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VAGUS NERVE AND ITS DESORDERS AND TREATMENT

VAGUS NERVE AND ITS DESORDERS AND TREATMENT

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VAGUS NERVE AND ITS DESORDERS AND TREATMENT

  1. 1.  Is the tenth cranial nerve or CN X  Interfaces with parasympathetic control of the heart, lungs and digestive tract  It is the longest nerve of the autonomic nervous system in the human body.  vagus nerve has two ganglia 1.Superior ganglion - round and lies in the jugular foramen 2.inferior ganglion - cylindrical and lies near the base of skull
  2. 2.  vagus nerve includes axons which emerge from or converge onto four nuclei of the medulla: The dorsal nucleus of vagus nerve — which sends parasympathetic output to the viscera, especially the intestines The nucleus ambiguus — which gives rise to the branchial efferent motor fibers of the vagus nerve and preganglionic parasympathetic neurons that innervate the heart The solitary nucleus — which receives afferent taste information and primary afferents from visceral organs The spinal trigeminal nucleus — which receives information about deep/crude touch, pain, and temperature of the outer ear, the dura of the posterior cranial fossa and the mucosa of the larynx
  3. 3.  vagus nerve leaving the medulla oblongata between the pyramid and the inferior cerebellar peduncle, the vagus nerve extends through the jugular foramen, then passes into the carotid sheath between the internal carotid artery and the internal jugular vein down to the neck, chest and abdomen, where it contributes to the innervation of the viscera. Besides giving some output to various organs, the vagus nerve comprises between 80% and 90% of afferent nerves mostly conveying sensory information about the state of the body's organs to the central nervous system  The vagus nerves are paired(right/left) 1. right vagus nerve gives rise to the right recurrent laryngeal nerve, which hooks around the right subclavian artery and ascends into the neck between the trachea and esophagus. The right vagus then crosses anterior to the right subclavian artery, runs posterior to the superior vena cava, descends posterior to the right main bronchus, and contributes to cardiac, pulmonary, and esophageal plexuses. It forms the posterior vagal trunk at the lower part of the esophagus and enters the diaphragm through the esophageal hiatus.
  4. 4. 2. The left vagus nerve enters the thorax between left common carotid artery and left subclavian artery and descends on the aortic arch. It gives rise to the left recurrent laryngeal nerve, which hooks around the aortic arch to the left of the ligamentum arteriosum and ascends between the trachea and esophagus. The left vagus further gives off thoracic cardiac branches, breaks up into the pulmonary plexus, continues into the esophageal plexus, and enters the abdomen as the anterior vagal trunk in the esophageal hiatus of the diaphragm.  Pharyngeal nerve  Superior laryngeal nerve  Superior cervical cardiac branches of vagus nerve  Inferior cervical cardiac branch  Recurrent laryngeal nerve  Thoracic cardiac branches  Branches to the pulmonary plexus  Branches to the esophageal plexus  Anterior vagal trunk  Posterior vagal trunk  Hering-Breuer reflex in alveoli
  5. 5. The vagus nerve supplies motor parasympathetic fibres to all the organs except the suprarenal (adrenal) glands, from the neck down to the second segment of the transverse colon. The vagus also controls a few skeletal muscles such as  Cricothyroid muscle  Levator veli palatini muscle  Salpingopharyngeus muscle  Palatoglossus muscle  Palatopharyngeus muscle  Superior, middle and inferior pharyngeal constrictors  Muscles of the larynx (speech)
  6. 6.  vagus nerve is responsible for such varied tasks as heart rate, gastrointestinal peristalsis, sweating, and quite a few muscle movements in the mouth, including speech (via the recurrent laryngeal nerve).  It also has some afferent fibers that innervate the inner (canal) portion of the outer ear (via the auricular branch, also known as Alderman's nerve) and part of the meninges  (This is the reason why a person may cough when tickled on the ear, such as when trying to remove ear wax with a cotton swab) Efferent vagus nerve fibres innervating the pharynx and back of the throat are responsible for the gag reflex. In addition, 5-HT3 receptor-mediated afferent vagus stimulation in the gut due to gastroenteritis and other insults is a cause of vomiting
  7. 7. • General visceral efferent (GVE) — provides parasympathetic innervation to glands of mucous membranes of the pharynx, larynx, organs in the neck, thorax, and abdomen. • Special visceral efferent (SVE) — innervates skeletal muscles of the pharynx and larynx. • General somatic afferent (GSA) — carries sensation from the external auditory meatus and tympanic membrane. • General visceral afferent (GVA) — carries information from the thoracic and abdominal viscera; aortic body and arch. • Special visceral afferent (SVA) — carries taste of the epiglottis region of the tongue.
  8. 8. Parasympathetic innervation of the heart is partially controlled by the vagus nerve and is shared by the thoracic ganglia  vagal and spinal ganglionic nerves mediate the lowering of the heart rate. right vagus branch innervates the sinoatrial node. Parasympathetic tone from these sources are obviously well matched to sympathetic tone in healthy people Hyperstimulation of parasympathetic influence promotes bradyarrhythmias hyperstimulated, the left vagal branch predisposes the heart to conduction block at the atrioventricular node.
  9. 9.  Activation of the vagus nerve typically leads to a reduction in heart rate, blood pressure, or both. This occurs commonly in the setting of gastrointestinal illness such as viral gastroenteritis or acute cholecystitis, or in response to other stimuli, including carotid sinus massage, Valsalva maneuver or pain from any cause, in particular, having blood drawn.  Activation of the vagus nerve typically leads to a reduction in heart rate, blood pressure, or both. This occurs commonly in the setting of gastrointestinal illness such as viral gastroenteritis or acute cholecystitis, or in response to other stimuli, including carotid sinus massage, Valsalva maneuver or pain from any cause, in particular, having blood drawn.  Symptoms of irritable Bowel Syndrome are thought to cause activation of the vagus nerve with many people reporting fainting, vision disturbances and dizziness
  10. 10. Excessive activation of the vagal nerve during emotional stress, which is a parasympathetic overcompensation of a strong sympathetic nervous system response associated with stress, can also cause vasovagal syncope due to a sudden drop in cardiac output, causing cerebral hypoperfusion. Vasovagal syncope affects young children and women more than other groups. It can also lead to temporary loss of bladder control under moments of extreme fear 1. Pain - most common nerve pain symptoms are due to pinched nerve (when nerve exits through tiny foramina in the skull). 2. Organ Dysfunction - a branch or tributary of nerve is affected that leads to localized symptoms of organ dysfunction due to damage to nerve fibers or discrepancy in the synthesis of neurotransmitters.
  11. 11. 3. Muscle Cramps - painfull and involuntary muscular contraction 4. Difficulty in Swallowing - Glottis is normally closed when a person is swallowing in order to prevent the aspiration of food. This is managed by gag - reflex (gagging sensation if the back of throat is touched). In patients of head injury or stroke, gag reflex may get impaired leading to choking while eating and difficulty in swallowing. 5. Peptic Ulcer - Defects in the normal functioning of Vagus nerve may impair the normal control mechanisms that modulate the gastric acid secretion. Excessive secretion of peptic acid can lead to ulceration, dyspepsia and gastro- esophageal reflux disease. 6. Gastroparesis - under-activity of vagus nerve may interfere with the blood supply of stomach after ingestion of food that leads to improper digestion. Gastroparesis is marked by painful spasms in the stomach that affect normal food intake, heartburn, nausea and weight loss.
  12. 12. 7. Fainting - Over-activity of Vagus nerve increases the firing rate of receptors that presents with sudden episodes of collapse and fainting (also referred to as vasovagal reflex). Although, it is not dangerous, but fainting episodes may increase the risk of accidental injuries that may prove life threatening. 8. Other Symptoms - Other symptoms include changes in the rhythm of heart, urinary difficulties and changes in vocal tone.  Nerves are protected by myelin sheaths that serve to prevent the delicate nerve fibers from damage and destruction; however, aberrations in normal biochemical environment due to excessive alcoholism or persistently raised blood sugar levels can lead to swelling of myelin sheaths that lead to permanent destruction of nerve fibers leading to inactivity of nerves. Other causes includes inflammatory disorders, autoimmune destruction of nerves (in the setting of diseases like amyotrophic lateral sclerosis, multiple sclerosis and other), viral infections and damage due to neoplastic conditions that press upon nerves causing mechanical damage.
  13. 13.  Ask person to swallow  Ask person to say ah-h-h to check movement of the plate uvula  Back of the throat may be touched with a tounge blade which evokes the gag reflexin most peoples  Person is asked to speak to determine whether the voice sounds nasal (for palate movement)
  14. 14. 1. Vagus Nerve Stimulation - Vagal nerve stimulation can be achieved by a device (similar in activity to cardiac pacemaker) that is implanted beneath the skin and helps in generating impulses that can help in managing symptoms of depression and seizures. 2. Neck Extension Exercises - Often times, pressure in the tendons or tense muscles can press upon vagus nerve that may lead to hyper or hypoactivity of nerves. 3- Dimensional exercises like neck extension (moving your chin away from chest as far as possible), neck flexion (touching your chin with your chest) and neck retraction exercises can help in decreasing pressure on nerve.
  15. 15. 3. Yoga 4. For Gastroparesis - In order to manage symptoms of Gastroparesis and reduce the risk of severe malnutrition, healthcare providers suggest the use of feeding tube that supply the nutrients directly to intestines without crossing stomach. In order to reduce the symptoms of nausea and vomiting, medications like ondansetron can be employed. Metoclopramide is usually reserved for severe cases 5. For Fainting - Different medications are employed to manage the fainting episodes (that mostly involve controlling vasovagal discharge). Sertraline or paroxetine are currently the treatment of choice for such cases.

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