Cranial Neuropathies I, V, and VII–XII
Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw in Hankey's Clinical Neurology, 2020
The vestibulocochlear nerve is a special somatic afferent nerve consisting of two functional divisions: the vestibular nerve, mediating equilibrium and balance information from the vestibular apparatus (semicircular canals, saccule, and utricle), and the cochlear nerve, mediating auditory information from the cochlear apparatus (organ of Corti in the spiral ganglion). Both of these structures are in the inner ear, which is located deep in the temporal bone within a space called the bony labyrinth (Figure 21.13). The bony labyrinth contains the membranous labyrinth and is filled with perilymph, a fluid with a chemical content similar to that of CSF and plasma. The membranous labyrinth is filled with endolymph, a highly specialized fluid with high protein content. The membranous labyrinth is further divided in two portions: vestibular and cochlear. The hair cells are the sensory receptors for both the vestibular and the cochlear systems.2
Canine Audiology
Stavros Hatzopoulos, Andrea Ciorba, Mark Krumm in Advances in Audiology and Hearing Science, 2020
The auditory system is closely associated with the vestibular system in the dog (Kent et al., 2010; DeLahunta and Glass, 2009) like that of the human (Fig. 5.3). Likewise, the vestibular system is closely associated with the visual system for control of eye movements along with balance. Both the auditory and vestibular systems send signals along the afferent pathway along the vestibulocochlear nerve. Included within the peripheral vestibular apparatus are the three semicircular canals aligned approximately at right angles to one another, enabling sensory perception of movement in any direction (Kent et al, 2010). The vertical semicircular canals and the saccule control vertical eye movements whereas the horizontal semicircular canal and utricle control horizontal eye movements (Kent et al., 2010). Connected to the vestibule at the end of each semicircular canal is a structure known as the ampulla. The ampulla holds the vestibular sensory receptors within the membranous labyrinth, the cristae ampullares. The cristae ampullares houses sensory hair cells, stereocilia, and kinocilia, that function as transducers of mechanical stimulation. The sensory receptor of the utricle and saccule is the macula. Overlying the maculae is the otolithic membrane which embeds calcium carbonate crystals known as otoliths. The macula is responsible for sensing static positions of the head, linear acceleration, deceleration and gravitational forces (DeLahunta and Glass, 2009). Refer to DeLahunta and Glass (2009) and Kent et al. (2010) for a comprehensive review of the peripheral and central vestibular system in dogs.
Physiology of Hearing
John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed in Paediatrics, The Ear, Skull Base, 2018
The auditory or cochlear nerve, cranial nerve VIII, originates from the joining of the spiral ganglion cells in the cochlea where their cell bodies lie. There are two types of nerve fibres originating from the spiral ganglion cells: type 1, which have large diameters, innervate the IHCs constituting 95% of the nerve fibre population and are myelinated, and type 2 fibres, which are smaller diameter, innervate the OHCs and are unmyelinated. The nerve traverses the internal auditory canal and joins with the vestibular nerve forming the vestibulocochlear nerve. One type 1 fibre innervates one IHC but one IHC may synapse with several nerve fibres. The cochlear nerve fibres terminate at the cochlear nuclear complex located in the medulla of the brainstem.
Current perspectives on galvanic vestibular stimulation in the treatment of Parkinson’s disease
Published in Expert Review of Neurotherapeutics, 2021
Soojin Lee, Aiping Liu, Martin J. McKeown
Anatomically, the vestibular nerve combines with the cochlear nerve and becomes the vestibulocochlear nerve. Traveling by the cerebellopontine angle, this nerve enters the brainstem at the pontomedullary junction where the vestibular and cochlear nerves separate [49]. Some of the nerve fibers project to the flocculonodular lobe and nearby vermis of the cerebellum, while the majority of the fibers project to the ipsilateral vestibular complex in the pons [49]. The vestibular complex is where the vestibular inputs are primarily processed, and consists of four major nuclei including medial, lateral, superior, and inferior [50] as well as several adjacent cell groups. The vestibular pathways from the vestibular nuclei have different functional roles. Projections to the spinal cord are essential for postural reflexes to adjust head and body movements [51], and projections to the ocular motor nuclei are critical for compensatory eye movements during head motion (the vestibular-ocular reflex). Projections to the cerebellum are important for balance, postural control, and movement coordination [49], and pathways to the thalamus, hippocampus, and ultimately to the cortical areas are responsible for multisensory integration [50,52], contributing to movement planning and execution, spatial navigation and memory, attention, and emotional processing [52–54].
3 T – MRI improves intrameatal cranial nerve detection in CI-candidates
Published in Acta Oto-Laryngologica, 2019
Herbert Stimmer, Hans-Peter Niedermeyer, Lynne Stecher, Markus Wirth, Benedikt Hofauer
The relevant anatomical basics for our study: vestibulocochlear (VIII) and facial (VII) nerve enter the internal auditory canal (IAC) from the cerebellopontine angle cistern as two separate nerves. The facial nerve runs together with the N. intermedius through the anterosuperior part of the internal auditory canal to reach the labyrinthine part of the facial nerve canal in the temporal bone. The vestibulocochlear nerve is positioned in the posteroinferior part of the IAC, in lateral direction the shape of the nerve changes from round or tubular to crescent. The cochlear and vestibular nerve separate in most cases 3–4 mm distant from the lateral end of the IAC. The vestibular nerve divides into inferior and superior vestibular nerve in variable position, in some cases not before the most lateral part of the IAC respectively the IAC-fundus, sometimes they are separated just before reaching the bony crest of the crista falciforme [4].
Dysfunction along the continuum of vestibulocochlear anatomy, and the corresponding spectrum of clinical presentation: how little we know, and what else we need to learn
Published in Hearing, Balance and Communication, 2021
Marcello Cherchi, Darío Andrés Yacovino
Almost all textbooks, and much of the medical literature, depict vestibular neuritis, labyrinthitis and sudden sensorineural hearing loss as distinct clinical entities, which may be didactically useful, but is probably an oversimplification. The reality is likely more complex since damage can occur to varying proportions of the vestibulocochlear nerve, varying proportions of the labyrinth, and varying combinations thereof; in other words, the underlying pathobiology probably spans a continuum, with a corresponding range of clinical presentations – with different combinations/degrees of vestibular symptoms (dizziness/imbalance) and ear symptoms (hearing loss, tinnitus). In view of the anatomical proximity of these structures, their shared vascular supplies, and (in the case of the labyrinth) shared endolymph, this ‘continuum’ is not surprising.
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