The lesion affects the horizontal gaze because the lateral rectus muscle abducts the eye on the horizontal plane. Superior oblique myokymia, episodes of involuntary superior oblique muscle tightening that distort vision. Abducens Nerve Palsy (Sixth Cranial Nerve Palsy): Background, Pathophysiology, Epidemiology. The abducens nerve is examined in conjunction with the oculomotor and trochlear nerves by testing the movements of the eye. The trochlear nerve transmits general somatic efferent impulses, which synapse in the skeletal fibers of the superior oblique muscle. Clinical Anatomy of the Cranial Nerves (pp. Treatment of trochlear nerve palsy depends on what's causing the problem. and grab your free ultimate anatomy study guide! In the primary position, the primary action of the superior oblique muscle is intorsion. The treatment thats right for you depends on whats causing your symptoms. This gives a false impression that the light source is centered in the deviating eye. It then passes through Dorellos canal, before entering the middle of the cavernous sinus. In children, it is most often present at birth (congenital). Proptosis, chemosis, and orbital edema may also be seen. On the other hand, acquired trochlear nerve lesion is more likely to occur from head trauma. Our engaging videos, interactive quizzes, in-depth articles and HD atlas are here to get you top results faster. Both nerves are basal plate derivatives arising from the somatic efferent column at their respective locations. Cranial nerves examination: Trochlear & abducens nerves: want to learn more about it? 00:00 Intro doi:10.12968/hmed.2017.78.3.C38, Brazis PW. Cranial nerves help control sensory innervation: i.e., the ability to . Fix, J., & Brueckner, J. The force of depression rises when the eye is adducted (looking toward the nose). Physiopedia is not a substitute for professional advice or expert medical services from a qualified healthcare provider. 2 [2] for an image of a Snellen chart. Furthermore, careful history including associated symptoms and other past medical history can help distinguish a CN 4 palsy from other items on the differential. The fibers arising from the nucleus of CN VI travel anteroinferiorly toward the pontomedullary junction. That can help doctors identify the cause of diplopia so that it can be treated properly. They allow the eyes to move in the two principal planes and also about the visual axis. I would honestly say that Kenhub cut my study time in half. If the peripheral nerves are impaired, this test causes a reduced or absent response. The human brain: an introduction to its functional anatomy. The trochlear nerve has the longest intracranial course of all of the cranial nerves. Orbit. It also runs farther on the inside of the skull than any other cranial nerve and is the thinnest of them.. A collection of interactive medical and surgical clinical case scenarios to put your diagnostic and management skills to the test. The cranial nerve exam is a type of neurological examination.It is used to identify problems with the cranial nerves by physical examination.It has nine components. If you or somebody else notices these symptoms, you should consult with a healthcare provider. These include blurry or double vision. A guide to the evaluation of fourth cranial nerve palsies. Does the hypertropia worsen in left or right gaze? Haines, D. (2013). - 800+ OSCE Stations: https://geekymedics.com/osce-stations/ One major confounding factor is the patients visual acuity is higher in the paretic eye than it is in the non-paretic eye. It is divided into brainstem, cisternal, tentorial . https://www.ophthalmologytimes.com/article/seven-easy-steps-evaluation-fourth-nerve-palsy-adults, https://eyewiki.org/w/index.php?title=Cranial_Nerve_4_Palsy&oldid=90774, Hemisensory loss, ataxia, internuclear ophthalmoplegia, hemiparesis, central Horner syndrome, cranial nerve III palsy, Frequently due to infarction or hemorrhage. Motorcycle accidents are a common cause, but sometimes it can result from even minor head injuries. Given the small size of the trochlear nerve, it is prone to injury from shearing forces seen in head trauma. Gaillard, F., & Hacking, C. Trochlear nerve | Radiology Reference Article | Radiopaedia.org. How to use trochlear in a sentence. Both medical and surgical options are available for treating a blow out fracture of the medial orbital wall. If you believe that this Physiopedia article is the primary source for the information you are refering to, you can use the button below to access a related citation statement. Some authors recommend following such patients for resolution over time and control of the vasculopathic risk factors alone. Alexandra Osika Next: History of the Procedure In some cases, nystagmus is a physiological response to extremes of gaze. Since divergence would be facilitated by the lateral recti muscles, the patient experiences worsening diplopia under these circumstances. ; Dysosmia (also called phantosmia), unpleasant or strange odors that occur spontaneously. ptosis,miosis, etc.). Tilting your head up and to the side may help you compensate for the vision changes. The long-term benefit of steroid injection varies from individual to individual. Microvascular causes may spontaneously resolve over the course of weeks or months. A relative afferent pupillary defect without any visual sensory deficit. Skew deviation may display incyclotorsion of the affected eye or bilateral torsion. Often doctors cannot identify the cause, but when they can, the cause is usually a head injury, sometimes a minor one. It thereafter courses through the lateral wall of the cavernous sinus and joins three other cranial nerves oculomotor nerve (CN III), abducens nerves (CN VI), as well as the first two branches of the trigeminal nerve (CN V), ophthalmic (V1) and maxillary (V2). 39-45). The trochlear nerve travels anteriorly in the lateral wall of the cavernous sinus before passing though the superior orbital fissure. In abducted gaze, the SOM acts to intort the eye and abducts the eye. Some people need special glasses or surgery. Glossopharyngeal and taste (taste, proprioception, monitors blood pressure and oxygen and carbon dioxide levels in blood, swallowing, saliva secretion) . It is part of the autonomic nervous system, which supplies (innervates) many of your organs, including the eyes. The long-term pain relief, if steroid is also injected for inflammation, may take two or three days to take effect. J Neuro-Ophthalmology. There are steps you can take to prevent head injuries that damage the trochlear nerve. Ehrenhaus, M., & Hajee, M. (2018). Br J Ophthalmol. It's common for trochlear nerve damage and associated eye-movement problems to make it hard for people to see where they're walking, especially when going down the stairs. These large vertical fusional ranges characteristic of congenital cases. The trochlear nerve is one of 12 sets of cranial nerves. https://www.youtube.com/watch?v=IQxs9PeWb1s, https://www.youtube.com/watch?v=nzrAxyzR6VI&list=PLlnL4HAGL-ONPYJBFq8No4AWJsd-OfYc0&index=4, https://www.youtube.com/watch?v=48MSBKRIrno, http:///index.php?title=Trochlear_Nerve&oldid=302839, Neurological - Assessment and Examination. This cartilaginous tissue holds the tendon of the superior oblique muscle. Atlas of Human Anatomy. The Neurological Institute is a leader in treating and researching the most complex neurological disorders and advancing innovations in neurology. Finally, the trochlear nerve reaches the eye socket and passes above a ring of muscles called the extraocular muscles. Patients may report vertical and/or torsional diplopia that is usually worse on downgaze and gaze away from the affected side. As a result, it causes the eyeball to move downward and inward. Kim SY, Motlagh M, Naqvi IA. The trochlear nerve is one of the more fragile cranial nerves because its thin and long. What is the name and function of cranial nerve VIII? This tool is so easy to use when taking medical histories Don't forget to follow Geeky Medics for more videos. Incidence and Etiology of Presumed Fourth Cranial Nerve Palsy: A Population-based Study. This muscle moves the eyeball up and down and left and right. 2017;61(3):166-170. The presentation of vertical or torsional diplopia is related to the fact that the superior oblique muscle is no longer functional. This page was last edited on March 23, 2023, at 07:24. During downward gaze there is a tendency of the upper eyelids to droop, therefore use two fingers to elevate the upper eyelids while the patient is gazing downwards. penlight (How to test) Abducens . This muscle works alongside other extraocular muscles to rotate your eyeball downward. The patient is asked to follow a point with their eyes (commonly the tip of a pen) without moving their head. 2023 Dotdash Media, Inc. All rights reserved, Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Consequently, they will fix on the visual stimulus with the eye with better acuity. A recent population-based study finds only 4% of trochlear nerve palsies to be idiopathic, citing increased improved identification of vasculopathic risk factors. Cranial nerve palsy sometimes occurs after minor injuries. An area located near the dura (outer tissue that encases and protects the brain)., Cavernous sinus. Ocular mobility is an important feature of the eyes that help individuals collect as much visual input as possible. At eye level, move the penlight left to right, right to left, up and down, upper right to lower left, and upper left to lower right. Retrieved from https://emedicine.medscape.com/article/1198383-overview?pa=YhPsZCtn22PJ%2F6D75AcmYBy41navoRdjZ%2FhVXv%2BLuSYch3q%2BtquJTYKhKV6oyN7343mU9jD%2B1DtnxY47OmyybA%3D%3D. Rom J Ophthalmol. Observe the eye and note if it moves (medially, laterally, superiorly, or inferiorly) to focus. (2002). In other cases, it can be caused by internal ear, optic nerve (CN II), vestibulocochlear nerve (CN VIII), or cerebellar dysfunction. Strabismus. We describe the anatomical course of the trochlear through the skull, with consideration to its function and clinical relevance. The medial rectus muscle can become entrapped, making it difficult for the lateral rectus to pull the eyeball in the opposite direction. Anatomical Course You have twelve pairs of cranial nerves in your head. This nerve is the fourth set of cranial nerves (CN IV or cranial nerve 4). The function of the superior oblique muscle is a confusing area. The superior oblique muscles allow for depression, abduction, and medial rotation (intortion) of the eyeball. This variation is important for neurosurgeons to know so they can avoid causing damage to the nerve. Cranial nerve IV (trochlear nerve). The trochlear nerve passes adjacent to the ophthalmic division of the trigeminal nerve and the two share a connective tissue sheath. 2000. Determining the hypertropic eye reduces the potentially involved muscles to four. The practitioner then makes note of the position of the reflection on the cornea. [4], Trauma It is also called the dolls-eye test owing to the fact that the normal response should be similar to the movement of a dolls eyes when the toy is turned from side to side. The trochlear nerve is the fourth of 12 cranial nerves that emerge from the brain and extend down the head, neck, and torso. Join the Geeky Medics community: Philadelphia; Lippincott Williams and Wilkins, 2017, Netter FH. If you want to learn more about the cranial nerves, check out our summary. As is the case with trochlear nerve (CN IV), the abducens nerve (CN VI) is also vulnerable to traumatic injury because of its extensive intracranial course. See Figure 6.5. 0:00 / 3:16 Cranial Nerve Examination: CN 3, 4 & 6 oculomotor trochlear abducent Soton Brain Hub 39.2K subscribers Subscribe 86K views 8 years ago Cranial nerve clinical examination Eye. In the healthy, awake, older individual the response can be inhibited voluntarily with normal vision. 40:358-360. Many cases of fourth nerve palsy are idiopathic. In adults, it is most often caused by injury. Contraction of the superior oblique induces depression and intorsion in nearly equal proportions when the eye is in the primary position (seeing straight ahead). This muscle is near the top of the eyeball. He is the Anatomy Lead for Geeky Medics. It progresses through the lateral wall of the cavernous sinus. - Medical Finals Question Pack: https://geekymedics.com/medical-student-finals-questions/ Examiners should consider obtaining the following: visual acuity, motility evaluation, binocular function and stereopsis, strabismus measurements at near, distance, and in the cardinal positions of gaze, and evaluation of ocular structures in the anterior and posterior segments. The squint can occur superiorly (hypertropia), inferiorly (hypotropia), medially (esotropia), or laterally (exotropia). . The tendon attaches to the top (superior aspect) of the eyeball at a 51-degree angle to the eyeball's primary position (looking straight forward). In Merck manual online. #Trochlear nerve # 4th nerve. Common Neuro-Ophthalmic Pitfalls: Case-Based Teaching. Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins. Unfortunately, the test is not foolproof. This hollow cavity is located in the center of the skull.. This suggests a central CN IV palsy. [7] Fourth nerve palsy secondary to microvascular disease will frequently resolve within 4-6 months spontaneously. Philadelphia, Pa.: Wolters Kluwer, Lippincott, Williams et Wilkins. Conditions and Disorders What are symptoms of impaired olfactory nerve function? However, the deviating eye (the one with the extraocular muscle weakness) the light is not centered on the cornea. William is a final year medical student in Australia who has taught anatomy to tertiary science and medical students since 2010. Determining the onset, severity, and chronicity of symptoms can be vital in delineating between the various etiologies of a CN 4 palsy. Instagram: https://instagram.com/geekymedics Acute symptoms may indicate trauma, while chronic symptoms are mostly congenital. It has a purely somatic motor function. 00:30 Appearance, Behaviour & Speech Strabismus, also referred to as a squint, lazy eye, or crossed-eyes refers to malalignment of the eyeballs. Therefore the clinician should verify which image disappears while covering the eye during this test. Prism therapy is a reasonable treatment option for patients amenable to therapy. Ask the subject to see at a distant object. Unlike the other cranial nerves, the trochlear nerve doesn't branch out and snake through multiple areas; it's a short nerve that runs from the brain to the eye without dividing at all. Arch Ophthalmol. Bilateral CN IV palsy might show bilateral excyclotorsion. The trochlear nerve is one of 12 sets of cranial nerves. Because this symptom isn't present, the palsy is often misdiagnosed as a different problem, called torticollis. Last reviewed by a Cleveland Clinic medical professional on 08/10/2021. Am J Ophthalmol. That is usually the journal article where the information was first stated. They're symmetricaleach one has a right side and left side (but each pair is generally referred to as a single nerve). pulley-like nerve) also known as the fourth cranial nerve, cranial nerve IV, or CN IV, is a cranial nerve that innervates a single muscle - the superior oblique muscle of the eye (which operates through the pulley -like trochlea ). Some people find pain relief from the nerve block with steroids lasting several weeks . In most cases Physiopedia articles are a secondary source and so should not be used as references. For trauma-induced trochlear palsy, patients typically report symptoms immediately after injury. Lyme disease. Coup describes the part of the brain that is on the same side as the object of impact, while contrecoup refers to the side of the brain on the opposite side of the point of injury. Subsequently, it passes lateral to the common tendinous ring (also called the common annular tendon and the annulus of Zinn) and continues superiorly, where it pierces and innervates the superior oblique muscle. Some cranial nerves have both afferent and efferent functions.. Microsurgical anatomy of the trochlear nerve. Get Top Tips Tuesday and The Latest Physiopedia updates, The content on or accessible through Physiopedia is for informational purposes only. Patients with traumatic or congenital fourth nerve palsies may be considered for patch, prism, or surgical treatment, especially if they are symptomatic in primary gaze. Patients with mild or long-standing disease may have blurred vision, difficulty focusing and dizziness instead of diplopia.[1]. We then describe a novel clinical testthe upright-supine testto differentiate skew deviation from trochlear nerve palsy: a vertical deviation that decreases by 50% from the upright to supine position suggests skew deviation and warrants investigation for a lesion in the posterior fossa as the cause of vertical diplopia. Ask the patient to sit up if possible. This form of cancer causes slow-growing tumors to form on the meninges: layers of membranes that cover the brain. A tumor that presses on the trochlear nerve can cause fourth nerve palsy. It travels anterosuperiorly toward the middle cranial fossa, where it enters the lateral wall of the cavernous sinus. Arch Ophthalmol. The abducens nerve is examined in conjunction with the oculomotor and trochlear nerves by testing the movements of the eye. Keep the index finger in a vertical position and proceed to trace the letter H. The function of the vestibulocochlear nerve is purely sensory. [3]. Paralytic Strabismus: Third, Fourth, and Sixth Nerve Palsy. Management of diplopia. Vertical diplopia whereby injury causes weakness in the downward movement of the eyeball causing double vision due to unopposed actions of the other extraocular muscles, thereby producing two visual fields from either eye. In most cases, the palsy will go away eventually. This tests both the peripheral nerves and the spinal cord. The superior oblique muscle's body is behind the eyeball, but its tendon (which is guided by the trochlea) approaches it from the front. The force of intorsion increases when the eye is abducted (looking away from the nose), whereas the force of depression diminishes. Palsies of the Trochlear Nerve: Diagnosis and LocalizationRecent Concepts. The trochlear nucleus contains somatic motor neuronal cell bodies that exit the nucleus posteriorly. Damage to your trochlear nerve can severely impact your vision. Each clinical case scenario allows you to work through history taking, investigations, diagnosis and management. Read our, The Anatomy of the Superior Laryngeal Nerve, Microsurgical anatomy of the trochlear nerve, A new segment of the trochlear nerve: cadaveric study with application to skull base surgery, Fourth Cranial Nerve (Trochlear Nerve) Palsy. Isolated third, fourth, and sixth cranial nerve palsies from presumed microvascular versus other causes: A prospective study. Trochlear nerve palsy is a common cause of congenital cranial nerve (CN) palsy. In some people, its congenital, meaning they are born with this condition. Thank you, {{form.email}}, for signing up. The condition is called trochlear nerve palsy. When the eye is abducted the visual axis and the muscle plane become more perpendicular and the SOM function is mostly intorsion. Author: 2013. doi:10.1016/j.ophtha.2013.04.009, Lee AG. The meaning of TROCHLEAR is of, relating to, or being a trochlea. 2015;28(7):857-64. doi:10.1002/ca.22602. 2017;78(3):C38-C40. A doctor may suspect trochlear nerve problems when seeing characteristic problems with eye movement, especially if tilting the head helps. Watch this to learn the basics of ABG interpretation step by step. Papilledema is a sign of raised intracranial pressurea condition that can cause compression of CN VI. Patients may develop a compensatory head tilt to the contralateral side to reduce their diplopia. How do you test for trochlear nerve damage? In the fixating eye (the one without extraocular muscle weakness) the reflection of the light is centered. As such, they are purely motor nerves, which means they deliver general somatic efferent impulses to their respective target muscles. As the patients head is rocked from one side to the other, the eyes should move in the opposite direction. Read more. It's a motor nerve and provides movement to only one musclean eye muscle called the superior oblique, which connects to the top of the eyeball. The nuclei can be found in the inferodorsal aspect of the pons, beneath the facial colliculus of the fourth ventricle. Seven easy steps in evaluation of fourth-nerve palsy in adults. Fourth nerve palsy in pseudotumor cerebri. Reading time: 23 minutes. All rights reserved. 08:41 Insight & Judgement Presence of an ipsilateral or contralateral rAPD without loss of visual acuity, color vision, or peripheral vision in an apparently isolated CN IV palsy suggests superior colliculus brachium involvement. Both congenital and acquired disorders of the extraocular muscles may result in strabismus. Retrieved from https://radiopaedia.org/articles/abducens-nerve. Trigeminal nerve (CN V): One branch of this forked nerve controls the corneal reflex and the production of tears. If the insult occurs at the level of the nucleus or within the brainstem, then the contralateral eye would be affected. The information we provide is grounded on academic literature and peer-reviewed research. This muscle allows you to move your eyeball down and shift your gaze from side to side., Interesting facts about the trochlear nerve:, The cranial nerves supply autonomic, motor, and sensory stimulation to the head and neck, but each cranial nerve has a distinct function. There are several clinically significant features of the trochlear nerve anatomy. Careful examination is necessary in traumatic cases as the CN IV palsies can by asymmetric if bilateral and can be masked or become apparent after strabismus surgery for a presumed unilateral CN IV palsy. Using a seatbelt when youre in a car, even for short trips. While there are surgical procedures in which the length of the muscle is altered in order to reposition the eye, medical treatment options to treat the underlying cause should be considered first. The outer image corresponds to the affected eye and is a false image, while the inner image is the true image. - Geeky Medics OSCE App: https://geekymedics.com/geeky-medics-app/ The trochlear nerve is the cranial nerve with the longest intracranial course (60 mm) but also the smallest diameter (0.75-1.0 mm) (Villain et al., 1993). Subscribe to our newsletter to be the first to know about our latest content: https://geekymedics.com/newsletter/ 2018. doi:10.1016/j.ajo.2017.10.019, Purvin VA, Kawasaki A. Magnetic resonance imaging of the head (MRI) is often unremarkable in CNV IV palsy but may show a dorsal midbrain contusion or hemorrhage.[5]. In this article, the anatomical course, motor functions and clinical relevance of the nerve will be examined. Cavernous sinus syndrome, when an abnormal growth affects the trochlear nerve. The nerve supply of these muscles is provided by three cranial nerves - namely the oculomotor (CN III), trochlear (CN IV), and abducens (CN VI) nerves. In the sinus, the trochlear nerve is joined by several other nerves, including the third and sixth cranial nerves (which also serve the eye) and two branches of the trigeminal (fifth cranial) nerve: the ophthalmic and maxillary nerves, which supply sensory innervation to much of the face. - 150+ PDF OSCE Checklists: https://geekymedics.com/pdf-osce-checklists/ Vision is one of the most prized senses that most living organisms have. Inability to depress the eye manifests as vertical diplopia, where the one image lies atop the other. Centers for Disease Control and Prevention. Babyproofing your home if you have an infant by putting up a baby gate near stairs. The trochlear nerve innervates this muscle to lift the eyes so you can look down. Each test is designed to assess the status of one or more of the twelve cranial nerves (I-XII). It passes through the superior orbital fissure of the skull. Fast and jerky head movements can tear the fragile trochlear nerve. High-yield neuroanatomy (4th ed.). The patient is esotropic because the action of the medial rectus muscle is unopposed. Acquired Superior Oblique Palsy: Diagnosis and Management. So, in a patient with right hypertropia that worsens in left gaze, this suggests either right superior oblique or a left superior rectus involvement. Issues that affect your olfactory system can cause: Anosmia, complete loss of smell. Neuroanatomy, Cranial Nerve 4 (Trochlear). Lorenzo Crumbie MBBS, BSc A full neurological examination may also be warranted as this disorder can arise from supranuclear areas (corticobulbar tract). Test eye movement by using a penlight. Skew deviation may demonstrate decreasing vertical strabismus with position change from upright to supine. While some individuals have prominent crossed-eyes that can be seen initially, others are subtle. This phenomenon arises because the eyes are no longer evenly fixed on the object so there is an illusion that there is more than one item. Snell, R. (2010). Start by observing the patients behavior. The trochlear nerve interacts with two components related to the eye: Superior oblique muscle. This poorly understood syndrome occurs when your immune system attacks your nerve cells, causing numbness, temporary paralysis, and other symptoms. The trochlear nerve is the fourth of 12 cranial nerves that emerge from the brain and extend down the head, neck, and torso. The trochlear nerve doesn't transmit sensory signals. Between these locations, the fiber travels through several structures., Ambient cistern. Protecting your head from injury can help keep your trochlear nerve safe. What is the function CN III? Other authors however have suggested that patients with CN IV palsy should undergo neuroimaging and further neurological work-up. Signs and symptoms associated with CN II,III, V, VI and II. Check out our NEW quiz platform at app.geekymedics.com, To be the first to know about our latest videos subscribe to our YouTube channel . Reading the newspaper and descending the stairs are two common hobbies that necessitate convergent gaze. They often include vision changes that worsen when you look down. Patients with an acquired trochlear nerve palsy may respond to treatment of the underlying disease. It enables movement in the eyes superior oblique muscle. The superior oblique muscle is the only structure innervated by the trochlear nerve. 2005 - 2023 WebMD LLC, an Internet Brands company. The trochlear nerve is one of 12 sets of cranial nerves. Pearls and oy-sters: Central fourth nerve palsies. The trochlear nerve function is purely efferent. This could be ranging from a problem within the eye that disrupts the path of light (retinal detachment, cataracts, vitreous hemorrhages) or a problem in positioning the eyes to allow light to enter the eyeball (extraocular muscle weakness). A comprehensive collection of clinical examination OSCE guides that include step-by-step images of key steps, video demonstrations and PDF mark schemes. As a result, the trochlear nerve is tested by having the patient look 'down and in,' as the superior oblique contributes the most to this motion. Microvascular disease can involve CN IV and usually in older patients with cardiovascular risk factors. #geekymedics #fyp #fypviral #studytok #medicalstudent #medtok #studytips. Patching is also an acceptable alternative for patients who defer prisms or surgery. It then goes inside the cavernous sinus and runs along one of its walls. When the eye is adducted, the muscle plane and the visual axis align and the primary action is as a depressor. In a patient with hypertropia that worsens in left gaze and right head tilt is most compatible with a right superior oblique palsy. American Academy of Ophthalmology. Patients with extraocular palsies often tilt their heads to refocus the target image and correct the diplopia (visualization of the same object in two spatially separate locations; which is just a fancy way to say double vision). Another way to examine the trochlear nerve is with the Bielchowsky head tilt test. When a trochlear nerve palsy is suspected, the diplopia can be abolished by tilting the head toward the shoulder of the unaffected side. 2010;30(1):59-63. doi:10.1097/WNO.0b013e3181ce1b1d, Prasad S, Volpe NJ. Patients who are victims of polytrauma may also suffer from a blow out fracture of the medial orbital wall. Sheik, Z., & Hutcheson, K. (2018). Verywell Health's content is for informational and educational purposes only. The nerve also enables you to move your eyes toward your nose or away from it. The trochlear nerve, while the smallest of the cranial nerves, has the longest intracranial course as it is the only nerve to have a dorsal exit from the brainstem. This makes it possible to look down. These include: Contact your healthcare provider if you experience symptoms of fourth nerve palsy. The injury may also be unilateral or bilateral; which would change how the patient presents. Patients who are unfortunate enough to suffer from an abducens nerve palsy will be unable to abduct the eye that is ipsilateral to the CN VI nucleus (and lesion). 9500 Euclid Avenue, Cleveland, Ohio 44195 |, Important Updates + Notice of Vendor Data Event, (https://eyewiki.aao.org/Cranial_Nerve_4_Palsy).
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how to test trochlear nerve
