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Biomedical subjects

P W Nathan

Publications and source records attributed to P W Nathan.

At least 19 recordsLinked to original sources
PubMed1994

Effects on movement of surgical incisions into the human spinal cord.

In 44 patients having cordotomies for relief of the pain of cancer, a correlation was made between the location and extent of the incision in the spinal cord and the motor state. Post-mortem histological examination of the spinal cord was carried out in all areas. An incision cutting through one anterior quadrant of the cord at any segmental level could be made without causing any disturbance of motility. An incision in the thoracic segments cutting through the anterior half of the cord could be made without causing any disturbance of motility. This fact implies that tracts in the posterior half of the cord can supply the input from the brain necessary for the maintenance of functions normally mediated by tracts in the anterior half of the cord. The more posterior the incision reached in the posterolateral column, the greater were the defects in motility. A large unilateral lesion dividing most of the lateral corticospinal tract, and the descending fibres anterior to it, caused flaccid paralysis of the ipsilateral lower limb. Voluntary movements started to return within 5 h. An incision in the thoracic cord cutting through one lateral corticospinal tract and 85-90% of the opposite tract and reticulospinal fibres anterior to that tract caused total paralysis of the lower limbs. Recovery ensued over 2 months so that the patient eventually walked, though with severe spastic paraparesis. Recovery of some flexor and extensor movements of the ipsilateral fingers and toes occurred within 6 h of an incision being made in the upper cervical cord that divided the lateral corticospinal tract unilaterally. Division of only the anterior fibres of the lateral corticospinal tract above the cervical enlargement did not affect the motility of the ipsilateral upper limb. It is concluded that in the more cranial segments of the spinal cord, corticospinal fibres destined for the upper limb are in the more posterior part of the tract. Correlation of the clinical with the histological evidence of a lesion of the lateral corticospinal tract was carried out. When it was deduced on the clinical evidence that the tract was damaged, this was always found to be correct. On the other hand, the tract might show histological evidence of damage without manifesting any evidence of a lesion. The Babinski response was found, in general, to occur with lesions of the lateral corticospinal tract and not with lesions elsewhere in the cord.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1990

The corticospinal tracts in man. Course and location of fibres at different segmental levels.

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.

Adult↗
PubMed1990

Touch and surgical division of the anterior quadrant of the spinal cord.

An investigation was carried out to determine whether tactile sensibility was affected by anterolateral cordotomy. There were 65 patients who had cordotomies for painful forms of cancer. Thirty eight had necropsy examination with histological investigation of the spinal cord. No form of mechanoreception was removed in any of the 65 patients and in the majority no forms of tactile sensibility were altered by division of the pathways in the anterolateral and anterior columns. In no case was graphaesthesia affected. Knowledge of joint position and movement and awareness of vibration was normal in 62 of the 65 patients. But information carried by these anterolateral pathways does reach neural levels of consciousness, for with total lesions of the posterior columns, previously reported, touch and pressure are still felt. Itch was removed by division of the anterolateral pathways. Although the posterior columns are essential for discrimination in mechanoreception, discrimination may be disturbed by lesions of the anterolateral pathways, notably two-point discrimination. The evidence on the pathways essential for conveying impulses giving rise to tickle was inconclusive.

Afferent Pathways↗
PubMed1987

The location of descending fibres to sympathetic preganglionic vasomotor and sudomotor neurons in man.

Evidence is given of the location in the spinal cord of man of the central sympathetic fibres supplying vasomotor and sudomotor neurons of the body caudal to the head and neck. The evidence is based on anterolateral cordotomies. The fibres lie within the medial part of the equatorial plane, extending from the base of the posterior horn and the lateral horn across the medial half of the white matter. The evidence from a previous paper together with that of the present paper is that the pathway maintains this position throughout the spinal cord as far as the L2 segment. The sympathomotor fibres caudal to the head and neck are supplied from both sides of the cord: sympathetic activity is not removed, although it may be slightly diminished, by a hemisection of the cord. The evidence suggests that sympathetic fibres for vasomotor control leave the cord cranial to the Th 7 segment. The knowledge of the location of the pathways is of value to neurosurgeons so that they may be avoided in the operation of anterolateral cordotomy.

Efferent Pathways↗
PubMed1986

Sensory effects in man of lesions of the posterior columns and of some other afferent pathways.

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.

Animals↗
PubMed1986

The location of descending fibres to sympathetic neurons supplying the eye and sudomotor neurons supplying the head and neck.

Evidence is given of the location in man of the fibres going to the sympathetic neurons of the lateral horn that supply the intrinsic and extrinsic muscles of the eye and the sweat glands of the head and neck. For the region of the pons and medulla, the evidence is abstracted from the literature. For the cervical spinal cord, the evidence is from our cases of anterolateral cordotomy. In the medulla, thrombosis of the artery of the fossette latérale destroys the fibres; this locates the fibres in the posterolateral retro-olivary area. But not all fibres to the sudomotor neurons lie there: some run elsewhere, though they probably remain ipsilateral. In the cervical cord, the fibres supplying the sympathetic neurons of the intrinsic and extrinsic muscles of the eye run near the posterior angle of the anterior horn. Most of the fibres supplying the sudomotor neurons lie in the same region, though some lie outside this area but on the same side of the cord.

Adrenergic Fibers↗
PubMed1984

Sensory consequences of commissural myelotomy. A challenge to traditional anatomical concepts.

Twenty-five cases of commissural myelotomy were studied. Representative cases are reported, including a histological examination of the lesion in one. Although the purpose of the operation is to produce a cuirass of loss of pain sensibility by dividing the spinothalamic and spinoreticulothalamic fibres as they decussate in the anterior commissure of the cord, this result is not always obtained. Whether or not the expected sensory loss is obtained, the chronic pain for which the operation is performed can be relieved. Sensibility tends to return towards normal after myelotomy. Even with substantial recovery of sensory loss, the pain for which the operation was performed can remain absent. Asymmetrical sensory loss may be produced by the operation; reasons for this are suggested. Differences between the results of commissural myelotomy and anterolateral cordotomy are discussed. Unlike the results of anterolateral cordotomy, which can be accounted for on the basis of known anatomy, the results of commissural myelotomy are inexplicable on present anatomical knowledge. Attention is drawn to the results of myelotomy reported originally by Hitchcock and confirmed by other neurosurgeons in which a short myelotomy incision in the upper cervical cord caused loss of pain over a vast region of the body. The difficulty in explaining the patterns of sensory loss in these cases is discussed. The literature on pathways alternative to the spinothalamic and spinoreticulothalamic is reviewed. It is argued that the central incision cannot cause relief of pain merely by cutting an afferent pathway, and it is suggested that this lesion blocks impulses entering into, in, or leaving the spinothalamic complex. The accurate localization of pinprick and thermal stimuli via the spinothalamic tract is demonstrated.

Afferent Pathways↗
PubMed1984

Acupuncture versus medical treatment for migraine and muscle tension headaches.

In 48 patients with chronic migraine and muscle tension headaches, a comparison was made between a prophylactic course of acupuncture and of medical treatment. It was intended that all patients should have 3 months with both forms of treatment, but 19 were unwilling to change from one form of prophylaxis to the other. Twenty-four of 41 patients improved on acupuncture, the improvement being very marked in nine; nine of 36 patients improved on medical treatment, the improvement being marked in three. Of the 29 patients who changed from one form of treatment to the other, a larger proportion preferred acupuncture to medical treatment. A beneficial response to acupuncture was more likely when the patient had local tender muscular points. The presence of depressive features did not preclude satisfactory treatment with acupuncture. No major side effects were encountered with acupuncture.

Acupuncture Therapy↗
PubMed1982

The rubrospinal and central tegmental tracts in man.

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.

Adult↗
PubMed1981

Pain due to lesions of central nervous system removed by sympathetic block.

Eight patients were studied in whom a lesion within the central nervous system caused constant pain and hyperpathia. Blockade of the sympathetic supply to the periphery was carried out in each patient by stellate ganglion block or intravenous infusion of guanethidine 15 mg in 30 ml saline into a limb on the affected side. On almost every occasion the pain and hypersensitivity were reduced, sometimes completely. Thus chronic pain and hyperpathia arising from a lesion in the central nervous system may be abolished by blocking the sympathetic supply to the periphery; this effect may be achieved when not all the peripheral nerves of the affected region have had their sympathetic nerve supply blocked. Such blockade may be worth repeating in the hope of achieving lasting relief of the intractable pain.

Adult↗
PubMed1980

Transcutaneous electrical nerve stimulation for chronic pain.

The results of 7 years experience in treating pain with transcutaneous electrical stimulation are reported. It was used on a group of 74 patients with postherpetic neuralgia and on a mixed group of 161 patients with chronic pain due to other conditions for which other forms of treatment had been unsatisfactory. The patients were lent stimulators and electrodes of various kinds. A half of the patients returned their stimulators after one month, but a quarter of the patients were still using transcutaneous stimulation after 2 years. No particular disease responded better or less well than any other; no particular kind of pain responded particularly well or badly. One third of the patients with postherpetic neuralgia started improving from the commencement of stimulation.

Chronic Disease↗
PubMed1980

Clonus: the role of central mechanisms.

The peripheral and central components in sustained clonus were investigated. The excitability of the motoneurons responding to maintained stretch by clonus was examined by tendon taps, trains of vibratory stimuli and by H-reflex afferent volleys. Every burst of clonic discharge of the motoneurons was shown to be followed by a refractory period, which was followed by a shorter excitatory period. It was concluded that the motoneurons responding clonically to a continuous stretch cannot respond until their excitability has been regained after the refractory period. Attempts to change the rate of clonus in various ways failed to do so. Whether motoneurons of clonic muscles tend to respond maximally to other Ia volleys at the rate of clonus was examined by applying repeated taps to the tendon at rates from 1 to 15 Hz. There was a maximal response at the rate of clonus. Inputs other than those induced by stretch cause clonus; examples of cutaneous inputs causing it are given.

Afferent Pathways↗
PubMed1980

Effects of regional guanethidine infusion in certain painful states.

Guanethidine was infused by the regional intravenous technique into upper and lower limbs of patients with painful hyperpathic states, due to peripheral or central lesions. The relief of pain and hyperpathia occurred within 20 minutes of infusion and lasted between three and 128 hours; in a few patients, the relief has lasted for months. Great reduction in skin conductance and vasodilatation occurred, there being marked variation in the time of onset and duration of these effects. In some cases there was marked pilo-erection. Guanethidine given in this way did not completely block the sympathetic control of digital blood-vessels. There were no effects on sensibility of normally innervated regions.

Chronic Disease↗