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deep reflexes are normal. The muscles of both limbs react naturally to electricity, and do not show the “myasthenic reaction ” in which faradism soon fails to cause contraction whilst the constant current remains capable of stimulating the muscle fibres. The trunk muscles are also weak, but the inter-costals and diaphragm act well, and there is also good power in extension and flexion of the head. It is, however, in the face and eyes that the most striking anomalies appear. Owing to weakness in the orbicularis oris the lips cannot be closed, though they can be slightly approximated towards each other; paresis of the buccinator prevents any distension of the cheeks, and in smiling there is elevation alone of the angle of the mouth. If in attempting to smile a knitting needle is held vertically at the angle of the mouth, it is seen that there is no outward movement at all. The risorius and zygomaticus are paralysed. Sir William Gowers 1 describes the movement as nasal snarl," a graphic description for this striking appearance. With the paresis of the orbicularis oris there is an inability to contract the transverse muscles of the tongue, the two movements always being associated in action and probably innervated from the same cranial nucleus. There is ptosis, and the action of the levator palpebræ rapidly tires, so that whilst at first the pupils are visible, after a few attempts to raise the lids the effort becomes ineffectual, and the lids gradually drop until the pupils are covered. With repeated attempts an endeavour is made to compensate this weakness of the levator by greater extension of the head, whilst the frontales after a few feeble contractions remain motionless. When the patient is asked to gently close the eyes a narrow slit of sclerotic is still seen, and there is very feeble power of keeping the eyes shut against resistance. The pupils are equal and react to light and accommodation, so that the patient can read Jäger 1 at 12 inches. The eyeballs converge equally. The associated lateral conjugate movements are deficient in both directions, the upward movements very markedly affected and the downward movement less so. The limited range of these movements can be shown by a diagram similar to that used by Sir William Gowers.2 It is further to be noted that such limited upward movement as there is in the left eye, is always associated with some deviation towards
LEFT EYE. The outer circle represents the extent of normal movement, the inner the cornea. The lines indicate the extent of the movement possible in the several directions in the patient.
the inner side, and that a similar deviation inwards occurs on looking downwards. This would seem to indicate a special weakness in the superior and inferior oblique eye muscles. Fatigue is readily produced in the lateral conjugate movements, so that after repeated effort the range of movement is reduced to nearly one-half the original excursion. The muscles of mastication are distinctly weak, and become more so after effort. The palate moves rather sluggishly, though the range of its excursion does not seem to be lessened by repeated effort. The patient can repeat the physiological alphabet without any recognisable defect, but in talking it is often noticed that there is the initial difficulty already alluded to. The vocal cords move equally, but the impression is gained that the range of adduction and abduction is smaller than is natural. The electrical reactions of the facial muscles are important. As compared with a normal person, they are much less excitable whether a large nerve branch is stimulated or the “motor points," in particular it is impossible to succeed in drawing the angle of the mouth outwards. The muscles involved in this movement therefore give a partial reaction of degeneration. The orbicularis palpebrarum and orbicularis oris contract fairly and more movement is attained by this means than the patient is capable of producing by voluntary effort. The other facial muscles react fairly and the myasthenic reaction cannot be seen.
The patient has now been under observation about three months, and has been kept chiefly at rest in bed and given hypodermic injections and strychnine. There is undoubtedly some increase of strength, but in all essentials the condition has remained stationary, and though some movements can be performed which on admission were impossible, fatigue quickly follows, and the myasthenic reaction has appeared in the deltoid and biceps.
The case may be considered as a typical one of myasthenia, the symptoms of which are now fairly well known. Han's 3 recent analysis gives the records of 114 cases. The disease is characterised by weakness of great variability in many muscles, nearly always affecting the extremities, causing ocular palsies, especially ptosis, weakness of the jaw muscles, and often attacks of dyspnea; there is an absence of wasting in the affected muscles and no reaction of degeneration, and sometimes the so-called myasthenic electrical reaction mentioned before. Since microscopical examination reveals no changes in the nervous system, knowledge of its pathology depends on the interpretation of the clinical symptoms. The prognosis is very grave, sudden death with bulbar symptoms not infrequently occurs. The
diagnosis when there is familiarity with the clinical picture is usually easy, only superficial observation could mistake the condition for hysteria; true bulbar paralysis is sharply separated from it by the muscular wasting, altered electrical changes and often associated symptoms in the limbs. The aspect of the face resembles closely the form of myopathy described by Landouzy and Dejerine, a resemblance which may indeed imply a pathological alliance.
Wilfrid Harris 4 has described two cases of post-diphtheritic chronic bulbar paralysis, which presented considerable likeness to the clinical picture of myasthenia. In both there was almost complete paralysis of the orbicular oris and orbicularis palpebrarum, and hence inability to purse up the lips or close the eyes completely, also paralysis of the soft palate and of the tongue. In the first case the tongue was wasted and the abductors and tensors of the vocal cord paralysed, in the second case these symptoms were absent. In both again there was some reaction of degeneration though less in the second than the first case. Whilst the first case has remained stationary for nearly five years, the second, after a period of six years, completely recovered. These two cases are important, since the facial aspect simulated that of myasthenia, whilst the prognosis is comparatively good and at least life is not endangered. Harris distinguished them from myasthenia by the non-variability of the symptoms, the absence of the myasthenic reaction, the absence of ptosis, or weakness of the jaw muscles or of the neck or limbs, and by the presence of muscular atrophy and reaction of degeneration. There is a tendency to believe that the site of the lesion in myasthenia is in the nerve endings in the muscles. The absence of faradíc excitability which occurs in the myasthenic reaction may be accepted as evidence against the purely muscular origin of the symptoms. On the other hand, the paralysis of the associated movements of the eyeball seems to indicate that this part of the symptomatology at least may be due to a central nuclear cause. The ocular palsies of the disease constitute an interesting study.
Harris (loc. cit.) raises again the much-discussed question of the nuclear supply of the upper facial muscles. It will be remembered that in ophthalmoplegia there is sometimes met with
weakness in the orbicularis palpebrarum, and this has been attributed to an alleged identity of nuclear origin.
Leaving this question still sub judice, several points may be mentioned in studying these and other palsies.
1. A defect of movement may result from a lesion of the sensory nerve supply to muscles. Thus, as in the classical experiment of Bell, who showed that section of the fifth cranial nerve was followed by deficient movement of the face. Frankel 5 has recorded a case of tabes in which there was disease of the fifth nerve; the facial muscles on this side, though when tested individually contracted vigorously, did not move the lower part of the face during psychical states such as laughing and crying. Some of the transient ocular palsies of tabes may be sensorimotor in nature, more particularly because whilst the eye muscles do not possess muscle spindles, they are supplied with nerve endings undoubtedly sensory in nature and whose cells of origin probably reside in the oculo-motor nucleus itself, and thus that nucleus is sensori-motor. The well-known observations of Sherrington and Mott may also be quoted. These observers have shown that a limb deprived of sensation by sections of the posterior roots is also rendered motionless.
2. A defect of movement is also seen in a muscle when its opponent is paralysed, the normal tone of the paralysed muscle being absent, its opponent cannot act to advantage. This is seen well enough in paralysis of the extensors of the wrist and fingers when there results an apparent weakness of the flexor grasp. Ilarris suggests that a similar explanation may be given of the apparent ptosis, that is, inability to lift the eyelid at the first attempt, which was observed in the first of his cases, and, on the other hand, of the apparent weakness of the orbicularis in some cases of ophthalmoplegia with ptosis.
3. Because of the reciprocal innervation of muscles, muscles whose direct actions are ordinarily opposed act together in the performance of single actions. Thus Sherrington 6 divided intracranially the facial nerve on one side in a monkey; in the movement of blinking it was observed that whilst the lower lid on the side of the nerve section did not move at all, the
lid descended for a few millimetres over the globe of the eye and was
then synchronously with the eyelid of the opposite side lifted up again. The fall of the upper lid must have been done to inhibition of the tonus of the levator palpabræ superioris, and not to any action of the palpebral fibres of the orbicularis palpebrarum. I have seen exactly the same phenomenon in a case of recent and complete facial paralysis. When one observes the act of opening the eye in a person, by the elevation of the upper lid, the lower lid is also seen to slightly fall away from the eyeball.
4. Lastly, Hughlings Jackson? has often insisted that nervous centres represent movements not muscles. Hence one movement of a muscle may be represented in one centre, another movement in another centre. In the orbicularis oculi the palpebral portion is distinguished by its action from the orbital portion. The movement of blinking in the monkey is probably purely due to the palpebral portion with the inhibition of the levator pelpebræ. Moderate closure of the lids has a quite different significance from the movement of tightly screwing the lids together, in which the orbital portion acts strongly. Hughlings Jackson suggests " that one place for the representation of the orbicularis palpebrarum is that where the external ocular movements for directing the eyes for the estimation of distance are represented. Presumably the peering movements of a short-sighted person-movements helping him to see better-will be represented with certain movements of the eyeballs."
Such considerations have made it desirable to see whether experiment gives support to the view that the orbicularis palpebrarum is in part represented in the oculo-motor nucleus. The evidence is, however, as yet contradictory.
1 Brit. Med. Jour., 1902, p. 1,253.