Trigeminal nerve

“ If the vertebrate were derived from such an animal, then the trigeminal nerve, as the representative of these prosomatic appendage-nerves, ought to be found to supply the muscles of this accessory lip and of these five pairs of tentacles in the lowest vertebrate. ”

“ From such a comparison it follows that the segments, found in the antero-lateral region of the head-shield, were not segments of the cranium, but of parts beyond the region of the cranium, and from their position must have been segments supplied by the trigeminal nerve, and not by the vagus group; segments, therefore, which did not indicate gills and gill-slits, but muscles, innervated by the trigeminal nerve; muscles which, as indicated by the corresponding markings on the carapace of Phrynus, Mygale, etc., were the tergo-coxal muscles of the prosomatic appendages. ”

“ The analysis of these tentacular segments belonging to the trigeminal nerve presents greater difficulties than that of any of the other cranial segments, owing to the deficiency of our knowledge of what occurs at transformation. Light is required not only on the origin of the new muscles but also on the origin of the new and elaborate cartilages which are newly formed at this time. ”

“ One of the most common neuralgias is a pain in the eyes; it is felt in the region of the trigeminal nerve, and frequently becomes almost unendurable and very obstinate. It occurs usually in single attacks, which return at various intervals and last sometimes only a few minutes, and sometimes a quarter of an hour or more. ”

“ By simply keeping a sciatic patient in the prone posture, shielded from cold and from pressure on the nerve, we have it in our power to remove nearly all peripheral sources of irritation; but in trigeminal neuralgia there are many influences, particularly psychical ones, which cannot be shut out, and which will continue to act with disastrous effect in many cases. ”

“ The patient, a man sixty-five years old at the time of his death, had suffered for several years from the most violent and intractable epileptiform trigeminal neuralgia, complicated with interesting trophic changes of the tissues. Post-mortem examination showed that the pressure of an internal carotid aneurism had almost destroyed the Gasserian ganglion of the painful nerve, that the trunk and posterior root of the nerve were in a state of advanced atrophic softening, and the atrophic process had extended in less degree to the nerve of the opposite side. ”

“ The fourth root is much stronger, sometimes double, and its [106] elements pass again partly into the Trigeminal, partly into the Facial nerve. On the passage of these stems through the skull (through a foramen or foramina in the alisphenoid) they form a ganglionic plexus, in which the palatine ramus and the first stem of the Trigeminus generally possess discrete ganglia. The branches which issue from the plexus and belong exclusively to the Trigeminus, supply the organs and integuments of the frontal, ophthalmic, and nasal regions, and the upper and lower jaws with their soft parts. ”

“ Unlike headache in intracranial tumors, it is not a constant symptom. The headache of brain tumors is due in part at least to the conditions of tension which are produced by the growth interfering with the balance of pressure within the skull. Headache is also, as has been pointed out in the article on Brain Tumors, frequently due to the irritation of the membranes; but in this case the one great nerve through which pain expresses itself is the trigeminal, which has its distribution both within the skull and outside of it to all parts of the head. ”

“ If this is so, then this homology ought to throw light on the extraordinary innervation of these tubular muscles by the branchialis profundus branch of the facial nerve and the velar branch of the trigeminal. We ought, in fact, to find in Limulus a nerve arising exclusively from the ganglia belonging to the chilarial and opercular segments, which, instead of being confined to those segments, traverses the whole branchial region on each side, and gives off a branch to each branchial segment; this branch should supply the veno-pericardial muscle of that side. ”

“ The origin of the trigeminal motor fibres in the central nervous system is most striking. We may take it for granted that a nucleus of cells giving origin to one or more segmental motor nerves will possess a greater or less longitudinal extension in the central nervous system, according to the number of fused separate segmental centres it represents. Thus a nucleus such as that of the IVth nerve or of the facial is small and compact in comparison to the extensive conjoint nucleus of the vagus and cranial accessory. ”

“ Of these the mandibular or velar nerve (met.) is a large, conspicuous nerve, which arises so separately from the rest of the trigeminal as almost to deserve the title of a separate nerve. When it leaves the large posterior ganglion, it passes into the anterior part of the velum, runs along with the tubular muscles, which it supplies, to the ventral surface as far as the junction of the lower lip with the thyroid plate, and has not been followed further by Hatschek. ”

“ Resection of a branch of the trigeminal is valueless; facial elongation only causes a corresponding paralysis, and should this latter accident be transient, as in a case of Bernhardt's, so is the relief from the tic.
To obviate the much more frequent inconvenience of a permanent facial paralysis, J. L. Faure [215] suggests spino-facial anastomosis. In a woman suffering from contracture and spasmodic twitchings in the region of the facial, Kennedy, of Glasgow, divided the nerve and immediately anastomosed the cut end laterally with the spinal accessory. ”

“ The origins of the nerves are very imperfectly shown in the cast; only their exits from the cranial cavity are clear. The most interesting are the optic and trigeminal nerves, which pass out of the cranial cavity at first by a common exit, which is soon subdivided by a bony partition into two canals, the former no less than 0.08 m., the latter 0.045 m. ”

“ In view of these things, it is difficult to avoid the inference that both the epileptic and the neuralgic affections of this critical period of life are the expression of a morbid condition of the medulla oblongata, in which the sensory root of the trigeminus has its origin; and further, that this morbid condition (tending to explosive and atactic manifestations of nerve-force) must have its basis in defective nutrition. For, be it remembered, the epoch of sexual development is one in which an enormous addition is being made to the expenditure of vital energy ”

“ But the mere cessation of vaso-motion will not account for such facts as the rapid and simultaneous development of erysipelatous inflammation, of corneal clouding and ulceration, of iritis and glaucoma, of nutrition-changes in hair and mucous membrane. I must, for the present, be content to believe it probable that there is a special set of efferent fibres in the trigeminus, emanating from the motor-root, whose office it is in some unknown way to preside over the equilibrium of molecular forces in the tissues to which the nerve is distributed ”

“ When speaking of the tripartite arrangement of the cranial nerves, an arrangement which gave the clue to the meaning of the cranial segments, I spoke of the trigeminal as supplying the sensory nerves to the skin in the head-region, and I compared this dorsal system of afferent nerves to the system of epimeral nerves in Limulus which supply the prosomatic and mesosomatic carapaces of Limulus with sensory fibres. ”

“ Second period: recovery, to a large extent, of the nutrition of the posterior root of the trigeminus, complete recovery of the root of the vagus (hence alteration of the type of recurrence of the pains, which now occur at increasingly long intervals, and needed special provocation, e. g., excessive fatigue, to bring them on; hence, also, disappearance of the stomach symptoms) ; continuance of the affection of the motor portion of the nerve (hence, continuance of the tendency to trophic, secretory, and vaso-motor changes) ”

“ The trigeminus is, of all nerves in the body, that one whose affections are likely to cause secondary disturbances of wide extent and various nature, owing to its large peripheral expanse, the complex nature of its functions, and its extensive and close connections with other nerves. ”

“ The fatty matter, however, it must be borne in mind, is the expression of dissimulation of the actual substance of the proteids of the tissues, not of the splitting up of proteids or other carbonaceous nourishment supplied to them.
A part deprived of its natural nerve-supply sooner or later suffers from the effects of malnutrition. When the trigeminus nerve is divided (Majendie) , or when its root is compressed injuriously, say by a tubercular tumour, the cornea begins to show points of ulceration, which, increasing in area, may bring about total disintegration of the eyeball. ”

“ Consequently it is absent in the blind Amblyopsis, and the Myxinoids. In Lepidosiren the nerves supplying the muscles of the eye have no independent origin, but are part [105] of the ophthalmic division of the Trigeminus. In Petromyzon these muscles are supplied partly from the Trigeminus, partly by a nerve representing the Oculo-motor and Trochlearis, which are fused into a common trunk.
The Nervus trochlearis (fourth pair) , if present with an independent origin, is always thin, taking its origin on the upper surface of the brain from the groove between lobus opticus and cerebellum ”

“ Trigeminal neuralgia does not in itself lead to fatal results, but the continuous pain, the want of sleep, and the difficulty experienced in taking sufficient nourishment soon reduce the patient to such a miserable condition that, unless relieved by the surgeon, amelioration is sought in morphia or release in death. ”

“ Motor palsies are more frequent than sensory affections in syphilis, but hemianæsthesia, localized anæsthetic tracts, indeed any form of sensory paralysis, may occur. Numbness, formications, all varieties of paræsthesia, are frequently felt in the face, body, or extremities. Violent peripheral neuralgic pains are rare, and generally when present denote neuritis. Huguenin, however, reports42 a severe trigeminal anæsthesia dolorosa, which was found, after death from intercurrent disease, to have depended upon a small gumma pressing upon the Gasserian ganglion. ”

“ Afferent currents that do not traverse the thalamus cause reflexes only. It contains one of the roots of the optic nerve and its destruction will impair vision. Its injuries may also produce turning movements.
The Corpus Striatum transmits motor currents originating in the cerebral cortex. Lesions of its interior (lenticular nucleus) cause motor paralysis and sometimes anæsthesia on the opposite side of the body. Electrical stimulation of this nucleus causes general muscular contractions of the opposite side of the body. Irritation of the surface layers is painless and symptomless. ”

“ And certainly it is infinitely more probable that paralysis or spasm of a muscular viscus should occur as a reflex consequence of neuralgia occurring in a nerve whose central nucleus was closely connected with the motor centre of the organ, than that mere paralysis of the viscus should convey a reflex impression to sensitive nerves which should express itself in the form of acute pain. It must be confessed that the matter hangs in doubt; but the evidence is, on the whole, very strong for the belief that central nervous mischief is the most important element in angina. ”

“ In recent cases there is only slight thickening of the neuroglia, but when the disease is advanced the trabeculæ are thick, dense, and firm, and the nerve fibres have largely disappeared. The coats of the blood vessels adjacent to the sclerosis are thickened and their lumen is narrowed. Thickening of the meninges is not uncommon, either confined to those covering the diseased portion of the cord or extending completely around it. Atrophy of the nerve roots is often appreciable by the naked eye. ”

“ In the first place, he remarks that the site of the pain is by far less distinctly referred to definite foci on the outside of the skull than in trigeminal neuralgia; the patient's sensations very usually lead him to declare that the pain is in the brain itself. Secondly, he says that the points douloureux (in Valleix's sense) are almost constantly absent in true migraine. Thirdly, he specifies the character of the pain in migraine—dull, boring, straining, etc.—as differing from that of trigeminal neuralgia, which is ordinarily much more acute and darting. ”

“ J. K. Spender, of Bath, pointed out this fact [39] at a time when he had only seen my statement that the pain could be relieved in this way. In the case of the trigeminus, the same kind of reflex stimulation is most effectively obtained by applying the blister over the branches of the cervico-occipital, at the [166] nape of the neck; and it is remarkable what powerful effects are sometimes thus produced, even in cases that wear the most unpromising aspect. ”

“ Thus, if we suppose a neuralgia to depend on morbid action within the spinal cord, then we may galvanize the spine, taking care to make the current come out through any vertebra over which we detect tenderness. If we suppose the seat of the disease to be in the nerve-root in the mere ordinary sense of the word, then we apply the positive pole to the vertebra opposite the highest nerve-origin that can be concerned, and we stroke the negative pole down by the side of the spinous processes, some forty times in succession. ”

“ But the impression produced on this same peripheral expanse of nerve-branches by prolonged exposure to cold wind may, and often does, convey to the centres sensations which are quite different and provokes reflex movements which are altogether abnormal. Pain is the product in one direction; sneezing, perhaps, in the other. It seems absurd to say that sneezing is any part of the function of those motor nerves whose action regulates the performance of expiration. And it appears to me not less absurd to say that pain is the function of the sensitive fibres of the trigeminus. ”