Cervical Cord Segments Research Articles

Projection of nodose ganglion cells to the upper cervical spinal cord in the rat

Afferent fibers mediating pain from myocardial ischemia classically are believed to travel in sympathetic nerves to enter the thoracic spinal cord. After sympathectomies, angina pectoris still may radiate to the neck and inferior jaw. Sensory fibers from those regions are thought to enter the central nervous system through upper spinal cord segments. We postulated that axons from nodose ganglion cells might project to cervical cord segments. The purpose of this study was to determine the density and pathway of vagal afferent innervation to the upper cervical spinal cord. Following an injection of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) into the upper cervical spinal cord, approximately 5.8% of cells in the nodose ganglion contained reaction product. Cervical vagotomy did not diminish the density of WGA-HRP labeled cells in the nodose ganglion. However, a spinal cord hemisection cranial to the injection site eliminated labeling of nodose cells. These data indicate that a portion of vagal afferent neurons project from the nodose ganglion to the upper cervical spinal cord. In addition, vagal afferent fibers reach the spinal cord via a central route rather than through dorsal root ganglia.

Direct recording of somatosensory evoked potentials in the vicinity of the dorsal column nuclei in man: their generator mechanisms and contribution to the scalp far-field potentials

Somatosensory evoked potentials (SEPs) in the vicinity of the dorsal column nuclei in response to electrical stimulation of the median nerve (MN) and posterior tibial nerve (PTN) were studied by analyzing the wave forms, topographical distribution, effects of higher rates of stimulation and correlation with components of the scalp-recorded SEPs. Recordings were done on 4 patients with spasmodic torticollis during neurosurgical operations for microvascular decompression of the eleventh nerve. The dorsal column SEPs to MN stimulation (MN-SEPs) were characterized by a major negative wave (N1; 13 msec in mean latency), preceded by a small positivity (P1) and followed by a large positive wave (P2). Similar wave forms (P1′-N1′-P2′) were obtained with stimulation of PTN (PTN-SEPs), with a mean latency of N1′ being 28 msec. Maximal potentials of MN-SEPs and PTN-SEPs were located in the vicinity of the ipsilateral cuneate and gracile nuclei, respectively, at a level slightly caudal to the nuclei. The latencies of P1 and N1 increased progressively at more rostral cervical cord segments and medulla, but that of P2 did not. A higher rate of stimulation (16 Hz) caused no effects on P1 and N1, while it markedly attenuated the P2 component. These findings suggest that P1 and N1 of MN-SEPs, as well as P1′ and N1′ of PTN-SEPs, are generated by the dorsal column fibers, and P2 and P2′ are possibly of postsynaptic origin in the respective dorsal column nuclei. The peak latency of N1 recorded on the cuneate nucleus was identical with the scalp-recorded far-field potential of P13–14 in all patients, while no scalp components were found which corresponded to P2. These findings support the previous assumption that the scalp-recorded P13–14 is generated by the presynaptic activities of the dorsal column fibers at their terminals in the cuneate nucleus.

Examination of spinal cord in diseases of the craniocervical junction and high cervical spine.

A simple necropsy technique for the removal of the craniocervical junction was devised: a relatively small specimen comprising part of the clivus, the foramen magnum, and cervical vertebral canal is removed in one piece with the medulla and spinal cord inside, and examined systematically after fixation. This method, used in a series of patients with chronic craniocervical instability, allows both good clinicopathological correlations to be made and histological changes in the lower medulla or upper cervical cord segments to be related to sites of extrinsic compression.

Spinal distribution and collateral projections of rat spinomesencephalic tract cells

The distribution of cells belonging to the rat spinomesencephalic tract was studied by means of the retrograde transport of fluorescent dyes. Bilateral midbrain injections of cytoplasmic and nuclear tracers were made in order to evaluate the location of ipsilateral, contralateral, or bilaterally projecting cells. Spinal neurons with ascending projections to midbrain and descending propriospinal projections were identified by midbrain and spinal injections of different cytoplasmic labels. The locations of spinomesencephalic tract cells included seven regions of the spinal gray matter: marginal zone, lateral neck of the dorsal horn, nucleus proprius, the region around the central canal, the lateral cervical and spinal nuclei and the ventral horn. Cells projecting to the ipsilateral or contralateral midbrain had similar distributions and were frequently found in clusters with overlapping dendritic fields. Approximately 75% of spinomesencephalic cells projected to the contralateral midbrain. The largest contribution to the spinomesencephalic tract cell population was found in cervical cord segments 1–4. Cells with bilateral projections accounted for nearly 2% of all labeled cells, whereas 5% had both ascending and descending projections. Spinomesencephalic cells were found to have varying dendritic fields and morphology, e.g. fusiform, pyramidal, round/oval, and multipolar. The results of the present study lend further support to the view that the spinomesencephalic tract is a multi-component pathway with varied origins and projection targets.

Infrahyoid and accessory motoneurons in the japanese monkey (Mascaca fuscata)

The segmental and topographical organization of motoneurons innervating the infrahyoid (IH) and the spinal accessory (AC) muscles was studied in the Japanese monkey (Macaca fuscata) with the retrograde horseradish peroxidase (HRP) method after application of HRP to the peripheral nerve branches supplying the IH and AC muscles. IH motoneurons constitute two distinct slender cell columns, a longer medial and a shorter lateral one. The medial cell column extends from the most caudal level of the hypoglossal nucleus to the lower levels of the second cervical (C2) cord segment. In the medial column, motoneurons supplying the sternohyoid and sternothyroid muscles are distributed at the medullary and C1 levels, while those innervating the omohyoid muscle are primarily distributed at the C2 level. The lateral cell column consists of motoneurons supplying the thyrohyoid muscle and extends from the most caudal level of the hypoglossal nucleus to the middle levels of the C1 cord segment. Axons of thyrohyoid motoneurons follow a dorsomedially directed bent emergent course, making a hairpin turn. AC motoneurons supplying the sternocleidomastoid (SC) and trapezius (TZ) muscles form a single slender cell column extending from the most rostral level of the pyramidal decussation to the middle levels of the C6 cord segment. SC motoneurons are distributed from the most rostral level of the pyramidal decussation to the middle levels of the C3 cord segment, while TZ motoneurons are distributed from the upper levels of the C2 cord segment to the lower levels of the C6 cord segment. At the levels of the C2 and C3 cord segments, both SC and TZ motoneurons are distributed in the AC cell column; the cluster of SC motoneurons is located dorsomedial to that of TZ motoneurons.

Contralateral projections of trigeminal mandibular primary afferents in the guinea pig as seen by transganglionic transport of horseradish peroxidase

Transganglionic transport of horseradish peroxidase (HRP) was used to investigate contralateral projections of trigeminal mandibular fibers in the guinea pig. After application of HRP to the buccal, lingual, auriculotemporal, mylohyoid, mental and inferior alveolar nerves, crossing fibers and contralateral endings were found in the caudal region of the nucleus of the solitary tract (most of these belonging to the buccal and lingual nerves), the dorsomedial region of the subnucleus caudalis of the trigeminal sensory nuclear complex (TSNC), and the dorsal horns of the first 5 cervical spinal cord segments (C 1–C 5). The greatest numbers of crossing fibers in the medullary and cervical dorsal horn segments belonged to the mental and mylohyoid nerves, though these nerves did not project contralaterally to C 4–C 5. Contralateral buccal and lingual endings were scattered sparsely from the subnucleus caudalis to C 5, and only very few contralateral auriculotemporal terminals were observed. Though laminae I–V of the dorsomedial region of the medullary and cervical dorsal horns all exhibited contralateral endings of the mental and mylohyoid nerves, most such endings were found in laminae II i–III, followed by lamina IV, which suggests their involvement in the reception of mechanical stimuli and in the sensory motor reflexes of the orofacial region. The contralateral buccal and lingual terminals were distributed somatotopically in the first 5 cervical cord segments, with the lingual endings rostral to the buccal terminals within each segment. In C 4 and C 5 lingual endings appeared exclusively in laminae I and II o, suggesting that like the ipsilateral lingual projections at this level, which also terminate in these laminae, they may be involved in pain and temperature sensation.

The cells of origin of the hypoglossal afferent nerves and central projections in the cat

The cells of origin for the hypoglossal afferent nerves of the cat and their central projections were examined using the transganglionic and somatopetal transport of horseradish peroxidase (HRP). Primary afferent neurons from the hypoglossal nerve were located in the trigeminal ganglion, the superior ganglion of glossopharyngeal and vagal nerves, and the first 3 cervical ganglia. The central projections of hypoglossal afferents were organized in a selective manner according to their cells of origin. The primary afferent nerves originating from the trigeminal ganglion terminated in the subnucleus dorsalis (Vpd) of the principal nucleus (Vp), lateral margin of the caudal pars interpolaris (Vi), interstitial nucleus and laminae I and V of the pars caudalis (Vc). The projection of the afferent nerves for glossopharyngeal and vagal origins are similarly organized in the Vi and Vc to those of trigeminal origin, but differed in that they terminated ipsilaterally in the caudal half of the solitary nucleus and bilaterally in the commissural nucleus. The primary afferents arising from the first 3 cervical ganglia terminated in laminae I and V of the corresponding cervical cord segments.

Embryonic spinal cord neurons develop preferential cholinergic projections to sympathetic ganglia explanted from appropriate levels of the neuraxis

To determine whether cholinergic spinal cord neurons can develop preferential projections in vitro within sympathetic ganglia (SGs) of appropriate levels of the neuraxis, organotypic explants of fetal mouse spinal cord (E13) from cervical, thoracic (upper and lower) and lumbar segments were co-cultured with either pairs of neonatal SGs: the rostral superior cervical ganglion (SCG) or a caudally located upper lumbar ganglion (LG). After 3.5–4 weeks of co-culture, levels of the enzyme, choline acetyltransferase (ChAT), were measured in individual spinal cord explants and SCGs or double LGs (to match the target mass of a single SCG). Interaction was assumed to occur primarily between an SCG or LG doublet and the adjacent ipsilateral half of the co-cultured cord segment. An index of cholinergic interaction was defined as the ganglion ChAT activity per unit ChAT activity in half co-cultured cord segment. The index of interaction with the SCG was highest with the T 1/T 2 (1.4) as compared with the T 10/T 11 (0.79). L 1/L 2 (0.38) and C 2/C 3 (0.11) segments. In contrast, the index of cholinergic interaction with double LGs was highest with the more caudally located T 10/T 11 (0.62) cord segment as compared with the rostral T 1/T 2 (0.33), cervical C 2/C 3 (0.2) and lumbar L 1/L 2 (0.17) segments. Ganglion compound action potentials evoked in LGs by stimulation of the ipsilateral portion of T 10/T 11 cord were blocked by the ganglionic antagonist, hexamethonium, as previously observed in co-cultures of SCGs with T 1/T 2 cord. These results indicate that pools of preganglionic neurons in thoracic cord segments can develop in vitro preferential cholinergic projections within SGs of appropriate position. Cervical and lumbar cord segments which contain a preponderance of somatic motoneurons over preganglionic neurons did not interact as effectively with either type of SG. The preferential cholinergic projections from rostral thoracic cord explants within co-cultured SCGs and from caudal thoracic cord explants within LGs may reflect some degree of positional preference intrinsic to embryonic spinal cord neurons and/or their appropriate target SGs, consistent with the positional specificity expressed by preganglionic neurons and SGs in situ.

An Experimental Evaluation of Response to Contrast Media: Pantopaque, Iopamidol, and Iohexol in the Subarachnoid Space

Myelography in dogs was performed with Pantopaque, iopamidol and iohexol. The effects of these agents were evaluated by histologic study of the brain, spinal cord, and meninges four months after the procedure. Retained Pantopaque was always accompanied by some degree of arachnoidal reaction, mild in the cervical cord segment and severe in the most caudal part of the cul-de-sac. No apparent protection against Pantopaque arachnoiditis was provided by either intrathecal or intramuscular methylprednisolone. We found no histologic evidence of arachnoiditis in animals examined with iopamidol and iohexol.

Preferential cholinergic projections by embryonic spinal cord neurons within cocultured mouse superior cervical ganglia

The development of preferential cholinergic projections of spinal cord neurons within superior cervical ganglia (SCG) was analyzed in vitro using cocultures of SCGs (E17) with organotypic explants of fetal mouse cord (E13). The cord explants consisted of: (1) dorsal vs medioventral strips or mediodorsal vs ventral strips (dissected from levels C 8-T 4), or (2) transverse sections cut at various levels of the neuraxis. After 4 weeks of coculture, choline acetyltransferase (ChAT) was assayed in individual explants to quantify development of the cholinergic neurotransmitter enzyme (a) within the cord neurons, and (b) within the SCG. An index of cholinergic interaction was calculated as the relative ChAT activity in cocultured ganglion per unit ChAT activity in the ipsilateral cord strip. The highest index value (0.7) was obtained in cocultures with mediodorsal strips of cord. The index of interaction was progressively lower with medioventral (0.4), ventral (0.3) and dorsal (0.1) cord. In cocultures of transverse sections of spinal cord and SCGs, the highest indices of cholinergic interaction (expressed per hemisection of cord) were obtained with cord levels T 1/T 2 (1.0) and T 5 (0.9). The index decreased with T 9 (0.7) and was significantly lower with segments C 2/C 3 (0.3) and L 2/L 3 (0.19). Addition of a skeletal muscle target e explant to the cord-SCG cocultures did not alter the preferential index of interaction between SCG and upper thoracic cord levels. Furthermore, the cholinergic cord neurons in medioventral strips did not promote increase of ChAT activity into equally accessible cocultured ganglia of inappropriate phenotype, e.g. sensory dorsal root ganglia. Decentralization of SCGs after coculture with appropriate T 1/T 2 cord resulted in loss of ganglionic ChAT activity. Electrical stimulation of the medial region in T 1/T 2 cord explants evoked compound ganglion action potentials in cocultured SCGs. The ganglion responses were blocked by hexamethonium. These data suggested that neurons located in the medial region of upper thoracic cord (presumably autonomic preganglionic) are able to develop enhanced cholinergic projections within cocultured SCGs, in comparison with neurons located in ventral cord (presumably motoneurons). In contrast, dorsal cord neurons showed no significant cholinergic interaction with SCGs. Furthermore, neurons located in upper thoracic spinal cord segments develop enhanced cholinergic projections within cocultured SCGs in comparison with neurons located in cervical and lumbar cord segments.

Mystacial vibrissae representation within the trigeminal sensory nuclei of the cat

Somatotopic arrangements of axon terminals of primary afferent fibers innervating follicles of the mystacial vibrissae were examined in the cat by the transganglionic horseradish peroxidase (HRP) method. Forty to 60 hours after injecting HRP into a single or a group of vibrissal follicles, transported HRP was visualized by the tetramethylbenzidine technique. HRP-labeled axon terminals were distributed in the ventral subnucleus of the principal sensory trigeminal nucleus (ventral Vp), in the oral and interpolar spinal trigeminal nuclei (Vo and Vi), and in the caudal spinal trigeminal nucleus (Vc) (layer I, deep part of layer II, layers III-V) with its spinal extension into the dorsal horn of the first cervical cord segment (rostral C1). In cross sections through the caudal parts of the ventral Vp, Vi, and layer IV of the Vc and rostral C1, a single mystacial vibrissa was represented in a one-to-one fashion by a patch of dense terminal arbors of primary afferent fibers. The more dorsally a horizontal row of the mystacial vibrissae was located, the more ventrally was it represented in the ventral Vp, the more ventrolaterally in the Vi, and the more ventrally in layer IV of the Vc and the rostral C1. In addition, the more anteriorly a vibrissa was located in a horizontal row of the mystacial vibrissae, the more medially was it represented in the ventral Vp, the more ventromedially in the Vi, and the more laterally in layer IV of the Vc and rostral C1; the most posteriorly located vibrissae in the horizontal rows of the mystacial vibrissae were represented along the lateral border of the ventral Vp and Vi, and most medially in layer IV of the Vc and rostral C1. Thus, the representation pattern in the ventral Vp was rotated clockwise at about 45 degrees angle in the Vi, and projected as a mirror image in layer IV of the Vc and rostral C1. It was also indicated that the anterior-posterior arrangement of the mystacial vibrissae was represented in a rostral-caudal organization within layer IV of the Vc and rostral C1. It was also indicated that the anterior-posterior arrangement of the mystacial vibrissae was represented in a rostral-caudal organization within layer IV of the Vc and rostral C1. Patchy patterns probably replicating the distribution of the vibrissae on the face of the cat were also revealed by the cytochrome oxidase histochemical staining in cross sections through the caudal parts of the ventral Vp, Vi, and layer IV of the Vc and rostral C1.

Electron microscopy studies of the effect of interception of snout sensory input on the masticatory system

In order to obtain neuroanatomical evidences as to how the interception of the sensory input affects the masticatory system, the unilateral or bilateral transection of the infraorbital nerve was made on the Japanese shrew-moles and rats. The animals were sacrificed postoperatively for electron microscopy at intervals of 14 to 450 days. The masseter and temporal muscles, trigeminal ganglion with the proximal and distal stumps and the brain stem with the upper cervical cord segments were examined electron microscopically.The results obtained are summarized as follows:1. The preganglionic and postganglionic parts of the trigeminal nerve showed definitely degenerated changes, that is, the degenerated fibers disappeared completely in the former but the majority of the degenerated fibers were retained as debris in the latter. The ganglion cells underwent typical chromatolysis with lipidosis.2. In the trigeminal spinal tract nucleus, many of the transganglionically degenerated synapses were in contact with the degenerated dendrites of the secondary neurons. There were also degenerated sencondary neuron soma (lipidosis) .3. The alpha motor end-plates and muscle spindles of the masticatory muscles showed definitely degenerated features.From the results obtained it can be emphasized that the snout sensory input plays a great role in the performance of the masticatory activities in the animals.

Cells of origin of spinopontine fibers in the rat

When wheat germ agglutinin-horseradish peroxidase conjugate was injected into the caudal part of the medial, lateral, ventral and peduncular pontine nuclei in the rat, retrogradely labeled spinal neurons were found contralaterally in the intermediate basilar nucleus (IBN) in the upper two cervical cord segments, and in laminae VI and VII in the lumbar cord segments. The IBN appeared to send fibers mainly to the caudomedial part of the pontine nuclei, while laminae VI and VII of the lumbar cord segments of the caudolateral part of the pontine nuclei.

Amygdalospinal projections in the macaque monkey

Injection of horseradish peroxidase into the cervical cord in the macaque monkey led to the retrograde labeling of neurons in the caudal part of the central nucleus of the amygdala ipsilateral to the spinal half where the injection was made. Although the number of labeled neurons in the amygdala was small, they were constantly found in 7 macaque monkeys (3 Japanese monkeys, 3 crab-eating monkeys and 1 rhesus monkey) which were injected with the enzyme into the upper and middle cervical cord segments.

Localizing spinal-cord-projecting neurons in neonatal and immature albino rats.

According to results from the horseradish peroxidase (HRP) method of tracing neuronal connections, the spinal cords of neonatal and immature rats receive a large number of descending projections from the first cervical cord segment, various brain-stem nuclei, and deep cerebellar and diencephalic nuclei. All these projections are present at birth, though at this age some of them are not fully established. Thus, only a few cells in the trigeminospinal, solitariospinal, tectospinal, and cerebellospinal groups were labeled after HRP injection in the lumbosacral or cervical cord segments in neonatal animals. They were clearly labeled in older, immature animals. The labeled neurons in other descending pathways appeared to be equal in density in neonatal, immature, and adult rats. This visual impression was stregthened by the counts of neurons in the interstitial nucleus of Cajal, which showed no significant difference in the number of labeled neurons in the three age groups. However, counts of labeled cells in the lateral vestibular nucleus and nucleus of the posterior commissure showed that there is a steady rise in the number of labeled neurons as the animals increase in age.

Localizing the corticospinal neurons in neonatal, developing and mature albino rat

Following the administration of horseradish peroxidase (HRP) in the middle or lower cervical cord segments of neonatal (1–10 days), developing (15–20 days) and mature (2–4 months) albino rats, labeled pyramidal neurons were found in layer V of the cerebral cortex. They formed one continuous band of labeled neurons in the frontal and parietal isocortex in neonatal animals. The band began close to the frontal pole and extended distally for about 3600 μm. Mediolaterally the lateral limit of the band was at the dorsal lip of the rhinal sulcus. Neurons in the ‘shoulder’ region along the medial surface of the cerebral hemisphere were also labeled. As the animals increased in age it became increasingly more difficult to label the pyramidal neurons in the parietal band. The band appeared broken and discontinuous in the parietal region in the 15-day-old rats. In the 20-day-old and mature rats the labeled neurons appeared in two bands, a dorsolateral one and a parietal one, the two being separated by a variable gap of cortex where practically no or very few neurons were labeled. Labeled neurons in the ‘shoulder’ region were distinctly seen only in the rostral region of the frontal isocortex in older animals. Following the administration of HRP in lumbosacral cord segments, no labeled layer V pyramidal neurons were seen in the 2-day-old rats, but they were seen to form one continuous band in the dorsolateral part of the cerebral cortex in rats aged 5 days postnatally and older. They appeared in a caudo-rostral sequence, with neurons in the caudal part of the cerebral cortex projecting to the more caudal cord segments and those in the frontal part to the more rostral cord segments. Mediolaterally the band was about 2 mm wide. Neurons in the ‘shoulder’ region were infrequently seen in neonatal and developing animals.

The response of spinal cord blood flow to high-dose barbiturates.

The response of spinal cord blood flow (SCBF) to high-dose barbiturate therapy is documented. In nine mongrel dogs with an arterial pCO2 (PaCO2) of 40 mm Hg, sodium thiopental was administered to produce 30, 60, 120, and 240 seconds of electroencephalographic (EEG) burst suppression. At 30-second intervals of EEG suppression, cervical and thoracic cord segments demonstrated a decrease in SCBF of 47% and 39%, respectively, from control values. Isoelectric EEG intervals longer than 30 seconds were not associated with any further significant decrease in SCBF. In 13 other dogs and in the absence of barbiturates, hypocapnia to 20 mm Hg from PaCO2 of 60 mm Hg produced reductions in SCBF of 89% for the cervical and 82% for the thoracic segments. In the presence of thiopental-induced 30- to 60-second intervals of EEG silence, the decrement in SCBF in response to the same degree of hypocapnia was 83% and 75%, respectively, although the absolute value of this reduction was half that without barbiturates. These findings of a significant reduction in SCBF in response to high-dose barbiturate therapy are suggestive of a protective effect of barbiturates upon spinal cord injury as occurs in the brain. Further studies of the influence of barbiturates upon spinal cord compressive syndromes are indicated.

Parabrachial nucleus neurons projecting to the lower brain stem and the spinal cord. A study in the cat by the Fink-Heimer and the horseradish peroxidase methods

Direct projections from the parabrachial nucleus (PBN) to the lower brain stem and the spinal cord were examined in the cat by the Fink-Heimer and the horseradish peroxidase (HRP) methods. After placing lesions in the PBN, many fine degenerated fibers were seen contralaterally in the ventromedial portions of the caudal pontine reticular formation, and ipsilaterally in the lateral portions of the facial nucleus, the regions around the hypoglossal nucleus, and the regions around the ambiguus nucleus; some degenerated fibers were traced ipsilaterally down to the spinal cord. Subsequently, HRP injections were attempted into these regions where many fine degenerated fibers were observed. In cats injected with HRP into the lateral portions of the facial nucleus, the regions around the hypoglossal nucleus, the regions around the ambiguus nucleus, or the first cervical cord segment, many HRP-labeled neurons were seen in the ventral portions of the PBN. The mean of the average soma diameters of the PBN neurons labeled with HRP injected into the regions around the hypoglossal nucleus or the first cervical cord segment was significantly larger than that of the PBN neurons labeled with HRP injected into the lateral portions of the facial nucleus or the regions around the ambiguus nucleus.

Regulation of total and regional spinal cord blood flow.

SUMMARY Studies of the regulation of total spinal cord blood flow have been limited by methodology. Total flow has been difficult to measure and flow to the gray and white matter within the cord has not been previously assessed. We have used labeled microspheres to measure blood flow in the spinal cord. Our purpose was to examine the effects of several physiological stimuli on the regulation of blood flow to different regions of the spinal cord (cervical, thoracic, and lumbosacral) and to different tissue in the cord (gray and white matter). The four types of stimuli examined were: chemical stimulation (alterations in systemic blood gases); autoregulation (increases in systemic pressure); neurogenic stimulation (activation of chemo- and baroreceptor reflexes); and metabolic stimulation (activation of spinal cord neurons). Studies were performed in dogs, sheep, and lambs; cerebral flow and spinal cord flow were measured simultaneously. Mean blood flow to the cervical and lumbosacral cord segments was 40% higher than flow to the thoracic cord. Under control conditions gray and white matter flows to the lumbosacral cord of sheep were 110 ± 15 (mean ± SE) and 25 ± 6 ml/min per 100 g, respectively. Chemical stimulation markedly altered spinal cord blood flow (hypoxia and hypercapnia increased flow; hypocapnia decreased flow), and distribution of flow to gray and white matter was unchanged. Autoregulation maintained total and regional spinal cord flow constant during increases in systemic pressure. Neurogenic stimulation did not alter the tone of spinal cord blood vessels. Metabolic stimulation selectively increased blood flow to gray matter of the stimulated region. Regulation of total and regional spinal cord blood flow generally parallels that of the brain; chemical, autoregulatory, and metabolic factors are important determinants in the control of spinal cord blood flow.

A clinical and neuropathological study of a patient with abrachia (congenital absence of both arms)

This paper presents the life history and clinical history of a male patient with abrachia (congenital absence of both arms), who died at the age of 67 as a result of compression of the thoracic spinal cord caused by gibbus formation. Neuropathological examination of the spinal cord revealed unusual changes in the cervical and high-thoracic cord segments: accumulations of ependymal cells, strikingly few motor anterior horn cells and a chaotic arrangement of cell systems, along with complete absence of the cervical intumescence. These findings prompted some embryological considerations.