Maxillary nerve compression in cynomolgus monkey Macaca fascicularis: altered somatic sensation and peripheral nerve firing

A morphological study and the variability in the number of infraorbital foramina in the African green monkey (Grivet) (Chlorocebus aethiops) using microcomputed tomography

Knowledge of the nonhuman primate morphology and anatomy related to craniofacial mechanoreception is essential for a fundamental understanding of the incidents that have occurred during the evolution of craniofacial features. The present study focuses on the variability in the number of infraorbital foramina and associated anatomical structures such as the infraorbital canal (IOC) and the infraorbital groove (IOG), as they are considered to play an important role in the behavioral ecology of these animals. A total of 19 skulls of Chlorocebus aethiops were analyzed. The number of infraorbital foramina was assessed macroscopically using a magnifying glass and a small diameter probe. Three dimensional (3D) projections and morphometric analysis of the infraorbital foramina, IOCs, and IOGs were performed using microcomputed tomography (micro-CT) for two skulls that represent one of the most common morphological types. Regardless of sex and body side, the most common morphological type observed in the studied species is the presence of three infraorbital foramina. The IOC takes a funnel or pinched shape. 3D projections were made to assess the course of the infraorbital vascular and nerve bundles in selected individuals. The results indicate a high morphological diversity within the species, although there appears to be a consistent distribution pattern of infraorbital neurovascular bundles in species of the Cercopithecidae family. The use of X-ray micro-CT allowed 3D visualization of the maxillary region to determine the variability of the infraorbital foramina and to track the division of the infraorbital neurovascular bundle in the case of the most common macroscopic expression of the number of the infraorbital foramen in C. aethiops, as well as the morphometric of the IOCs and IOGs which are related to mechanoreception of the primate's snout.

Transcranial segment of the trigeminal nerve: macro-/microscopic anatomical study using sheet plastination

BACKGROUND

Trigeminal neuralgia (TN) may be caused by the mechanical compression of the trigeminal nerve. In the studies on the location of mechanical irritation and entrapment of the nerve, attention has been paid mostly to vascular structures in the subarachnoid space. Few studies have explored the relationship between the trigeminal nerve and its surrounding structures along its course in the skull base. The aim of this study was to examine and trace the root, ganglion and three divisions of the trigeminal nerve and their relationships with surrounding soft and bony structures in the skull base, and to identify the likely mechanical compression points.

METHODS

A total of 26 adult cadavers (ten females, 16 males; age range, 45-81 years) were examined in this study, eight for dissection and 16 for sheet plastination study.

RESULTS

Anatomical structures that may make the trigeminal nerve susceptible to entrapment in the skull base were located at (1) the inferolateral edge of the mouth of Meckel's cave, (2) the middle cranial fossa dura and the lateral wall of the anterior intracavernous portion of the internal carotid artery, (3) the ridge of the medial wall of the foramen rotundum, and (4) the twisted periosteum and venous plexus of the foramen ovale.

CONCLUSION

This study identified four likely mechanical compression points along the course of the trigeminal nerve in the skull base. Knowledge of these TN-susceptible sites may be useful to both skull base surgeon and TN-animal model researcher, particularly when they study TN without vascular compression.