The exact nature of the lesion is more difficult to determine. A review of the details of the facial palsy suggests its vascular origin, to which theory the headache, nausea, and photophobia of succeeding days and months—indicating, as they do, a circulatory disturbance in the basilar region—lend support. With the gradual restoration of vascular equilibrium the migrainous attacks lessened in frequency and severity, though the facial trunk remained compressed, till the spasm appeared, no less suddenly than had the paralysis. It is feasible that the former, too, is the derivative of a minute hæmorrhage irritating either the centrifugal or the centripetal arm of the facial reflex arc, probably the latter, which would explain the paræsthesiæ.

The possibility of this explanation being accurate is confirmed by a case reported by Schültz, where facial spasm of ten years' duration was shown at the autopsy to have been caused by an aneurism of the left vertebral artery impinging on the facial nerve in the neighbourhood of the basilar trunk.

The arguments, therefore, which plead in favour of the spasmodic nature of the condition seem to us so cogent that the hypothesis of tic must be rejected. We ought not to forget, on the other hand, that a spasm, of whatsoever origin, may be transformed into a tic by the perpetuation of a morbid habit.

Let us take a second case, no less instructive than the preceding.

Madame L. was sent to one of us by Professor Pierre Marie. She had always been nervous, impressionable, and high-spirited, but had never suffered from fits. At the age of eight years, during convalescence from one of the exanthemata, she got a chill, and the very next day developed an acutely painful torticollis, the head resting on the right shoulder and the chin touching the left clavicle. A complete cure ensued, but from that time a certain degree of facial asymmetry was remarked. At the age of eight and a half menstruation commenced, and it still continues, at the age of fifty-nine.

From youth she had at intervals been stricken with pains in the limbs, and with recurrent bilious attacks. Two years ago the death of her husband was the occasion of great mental strain and distress. Sixteen months ago she noticed a curious sensation in the right eye, not painful, accompanied from time to time by blinking of the lids. Very gradually the convulsive movements spread over the whole of the right face, and for the last month their frequency and intensity have been such that rest is an impossibility.

When she came under observation what impressed the mind first was the remarkable asymmetry of her figure: the right side of the face was smaller than the left, the right eye appeared to be at a lower level than the other, while the mouth was strongly deviated to the right and the chin twisted in the same direction. For a minute or two the facial contortion held sway, disappearing only to reappear quickly.

Not solely to the old torticollis was the facial asymmetry attributable, but also to the convulsive movements of the right half of the face. The effect of these was to close the right eye, deflect the nose to the same side, drag the mouth in a similar fashion, and wrinkle the skin of the chin and neck. Hence was evolved a unilateral grimace quite unlike any ordinary expression, resembling rather the facies in contracture secondary to facial paralysis.

During the next few months there was a gradual change from this tonic to a clonic stage, in which the movements were of less frequent occurrence, but more rapid. In repose there was no further indication of the old facial palsy than the flattening of the facial lines on the right. Under the influence of any emotion, or any passing contrariety, or in the course of an animated conversation, or if circumstances call for their repression, the spasms increase in number and degree, whereas solitude and tranquillity favour their subsidence.

A recent development has been the discovery of a means of checking the spasm—viz. by compressing the larynx with the fingers of the two hands. Madame L. admits the illogical nature of the manœuvre, but extols its efficacy. As a matter of fact, it sometimes fails of its object.