Trigeminal nerve

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Anatomical representation of the trigeminal ganglion (semilunar ganglion) and the three branches of the trigeminal nerve:
V1 = ophthalmic nerve,
V2 = maxillary nerve,
V3 = mandibular nerve.

The trigeminal nerve (from Latin trigeminal , Drilling ' ), short trigeminal , also the fifth cranial nerve , N. V called sensitive (→ leads trigeminal perception ) and motor fibers with which it supplies the face, nasal cavity, oral cavity and jaw muscles. The paired nerve found in vertebrates owes its name to its division into three main branches:

Historically , the mandibular nerve is the nerve of the first branchial arch .

anatomy

Nerve nuclei in the brain

The trigeminal nerve, four cores ( nuclei assigned), three sensitive and a motor, to the cranial nerve nuclei include:

  • Nucleus mesencephalicus nervi trigemini,
  • Nucleus pontinus nervi trigemini ( Nucleus principalis nervi trigemini ) and
  • Nucleus spinalis nervi trigemini lie columnar one below the other in the brain stem .
  • The nucleus motorius nervi trigemini is located in the upper rhombencephalon .

In the nucleus mesencephalicus nervi trigemini of the midbrain ( mesencephalon ) there are nerve cells that conduct proprioceptive signals. However, it is not a termination nucleus, but simply a centrally located collection of primary afferent pseudounipolar neurons (unconscious depth sensitivity : tension of the muscles, stretching of the ligaments and the capsule of the temporomandibular joint , stretching of the tooth support apparatus ). The remaining primary afferent neurons of sensory fibers of the trigeminal nerve are located in the peripheral trigeminal ganglion (semilunar ganglion [Gasseri]). Afferents from the oculomotor nerve , trochlear nerve , abducens nerve (for the proprioception of eye movements), the facial nerve (for the proprioception of the facial muscles) and the hypoglossal nerve (for the proprioception of the tongue muscles) also run via the nucleus mesencephalicus . These proprioceptive signals are passed on to the nucleus spinalis nervi trigemini and the nucleus supratrigeminalis .

The nucleus pontinus nervi trigemini (also: nucleus principalis nervi trigemini ) is a termination nucleus in which primary afferents for epicritical sensitivity (pressure, touch, vibration, two-point discrimination) end and are switched to secondary afferent neurons. The nucleus principalis nervi trigemini projects over the lemniscus trigeminalis and the tractus trigeminothalamicus dorsalis to the nucleus ventralis posteromedialis in the thalamus .

The nucleus spinalis nervi trigemini is a caudally adjoining termination nucleus to which signals of protopathic sensitivity (gross pressure, pain, temperature, itching, trigeminal smell) are sent.

These sensitive cranial nerve nuclei are not only reached by fibers of the trigeminal nerve, but also receive inflows from other cranial nerves, especially the facial nerve , glossopharyngeal nerve and vagus nerve .

The nucleus motorius nervi trigemini is a nucleus of origin and sends motor fibers to muscles ( masticatory muscles , anterior abdomen of the digastric muscle and mylohyoid muscle from the floor of the mouth, tensor veli palatini muscle , tensor tympani muscle ).

Nerve roots

The nerve is most Pons to the brain surface . Already there one can differentiate two roots, the radix sensoria and the radix motoria . The sensitive fibers from the radix sensoria are called portio major nervi trigemini after the trigeminal ganglion . The motor fibers from the radix motoria pass through the trigeminal ganglion and nestle against the mandibular nerve . They form the portio minor nervi trigemini .

The portio major ( radix sensoria ) contains epicritic, protopathic and some proprioceptive fibers and is therefore purely sensitive. It is associated with a pseudounipolar ganglion , the trigeminal ganglion. This largely corresponds to the ganglia of the spinal nerves , apart from the fact that there are no nerve cell bodies of proprioceptive neurons in them . For developmental reasons, these lie in the brain stem and form the nucleus mesencephalicus nervi trigemini.

The portio minor ( radix motoria ) contains motor and proprioceptive fibers. It is mixed with it. Of the proprioceptive fibers, it probably only contains those that convey information from the muscles or tendons it supplies. However, these fibers also come from the radix sensoria and can therefore also be counted as part of the portio major.

The proprioceptive fibers have a special feature: regardless of whether they run in portio major or portio minor, their cell body is not in the trigeminal ganglion, but directly in the nucleus mesencephalicus nervi trigemini. Its morphology then corresponds to the pseudounipolar ganglion. It is an exception, since all other cranial nerve nuclei or core areas in the brain have a multipolar structure.

The portio major is divided into the three major nerves: ophthalmic nerve (branch of the eye), maxillary nerve (branch of the upper jaw) and mandibular nerve (branch of the lower jaw). The entire portio minor is also attached to the mandibular nerve. All nerves now leave the skull . The mandibular nerve runs through the foramen ovale. The ophthalmic nerve and the maxillary nerve initially run through the cavernous sinus together with the oculomotor nerve , the trochlear nerve , the abducens nerve and the internal carotid artery . Then the ophthalmic nerve leaves the middle cranial fossa ( fossa cranii media ) through the fissura orbitalis superior towards the eye socket (orbit). The maxillary nerve runs through the rotundum foramen .

Diseases

examination

The medical status assessment includes palpatory checking of the pressure points of the trigeminal nerve. The left and right three trigeminal pressure points can be found on each side of the face above and below the eye socket and on the chin. At these points, the peripheral branches of the three main branches ophthalmic nerve, maxillary nerve and mandibular nerve emerge from the bone: above the eye the supraorbital nerve from the supraorbital notch and the supraorbital foramen ; under the eye the infraorbital nerve from the infraorbital foramen ; on the chin the mental nerve from the mental foramen . Usually these pressure points are not painful.

The cause of a Trigeminusdruckschmerz come intracranial pressure (ICP), meningitis (meningitis), inflammation of the sinuses (sinusitis) and trigeminal neuralgia (see below) in question.

Lesions

Sensitive deficits in the case of a trigeminal lesion, on the right in the picture central lesion (red) along the Sölder lines , on the left peripheral lesion (blue), corresponding to V 1 , V 2 and V 3

When the trigeminal nerve is injured , a distinction is made between a central and peripheral loss of sensitivity.

If the nerve is damaged in its original nucleus, the nucleus spinalis nervi trigemini, which is responsible for the sensation of pain and temperature (i.e. centrally), then, depending on the location of the lesion in this core area, circular loss of sensitivity occurs from the area around the mouth (so-called Sölder Lines).

A peripheral lesion usually damages a branch of the trigeminal nerve after its exit from the trigeminal ganglion and leads to sensitive deficits in the respective facial areas, which, however, differ from the sensitive areas of the nuclei. If the mandibular nerve is affected, the portio minor - the motor fibers - is also interrupted and chewing is no longer possible. Difficulty swallowing can occur due to damage to the branches for the mylohyoid and digastric muscles (venter anterior). In addition, the corneal reflex cannot be triggered by a lesion of the nerve . Varicella viruses can also penetrate the branches of the ophthalmic nerve and cause ophthalmic zoster ( facial rose ).

Trigeminal neuralgia

In trigeminal neuralgia , severe pain in the trigeminal area can occur. These are sometimes described as the most severe pain known. However, treatment is possible.

Trigeminal neuroma

The trigeminal neuroma is a nerve sheath tumor of the trigeminal nerve. A distinction is made between three sub-forms, depending on the localization in relation to the porus trigeminus (anatomically completely infratentorial course of the nerve from the posterior fossa to the middle through the pore; nomenclature, however, transition from intra- to supratentorial).

literature

  • Martin Trepel: Neuroanatomy. Structure and function. 3rd, revised edition. Urban & Fischer, Munich a. a. 2004, ISBN 3-437-41297-3 .
  • Franz-Viktor Salomon: nervous system, systema nervosum . In: Franz-Viktor Salomon, Hans Geyer, Uwe Gille (Ed.): Anatomy for veterinary medicine. Enke, Stuttgart 2005, ISBN 3-8304-1007-7 , pp. 464-577.

Web links

Commons : Trigeminal Nerve  - Collection of images, videos and audio files
Wiktionary: trigeminal nerve  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ^ Klaus Holldack, Klaus Gahl: Auscultation and percussion. Inspection and palpation. 10th, revised edition. Thieme, Stuttgart 1986, ISBN 3-13-352410-0 , p. 41.