A system of practical medicine. By American authors. Vol. 5

by Unknown

⁴⁴ Rosenthal's Diseases of the Nervous System, vol. i. p. 125.

This deviation, both of head and eyes, occurs, however, not only from lesions of the pons and cerebellar peduncles, but also from disease or injury of various parts of the cerebrum—of the cortex, centrum ovale, ganglia, capsules, and cerebral peduncles. It is always a matter of interest, and sometimes of importance, with reference especially to prognosis, to determine what is the probable seat of lesion as indicated by the deviation and rotation.

Lockhart Clarke, Prevost, Brown-Séquard, and Bastian, among others, have devoted considerable attention to this subject. To Prevost we owe an interesting memoir. Bastian, in his work on Paralysis from Brain Disease, summarizes the subject up to the date of publication (1875). Ferrier, Priestly Smith, and Hughlings-Jackson have investigated the relations which cortical lesions bear to the deviation of the eyes and head.

It has been pointed out by several of the observers alluded to that when the lesion is of the cerebrum the deviation is usually toward the side of the brain affected, and therefore away from the side of the body which is paralyzed. In a case of ordinary left hemiplegia it is toward the right; in one of right hemiplegia, toward the left. In several cases of limited disease of the pons, however, it has been observed that the deviation has been away from the side of the lesion. In our case (Case 84) the conjugate deviation was to the right, while the tumor was entirely to the left of the median line, thus carrying out what appears to be the usual rule with reference to lesions of the pons.

During the life of the patient it was a question whether the case was not one of oculo-motor monoplegia or monospasm from lesion of cortical centres. It is probable, as Hughlings-Jackson believes, that ocular and indeed all other movements are in some way represented in the cerebral convolutions. In the British Medical Journal for June 2, 1877, Jackson discusses the subject of disorders of ocular movements from disease of nerve-centres. The right corpus striatum is damaged, left hemiplegia results, and the eyes and head often turn to the right for some hours or days. The healthy nervous arrangement for this lateral movement has been likened by Foville to the arrangement of reins for driving two horses. What occurs in lateral deviation is analogous to dropping one rein; the other pulls the heads of both horses to one side. The lateral deviation shows, according to Jackson, that after the nerve-fibres of the ocular nerve-trunks have entered the central nervous system they are probably redistributed into several centres. The nerve-fibres of the ocular muscles are rearranged in each cerebral hemisphere in complete ways for particular movements of both eyeballs. There is no such thing as paralysis of the muscles supplied by the third nerve or sixth nerve from disease above the crus cerebri, but the movement for turning the two eyes is represented still higher than the corpus striatum.

It would seem a plausible theory that we have in this conjugate deviation of the eyes and head a distinct motor analogue to the hemianopsia which results from certain lesions high in the optic tracts. The fact that we never have a distinct oculo-motor monoplegia from high lesions, but always a lateral deviation of both eyes in the same direction, suggests that only a partial decussation of the fibres of the motor nerves of the eyes occurs, and that each hemisphere does not control the whole motor apparatus of the opposite eye, but half of this apparatus in each eye.

Alternating hemiplegia, or paralysis of one side of the body followed by a paralysis of the other side, is observed in tumors of the pons, and is readily accounted for by the close proximity of the motor tracts, a lesion which affects one tract first being very likely, sooner or later, to involve, partially at least, the other, as in Case 84. Cross-paralysis of the face and body may be seen, and like crossed anæsthesia (seen also in Case 84) depends upon the fact that both motor and sensory fibres to the limbs do not decussate at the same level as these fibres to the face. Trigeminal neuralgia, from involvement of the nerve by pressure or otherwise, is recorded in this characteristic group of symptoms. The association of the general with the local paralytic symptoms in the manner stated, the involvement of sensory functions, and the deviation of the eyes and head serve to distinguish tumors of the pons from cortical or high cerebral local lesions. Cases 81, 84, 89, and 90 illustrate these facts in various ways. Case 82, involving the floor of the fourth ventricle, appears to be an exception, as the deviation is toward the side of the lesion.

The special localizing symptoms which indicate a tumor of the crus cerebri are paralysis of the oculo-motor nerve upon the same side as the tumor, and especially the tendency of this paralysis to pass to the other side later in the case; disturbance of the innervation of the bladder; and involvement of the vaso-motor functions. In considering these symptoms in detail it becomes very evident why we have the alternating paralysis of the two oculo-motor nerves. As this trunk arises from the crus, it is in direct risk of injury by the neoplasm, and the extension of the new growth even slightly must later in the case involve its fellow. Therefore a ptosis, followed by a similar symptom on the other side, or other third-nerve symptoms passing from one side to the other, with other characteristic and corroborating symptoms, furnish strong evidence of this lesion, as in Case 93. Rosenthal refers especially to involvement of the bladder, as difficulty of micturition, but the three cases in the table do not present such a symptom. He says that experiments prove that irritation of the peduncle is followed by contraction of the bladder, and that it has been shown that lesions of the crus abolish the influence of the will upon micturition. As this occurs at all levels of the cord, its occurrence with lesions of the crus is not to be considered a very distinctive symptom. The involvement of the vaso-motor functions is one of much interest. Its occurrence is not recorded in the cases of tumors of the crus included in the table, but in Case 94 of twin tumors in front of the optic chiasm it is recorded that profuse perspiration occurred. We believe that the centres for the vaso-motors are not well determined: they seem to be affected by various lesions, especially about the base of the brain. Among other corroborating symptoms may be mentioned rotatory movements and deviation of the head: these rotatory movements are probably caused by the action of the sound side not antagonized by the muscles of the paralyzed side. Lateral deviation of the head is referred to by some. Partial or complete hemiplegia, with facial paralysis on the side opposite to the lesion, may occur; whereas the oculo-motor palsy is seen on the same side as the lesion. Diminution of sensibility happens on the opposite side, or occasionally pain in the legs, as recorded in Case 92. It is of interest to note, with Rosenthal, that the reactions of degeneration are not likely to appear in the facial muscles in this lesion, as it occurs above the nucleus of that nerve, and thus causes a true centric paralysis. The absence of psychic symptoms is usually to be noted.

Tumors anywhere in the middle portion of the base of the brain and floor of the skull, the region of the origin of the various cranial nerves, can of course be diagnosticated with comparative ease by a study of the various forms of paralysis and spasms in the distribution of these nerves, in connection with other special and general symptoms. Varieties of alternate hemiplegia are to be looked for, and also isolated or associated palsies of the oculo-motor, pathetic, facial, trigeminal, and other cranial nerves. In studying these palsies it must be borne in mind that although the lesions producing them are intracranial, the paralyses themselves are peripheral.

In most cases apparent exceptions to the ordinary rules as to localization are capable of easy explanation; thus, for instance, in a case of tumor of the occipital lobe (Case 44) numbness and pain were present in the right arm, although the tumor was situated in the right hemisphere. The tumor was of considerable size, and may have affected by pressure the adjoining sensory tracts.