ON CERTAIN POINTS

IN THE

PHYSIOLOGY AND PATHOLOGY

OF THE

FIFTH PAIR OF CEREBRAL NERVES.

BY

JULIUS ALTHAUS, M.D., M.R.C.P. LOND.,

PHYSICIAN TO THE INFIRMARY FOR EPILEPSY AND PARALYSIS.

Received Sept. 24th.-Read Nov. 24th, 1868.

THE knowledge which we at present possess respecting the functions of the cerebral nerves is mainly derived from two sources, viz. from the results of vivisections in animals, and from pathological cases in which the energy of one or more of these nerves had been impaired during life. By combining the two series of observations, and correcting the one with the aid of the other, it has been possible to establish, on the whole, pretty accurate notions on this matter; and no diversity of opinion can now be said to exist amongst physiologists and physicians about the functions of the majority of the nerves in question. In fact, the only two cerebral nerves the physiology of which still remains in an unsettled condition are the pneumogastric and the fifth.

That so much uncertainty should still exist concerning the functions of these two important pairs of nerves is easily accounted for by their being endowed with far more complex

functions than the rest of their fellows, which either preside over the organs of special sense or impart motive power to certain muscles or sets of muscles, to which the anatomist's scalpel has traced them long ago. Moreover, it should be considered that, while disease of the other cerebral nerves is comparatively frequent, affections of the pneumogastric and the fifth, without simultaneous lesions of important neighbouring organs, are exceedingly rare. We have, therefore, up to the present time been obliged to trust almost exclusively to the results of vivisections as a guide to their physiology, while the corrective influence of pathological observations has been wanting. It appears to me, however, indisputable that the evidence derived from pathological cases, occurring in otherwise healthy adults, who can give a reasonable account of their symptoms, must be far superior to that which is merely deducted from vivisections, since animals cannot inform us of their sensations; and the conclusions drawn from their actions, reflex movements, and general aspect after operation, must to some extent be guesswork, depending upon the interpretation given of those phenomena by individual observers, and which may be, and often is, influenced by bias or prejudice. Moreover, animals frequently die a few days after the operation, so that any ulterior effects of the vivisection cannot be clearly ascertained.

Having been fortunate enough to observe, in the practice of the Infirmary for Epilepsy and Paralysis, a case of complete loss of function of the whole fifth pair of cerebral nerves, unaccompanied by any other affection of cerebral or nervous matter, an excellent opportunity has been afforded me of fully investigating the functions of the trifacial nerve, with special regard to certain points which are still involved in obscurity, and on which I trust that my observations will shed some light. A careful perusal of neuro-pathological literature has shown me that this case is unique in its kind, and may be looked upon, in a certain sense, as a complete physiological dissection of the fifth nerve, which has hitherto been wanting. I therefore consider it sufficiently important

to be brought before the Society, together with such remarks and conclusions as have been suggested by the phenomena observed.

He

P. G—, æt. 27, unmarried, a sheep-farmer living in Australia, had been in good health until June, 1866, when, on riding across a vast plain in Queensland, and being exposed to a keen wind blowing steadily into his face, he was suddenly seized by severe pain in the left side of the head, eyes, and face. At first the sensation was as if the face were frost-bitten. The pain then became of a dull, throbbing character, and continued so for five weeks. put himself under the care of a local practitioner, who prescribed iodide of potassium and a blister. Some time after, on a similar exposure again taking place, the right side of the face became affected in the same manner, but the pain was not so severe, and the attack did not last so long as the first. When the pain was quite gone the corneæ of both eyes became covered with thick opacities, and the patient completely lost his sight on the right side, while on the left he could still faintly distinguish light and objects at a short distance. The power of mastication also became completely lost, and the skin and mucous membranes of the face quite numb. He then went to Sydney, where he was admitted into the hospital, in which he remained five months. The surgeon under whose care he was there ordered the eyes to be strapped up, probably with the intention of preventing perforation of the cornea (Snellen). As time went on, some of the symptoms were rather improved, but as the patient was still incapacitated from doing any work whatever, he came to England, and placed himself under my care.

I first saw the patient on April 21st, when I found him in the following condition :

His intellect and memory were in no way impaired. He was able to fix his attention on subjects just as well as previous to this affection; indeed, he complained much of the enforced idleness caused by the loss of his sight. This made him occasionally irritable and low-spirited.

There

was a peculiarly hard, almost statuesque expression of the features, which was due partly to a slight oedematous effusion into the cellular tissue of the face and partly to the complete loss of muscular sensibility. On applying Faradisation by moistened conductors to the muscles of the face, these responded readily by contraction to the electric stimulus, but there was a complete absence of that peculiar sensation which, in a healthy person, always accompanies electromuscular contractions, and which is caused by the stimulation of the sentient nerve-fibres which are distributed in the muscular substance. This latter was in no way affected, showing that the morbid influence had not reached the portio dura. Indeed, all the varieties of physiognomical expression could be produced at will, but the effect made was more like that of an automaton than the natural appearance of sentient and animated features.

The sense of smell was quite normal, and had never been impaired. On applying a sufficiently powerful continuous galvanic current to the mucous membrane of the nose, a decided phosphorous smell was perceived by the patient.

Vision was obstructed by thick leucoma of both corneæ, although the optic nerve was not affected. Indeed, the patient was able not only to distinguish light and shade with both eyes, but he could also see near objects, and read single letters of No. 20 (8-line Roman) of Jäger's test-types with the left eye, where the leucoma was not so thick as in the right. He was, however, quite unable to guide himself in the streets. He suffered a great deal from photophobia, and had to wear an eye-shade. This was a remarkable circumstance, as, in consequence of the leucoma of both corneæ, only very little light could penetrate to the retina.

Mr. Soelberg Wells has been kind enough to make a careful ophthalmoscopic examination of the fundus of the eye, and has furnished me with the following report of the appearances noticed by him:

"In both eyes the pupils became well dilated under atropine. In the right there are very delicate, thread-like adhesions between the edge of the pupil and the leucomatous

portion of the cornea. In the left eye there are slight remnants of uveal pigment on the central portion of the anterior capsule, indicating that a slight iritis had formerly existed. The lens and vitreous humour are clear, and the back-ground of the eye is quite normal. In the right eye, on account of the dense central leucoma, the optic disc, &c., could only be very imperfectly seen, but in the left eye it was quite visible."

The motor nerves of the eye were in their normal state, there being neither ptosis, nor strabismus, nor double vision, and all movements of the eyes, upwards, downwards, and laterally, being easy of execution.

The pupils were rather constricted, and were only very slightly influenced by variations of light and shade.

In describing the condition of the fifth nerve, I shall speak —1st, of the skin of the face and scalp; 2nd, of the mucous membranes of the eye, nose, and mouth; and 3rd, of the muscles of mastication.

1st. The common sensation of the face and scalp was entirely lost in both sides, the limit of the anesthesia being, vertically, a line running one sixth part of an inch inwards from the horizontal and ascending branches of the lower jaw, and, horizontally, a line drawn from the tragus of one ear, right across the skull, to the tragus of the other ear. All the parts comprised between these lines, including the temples, forehead, nose, cheeks, and chin, had lost their sensibility. As regards the ears, the tragus was anæsthetic, and part of the external meatus benumbed, while the concha was perfectly sensible. In like manner the skin of the back part of the skull and the skin of the neck had preserved their ordinary sensibility.

In the anaesthetic parts of the face and scalp just alluded to, neither pricking, pinching, nor any other mechanical irritation, was in the least degree perceived by the patient. With regard to electricity, it appeared that Faradisation by dry conductors did not produce any sensation, even when a powerful current was used. On applying to the face the continuous galvanic current of ten cells of Daniell's battery,