Innervation of Orbicularis Oculi by Trochlear Nerve: Word of Caution (original) (raw)
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Anatomical study of the variations in innervation of the orbicularis oculi by the facial nerve
Surgical and Radiologic Anatomy, 2004
While the divisions of the facial nerve in the face are well known, the innervation of the orbicularis oculi by the different distal branches of the facial nerve is poorly described. To determine which branches of the facial nerve play a role in this innervation, the facial nerve was dissected in 30 fresh cadavers. The innervation of this muscle was in the form of two plexuses, a superior one, most often (93%) formed by the union of the temporal and superior zygomatic branches, and an inferior one, usually formed (63%) by the union of the inferior zygomatic and superior buccal branches. This new mode of innervation explains how, without damage to both plexuses, innervation of orbicularis oculi by the facial nerve remains functional. It also explains the often unsatisfactory results of treatment of primary blepharospasm, and the unusual character of palsies of this muscle in cervicofacial lifts.
The human trochlear and abducens nerves at different ages - a morphometric study
Aging and disease, 2015
The trochlear and abducens nerves (TN and AN) control the movement of the superior oblique and lateral rectus muscles of the eyeball, respectively. Despite their immense clinical and radiological importance no morphometric data was available from a wide spectrum of age groups for comparison with either pathological or other conditions involving these nerves. In the present study, morphometry of the TN and AN was performed on twenty post-mortem samples ranging from 12-90 years of age. The nerve samples were processed for resin embedding and toluidine blue stained thin (1µm) sections were used for estimating the total number of myelinated axons by fractionator and the cross sectional area of the nerve and the axons by point counting methods. We observed that the TN was covered by a well-defined epineurium and had ill-defined fascicles, whereas the AN had multiple fascicles with scanty epineurium. Both nerves contained myelinated and unmyelinated fibers of various sizes intermingled wi...
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.
Effects of Intracranial Trochlear Neurectomy on the Structure of the Primate Superior Oblique Muscle
Investigative Ophthalmology & Visual Science, 2010
Although cyclovertical strabismus in humans is frequently attributed to superior oblique (SO) palsy, anatomic effects of SO denervation have not been studied. Magnetic resonance imaging (MRI) and orbital histology was used to study the effects of acute trochlear (CN4) denervation on the monkey SO. METHODS. Five juvenile macaque monkeys were perfused with formalin for 5 weeks: 15 months after unilateral or bilateral 10-mm intracranial trochlear neurectomy. Denervated and fellow orbits were imaged by MRI, embedded whole in paraffin, serially sectioned at 10-m thickness, and stained with Masson trichrome. Whole muscle and individual fiber cross sections were quantified in SO muscles throughout the orbit and traced larger fibers in one specimen where they were present. RESULTS. MRI demonstrated marked reduction in midorbital cross section in denervated SO muscles, with anterior shift of SO mass preserving overall volume. Muscle fibers exhibited variable atrophy along their lengths. Denervated orbital layer (OL) fiber cross sections were slightly but significantly reduced from control at most anteroposterior locations, but this reduction was much more profound in global layer (GL) fibers. Intraorbital and intramuscular CN4 were uniformly fibrotic. In one animal, there were scattered clusters of markedly hypertrophic GL fibers that exhibited only sparse myomyous junctions only anteriorly. CONCLUSIONS. CN4 denervation produces predominantly SO GL atrophy with relative OL sparing. Overall midorbital SO atrophy was evident by MRI as early as 5 weeks after denervation, as denervated SO volume shifted anteriorly. Occasional GL fiber hypertrophy suggests that at least some SO fibers extend essentially the full muscle length after trochlear neurectomy. (Invest Ophthalmol Vis Sci.
Clinical Neurology and Neurosurgery, 2011
Objective: Greater occipital nerve (GON) blockade is an effective method for treatment of occipital neuralgias. Occipital neuralgia or neuropraxis of this region may be seen particularly as a result of compression of the GON. This study shows the relationship between the GON and its external bone landmarks, in order to prevent complications and to perform nerve blockades safely. The study also defines the points where the GON pierces the semispinalis capitis (SSC) and the trapezius, and where the GON passes the obliquus capitis inferior (OCI), and identifies bone landmarks for places where the GON may be entrapped. Materials and methods: In the laboratories of Dokuz Eylül University, Faculty of Medicine Department of Anatomy, 12 GON's belonging to male adult cadavers fixed in formaldehyde were dissected. Colored silicone was injected to all cadavers and then microdissections were performed under a dissection microscope. The lesser occipital nerve, the GON, the greater auricular nerve, and the occipital artery (OA) were dissected. All measurements were made with a 0.1 mm sensitive calipometer. Results: The GON's diameter at the point where the GON pierces the SSC was found to be 2.5 ± 0.3 mm. The distance between the point where the GON pierces the SSC and the external occipital protuberance (EOP) was 53.6 ± 5.0 mm. The distance between this point and the midline was 9.0 ± 1.9 mm, the distance between this point and the intermastoid line was 11.5 ± 3.9 mm and the distance between this point and the mastoid process was 65.5 ± 5.9 mm. The distance between the midline and the point where the GON pierces the aponeurosis of trapezius (AT) was 47.9 ± 8.0 mm, the distance between this point and the EOP was 15.1 ± 7.0 mm, the distance between this point and the intermastoid line was 17.1 ± 2.8 mm, and the distance between this point and the mastoid process was 59.4 ± 2.3 mm. We measured the distance between the OA and the intermastoid line to be 8.5 ± 6.1 mm vertically and 32.3 ± 3.9 mm horizontally to the midline. Conclusion: In this study, we define the GON's route in the suboccipital and the occipital region where the nerve pierces the SSC and the AT and where blockade or surgery can be performed. These data will help the surgeon and clinician to avoid complications in this region. .tr (M. Güvenç er). and then pierces the latter muscle. After piercing the aponeurosis of trapezius (AT), it travels with the occipital artery to supply the integument of the scalp as far anterior as the vertex of the skull .
Surgical and Radiologic Anatomy, 2001
The canal of the posterior ampullar nerve is located between the inferior part of the internal acoustic meatus and ampulla of the posterior semicircular canal. It permits a more accurate localisation of the underlying labyrinth in innerear surgery. An anatomical and radiological study was undertaken to determine the importance the relationship between the canal and the labyrinth. Ten dry and 10 cadaveric temporal bone dissections, together with 20 high resolution CT scans of the same temporal bones were studied in an attempt to describe the anatomy of the canal of the posterior ampullar nerve. The length of the canal of the posterior ampullar nerve, the length of internal acoustic meatus, and distances from porus acusticus to the singular foramen and the transverse crest, and from the singular foramen to the vestibule and transverse crest, and from operculum to the sigmoid sinus and to the porus acusticus were measured. During the transmeatal posterior cranial fossa approach using the canal of the posterior ampullar nerve as a landmark enables more bone to be safely removed from the internal acoustic meatus thus preserving hearing.
An anatomical study of the inferior oblique muscle with emphasis on its nerve entry
Chang Gung medical journal
Anatomical studies regarding the inferior oblique muscle are scarce and the exact location of the entry of oculomotor nerve to the muscle has not been reported. In the present study, the objectives were to examine the exact location of the entry of oculomotor nerve to the inferior oblique muscle and to study the topographical anatomy of the muscle. The study included 56 intact orbits from 28 embalmed south Indian adult cadavers. The entire course of the nerve to the inferior oblique was exposed from both anterior and posterior aspects in all specimens. The exact location of the entry of nerve supplying the inferior oblique muscle was identified and the distances of the muscle from inferior and medial orbital margins were measured. The oculomotor nerve entered the inferior oblique muscle through the orbital surface in 42 (75%) cases, through the ocular surface in 10 (17.9%) cases and through the posterior border in 4 (7.1%) cases. The distance of the muscle from the inferior orbital ...