The course and location of vestibulospinal, reticulospinal and descending propriospinal fibres in man are reported. The investigation was carried out on three patients with supraspinal lesions, four with transection of the spinal cord and 33 with anterolateral cordotomies. The lateral vestibulospinal tract at the medullospinal junction and in the first three cervical segments lies on the periphery of the spinal cord lateral to the anterior roots. It moves to the sulcomarginal angle in the remaining cervical segments. In the thoracic cord, it moves laterally, being traversed by the most lateral of the anterior roots. Reticulospinal fibres descend bilaterally in the spinal cord with a preponderance of ipsilateral fibres. Reticulospinal fibres in general do not form well-defined tracts, but are scattered throughout the anterior and lateral columns. They are intermingled with propriospinal fibres and with ascending and descending fibres of other systems. Most reticulospinal fibres move posterolaterally as they descend. It follows that fibres from the brainstem that enter the cord in the anterior column may be in the lateral column anterior to the lateral corticospinal tract at lower levels. Reticulospinal fibres within the lateral column lie anterior to the lateral corticospinal tract. They consist of scattered fibres between the lateral horn and the periphery, most of them in the medial two-thirds of the column. In addition, they are present in a more compact group, forming a triangle on transverse section on the periphery of the lateral column, immediately anterior to the lateral corticospinal tract. On the periphery of the anterior and anterolateral columns reticulospinal fibres descend as small groups or as a continuous band of fibres. The most medial of these reaches the sacral segments and is included in the sulcomarginal fasciculus. A compact group of fibres, shown previously to be central sympathetic fibres ending in the intermediolateral and intermediomedial cell columns, surrounds the lateral horn. They do not extend throughout the thoracic cord in all cases. Anterior to this group is another group of fibres lying on the anterolateral surface of the anterior horn. As these fibres were degenerating following a pontine lesion, they must be reticulospinal fibres. The fibres were not seen in all cases and they did not always reach the lowest thoracic segments. Reticulospinal fibres enter the grey matter in the zona intermedia and along the anterolateral and anterior surfaces of the anterior horns. Caudal to the cervical enlargement, the number of reticulospinal fibres decreases, and their place is taken by propriospinal fibres. But they are not totally replaced by the propriospinal fibres, for reticulospinal fibres continue down into the lowest sacral segments. Of the propriospinal fibres, the majority are short: descending fibres within the juxtagriseal layer are one to two segments long or less.

The purpose of this paper is to report briefly some findings concerning the distribution of degenerating myelinated nerve fibres in the brains of patients who had amyotrophic lateral sclerosis. It is not intended to report in detail the distribution of degenerating fibres throughout the central nervous system in this condition, nor to review the lengthy literature concerning it. In order to establish that the patients did in fact suffer from amyotrophic lateral sclerosis a few sections from the spinal cord and brain-stem showing the classical picture of the condition are included. Further, these sections are used to validate the staining methods used in the brain sections.The customary concept of amyotrophic lateral sclerosis is of a degenerative process affecting mainly the motor neurones of the central nervous system. The lower motor neurones in the spinal cord are usually affected and, to a variable extent, those of the cranial nerves. The upper motor neurones in the hemispheres may also be affected. In the spinal cord the typical fibre picture is of degeneration of cortico-spinal fibres; there is sometimes also degeneration of spino-cerebellar and other anterior and lateral column fibres.Cases have been described in which degeneration was found to extend throughout the entire corticospinal system, from the motor cortex through the cerebral peduncle, pons, medulla, and cord. But it is more frequently stated that the degeneration in the cortico-spinal tract is, in most cases, limited to the distal part of the fibres, and that it often cannot be traced further rostrally than the medulla or pons. This was the experience of Davison, who reported in 1941 (a and b) that in the 37 cases which he had studied he could not find any degeneration above the medulla in 16 cases, nor above the peduncle in 25 cases. On the other hand, Holmes had found degeneration throughout the cortico-spinal system, from cortex to cord inclusively, in all 10 of the 10 cases he reported in 1909. Later workers have tended to neglect both his work and the methods he used.Apart from the degeneration in the cortex, a little degeneration has been occasionally noted in other parts of the brain. Holmes found a few fibres passing between the main mass of degenerating cortico-spinal fibres in the internal capsule and the lateral nucleus of the thalamus. These degenerating fibres were observed in three of the 10 cases he studied. Other workers do not seem to have confirmed this finding. A very few degenerating fibres have also been occasionally seen in the brain-stem. These observations have never been adequately illustrated nor confirmed; nor have they been generally accepted. Material and MethodsThe material consists of the central nervous system from seven patients who were diagnosed as suffering from amyotrophic lateral sclerosis.In the first three cases representative blocks from different regions of the brain and cord were examined. In the last four cases a large series of blocks was taken from the hemispheres. As the first three cases had reve...

Ten cases are presented which illustrate aspects of the anatomy of the rubrospinal and central tegmental tracts in man. It is concluded that the number of large fibres arising from the magnocellular part of the red nucleus and constituting the classical rubrospinal tract is small and that only a few fibres project into the spinal cord; these cannot usually be traced caudal to the upper cervical segments. There is a very large number of rubro-olivary fibres arising from the parvocellular part of the red nucleus, which run in the central tegmental tract. This tract also contains descending fibres that do not originate in the red nucleus and fibres that do not terminate in the olive. The literature on the rubrospinal tract and the rubro-olivary component of the central tegmental tract in primates in reviewed. Comparative anatomical studies are also briefly reviewed; they accord with the findings reported here for man.

Clinical observations are presented on the sensory effects of lesions of different afferent pathways of the spinal cord, correlated whenever possible with histological evidence of the location and extent of the lesions. They are based on personal cases and on significant cases in the literature, including posterior column section, other causes of damage to the posterior columns, and cases of commissural myelotomy. It is concluded that the traditional view of the effects of lesions of the posterior columns is correct, but that evidence from cases proved by postmortem examination is still needed. When the information normally supplied by the posterior columns is cut off, primary sensibility for light touch and pressure is not lost, but any kind of discrimination is disturbed. There is also a disturbance in knowledge of movement and position, ataxia, and clumsiness in the use of the hands. These defects greatly affect the palpatory examination of objects and, although they may appear slight on routine neurological examination, they can cause severe disturbances in the activities of daily living. For tactile modalities, a lesion of the spinothalamic complex causes minimal or no defects and a lesion of the posterior columns causes only slight defects, whereas a lesion of both pathways gives rise to total loss of tactile and pressure sensibility in the part of the body served by both pathways. This conclusion is based on 2 cases with combined commissural myelotomy and anterolateral cordotomy. The following disturbances of mechanoreception attributed to lesions of the posterior columns are discussed: lability of threshold, persistence of sensation, tactile and postural hallucinations and temporal and spatial disturbances. In man, lesions of the posterior columns cause an increase in pain, tickle, warmth and cold. Cases are presented with and without lesions of the posterolateral columns in conjunction with lesions of one or both anterolateral columns. As these lesions did not affect sensation and as there was no difference in the sensory state following anterolateral cordotomies with or without involvement of the posterolateral column, it is concluded that lesions of this column have no effect on sensation. Cases with lesions of the anterior two-thirds of the cord are also presented to illustrate the sensory state with only the posterior third of the cord intact. In these cases, tactile and pressure sensibility and knowledge of movement and position are normal.

The course, location and relations of the corticospinal tracts within the spinal cord of man are demonstrated on the basis of cases with lesions above the spinal cord restricted to the corticospinal tracts, of motor neuron disease, and of anterolateral cordotomies; control cases were of normal spinal cords. The following features of the lateral corticospinal tract are emphasized in the cervical cord: (1) the large extent of the white matter of the cord covered by the tract, and the anterior extent of the tract, the border being anterior to the central canal; (2) in the lower cervical cord, the separation of fibres from the main mass of the tract, which reach the periphery of the cord in the anterolateral sector; (3) the presence in many cords of the ventral crossed bundle; and (4) the relationship of the denticulate ligament to the tracts in the cervical segments. The following features of the anterior corticospinal tracts are emphasized: (1) their location, caudal extent and asymmetry; and (2) the changes in location in relation to the median fissure as the tract descends and its relationship to other tracts of the anterior column. Three-quarters of spinal cords are asymmetric and in three-quarters of asymmetric cords the right side is the larger. The asymmetry is due to a greater number of corticospinal fibres crossing to the right side. As more fibres have crossed in the decussation, the anterior tract opposite the large lateral tract is smaller than the ipsilateral anterior tract: that accounts for the asymmetry of the two halves of the cord. The greater number of corticospinal fibres in the right side of the cord is unrelated to handedness, but correlates with the fact that in three-quarters of corticospinal decussations, the crossing from left to right occurs at a more cranial level than the opposite crossing. A group of short peripheral ascending fibres is described running along the sides of the median fissure in the thoracic cord.