This is “Advance Publication Article” Kurume Medical Journal, 65, 1-5, 2018 Review Article Clinical Anatomy of Blockade of the Pterygopalatine Ganglion: Literature Review and Pictorial Tour Using Cadaveric Images JOE IWANAGA*, **, CHARLOTTE WILSON*, EMILY SIMONDS*, MARC VETTER*, CAMERON SCHMIDT*, EMRE YILMAZ†, PAUL J. CHOI*, ROD J. OSKOUIAN*, † AND R. SHANE TUBBS*, ‡ *Seattle Science Foundation, Seattle, WA 98122 USA, **Division of Gross and Clinical Anatomy, Department of Anatomy, Kurume University School of Medicine, Kurume 830-0011 Japan, †Swedish Neuroscience Institute, Swedish Medical Center, Seattle WA 98122 USA, ‡Department of Anatomical Sciences, St. George’s University, St. George’s, Grenada, West Indies Received 28 November 2017, accepted 18 February 2018 J-STAGE advance publication 30 August 2018 Edited by TETSUSHI FUKUSHIGE Summary: Pterygopalatine ganglion block (sphenopalatine ganglion block) is a well-known procedure for treating cluster headache and for relieving cancer pain. In this review, the history and anatomy of the pterygopala- tine ganglion are discussed, and images, including computed tomography and endoscopy, are presented to improve understanding of the clinical anatomy of the ganglion regarding the block procedure. Key words cluster headache, pterygopalatine ganglion block, sphenopalatine ganglion block, anatomy, cadaver ing difficult. Our aim is to review the anatomy of the INTRODUCTION PPG and clarify the correct needle trajectory towards Pterygopalatine ganglion (PPG) block, which is also the SPF required to reach the PPF, with anatomical doc- known clinically as sphenopalatine ganglion block, is umentation and cadaveric dissection, to improve un- a well-known procedure for treating cluster headache derstanding of the PPG block procedure. and for relieving cancer pain, and as such it can have a great influence on patients’ quality of life. Sluder [1] is HISTORY OF PPG: recognized as the first physician to block the PPG with FROM MECKEL TO SLUDER a transnasal approach in 1908. Ruskin [2] reviewed the remote effects of blocking the PPG and reported its PPG was first described in 1749 by Johann Friedrich efficacy for headaches, facial neuralgias, low back Meckel, who eponymously named it Meckelii majus pain, temporomandibular joint dysfunction, and even [8, 9]. Meckel contemplated the functions of the gan- hiccups. Subsequently, the classic and modified tech- glia, suggesting they increased the number of nerve niques and related anatomy have been well documented branches by subdividing small nerves, projected nerves in numerous clinical studies [3-5] and reviews [6, 7]. in multiple directions, and bundled smaller nerves into Because of the anatomical complexity of the pterygo- larger ones [8]. palatine fossa (PPF) and sphenopalatine foramen (SPF), In 1909, Sluder noted the close relationship be- depiction and clarification of the needle trajectory for tween the PPG and the external bony wall of the nose PPG blockade has been challenging. Changes in ter- [10, 11]. He also noted that the PPG was related to pain minology regarding PPG have also made understand- at the root of the nose, in and around the eye, the upper Corresponding Author: Joe Iwanaga, Seattle Science Foundation, 550 17th Ave, James Tower, Suite 600, Seattle, WA 98122, USA. Tel: +1-206-732-6500, Fax: +1-206-732-6599, E-mail: [email protected] Abbreviations: PPF, pterygopalatine fossa; PPG, Pterygopalatine ganglion; SPF, sphenopalatine foramen. 2 IWANAGA ET AL. and lower teeth, the maxilla and mandible, the ear, oc- Typically, two nerve branches connect the maxil- ciput and neck, shoulder, axilla, and the entire arm [10]. lary nerve to the PPG [17, 19]; however, these sensory This was the earliest description of what are now known branches pass through the ganglion without synapsing as cluster headaches. [15, 20, 21]. Pre-ganglionic parasympathetic fi bers of Sluder [1, 12] suggested a procedure that involved the PPG run fi rst in the greater petrosal branch of the applying cocaine just posterior to the posterior tip of facial nerve, having originated in the superior salivatory the middle turbinate over the ganglion. He also experi- nucleus as the nervus intermedius, and then reach the mented with 2% silver and 0.5% formaldehyde solu- nerve of the pterygoid canal. The deep petrosal nerve tions. In 1913, he reported a treatment that included is given off from the internal carotid plexus and carries phenol-alcohol injections into the region of the sphe- post-ganglionic sympathetic fi bers to the PPG through nopalatine foramen [12, 13]. These were the fi rst ac- counts of any procedure intended to alleviate pain as- sociated with what were fi rst described as “nasal headaches” [1]. ANATOMY OF THE PPG The PPG is the largest peripheral parasympathetic ganglia and is triangular in shape [14, 15]. It is located deep within the PPF and lies lateral to the SPF and below and slightly medial to the foramen rotundum and the maxillary nerve [15] (Figs. 1 and 2). The dimensions and variability of the SPF are clini- cally signifi cant in the procedure discussed herein. The foramen lies on the lateral nasal wall and can be oval, square, triangular, or piriform [16]. The average hori- Fig. 2. Location of the sphenopalatine foramen (circle). zontal diameter is 5.1 mm (range: 4-7 mm) and the av- IC; inferior nasal concha, MC; middle nasal concha, SS; erage vertical diameter 6.2 mm (4.5-7.5 mm) [16-18]. sphenoidal sinus Fig. 1. Anatomy of the pterygopalatine fossa (light blue triangles). Note the pterygopalatine fossa is continuous with the foramen rotundum (arrowhead) and pterygoid canal (vidian nerve) (blue arrows). A: Sagittal CT section of the nasal cavity B: Sagittal CT section of the maxillary sinus C: Cadaveric dissection of the pterygopalatine fossa (surrounding bone removed) IC; inferior nasal concha, MS; maxillary sinus Kurume Medical Journal Vol. 65, No. 1 2018 CLINICAL ANATOMY PTERYGOPALATINE GANGLION 3 the pterygoid canal (vidian nerve) [15, 19]. mediate vicinity. The zygomatic arch serves as a paral- The pre-ganglionic fi bers synapse with post-gan- lel reference to the middle nasal concha [26], although glionic fi bers within the ganglion, and the latter travel it is not always a reliable landmark. Nose abnormali- along the trigeminal nerve branches, providing both ties such as deviation of the nasal septum can make vasomotor function to the surrounding vascular struc- this route diffi cult, uncertain, and sometimes danger- tures and secretomotor function to the nasal mucosa ous [27]. and lacrimal glands [19, 22]. The increased risk of nasal mucosa injury during The PPG gives rise to the nasopalatine nerve, the needle insertion led to the development of the transna- greater and lesser palatine nerves, the posterior superior sal endoscopic technique for needle insertion under and inferior lateral nasal branches and the pharyngeal direct vision using a rigid sinuscope (Fig. 3). Transnasal branch of the maxillary nerve [19, 21]. Small orbital endoscopic needle insertion was fi rst described in branches also arise from it [23, 24. The greater palatine 1993 by Prasanna and Murthy [28] focusing on the nerve supplies general sensation to the hard palate, postero-superior aspect of the middle nasal concha gingiva, and mucosa of the buccal cavity; the lesser (Fig. 4). Felisati et al. [29] approached the PPF using palatine nerve supplies sensation to the uvula, tonsils, endoscopy via the lateral nasal wall between the mid- and soft palate [19]. dle and inferior nasal concha (Fig. 5). At the posterior edge of the middle nasal concha there is a sharp crest called the ethmoidal crest. The NEEDLE TRAJECTORY OF THE PPG BLOCK- sphenopalatine foramen is located immediately behind ADE USING CADAVERIC IMAGES it and is oriented at an angle of 15 to 20 degrees in the An intranasal PPG blockade procedure allows the sagittal plane, or is located just behind or slightly above needle to approach the PPF relatively easily. Cocaine the attachment of the posterior edge of the middle na- and lidocaine are usually placed on the nasopharyn- sal concha and at the junction of the superior and lat- geal mucosa just posterior to the middle nasal concha eral nasal walls, 12 mm superior and lateral to the su- with a cotton-tipped applicator. According to Sluder perior border of the choana [30]. The superior nasal [11, 25], a straight needle goes through the nostril pos- concha acts as a landmark for the sphenopalatine fora- teriorly, superiorly and slightly laterally, approaching men located posterior and superior to the middle nasal the lateral wall of the nasal cavity in the middle nasal concha. A valid landmark is the constant convergence meatus marked by the origin of the posterior edge of the of some of the vessels of the lateral wall towards the bony middle nasal concha, and arrives almost immedi- sphenopalatine foramen due to the disappearance of ately on the anterior wall of the PPF. Its point is then vessels into the foramen. This point is called ‘the van- pushed backward 0.66 cm to enter the PPG or its im- ishing point [31]. The ganglion is covered with a 1-5 Fig. 3. Transnasal endoscopic observation. A: Inferior nasal concha B: Middle nasal concha IC; inferior nasal concha, MC; middle nasal concha, S; nasal septum Kurume Medical Journal Vol. 65, No. 1 2018 4 IWANAGA ET AL. Fig. 4. Transnasal endoscopic needle insertion. A: The needle pierces the mucosa postero-superior to the middle nasal concha B: Lateral view fluoroscopy. Note the tip of the needle reaches the pterygopalatine fossa (arrow) MC; middle nasal concha, SC superior nasal concha Fig. 5. Needle piercing the lateral nasal wall between the middle and inferior nasal conchae to reach the sphenopalatine foramen (arrow). A: before removing mucosa B: without mucosa IC; inferior nasal concha, MC; middle nasal concha, SC superior nasal concha, SS; sphenoidal sinus mm layer of connective tissue and mucous membrane [32].