Corpus: Trigeminal ganglion

The trigeminal ganglion is a sensitive ganglion located within the cranial cavity that represents the division point of the trigeminal nerve.

The trigeminal ganglion is located in a protrusion of the dura mater in a space at the tip of the petrous temporal bone (pars petrosa ossis temporalis), which is known as the cavum Meckeli or cavitas trigeminalis. It in turn projects into a bony depression, the impressio trigeminalis, in the pars petrosa of the temporal bone (os temporale). Within the dural pouch, the trigeminal ganglion is surrounded by a continuation of the subarachnoid space, the trigeminal cistern.

The roughly crescent-shaped form of the ganglion points with its convex side towards the rostral side. The three branches of the trigeminal nerve arise from it:

• ophthalmic nerve
• maxillary nerve
• Mandibular nerve

On its medial side, the ganglion is closely connected to the internal carotid artery and the posterior part of the cavernous sinus.

The ganglion has a motor root (radix motoria) and a sensory root (radix sensoria). The motor root passes under the ganglion. It leaves the cranial cavity through the foramen ovale and rejoins the mandibular nerve immediately below the foramen.

The ganglion itself contains the pseudounipolar nerve cell bodies of the afferent, sensitive nerve fibres. Their projections pointing towards the CNS run to the cranial nerve nuclei, the peripherally running projections unite to form the main branches of the trigeminal nerve.

The pseudounipolar neurones of proprioceptive trigeminal pathways, e.g. from the masticatory muscles and the external eye muscles, are an exception. They are not located in the trigeminal ganglion, but in the mesencephalic nervi trigemini nucleus in the midbrain.

The ophthalmic nerve and the maxillary nerve are purely sensitive branches of the trigeminal ganglion. The mandibular nerve is a mixed nerve that carries extracranial sensitive and special visceromotor fibres after its union with the motor root.

The arterial supply to the trigeminal ganglion is via the trigeminal ganglion ramus of the internal carotid artery.

The trigeminal ganglion forms from a thickening of the surface ectoderm, the trigeminal placode.

The trigeminal ganglion is important in the treatment of trigeminal neuralgia. The non-myelinated, pain-conducting C-fibres run in the area of the ganglion and can be selectively switched off here - e.g. by means of percutaneous thermocoagulation or balloon compression. Drug treatment with localised opioid application (GLOA) also targets the ganglion.

Furthermore, if the above-mentioned procedures fail, curative radiotherapy with ionising radiation is possible in order to achieve denervation.

The ganglion is also called "Ganglion Gasseri" after the Austrian anatomist Johann Lorenz Gasser (* 9 March 1723 in Maria Saal and † 3 April 1765 in Vienna). This name was given to him in 1765 by his pupil Raimund Balthasar Hirsch. However, Gasser was not the first to describe it, as it had already been described by the Italian anatomist Giovanni Domenico Santorini.