Connections between the facial, vestibular and cochlear nerve bundles within the internal auditory canal (original) (raw)
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Nerve Endings of the Corti's Organ (Scanning Electron Microscopic Study)
Ear Research Japan, 1981
Since several years, scanning electron microscopic (SEM) study of the organ of corti has been carried out. SEM gives a very good possibility to evaluate large portion of the organ of corti and to study in detail the course of the nerve fibres. Three types of nerve fibres, the afferent neuron of the cochlear nerve, the efferent and the adrenergic fibres participate in the innervation of cochlear receptor. Afferent and efferent nerve endings at the lower pole of the outer hair cells has been demonstrated in many animals (Spoendlin, Bredberg, and others). In the basal turn each outer hair cell is provided with 6-8 efferent nerve endings and about 4 afferent nerve endings (Spoendlin). This number is gradually reduced toward the apical turn. The efferent nerve endings are larger than and partially enclose the smaller afferent nerve endings (Bredberg). The size of these nerve endings are also gradually diminishes as the upper turn is approached more closely (Bredberg). In the basal turn o...
TURKISH JOURNAL OF MEDICAL SCIENCES, 2017
Introduction Supratrochlear (STN) and supraorbital (SON) nerves are the terminal branches of the frontal nerve. The STN courses in the roof of the orbit and exits between the supraorbital foramen and the trochlea at the frontal notch. The SON exits from the supraorbital notch or foramen (1). These nerves supply the conjunctiva, the upper eyelid, the mucosa of the glabella, and the skin of the lower forehead close to the midsagittal line (1-4). The zygomaticotemporal nerve (ZTN) is the terminal branch of the maxillary nerve. It passes through the temporal bone, pierces the temporalis and temporal fasciae, and innervates the skin over the temple (1,5-8). Knowledge of the localizations of the STN, SON, and ZTN nerves is crucial for botulinum toxin and topiramate injections and for ophthalmologic and facial plastic surgeries, particularly in forehead and brow lifts and for frontal sinus and cancer surgeries (2,9-14). In recent years, migraine surgery, defined by Bahman Guyuron in 2000, has received wide attention and has been frequently used (3-5,15,16). Migraine surgery comprises decompression and avulsion of the peripheral nerves (frontal, temporal, nasal, and occipital sites), which are believed to be the trigger points of migraines (3-8,16,17). In these procedures, the exact localization of these nerves becomes crucial. This study was designed to provide detailed anatomic knowledge of the exiting points of the STN, SON, and ZTN nerves preoperatively for relevant surgeries. 2. Materials and methods The study was conducted on the 28 hemifaces of 5 fresh frozen and 11 embalmed heads of 5 female and 11 male cadavers with no visible external abnormalities on their faces. The age of the cadavers was between 35 and 94 years. These cadavers were obtained from the collection of the Department of Anatomy of Mersin University. All procedures were performed according to the Helsinki Declaration of 1964. Background/aim: We evaluated the relations of the exiting points of supratrochlear (STN), supraorbital (SON), and zygomaticotemporal (ZTN) nerves with certain landmarks to provide improved anatomic knowledge. Materials and methods: The twenty-eight hemifaces of 5 fresh frozen and 11 embalmed heads (5 female and 11 male cadavers) were dissected. Distance and angular measurements were made between the exiting points of the nerves to the midline, lateral, and medial canthi. Comparisons of side, sex, and cadaver groups were evaluated. Results: Mean values were determined for all parameters. There was no difference between side measurements. There were significant differences between sexes and cadaver groups regarding STN and lateral canthus in both sides. The angle of the ZTN to the lateral canthus was found to be higher in embalmed cadavers than in fresh frozen ones. Conclusion: This study is the first to supply both distance and angular measurements to reach the exact locations of the nerves. Quantitative and topographic information about the localizations of the STN, SON, and ZTN is crucial for forehead lifting and migraine treatment, as well as for injection and local surgical interventions.
The general visceral efferent component of the eighth cranial nerve
The Journal of Comparative Neurology, 1969
Study of the brain stem, stato-acoustic nerve, and inner ear of the mouse by a cholinesterase technique has disclosed that the acetylcholinesterase-positive centrifugal fibers to the inner ear are part of a general visceral efferent system which supplies fibers to the facial, vestibular and cochlear nerves. This system largely corresponds in its central course to that of the bundle of fibers which has been called "olivocochlear," but its cells of origin do not appear to lie in the superior olivary complex. Instead, the preganglionic cells of origin are chiefly organized into four nuclei: one medial to the genu of the facial nerve; one lateral to the genu; the superior salivatory nucleus; and a small nucleus lying within the borders of the lateraI vestibular nucleus. The fibers to the inner ear synapse, perhaps completely, o n postganglionic cells located along their peripheral courses. Additionally, orthosympathetic acetylcholinesterasepositive fibers are present in the cochlear nerve; they arrive via the anterior inferior cerebellar artery. Postganglionic fibers supply not only vascular walls and secretory epithelium in the inner ear but also (1) contact the somata of some acetylcholinesterase-positive, bipolar cochlear neurons and (2) ramify among, or terminate upon, distal, acetylcholinesterase-positive processes of some sensory neurons at the foramina nervosa. These findings indicate that, o n morphological grounds, autonomic nerve activity may influence auditory input at the periphery.
Surgical and Radiologic Anatomy, 2001
The peripheral topography of the supraorbital (SON) and supratrochlear (STN) nerves and the superficial temporal branch of the auriculotemporal nerve (ATN) was investigated in 10 cadavers. The aim was to define the optimal locations for anaesthetic nerve blocks, as well as to help surgeons prevent nerve injuries. Specific measurements on the nerve "exits" in relation to defined landmarks are presented. The variability of the supraorbital notches and peripheral branching of the dissected nerves suggests several methods for anaesthetic blocks in cases of surgical and clinical head pain. The optimum injection site for a selective SON block is 20-30 mm from the midline (range 15-33 mm) reinjection at 30-50 mm from the midline might complete inefficient nerve block. For selective SON block the distance between the main SON and STN branches (mean 15.3 mm) should also be considered. The ATN is best blocked at a point located at the level with and 10-15 mm (range 8-20 mm) anterior to the upper origin of the helix. Separate exits for the medial and lateral SON branches were observed in eight of the 20 nerves examined. Twenty of the 28 exits were foraminae completed by bony or connective tissue. In many cases both the SON and STN ascended close to the associated artery in six cases a tissue band covered the nerve and vessel at the orbital exit. Some of the observed structures associated with the nerve might be pain-generators, however the present study does not provide any evidence for such a hypothesis.
Study of afferent nerve terminals and fibers in the gerbil cochlea: distribution by size
Hearing Research, 2000
The purpose of the present study was to determine if the synaptic terminals and nerve fibers in the gerbil cochlea fall into morphologically and spatially classified groups. In cats and guinea pigs, these groups, based on size, location on inner hair cell (IHC) and stratification within the osseous spiral lamina, have been found to correlate with spontaneous rate, threshold sensitivity and projection pattern to the cochlear nucleus. Thus, there may be anatomical data to suggest mechanisms for intensity coding of different frequencies of sound. Afferent nerve terminals contacting IHCs in the gerbil cochlea were analyzed with regard to size and location. Data were obtained from serial thin sections (700 for each IHC) cut perpendicular to the long axis of eight IHCs (two apical and two basal IHCs from two cochleas), observed and photographed using a transmission electron microscope. Results indicate that the percentage of modiolar versus pillar-side terminals around each IHC varies from cell to cell. In some cases, the smallest fibers were located on the modiolar side, but a consistent distribution of the smallest fibers on this side of the cell was not characteristic. While a size-based segregation of terminals does not appear around the perimeter of the IHC, modest size-based segregation of nerve fibers is found in the osseous spiral lamina. Perimeter measurements were made from myelinated fibers cut in cross-section, obtained from semi-thin sections in the distal (near the IHCs) and proximal (near the spiral ganglion) regions of the osseous spiral lamina. Best-fit line analysis indicates there is a modest nerve fiber size/vertical organization along the scala tympani/scala vestibuli (SV) axis of the nerve bundles within the osseous spiral lamina such that more of the smaller perimeter fibers are located on the SV side and more of the larger perimeter fibers are located on the ST side. Our data for terminals at the IHC are different from those seen in the cat; our data for nerve fibers in the osseous spiral lamina support those seen in the cat and guinea pig.
Landmarks for the identification of the cutaneous nerves of the occiput and nuchal regions
Clinical Anatomy, 2006
Although surgical procedures are often performed over the posterior head and neck, surgical landmarks for avoiding the cutaneous nerves in this region are surprisingly lacking in the literature. Twelve adult cadaveric specimens underwent dissection of the cutaneous nerves overlying the posterior head and neck, and mensuration was made between these structures and easily identifiable surrounding bony landmarks. All specimens were found to have a third occipital nerve (TON), lesser occipital nerve (LON), and greater occipital nerve (GON), and we found that the TON was, on average, 3 mm lateral to the external occipital protuberance (EOP). Small branches were found to cross the midline and communicate with the contralateral TON inferior to the EOP in the majority of sides. The mean diameter of the main TON trunk was 1.3 mm. This trunk became subcutaneous at a mean of 6 cm inferior to the EOP. The GON was found to lie at a mean distance of 4 cm lateral to the EOP. On all but three sides, a small medial branch was found that ran medially from the GON to the TON *1 cm superior to a horizontal line drawn through the EOP. The GON was found to pierce the semispinalis capitis muscle on average 2 cm superior to the intermastoid line. The mean diameter of the GON was 3.5 mm. The GON was found to branch into medial and lateral branches on average 0.5 cm superior to the EOP. The LON was found to branch into a medial and lateral component at approximately the midpoint between a horizontal line drawn through the EOP and the intermastoid line. The main LON trunk was found on average 7 cm lateral to the EOP. In specimens with a mastoid branch of the great auricular nerve (GAN), this branch was found at a mean of 9 cm lateral to the EOP. The main trunk of this branch of the GAN was found to lie on average 1 cm superior to the mastoid tip. Easily identifiable bony landmarks for identification of the cutaneous nerves over the posterior head and neck can aid the surgeon in more precisely identifying these structures and avoiding complications. Although the occipital nerves were found to freely communicate with one another, avoiding the main nerve trunks could lessen postoperative or postprocedural morbidity. Moreover, clinicians who need to localize the occipital nerves for the treatment of occipital neuralgia could do so more reliably with better external landmarks.
Electron microscopic observations of the nucleus, glial dome, and meninges of the rat acoustic nerve
The American journal of anatomy, 1971
The rat acoustic nerve is separated into central and peripheral portions by an astrocytic glial dome which is convex peripheralward. The long central portion is of typical central nervous system structure with narrow extracellular space (100-200 A in width), oligodendrocytes and astrocytes. The glial dome is penetrated by acoustic nerve fibers at a node of Ranvier; the basal lamina of the astrocytes is reflected back over the peripheral Schwann cells at this site. Centrally, the myelin is thinner than peripherally. Acoustic nerve neurons, ranging in size from 25-60 P, occur in the central portion of the nerve and may be divided into two groups based upon size and density of organelles: large and medium-sized. All the neurons possess an eccentric nucleus and a peripheral clear zone in the perikaryon beneath which Nissl substance is aggregated, but the medium-sized neurons have fewer organelles than the large cells. Dendrites and axons are similar in ultrastructure. While collagenous fibrils, fibroblasts, Schwann cells and extensive extracellular space occur in the peripheral portion of the nerve, no structure corresponding to perineurium or epineurium exists. Instead, dura mater surrounds the acoustic nerve within the modiolus and the pia mater encloses bundles of nerve fibers up to the modiolar foramina where it is reflected back as arachnoid mater. Nerve fibers traversing the modiolar foramina are devoid of a meningeal or perineurial covering; this condition also prevails in the osseous spiral lamina, although wisps of pia-like cells enclose groups of ganglion cells and nerve fibers in the spiral tract. These findings may help to explain acoustic nerve involvement in pathological processes such as meningitis and encephalitis.
Supratrochlear and Supraorbital Nerves
Ophthalmic Plastic & Reconstructive Surgery, 2013
Background: This article elucidates the anatomical details of the course and territory of the supraorbital (SO) and supratrochlear (ST) nerves. Possible applications of the SO and ST nerves for sensory nerve transfer are also examined. Methods: The dissection of 3 fresh cadaver heads (6 hemifaces) was performed. In each hemiface, the ST and SO nerves were identified. The following data were recorded: 1) number of branches, 2) skin boundaries, 3) communicative branches, and 4) branch length. The feasibility of specific nervetransfer procedures was also examined. Results: In 4 hemifaces the SO nerve exited from the SO notch and in 2 hemifaces from the SO foramen. The position was lateral to the midline, with a mean distance of 1.93 cm. In all dissections, a maximum of 4 SO branches (range 2-4) were identified. The ST nerve exited the orbital rim medial to the SO nerve, and lateral to the midline with a mean distance of 0.866 cm. The mean distance between the SO and ST nerves at the level of the SO rim was 1.06 cm. In 5 of 6 hemifaces, several sub-branches emerged from the main trunk of the ST nerve. In 1 hemiface the ST nerve was divided in 2 main branches. Conclusions: The data presented in the current study are in agreement with previous anatomical studies. Both ST and SO nerves can be used as sensory nerve donors in the head and neck area for numerous expanding applications.