Radioanatomic Assessment of the Geniculate Ganglion Dehiscence and Dimension: A Cadaveric Study

Identification of cranial nerve ganglia using sectioned images and three-dimensional models of a cadaver

Background

Cranial nerve ganglia, which are prone to viral infections and tumors, are located deep in the head, so their detailed anatomy is difficult to understand using conventional cadaver dissection. For locating the small ganglia in medical images, their sectional anatomy should be learned by medical students and doctors. The purpose of this study is to elucidate cranial ganglia anatomy using sectioned images and three-dimensional (3D) models of a cadaver.

Methods

One thousand two hundred and forty-six sectioned images of a male cadaver were examined to identify the cranial nerve ganglia. Using the real color sectioned images, real color volume model having a voxel size of 0.4 × 0.4 × 0.4 mm was produced.

Results

The sectioned images and 3D models can be downloaded for free from a webpage, anatomy.dongguk.ac.kr/ganglia. On the images and model, all the cranial nerve ganglia and their whole course were identified. In case of the facial nerve, the geniculate, pterygopalatine, and submandibular ganglia were clearly identified. In case of the glossopharyngeal nerve, the superior, inferior, and otic ganglia were found. Thanks to the high resolution and real color of the sectioned images and volume models, detailed observation of the ganglia was possible. Since the volume models can be cut both in orthogonal planes and oblique planes, advanced sectional anatomy of the ganglia can be explained concretely.

Conclusions

The sectioned images and 3D models will be helpful resources for understanding cranial nerve ganglia anatomy, for performing related surgical procedures.

Suprameatal-transzygomatic root endoscopic approach to the geniculate ganglion: an anatomical and radiological study

PURPOSE

To describe the suprameatal-transzygomatic root endoscopic approach (STEA) to the geniculate ganglion (GG), the labyrinthine facial nerve (FN) and epitympanum.

METHODS

The feasibility and limits of the STEA, maintaining the integrity of the ossicular chain, were analysed. Ten human cadaveric ears were dissected. Step-by-step description of the technique and relevant measurements were taken during the approach. The visualization and surgical working field on the anterior and posterior medial epitympanum, GG, greater superficial petrosal nerve, the labyrinthine FN and suprageniculate area were evaluated. The range of motion through the approach and the rate of the decompression of the GG and the labyrinthine portion of the FN were assessed as well. CT-scan measurements were compared with those obtained during the dissection.

RESULTS

A complete exploration of the epitympanum was possible in every specimen. Decompression of the GG and first portion of the FN was achieved without any trauma to the ossicular chain in nine ears. The endoscope movements were mainly limited by the distance between bony buttress-short process of the incus-tegmen. The working space, during GG and labyrinthine FN decompression, was limited by the distance between malleus head-medial epitympanic wall and malleus head-GG. Radiologic measurements were consistent with those obtained during the dissections.

CONCLUSION

The STEA is a promising minimally invasive approach for decompression of the GG and FN's labyrinthine portion. The applications of this corridor include the exploration and surgery of the medial epitympanum, preserving the ossicular chain.