Glossopharyngeal Nerve

Glossopharyngeal nerve
Anatomy
Glossopharyngeal nerve, 9th cranial nerve, is a mixed nerve which carries afferent sensory and efferent motor information.
It exists the brainstem from the side of upper medulla, rostral to the vagus nerve. From the anterior portion of the medulla oblongata, it passes laterally across or below the flocculus, and leaves the skull through the central portion of the jugular foramen between internal jugular vein and internal carotid artery. It descends in front of the internal carotid artery and beneath the styloid process to the lower border f stylopharyngeus. It then curves forward, forming an arch on the side of the neck and lying upon the  stylopharyngeus and middle pharyngeal constrictor muscle. It then passes under cover of the hypoglossus muscle, and is finally distributed to the palatine tonsil, the mucous membrane of the fauces and the base of the tongue and the mucous glands of the mouth.
Branches:
1. Tympanic
2. Pharyngeal
3. Tonsillar
4. Carotid
5. Lingual branches
6. Muscular branch to stylopharyngeus
7. Branches to the posterior third of tongue
Glossopharyngeal nerve has following functions:
1. Branchial motor: supplies stylopharyngeus muscle
2. Visceral motor: provides innervations to the parotid gland
3. Visceral sensory: carries information from carotid sinus and carotid body
4. General sensory: skin of external ear, internal surface of the tympanic membrane, upper pharynx and posterior one third of tongue
5. Special sensory: provides taste sensation from posterior one third of tongue.
 
Glossopharyngeal nerve block
Glossopharyngeal nerve innervates oropharynx, soft palate, posterior portion of tongue and pharyngeal surface of epiglottis.
Indications of the block:
• Avoid gag reflex which is stimulated by direct laryngoscopy
• Facilitate nasotracheal intubation by anesthetizing posterior pharyngeal wall
• For pain relief after pediatric tonsillectomy
Source: Bean-Lijewski JD. Glossopharyngeal nerve block for pain relief after pediatric tonsillectomy: retrospective analysis and 2 cases of life threatening upper airway obstruction from an interrupted trail. Anesthesia and Analgesia. June 1997. Vol 84, Issue 6, Page 1232-1238.
• Intraoral nerve block for glossopharyngeal neuralgia.
Source: Sotaro Funasaka, Kazuoki Kodera. Intraoral nerve block for glossopharyngeal neuralgia. Archives of oto-rhino-laryngology. 1977. Vol 215, Issue 3-4, Page 311-315.
• It provides greater comfort and tolerance to the patients undergoing upper gastrointestinal endoscopy.
Source: glossopharyngeal nerve block versus lidocaine spray to improve tolerance in upper gastrointestinal endoscopy. Gastroenterology Research and Practice. Volume 2013 (2013). Article ID 264509, 4 pages
• Palliation of post tonsillectomy pain.
Source: Park, Hee Pyoung, Hwang Jung-won, Park, Sang-Hyun, Jeon, Young-Tae, Bahk, Jae-Hyon, Oh, Yong-Seok. The effects of glossopharyngeal nerve block on post operative pain relief after tonsillectomy: the importance of the extent of obtunded gag reflex as a clinical indicator. Anesthesia and Analgesia. July 2007. Vol 105, Issue 1, Page 267-271.
• Relief of chronic refractory hiccups
Source: Babacan A, Ozturk E, Kaya K. Relief of chronic refractory hiccups with glossopharyngeal nerve block. Anesth Analg 1998 Oct; 87(4): 980
• Management of exaggerated gagging in prosthodontic patients.
Source: Murthy V, Yuvraj V, Nair PP, Thomas S, Krishna A, Cyriac S. Management of exaggerated gagging in prosthodontic patients using glossopharyngeal nerve block. BMJ Case Rep. 2011 Aug 31; 2011.
It can be blocked by 2 approaches:
1. Intraoral approach
• Mouth is opened and tongue is anesthetized by topical anesthesia
• Palatopharyngeal fold (posterior tonsillar pillar) is identified and a tongue blade is introduced into the mouth to displace the tongue to the contralateral side creating a gutter between tongue and teeth
• A 22 G needle is inserted into the membrane near the floor of the mouth at the base of cul-de-sac and advanced slightly
• After aspiration test, 2 ml of 1% lidocaine is injected into the anterior tonsillar pillar 0.5 cm lateral to the base of tongue
 
2. Peristyloid approach
• The patient is placed supine and a line is drawn between the angle of mandible and the mastoid process
• Using deep pressure, the styloid process is palpated just posterior to the angle of jaw along this line
• A short, small gauge needle is seated against the styloid process
• The needle is then withdrawn slightly and directed posteriorly off the styloid process
• 5-7 ml of local anesthetic is injected after careful aspiration for blood.
Laryngoscope is used as an aid in performing intraoral glossopharyngeal nerve block.
Source: Atlas G, Sifonios A, Otero J. Use of a laryngoscope, held sideways, as an aid in performing an intraoral glossopharyngeal nerve block. J Anesthiol Clin Pharmacol 2013 Jan; 29(1): 129-30.
Glossopharyngeal nerve block under ultrasound guidance
This will decrease complications and increase the efficacy of block for pain relief in cancer patients.
Source: MD Bedder, D Lindsay. Glossopharyngeal nerve block using ultrasound guidance: a case report of new technique. Regional anesthesia 01/1989; 14(6): 304-7.
 
Complications
• Hematoma
• Intravascular injection of local anesthetic
• Blockade of motor function can lead to dysphagia from weakness of stylopharyngeus muscle
• Systemic toxicity: topical anesthetic enter the circulation when injected into the tissues and can be absorbed in the respiratory and GI tract.
• Methemoglobinemia: can lead to cyanosis, stupor, coma and death
• Inadvertent blockade of hypoglossal and spinal accessory nerve during glossopharyngeal nerve block results in weakness of tongue.
• Life threatening upper airway obstruction.
Source: Sher MH, Laing DI, Brands E. Life threatening upper airway obstruction after glossopharyngeal nerve block: possibly due to an inappropriately large dose of bupivacaine?. Anesth Analg. 1998 Mar; 86(3): 678.