Reflex sympathetic dystrophy can be associated with lumbar disc herniations. Both central and peripheral neuroanatomic pathways can be implicated in the development of this syndrome. Clinical findings of vasomotor instability in the leg supported by plain roentgenograms showing osteopenia, bone scan showing increased uptake, and a favorable response with sympathetic blocks suggest the diagnosis. Symptoms should be relieved with appropriate nerve root decompression but may require, in addition, a therapeutic lumbar sympathetic blockade.

Aged↗

PubMedDate not supplied

Ischemic brain edema: comparative effects of barbiturates and hypothermia.

The effect of pentobarbital and hypothermia on the development of ischemic brain edema was studied in 23 rhesus monkeys undergoing transorbital middle cerebral artery occlusion. Fifteen additional animals served as unclipped controls. Regional cortical cerebral blood flow (rCBF), arteriovenous oxygen content difference (AVDO2), and regional cortical metabolic rate of O2 (rCMRO2) were measured hourly until sacrifie 11 hours postocclusion, at which time ischemic cerebral edema was measured. In 8 animals no treatment followed the occlusion, and these developed edema. In 7 animals pentobarbial 14 mg/kg was administered intravenously 30 min after occlusion and 7 mg/kg every 2 hours thereafter. In this group ischemic brain edema was negligible. In 8 animals, hypothermia to 25.9 +/- 0.5 degrees C was started 30 min after occlusion and maintained until sacrifice; ischemic brain edema was not significantly altered from untreated-clipped animals. On the basis that both pentobarbital and hypothermia produced similar changes in rCBF, AVDO2, and rCMRO2, but only pentobarbital prevented edema, it is postulated that the mode of action of barbiturates in preventing ischemic brain edema is not entirely related to their known effect on blood flow and metabolism.

Animals↗

PubMedDate not supplied

Role of adrenergic nerves in blood-induced cerebral vasospasm.

Cerebral arteries have an abundant supply of adrenergic nerve fibers which are believed to release vasoactive substances responsible for the induction of cerebral vasospasm. To assess the importance of adrenergic nerves in this phenomenon, high doses (600 microgram/ml) of 6-hydroxydopamine (6-OHDA) were used to produce in vitro chemical sympathectomy in bovine middle cerebral artery. 6-OHDA reduced catecholamine fluorescence to undectable limits. H3-norepinephrine re-uptake was reduced to 1.5% of intact controls. Arterial norepinephrine content was reduced by 92%. Contractile responses to norepinephrine, serotonin, and fresh human whole blood were modestly reduced after denervation. This reduction was probably due to alpha receptor inactivation by 6-OHDA, because after protection of the alpha receptors with phentolamine the vessel response was the same as in untreated controls. Contractions in response to aged human whole blood were not affected by denervation. The results suggest that the endogenous release of catecholamines does not play a major role in the initiation or spread of blood-induced vasospasm in large cerebral arteries.

Adrenergic Fibers↗

PubMedDate not supplied

Hemodynamic and clinicopathologic verification of a stroke model in the dog.

Twenty-five mongrel dogs had intracranial internal carotid and proximal middle cerebral artery occlusions. The animals were followed for one week and subsequently sacrificed. This method of clipping produced a mean drop in cortical cerebral blood flow of 48.4% as measured by the 85Kr washout technique. Cerebral blood flow was not affected by the brain retraction necessary for clip placements. Mortality in the first week was 16% and neurological deficits were observed in 73% of the animals. Infarction was present in 80% of the animals, and the mean percent infarction of the affected hemisphere was 17.00 +/0 3.98SE. This is a useful stroke model in an animal which is easily available, inexpensive, and suitable for microvascular intracranial surgery research.

Animals↗

PubMedDate not supplied

Cerebral autoregulation: an in vitro study.

Cerebral autoregulation can be duplicated in vitro using the large middle cerebral arteries from a calf. The limits of autoregulation were between 50 and 150 mm Hg. Excessively high pressures may lead to the appearance of the "sausage- or bead-string" response followed by forced dilation. These results suggest the existence of an intrinsic myogenic mechanism responsive to intraluminal pressure changes.

Animals↗

PubMedDate not supplied

Failure of the somatosensory evoked potential following middle cerebral artery occlusion and high-grade ischemia in the cat--effects of hemodilution.

Acute focal ischemia was created in 10 cats by unilateral retro-orbital middle cerebral artery (MCA) occlusion. Regional cerebral blood flow (CBF) was determined utilizing the hydrogen clearance technique from electrode recordings within the gray matter and white matter of the ectosylvian gyrus of both hemispheres. The somatosensory evoked potential (SSEP) was obtained during contralateral median nerve stimulation. When the MCA was clipped the white and gray matter blood flows in the ipsilateral ectosylvian gyrus were reduced to 14.8 +/- 19.6% and 19.3 +/- 23.7% of control, and the cortical component of the SSEP was abolished. In the contralateral hemisphere an average increase of 3.5% above the control latency and a 10% mean depression in the amplitude of the cortical component of the SSEP were observed following occlusion. CBF in the contralateral hemisphere was unaffected by the MCA clip. Infusion of saline or dextran to lower the hematocrit by approximately 45% did not significantly improve blood flow or restore the SSEP in the hemisphere ipsilateral to the MCA clip. However, significant increases in the contralateral hemisphere gray matter CBF occurred following hemodilution while the latency of the cortical component of the SSEP in this same hemisphere was significantly extended. Elevations in gray and white matter blood flows were achieved in the experimental hemisphere of 3 of 10 cats suggesting a wide range of variation in the collateral circulation.

Animals↗

PubMedDate not supplied

Effects of oxygen and glucose deprivation on vasoactivity in isolated bovine middle cerebral arteries.

The effects of oxygen and glucose deprivation on vasoactivity were investigated using helical strips of bovine middle cerebral artery. Hypoxia, created by reducing the PO2 of the bath, or oxidative inhibition with 2,4 dinitrophenol (DNP) or sodium azide, significantly reduced contractions induced by serotonin. Normal tonic contractions induced with fresh and aged whole blood, or 5-HT became phasic and quickly relaxed to baseline in a hypoxic environment. Glucose elimination from the Krebs medium, or the inhibition of the glycolytic pathway with iodoacetic acid (IAA), did not significantly reduce serotonin-induced contractions. However, contractions were inhibited more with the combination of oxygen and glucose deprivation, or DNP + IAA, than with oxygen deprivation alone. Efforts to produce rigor in this preparation by oxygen/substrate reduction or metabolic inhibition were unsuccessful. Tonic contractions induced by 70 mM potassium became phasic as the Ca++ concentration was reduced. Contractions resulting from the readdition of Ca++ to arteries exposed to calcium-free high potassium solution were significantly reduced in the presence of oxidative and/or glycolytic inhibitors. The uptake of 45Ca++, as measured by the lanthanum technique, decreased as the bath PO2 was reduced in both serotonin stimulated and unstimulated arteries. Glucose deprivation alone did not affect 45Ca++ uptake. This study suggests that hypoxia has a direct inhibitory affect on cerebral vasoactivity mediated by reductions in sarcoplasmic Ca++ uptake.

2,4-Dinitrophenol↗

PubMedDate not supplied

Comparison of the somatosensory evoked potential and the direct cortical response following severe incomplete global ischemia: selective vulnerability of the white matter conduction pathways.

Eight cats were subjected to graded hemorrhagic hypotension following bilateral carotid ligation to produce incomplete global cerebral ischemia. Three additional cats served as controls. The somatosensory evoked potential (SEP) and direct cortical response (DCR) were monitored in all animals and in each case, the cortical component of the SEP was abolished during progressive ischemia while the morphology of the DCR was well-preserved but with reduced amplitude. Determinations of adenosine triphosphate (ATP), phosphocreatine (PCr), and lactate levels in cerebral cortex and white matter were made in five experimental cats and the three controls. At the time of failure of the cortical SEP, PCr was dramatically reduced and lactate moderately elevated in the white matter while ATP remained unchanged. Cortical lactate was only mildly elevated and PCr and ATP were unchanged accounting for preservation of the DCR. In this model of global ischemia, abolition of the cortical SEP is due to a block of stimulus conduction in white matter projection pathways. A hypothesis to explain the observed metabolic changes is presented and correlation is made to clinical situations.

Adenosine Triphosphate↗

PubMedDate not supplied

Cerebral blood flows and tissue oxygen levels associated with maintenance of the somatosensory evoked potential and cortical neuronal activity in focal ischemia.

The middle cerebral artery was occluded in 18 cats to evaluate the physiological consequences of cerebral blood flow reductions on the somatosensory evoked potential, spontaneous neuronal activity, and oxygen availability in the ipsilateral and contralateral hemispheres. In the ipsilateral ectosylvian gyrus high-grade ischemia was produced as blood flow in the gray matter was reduced from 52.1 +/- 8.6 (mean +/- SE) to 13.3 +/- 9.0 ml/100 g/min and in the white matter from 33.8 +/- 5.6 to 6.1 +/- 6.4 ml/100 g/min. This significant reduction (p less than 0.05) was associated with abolition of the cortical component of the somatosensory evoked potentials. In all animals occlusion resulted in a predictable extended latency change and a variable amplitude response of the cortical component of the contralaterally recorded somatosensory evoked potentials. In 5 animals, oxygen availability was measured and spontaneous neuronal activity in the contralateral hemisphere was recorded. Volume expansion and hemodilution with either dextran or saline infusions elevated cerebral blood flow in the contralateral gray matter significantly (p less than 0.05) compared with the control and clip values. Ipsilateral spontaneous activity stopped within 4-12 minutes of occlusion, while contralateral spike activity persisted at rates at least equal to those recorded immediately following occlusion.

Animals↗