Abducens Nerve

To our knowledge, no published functional map of the human lower brainstem exists. Our purpose was to use 1.5-T functional MR imaging (fMRI) to visualize the location of cranial nerve (CN) nuclei and other pontine, bulbar, and cervical spinal cord nuclei by using specific sensory stimulation or motor performance. We localized nuclei by using cross-correlation analysis of regional blood oxygen level-dependent (BOLD) signal intensity during specific motor and sensory procedures based on known functions of specific nuclei. Statistical parametric mapping (SPM) analysis was used for comparison. Head, cardiac, and respiratory motion artifact correction was applied. Histologic atlases aided localization. We obtained evidence of localization of the following nuclei by using tests, as follows: main trigeminal sensory (CN V), brushing the face; abducens (CN VI), left-right eye movement; facial (CN VII), smiling and lip puckering; hypoglossal (CN XII), pushing the tongue against the hard palat...

Lyme borreliosis is the most common tick-born infection in Europe. Global climate change expanding the range of tick vectors and an increase in the incidence suggest that this disease will remain an important health issue in the forthcoming decades. Lyme borreliosis is a multisystem organ disorder affecting the nervous system in 10% to 15% of cases. Lyme neuroborreliosis can present with any disorder of the central and peripheral nervous systems. The neuro-ophthalmological manifestations are a rare feature of the disease. The intrathecal synthesis of Borrelia burgdorferi antibodies is of diagnostic importance, but in rare cases, immunoglobulins against the Borrelia burgdorferi antigen may not be detected. We report a case of possible Lyme neuroborreliosis presenting with sixth cranial nerve neuropathy at the onset of the disease further developing into typical meningoradiculitis and multiple mononeuropathy. Surprisingly, Borrelia burgdorferi antibodies were not detected in the cereb...

Petroclival canal (PCC), which occurs as a result of petrosfenoidal ligament (PSL) calsification is a different passage for the
abducens nerve path. During performing the anatomic dissection of petroclival region of a the cadaveric specimen, we incidentally
noted existence of a bony canal in which abducens nerve was passing through petro-occipital fissure (POF), petroclival
canal. This variation was also confirmed by thin sections of computed tomography images. PSL was found as a thin fibrous band
between the petrous apex and posterior clinoid process at an interdural space, however the sixth cranial nerve were passing
through bony canals in the petro-occipital fissures to the superior posterior side of the lacerum segment of the internal carotid
artery on both sides. Passage of the abducens nerve through a bony canal is presumed to be clinically important in terms of fractures
reaching up to the petroclival region and there is a risk of nerve injury during both anterior transpetrosal or endoscopic
approaches through the petroclival region.

✓ The microsurgical anatomy of Dorello's canal has been studied in 20 specimens obtained from 10 cadaver heads fixed in formalin. The bow-shaped canal through which courses the abducens nerve before reaching the cavernous sinus is located inside a venous confluence which occupies the space between the dural leaves of the petroclival area. The petrosphenoidal ligament (Gruber's ligament), which forms the posteromedial wall of the canal, appears as a fibrous trabecula surrounded by venous blood. Canal measurements were performed and its anatomical relationship with the sixth cranial nerve is described. Angulations of variable degrees were observed in the course of the nerve inside and outside the canal. The influence of this relatively tortuous course of the abducens nerve upon its vulnerability in some pathological conditions is discussed.

Abducens interneurons project to the medial rectus subdivision of the contralateral oculomotor nucleus and have a role in the mediation of horizontal conjugate gaze. Two types of interneurons have been reported based on shape (fusiform and circular) and differences in organelles. In this study, 41 abducens interneurons from three young adult cats were examined in the transmission electron microscope and were classified, on the basis of eccentricity (e), as circular (e less than 0.82; N = 18) or fusiform (e greater than or equal to 0.82; N = 23). The volume fraction of nucleus, nucleolus, mitochondria, rough endoplasmic reticulum, polyribosomes, and Golgi complex and the number of synaptic profiles per 100 microns of membrane were determined. Although there is a qualitative difference in these cell types, statistical analyses indicate no significant differences in organelle content, mean area, number of synaptic profiles per 100 microns of membrane, or diameter. While the differences...

 Lateral rectus palsy with hypotropia constitutes a portion of sixth nerve palsy cases in which only the superior compartment of the lateral rectus is palsied. We present such a case in a 10-year-old girl who presented with a peculiar appearing right esotropia and hypotropia due to acquired lateral rectus palsy along with apparent ipsilateral superior rectus underaction. Neuroimaging confirmed atrophy of the superior part of lateral rectus as compared to the inferior half. Augmented superior rectus transposition to the lateral rectus along with adjustable bimedial recessions and bilateral inferior oblique myectomies were done to restore her cosmetic appearance.

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.

1. The aim of the present study is to describe the behaviour of identified second-order vestibular neurones in the alert cat during eye saccades. A selection of neurones which are involved in horizontal eye movements has been made. The activity has been compared with a selected sample of abducens motoneurones recorded in the same animals. 2. Alert head-fixed cats were used for this study. Eye movements were recorded by the scleral search coil technique. Abducens motoneurones were identified by antidromic stimulation from the VIth nerve with chronically implanted electrodes. They were recorded extracellularly. 3. Second-order vestibular neurones were identified by orthodromic stimulation from the vestibular organs. They were recorded intra-axonally and injected with horseradish peroxidase after recording of their physiological characteristics. Their morphology was reconstructed from frozen sections. 4. All the recorded vestibular neurones showed various amounts of eye position sensit...

A 17-year-old woman presented with a history of 1-week of headache and 3 days of horizontal diplopia. Examination revealed 20/20 vision in both eyes, no papilledema, and an abduction deficit in her left eye. Lumbar puncture revealed an opening pressure of 440 ...

Given reported interactions between vergence and version dynamics, ocular reflexes cannot be properly modelled as separate independent subsystems. Using a model structure compatible with known anatomy, we show that a single bilateral system can produce results consistent with observed data both at the central and ocular levels. This model provides for both vergence and conjugate integrators in a single controller,