trigeminal nerve

Information about trigeminal nerve

Published on October 22, 2009

Author: sahil979



Trigeminal Nerve : Trigeminal Nerve Dr. Nazim Nasir Department of Anatomy Jawahar Lal Nehru Medical College A.M.U., Aligarh INDIA Definition : Definition The fifth vertebrate peripheral nerve that emerges from within the skull. It is sensory from the head, but motor to the jaw muscles. L. trigerninus, three-fold. Trigeminal nerve has three divisions. It was described by Fallopius and again by Meckel in 1748. The name trigeminal was given by Winslow on account of its three divisions. Function : Function The sensory function of the trigeminal nerve is to provide the tactile, proprioceptive, and nociceptive afference of the face and mouth. The motor function activates the muscles of the mastication, the tensor tympani, tensor veli palatini, mylohyoid, and anterior belly of the digastric. Peripheral Anatomy : Peripheral Anatomy The trigeminal nerve exits from the anterolateral surface of the pons as a large sensory root and a small motor root. These roots continue forward out of the posterior cranial fossa and into the middle cranial fossa by passing over the medial tip of the petrous part of the temporal bone. In the middle cranial fossa the sensory root expands into the trigeminal ganglion. The ganglion is in a depression (the trigeminal depression) on the anterior surface of the petrous part of the temporal bone, in a dural cave (the trigeminal cave). The motor root is below and completely separate from the sensory root at this point. General Consideration : General Consideration Arising from the anterior border of the trigeminal ganglion are the three terminal divisions of the trigeminal nerve, which in descending order are: Ophthalmic (V1), Maxillary (V2), and Mandibular (V3) Fibers run from the face to the pons via the superior orbital fissure (V1), the foramen rotundum (V2), and the foramen ovale (V3) Conveys sensory impulses from various areas of the face (V1) and (V2), and supplies motor fibers (V3) for mastication Various Components : Various Components Sensory component Branchial Motor component Visceral motor component SENSORY COMPONENT : SENSORY COMPONENT Ophthalamic division Maxillary division Mandibular division Ophthalamic Division : Ophthalamic Division Enters the middle cranial fossa through the superior orbital fissure and courses within the lateral wall of the cavernous sinus on its way to the trigeminal ganglion. Branches of the ophthalmic nerve (V1) {frontal nerve, nasociliary nerve, and lacrimal nerve} convey sensory information from the skin of the forehead, upper eyelids, and lateral aspects of the nose Maxillary Division : Maxillary Division Enters the middle cranial fossa through foramen rotundum and may or may not pass through the cavernous sinus en route to the trigeminal ganglion. Branches of the maxillary nerve (V2) {zygomatic nerve and infraorbital nerve}convey sensory information from the lower eyelids, zygomae, and upper lip. Mandibular division : Mandibular division Enters the middle cranial fossa through foramen ovale, coursing directly into the trigeminal ganglion Branches of the mandibular nerve (V3) {buccal nerve, lingual nerve, inferior alveolar nerve, and auriculotemporal nerve}convey sensory information from the lateral scalp, skin anterior to the ears, lower cheeks, lower lips, and anterior aspect of the mandible. BRANCHIAL MOTOR COMPONENT : BRANCHIAL MOTOR COMPONENT Consists of lower motor neurons whose cell bodies are located in the motor nucleus of the trigeminal nerve in the brainstem. These nerves exit the mid-lateral aspect of the pons, course within the trigeminal nerve, pass through the trigeminal ganglion, and within the mandibular nerve before branching. The muscles innervated- temporalis, masseter, medial and lateral pterygoids, tensor veli palatini, tensor tympani, anterior belly of diagastric and mylohyoid. VISCERAL MOTOR COMPONENT : VISCERAL MOTOR COMPONENT Visceral motor nerves are not a true component of the trigeminal nerve, but “hitchhike” . Vidian nerve (a.k.a. nerve of the pterygoid canal) emerges from the pterygoid canal carrying pre-ganglionic fibers to the pterygopalatine ganglion. After synapse, post-ganglionic fibers exit the ganglion and hitchhike along trigeminal nerve branches en route to the lacrimal gland and minor salivary glands of the palate and mouth. Contdd….. Slide 14: Chorda tympani exits the skull through the petrotympanic fissure, courses extracranially to join the lingual nerve. It carries pre-ganglionic fibers to the submandibular ganglion which "hangs" from the lingual nerve. After synapse, post-ganglionic fibers exit the ganglion to innervate the submandibular gland and sublingual gland. The lesser petrosal nerve after exiting the skull through or near the foramen ovale, carries pre-ganglionic fibers to the otic ganglion. After synapse, post-ganglionic fibers exit the ganglion, hitchhiking along the auriculotemporal nerve to innervate the parotid gland. Trigeminal Nuclei : Trigeminal Nuclei The sensory trigeminal nerve nuclei are the largest of the cranial nerve nuclei, and extend through whole of the brainstem. The nucleus is divided into three parts, from rostral to caudal (top to bottom in humans): The mesencephalic nucleus The chief sensory nucleus (or "pontine nucleus" or "main sensory nucleus" or "primary nucleus") The spinal trigeminal nucleus Slide 16: The mesencephalic nucleus is involved with proprioception. Neurons of this nucleus are pseudounipolar cells receiving proprioceptive information from the jaw, and sending projections to the motor trigeminal nucleus to mediate monosynaptic jaw reflexes. Slide 17: The principal sensory nucleus (or chief sensory nucleus) receives information about discriminative sensation and light touch of the face as well as conscious proprioception of the jaw. The spinal trigeminal nucleus is a nucleus in the medulla that receives information about deep/crude touch, pain, and temperature from the ipsilateral face. The facial, glossopharyngeal, and vagus nerves also convey pain information from their areas to the spinal trigeminal nucleus. Pathways : Pathways Slide 19: #1 – Large Afferents #2 – Small Afferents #3 – Muscle Afferents Motor Trigeminal Pathway - Efferents : Motor Trigeminal Pathway - Efferents Origin – Motor neurons of trigeminal motor nucleus. Course – Exit via trigeminal nerve Laterality – Uncrossed. Topographical Organization – Organized by muscle group. Destination – Muscles of mastication. Function – Voluntary movement of the jaw; mastication. Dysfunction – Paralysis of the jaw Slide 21: Part 1--Trigeminal Large Primary Afferents Trigeminal Large Primary Afferents : Trigeminal Large Primary Afferents Origin - Trigeminal ganglion, Ab and Ad fibers Course – Trigeminal nerve, enter at pons Laterality - Uncrossed Topographical Organization - yes Destination – Principal sensory nucleus of trigeminal Function – fine touch, vibration, two-point discrimination, proprioception Dysfunction – loss of above senses on half of face. Trigeminal Lemniscus : Trigeminal Lemniscus Origin – Principal sensory nucleus of trigeminal (nV) Course – Trigeminal lemniscus Laterality – Mostly crossed; bilateral projections for oral cavity receptive fields. Topographical Organization - yes Destination – Ventroposterior Medial nuc. (VPM) of thalamus Function – Vibration, proprioception, fine touch, two-point discrimination Dysfunction – loss of sensation mostly contralateral face. Thalamocortical Pathway : Thalamocortical Pathway Origin - VPM Course – Posterior limb of internal capsule Laterality - Uncrossed Topographical Organization – yes; head area Destination – Primary somatosensory cortex, areas 1, 2, 3 Function – Fine touch, vibration, proprioception Dysfunction – Loss of somatic sensations Slide 26: THERMAL RECEPTORS TEMPERATURE Cool receptors A d III Skin cooling (25°C) Warm receptors C IV Skin warming Heat Nociceptor A d III Hot temp Cold Nociceptors C IV Cold temp NOCICEPTORS PAIN Mechanical A d III Sharp pain Thermal-mechanical A d III Burning pain Thermal-mechanical C IV Freezing pain Polymodal C IV slow, burning pain Chemoreceptors C IV Insect venom, histamine Part 2--Small Trigeminal Primary Afferent Pathway Small Trigeminal Primary Afferent Pathway : Small Trigeminal Primary Afferent Pathway Origin - Nociceptors, small trigeminal ganglion cells; Ad and C fibers. Course - Enter trigeminal nerve; descend in spinal trigeminal tract. Laterality – Uncrossed. Topographical Organization – Yes. Separate dermatomes are distributed in segments; most oral are rostral Destination - Spinal trigeminal nucleus. Function - Pain and temperature sensation Dysfunction – Numbness, loss of temp sense Slide 28: 5 1 3 Trigeminal Lemniscus, part 2Pain and Temp Pathway : Trigeminal Lemniscus, part 2Pain and Temp Pathway Origin – Neurons of spinal trigeminal nucleus. Course – Axons cross in spinal cord or medulla and join the trigeminal lemniscus. Laterality - Crossed Topographical Organization - Yes Destination – VPM in thalamus Function - Information from A-delta fibers on fast pain, temp, and innocuous stimuli. Dysfunction – Numbness on opposite face Spino-Reticular Pathway : Spino-Reticular Pathway Origin – Neurons of spinal trigeminal nucleus. Course – Same as trigeminal lemniscus Laterality – Mostly crossed Topographical Organization - Poor Destination – Reticular formation of medulla Function – slow pain Dysfunction – partial analgesia Thalamocortical Pathway : Thalamocortical Pathway Same as for the large afferent pathway. Both go the head and face area of S1. Slide 33: Part 3 – Mesencephalic Trigeminal Afferents Part 3 – Mesencephalic Trigeminal Afferents Mesencephalic Trigeminal Afferents : Mesencephalic Trigeminal Afferents Origin – Ganglion cells in mesencephalon; sensory endings from muscle spindles and golgi tendon organs. Course – Enter trigeminal nerve; ascend in mesencephalic division to midbrain near inferior colliculus where cell bodies are located. Fibers then descend back to pons. Laterality – Uncrossed. Topographical Organization – Organized by muscle group. Destination – Motor nucleus of trigeminal nerve. Function – Muscle stretch and tension; proprioception. Substrate for jaw stretch reflex – myotatic jaw-jerk reflex. Clinical Consideration : Clinical Consideration Wallenberg Syndrome (Lateral Medullary Syndrome) In the medulla, the ascending spinothalamic tract (which carries pain/temperature information from the opposite side of the body) is adjacent to the descending spinal tract of the fifth nerve (which carries pain/temperature information from the same side of the face). A stroke that cuts off the blood supply to this area (e.g., a clot in the posterior inferior cerebellar artery) destroys both tracts simultaneously. The result is loss of pain/temperature sensation (but not touch/position sensation) in a unique “checkerboard” pattern (ipsilateral face, contralateral body) that is entirely diagnostic. Trigeminal Neuralgia : Trigeminal Neuralgia Trigeminal neuralgia (TN), also known as “tic douloureux” (pronounced “tick-doo-la-roo”), is a condition affecting the trigeminal nerve or fifth cranial nerve characterized by sudden attacks of pain to the face, commonly described as sudden, severe, electric-shock-like, or stabbing. Because sufferers of TN may contort their face in pain or become noticeably still during an attack, the disease has sometimes been confused with a seizure disorder, hence the term “tic douloureux” which means “twitching pain.” A patient’s description of the pain and a therapeutic trial of medications are generally the most reliable methods to confirm TN. Peripheral lesions----- : Peripheral lesions----- craniofacial trauma, basilar skull features, dental trauma, maxillary sinusitis, primary or metastatic tumors, aneurysm of the internal carotid artery, cavernous sinus thrombosis, stilbamidine, trichlorethylene, lupus, scleroderma, Sjøgren's syndrome, sarcoidosis, probably amyloidosis, and a fairly common idiopathic benign sensory neuropathy. Horner's syndrome can be produced by lesions of the nasociliary nerve as it runs with the ophthalmic division. Lesions of the ganglion: herpes zoster infection, primary and metastatic tumors. Trigeminal root lesions: adjacent tumors and vascular malformations, especially acoustic neurinoma and cholesteatomas. These lesions are prone to produce facial pain that is often misdiagnosed as tic douloureux or tooth pain. Refrences : Refrences Grays Anatomy Snells Neuroanatomy Grants Anatomy Pocket Atlas of Human Anatomy 4th edition Slide 40: Slide 41: Thanks To ALL : Thanks To ALL

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