Greater superficial petrosal nerve dissection: back to front or front to back?

OBJECTIVE: To introduce a novel surgical technique for the dissection of the greater superficial petrosal nerve (GSPN) in the middle fossa approach. METHODS: Interdural temporal elevation was performed with a front-to-back technique to preserve the GSPN in 12 sides of 6 injected cadaveric heads dissected through a middle fossa approach. RESULTS: The GSPN emerged from the facial hiatus in a shallow bony groove proximally, ran into a deeper sphenopetrosal groove, and eventually reached the mandibular nerve. With front-to-back dissection, this nerve was easily identified at the posterior border of the mandibular nerve. Dissection from front to back minimized the retraction force applied to the proximal part of the GSPN, which was preserved in all specimens. CONCLUSION: The temporal dura can be elevated safely with a front-to-back technique to preserve the GSPN and to help maintain the physiological integrity of the facial nerve.

Endoscopic anatomy of the pterygopalatine fossa and the transpterygoid approach: development of a surgical instruction model.

INTRODUCTION: The pterygopalatine fossa (PPF) is a narrow space located between the posterior wall of the antrum and the pterygoid plates. Surgical access to the PPF is difficult because of its protected position and its complex neurovascular anatomy. Endonasal approaches using rod lens endoscopes, however, provide better visualization of this area and are associated with less morbidity than external approaches. Our aim was to develop a simple anatomical model using cadaveric specimens injected with intravascular colored silicone to demonstrate the endoscopic anatomy of the PPF. This model could be used for surgical instruction of the transpterygoid approach. METHODS: We dissected six PPF in three cadaveric specimens prepared with intravascular injection of colored material using two different injection techniques. An endoscopic endonasal approach, including a wide nasoantral window and removal of the posterior antrum wall, provided access to the PPF. RESULTS: We produced our best anatomical model injecting colored silicone via the common carotid artery. We found that, using an endoscopic approach, a retrograde dissection of the sphenopalatine artery helped to identify the internal maxillary artery (IMA) and its branches. Neural structures were identified deeper to the vascular elements. Notable anatomical landmarks for the endoscopic surgeon are the vidian nerve and its canal that leads to the petrous portion of the internal carotid artery (ICA), and the foramen rotundum, and V2 that leads to Meckel's cave in the middle cranial fossa. These two nerves, vidian and V2, are separated by a pyramidal shaped bone and its apex marks the ICA. CONCLUSION: Our anatomical model provides the means to learn the endoscopic anatomy of the PPF and may be used for the simulation of surgical techniques. An endoscopic endonasal approach provides adequate exposure to all anatomical structures within the PPF. These structures may be used as landmarks to identify and control deeper neurovascular structures. The significance is that an anatomical model facilitates learning the surgical anatomy and the acquisition of surgical skills. A dissection superficial to the vascular structures preserves the neural elements. These nerves and their bony foramina, such as the vidian nerve and V2, are critical anatomical landmarks to identify and control the ICA at the skull base.

A comparative study of three cranial sensory ganglia projecting into the oral cavity: in situ hybridization analyses of neurotrophin receptors and thermosensitive cation channels.

Peripheral cranial sensory nerves projecting into the oral cavity receive food intake stimuli and transmit sensory signals to the central nervous system. To describe and compare the features of the cranial sensory ganglia that innervate the oral cavity, i.e., the trigeminal, petrosal, and geniculate ganglia (TG, PG, and GG, respectively), in situ hybridization was conducted using riboprobes for neurotrophin receptors (TrkA, TrkB, and TrkC), a neurotransmitter (substance P), and ion channels important for thermosensation (VR1 and TREK-1). In TG, all in six probes yielded positive signals to various extent in intensity and frequency. In addition, a strong correlation between the expression of VR1 and those of TrkA and substance P was observed as in the case of the dorsal root ganglia. In PG, positive signals to all six probes were also detected, and the correlation of expression was similar to that shown by TG. On the other hand, most cells in GG were positive to the TrkB probe, and a small number of cells were positive to the TrkC probe, but no significant signal was observed for the other four probes. These results indicate that TG and PG consist of cells that are heterogeneous in terms of neurotrophin requirement and somatosensory functions, and that GG seems to consist mainly of a homogeneous cell type, gustatory neurons. In conclusion, TG, PG, and GG, show gene expression characteristics intrinsic to the three ganglia. It is also concluded that TG and a portion of PG project several types of somatosensory nerves. This is consistent with the finding that GG and a portion of PG project gustatory nerves.

Actualidades en: Anatomia: Nervio maxilar II / Updates in anatomy: the maxillary nerve II

El ganglio pterigopalatino (esfenopalatino), es el mayor de los ganglios periféricos del sistema parasimpático. Se sitúa profundamente en la fosa pterigopalatina, junto al forámen esfenopalatino y por delante del conducto vidiano. Es ligeramente aplanado, de aspecto rojo grisáceo, y se localiza inmediatamente por debajo del nervio maxilar, donde éste cruza la fosa. Aun cuando está conectado funcionalmente con el nervio facial (VII par). Topográficamente establece relaciones íntimas con el nervio maxilar y sus ramos. La raíz motora o parasimpática la forma el nervio vidiano, que penetra posteriormente en el ganglio. Se cree que sus fibras proceden de un núcleo lagrimal especial, en la porción inferior de la protuberancia, y corren por la raiz sensitiva del facial (nervio intermediario de Wrisberg), y su ramo petroso superficial mayor antes de que éste se una con el petroso profundo para formar el nervio vidiano. Estas fibras preganglionares hacen escala en el ganglio y las fibras postganglionares siguen un curso complicado hasta alcanzar su destino. Dejando el ganglio por uno de los ramos ganglionares, se anastomosan con el maxilar y pasan a su ramo orbitario. Desde aquí siguen generalmente por el nervio cigomaticotemporal y posteriormente parten por el anastomótico, por el que se conectan con el nervio lagrimal. Alcanzan así la glándula lagrimal, inervándola con fibras secretomotoras. Además, a las glándulas paltinas, faríngeas y nasales llegan fibras secretomotoras, de origen dudoso. Se cree que siguen una vía similar hasta su llegada al ganglio, donde hacen escala. Sus fibras posganglionares corren por los ramos palatinos y nasales del ganglio.

Anatomic study of the otic ganglion in humans.

The presentation in the literature of the anatomy of the human otic ganglion (OG) has not varied much over the past three quarters of a century. Precise, similar descriptions of its size, color, shape, and relation with neighboring structures are portrayed in numerous textbooks and articles. We have carried out a study of the OG in 30 infratemporal fossae of 15 cadavers. Otic ganglia resembling the classic description were found in less than 60% of the cases. In 13%, some thickening could be seen adjacent to the mandibular nerve and in 27%, no definite structure could be observed. Except for a fleeting mention of this occurrence in a textbook from 1927, substantiated by personal communication with an authority in the field, we could find no record of the possible absence of this structure in the available literature. We describe our findings and stress the apparent anatomic variability of the OG. The pertinent literature is reviewed.