Trigeminal ganglion

The trigeminal ganglion (or Gasserian ganglion, or semilunar ganglion, or Gasser's ganglion) is a sensory ganglion of the trigeminal nerve (CN V) that occupies a cavity (Meckel's cave) in the dura mater, covering the trigeminal impression near the apex of the petrous part of the temporal bone.

From the ganglion, the 3 major divisions of the trigeminal nerve emerge anteriorly and inferiorly, with the first two (ophthalmic and maxillary divisions) passing anteriorly to enter the cavernous sinus, and the third (mandibular division) descending into the foramen ovale.

medial: motor root of the trigeminal nerve and sphenoid bone

lateral: posterior part of the cavernous sinus, petrous apex and petrous segment of the internal carotid artery

anterior: cavernous sinus and cavernous segment of the internal carotid artery

posterior: prepontine cistern

inferior: greater petrosal nerve and middle cranial fossa

small ganglionic branches of the cavernous portion of the internal carotid artery

accessory meningeal artery (from the maxillary artery, via the foramen ovale)

The ganglionic epineurium is innervated by the nervus spinosus from the mandibular division of the trigeminal nerve which re-enters the skull via the foramen spinosum.

Earlier studies have shown that the trigeminal ganglion (TG) comprises several receptors and signal molecules that are involved in the process of peripheral sensitization, which influences the development and persistence of neuropathic pain. Targeting TG can modulate this sensitization pathway and mediate the pain-relieving effect. So far,there are few studies in which modulation approaches to TG itself have been suggested so far. “Trigeminal ganglion modulation” and “trigeminal neuralgia” were used as search phrases in the Scopus Index and PubMed databases to discover articles that were pertinent to the topic. Kc et al. in a review, addressed the role of the trigeminal ganglion in TN and underlying molecules and neuropeptides implicated in trigeminal pain pathways in processing pathological orofacial pain. They also reviewed different modulation approaches in TG for trigeminal neuralgia treatment. Furthermore, they discussed the prospect of targeting trigeminal ganglion to manage such intractable pain ¹⁾.

Traditionally, a pterional approach is utilized to access the Meckel cave. Depending on the tumor location, extradural dissection of the Gasserian ganglion can be performed. An endoscopic endonasal approach could potentially avoid a craniotomy in these cases.

An endoscopic endonasal approach as well as a lateral approach to the Meckel cave on six anatomic specimens, to access the Meckel cave endoscopically, a complete sphenoethmoidectomy and maxillary antrostomy followed by a transpterygoid approach was performed. For lateral access, a pterional craniotomy with extradural dissection was performed.

The endoscopic endonasal approach allowed adequate access to the Gasserian ganglion. All the relevant anatomy was identified without difficulty. Both approaches allowed for a similar exposure, but the endonasal approach avoided brain retraction and improved anteromedial exposure of the Gasserian ganglion ²⁾.