoiditis. He was treated with broad spectrum antibiotics. He was not anticoagulated for fear of pulmonary hemorrhage from pulmonary infarcts. Although cerebral venous sinus thrombosis commonly presents with elevated intracranial pressure, isolated ipsilateral 6th nerve palsy from its compression in Dorello's canal due to thrombosis of the ipsilateral inferior petrosal sinus is extremely rare. To our knowledge, only two patients have been reported with isolated abducens palsy due to IPS thrombosis; one caused by septic emboli and the other developed it during IPS cortisol level sampling.

Clinical correlation of imaging findings in congenital cranial dysinnervation disorders involving abducens nerve.

PURPOSE: High-resolution magnetic resonance imaging (MRI) of intracranial parts of sixth nerve and seventh nerve and the extraocular muscles (EOMs) in orbit to correlate the clinical characteristics in patients with two special forms of strabismus in congenital cranial dysinnervation disorders which are Duane's retraction syndrome (DRS) and Mobius syndrome. MATERIALS AND METHODS: Morphological analysis by 3T MRI of orbit (using surface coils) and brain (using 32 channel head coil) was performed on 6 patients with clinical DRS (1 bilateral), 2 cases with Mobius syndrome, and 1 case with congenital sixth nerve palsy. These were compared with findings in five controls. RESULTS: We observed absence/hypoplasia of sixth nerve in five out of seven eyes with DRS (71.42%), anomalous course in one eye, sixth and seventh nerve absence/hypoplasia in affected eyes with Mobius syndrome and bilateral absence/hypoplasia of the sixth nerve in congenital sixth nerve palsy. For EOMs we calculated maximum diameter, area, and circumference of muscles using Osirix software, and noticed significant hypoplasia of lateral rectus in comparison to controls (P < 0.001). CONCLUSIONS: MRI gives useful information regarding confirmation of clinical diagnosis and its neurological anomalies in complex cases and helps to plan tailor made surgical management.

Preoperative simulation of the running course of the abducens nerve in a large petroclival meningioma: a case report and literature review.

One of the most important and useful pieces of information in the preoperative evaluation of a large petroclival meningioma is the running course of the abducens nerve. The abducens nerve is small and has a long intracranial course, making it prone to compression by the tumor at various anatomical points. In relatively large tumors, it is difficult to confirm the entire course of the abducens nerve, even by heavy T2-thin slice imaging. We report a case of successful preoperative estimation of the course of the abducens nerve that aided in its complete preservation during the resection of a large petroclival tumor.

Abducens Nerve in Patients with Type 3 Duane's Retraction Syndrome.

BACKGROUND: We have previously reported that the presence of the abducens nerve was variable in patients with type 3 Duane's retraction syndrome (DRS), being present in 2 of 5 eyes (40%) and absent in 3 (60%) on magnetic resonance imaging (MRI). The previous study included only 5 eyes with unilateral DRS type 3. OBJECTIVES: To supplement existing scarce pathologic information by evaluating the presence of the abducens nerve using high resolution thin-section MRI system in a larger number of patients with DRS type 3, thus to provide further insight into the pathogenesis of DRS. DATA EXTRACTION: A retrospective review of medical records on ophthalmologic examination and high resolution thin-section MRI at the brainstem level and orbit was performed. A total of 31 patients who showed the typical signs of DRS type 3, including abduction and adduction deficit, globe retraction, narrowing of fissure on adduction and upshoot and/or downshoot, were included. The abducens nerve and any other extraocular muscle abnormalities discovered by MRI were noted. RESULTS: DRS was unilateral in 26 patients (84%) and bilateral in 5 patients (16%). Two out of 5 bilateral patients had DRS type 3 in the right eye and DRS type 1 in the left eye. Of the 34 affected orbits with DRS type 3 in 31 patients, the abducens nerve was absent or hypoplastic in 31 eyes (91%) and present in 3 eyes (9%). Patients with a present abducens nerve showed more limitation in adduction compared to patients with an absent abducens nerve (P = 0.030). CONCLUSIONS: The abducens nerve is absent or hypoplastic in 91% of DRS type 3. Patients with a present abducens nerve showed more prominent limitation of adduction. As DRS type 3 partly share the same pathophysiology with type 1 and 2 DRS, the classification of DRS may have to be revised according to MRI findings.

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.

Ossification of the petrosphenoidal ligament: multidetector computed tomography findings of an unusual variation with a potential role in abducens nerve palsy.

PURPOSE: The petrosphenoidal ligament (PSL) forms the roof of Dorello's canal in which the abducens nerve courses. An ossified PSL may play a role in abducens nerve palsy although it is controversial. Therefore, we aimed to investigate the incidence and the imaging features of PSL ossification using multidetector computed tomography (MDCT). MATERIALS AND METHODS: Consecutive head CT scans, performed between January 2014 and May 2014, were retrospectively evaluated by two radiologists to look for a partial or complete ossification at the expected site of the PSL using axial, reformatted coronal and sagittal images. RESULTS: We found 46 patients (32 men, 14 women) with ossification of the PSL out of 523 head CT scans (46/523, 8.8%). A total of 61 PSL ossifications (31 unilateral; 15 bilateral) were found in 1,046 petroclival regions (61/1,046, 5.8%). Of these 61 ossifications, 34 (34/523, 6.5%) were on the right and 27 (27/523, 5.1%) were on the left; 38 (38/1,046, 3.6%) were classified as partial and 23 (23/1,046, 2.2%) were classified as complete. CONCLUSION: Ossification of the PSL is not a rare finding on MDCT. This imaging technique can reliably demonstrate the imaging features of an ossified PSL.

Traumatic carotid-cavernous sinus fistula accompanying abducens nerve (VI) palsy in blowout fractures: missed diagnosis of 'white-eyed shunt'.

We report the case of a 32-year-old woman with bilateral blowout fractures. She presented with diplopia showing impaired abduction of the left eye soon after trauma. No other orbito-ocular signs, such as exophthalmos, ptosis, or chemosis, were found. Orbital reconstruction was performed, but no improvement in her ophthalmoplegia was observed after surgery. A carotid angiography showed that she was suffering from a posteriorly draining carotid-cavernous sinus fistula with isolated abducens nerve palsy. Coil embolization was conducted under the consultation of a neurosurgeon, after which her ophthalmoplegia resolved fully. This is a rare case of posteriorly draining carotid-cavernous sinus fistula without classic orbito-ocular signs, the absence of which may cause diagnostic confusion.

Noninvasive transcranial stimulation of rat abducens nerve by focused ultrasound.

Nonpharmacologic and nonsurgical transcranial modulation of the nerve function may provide new opportunities in evaluation and treatment of cranial nerve diseases. This study investigates the possibility of using low-intensity transcranial focused ultrasound (FUS) to selectively stimulate the rat abducens nerve located above the base of the skull. FUS (frequencies of 350 kHz and 650 kHz) operating in a pulsed mode was applied to the abducens nerve of Sprague-Dawley rats under stereotactic guidance. The abductive eyeball movement ipsilateral to the side of sonication was observed at 350 kHz, using the 0.36-msec tone burst duration (TBD), 1.5-kHz pulse repetition frequency (PRF), and the overall sonication duration of 200 msec. Histologic and behavioral monitoring showed no signs of disruption in the blood brain barrier (BBB), as well as no damage to the nerves and adjacent brain tissue resulting from the sonication. As a novel functional neuro-modulatory modality, the pulsed application of FUS has potential for diagnostic and therapeutic applications in diseases of the peripheral nervous system.