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ORIGINAL ARTICLE Clinical anatomy of greater petrosal nerve and its surgical importance
Prashant E Natekar, Fatima M De Souza Department of Anatomy, Goa Medical College, Bambolim, Goa, India
Background: Surgical approach towards greater petrosal nerve has to be done with caution as many surgeons Abstract are unfamiliar with the anatomy of the facial nerve. The anatomical landmarks selected must be reliable and above all easy to identify for identification of the greater petrosal nerve so as to avoid injury to the structures in the middle cranial fossa. Observation and Results: The present study is carried out on 100 temporal bones by examining the following measurements of the right and the left sides a) length of the hiatus for grater petrosal superficial nerve b) distance from superior petrosal sinus c) distance from lateral margin of middle cranial fossa d) arcuate eminence and e) distance from exit to the foramen ovale. Conclusion: The anatomical landmarks selected must be reliable and above all easy to identify. Bony structures are more suitable than soft tissue or cartilaginous landmarks because of their rigid and reliable location. These anatomical landmarks will definitely help the surgeon while performing vidian nerve neurectomy and also the anatomical relationship of the facial nerve in temporal bone. The middle fossa approach involves a temporal craniotomy in cases of perineural spread of adenoid cystic carcinomas hence these anatomical landmarks will serve as useful guide for the surgeons and radiologists.
Keywords: Foramen lacerum, Greater petrosal nerve, Middle cranial fossa, Superior petrosal sinus, Vidian nerve
Introduction ascending sphenoidal branch from otic ganglion. The vidian nerve exits its bony canal in the pterygopalatine fossa where The greater petrosal nerve is a branch of facial nerve which it joins the pterygopalatine ganglion. The postganglionic innervates the lacrimal gland, mucous membrane of the nasal parasympathetic fibers are distributed to the lacrimal gland cavity and palate. The fibers that form the greater petrosal and mucous membrane of the nose and palate providing nerve originate from the lower part of the pons. This nerve is secretory and vasomotor innervation. Surgical approach a mixed nerve containing both sensory and parasympathetic. toward greater superficial petrosal nerve has to be done with The bulks are sensory and are contained in the main facial caution as many surgeons are unfamiliar with the anatomy of nerve trunk. The parasympathetic fibers exit the brain stem this nerve. The present study is essential as bony structures are as a part of a separate division of the seventh nerve known as rigid and more suitable as anatomical guides so as to assess the nervous intermedius. At the geniculate ganglion, the greater anatomical relationship of the length of greater petrosal nerve, petrosal nerve breaks away and courses anteromedially to distance from superior petrosal sinus, distance from lateral exit the superior surface of the temporal bone via hiatus margin of middle cranial fossa, from arcuate eminence, and for the greater petrosal nerve. The nerve then continues its distance from exit to the foramen spinosum. anteromedially and slightly inferiorly and passes under Meckel’s cave toward the foramen lacerum, at which point it Since this nerve is mostly being unrecognized without a joins the deep petrosal nerve from the carotid sympathetic tailored high resolution approach, its anatomical knowledge plexus together forming the vidian nerve by post synaptic is essential preoperatively wherein the surgical approach can parasympathetic fibers and presynaptic sympathetic fibers.[1] This is also known as the “Nerve of pterygoid canal.” Nerves Access this article online that get involved in the formation of vidian nerve are greater Quick Response Code: Website: petrosal nerve (preganglionic parasympathetic fibers), deep www.indianjotol.org petrosal nerve (postganglionic sympathetic fibers), and
Address for correspondence: Dr. Prashant E Natekar, DOI: Department of Anatomy, Goa Medical College, Bambolim, Goa, India. 10.4103/0971-7749.108157 E-mail: [email protected]
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Natekar and De Souza: Clinical anatomy of greater petrosal nerve and its surgical importanc
be individually tailored minimizing the risk during surgical From this area, it passes forward through the pterygoid canal interventions. accompanied by artery of pterygoid canal.
Materials and Methods Vasomotor rhinitis is a condition characterized by profuse rhinorrhea and sneezing, with or without nasal obstruction, The present study is carried out on 100 temporal bones (dried occurring in attacks which may be either paroxysmal or and cadaveric) from the department of anatomy at Goa perennial. The running of the nose and sneezing may be so Medical College Bambolim, Goa, India, by examining the severe as to even disable the patient. hiatus for the greater petrosal nerve of the right and the left sides of both the sexes. Each hiatus was carefully examined and Studies showed conclusively that stimulation of the its relation to the following important anatomical landmarks parasympathetic or interruption of the sympathetic nerve was measured in millimeters of both the sides. supply to the nasal mucous membrane caused vasodilatation, [4] 1. Length of the hiatus for the greater petrosal nerve (a) to (b) hypersecretion, and sneezing. These anatomical landmarks 2. Distance from superior petrosal sinus (c) to hiatus for the will definitely help the surgeon while performing vidian nerve greater petrosal nerve (d) neurectomy. 3. Distance from lateral margin of middle cranial fossa (e) to hiatus for the greater petrosal nerve (d) The anatomical relationship of the facial nerve in temporal [5,6] 4. Distance from arcuate eminence (f) to hiatus for the greater bone is well known in surgical anatomy. Although no petrosal nerve (d) much study is being done regarding the bony anatomical 5. Distance from exit of hiatus for greater petrosal nerve (b) landmarks, earlier study has revealed the distance from IAM [7] to the foramen spinosum (g). to its neighboring normal anatomical structures. Greater petrosal nerve is visible on MR in healthy subjects if it is sought [8-10] Observations and Results if the radiologist is familiar with the anatomy.
From the above table, our present study reveals the distance In our present study, we have measured the length of greater in millimeters like length of the hiatus for greater petrosal petrosal nerve, distance from superior petrosal sinus, distance nerve, distance between the hiatus for greater petrosal nerve from lateral margin of middle cranial fossa, from arcuate to superior petrosal sinus, lateral margin of middle cranial eminence and its distance from exit to the foramen spinosum. fossa, arcuate eminence, and foramen spinosum. When our data were analyzed, it was found that the length of the hiatus for greater petrosal nerve was 24 mm, distance between the hiatus for greater petrosal nerve to superior petrosal sinus was 13 mm, distance from lateral margin of middle cranial fossa to the hiatus was 25 mm, distance from arcuate eminence to the hiatus for the greater petrosal nerve was 19 mm, and distance from exit of hiatus for greater petrosal nerve to the foramen spinosum was 13 mm. Our finding shows the difference in the above parameters when compared to the findings of Tubbs et al[2] as shown in Table 1, Figure 1.
Discussion
Bony structures are more suitable than soft tissue or cartilaginous landmarks because of their rigid and reliable [3] Figure 1: Left temporal bone showing length of hiatus for greater location. Vidian nerve is formed at the junction of greater petrosal nerve (a) to (b), superior petrosal sinus (c) midpoint of hiatus petrosal and deep petrosal nerves. This area is located in the for greater petrosal nerve (d) lateral margin of middle cranial fossa (e) cartilaginous substance which fills the foramen lacerum. arcuate eminence (f) and foramen spinosum (g)
Table 1: Distance from hiatus for greater petrosal nerve to its important anatomical landmarks Anatomical landmarks and measurements in mm Present study Studies by Tubbs[2] et al. Length of the hiatus for the greater petrosal nerve (a) to (b) 24 10 Distance from superior petrosal sinus (c) to middle of hiatus for the greater petrosal nerve (d) 13 – Distance from lateral margin of middle cranial fossa (e) to middle of hiatus for the greater petrosal nerve (d) 25 39 Distance from arcuate eminence (f) to hiatus for the greater petrosal nerve (d) 19 17.5 Distance from exit of hiatus for greater petrosal nerve (b) to the foramen spinosum (g) 13 7
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Natekar and De Souza: Clinical anatomy of greater petrosal nerve and its surgical importanc
The middle fossa approach involves a temporal craniotomy 2001;115:122-5. in cases of perineural spread of adenoid cystic carcinomas; 4. Malcomson KG. The vasomotor activities of the nasal mucous hence, these anatomical landmarks will serve as useful guide membrane. J Laryngol Otol 1959;73:73-98. 5. Donaldson J, Ducker L, Lambert P, Rubel E. Surgical anatomy of for the surgeons and radiologists. temporal bone. 4th ed. New York: Raven Press; 1962. 6. Schuknecht HF, Gulya J. Anatomy of the temporal bone with There may be variations in the distances from the landmarks surgical implications. Philadelphia: Lea and Febiger; 1986. in living as per the body compositions as this study was 7. Natekar PE, De Souza FM. Anatomical landmarks: A surgical performed on fixed cadaver material and the same needs aid for identification of facial nerve to internal acoustic meatus. to be studied in vivo as thorough knowledge of the distance Indian J Otol 2011;17:117-9. between the hiatus for greater petrosal nerve to important 8. Liu DP, Lo WM. Imaging of temporal bone. In: Som PM, Bergeron anatomical landmarks is basic and very important to RT, editors. Head and Neck Imaging. St. Louis Mo: Mosby; 1991. p. 944-59. the surgeons and radiologists before and during surgical 9. Gebarski SS, Telian SA, Niparko JK. Enhancement along the intervention. normal facial nerve in facial canal: MR imaging and anatomical correlation. Radiology 1992;183:391-4. References 10. Tien R, Dillon WP, Jackler RK. Contrast MR imaging of facial nerve in 11 patients with Bell’s palsy. AJNR Am J Neuroradiol 1. Susan S. Clinically oriented anatomy. 6th ed. Churchill Livingstone 1990;11:735-41. London: Lippincort Williams and Wilkins; 2010. p. 977. 2. Tubbs SR, Curtis JW, E Geroge S, Sheetz J, Zehren S. Landmarks How to cite this article: Natekar PE, De Souza FM. Clinical for the greater petrosal nerve. Clinical anatomy 2005;18:210-4. anatomy of greater petrosal nerve and its surgical importance. Indian 3. du Ru JA, van Benthem PP, Bleys RL, Lubsen H, Hordijk GJ. J Otol 2013;19:20-2. Landmarks for parotid gland surgery. J Laryngol Otol Source of Support: Nil. Conflict of Interest: None.
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