Neurosurgery
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Acute subdural hematoma (SDH) remains an important factor in head injury. The early effects of SDH on cerebral blood flow (CBF) and cerebral metabolic rate of oxygen consumption (CMRO2) in humans have not been clearly demonstrated. Patients admitted to the Medical College of Virginia with severe closed-head injury between 1982 and 1990 were studied with Xenon-133 regional CBF measurement. ⋯ Differences in mean CBF, CMRO2, and AVDO2 were evaluated on each day after injury with the application of Student's t-test for independent groups. Significant reductions in CBF were demonstrated in patients with SDH on Days 1 (P < 0.0005) and 2 (P < 0.01). CMRO2 differed notably on Days 1 (P < 0.005) and 2 (P < 0.05) in patients with SDH, but when corrected for the lower Glasgow Coma Score in patients with SDH, the P values were only 0.07 and 0.12, respectively (analysis of covariance).(ABSTRACT TRUNCATED AT 250 WORDS)
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Spinal cord evoked potentials (SCEPs) after spinal cord stimulation were used as a method of spinal cord monitoring during surgery of 6 extramedullary and 14 intramedullary spinal cord tumors. SCEPs were recorded from an epidural electrode placed rostral to the level of the tumor. Electrical stimulation was applied on the dorsal spinal cord from a caudally placed epidural electrode. ⋯ The position of the stimulating electrode, the difference in thresholds of the axons for electrical stimulation between the right and left side of the spinal cord, or the change of the distance between the electrode and the spinal cord surface may account for these false results. Thus, our analysis of the changes of SCEP wave forms and early postoperative symptoms indicates that the sensitivity of this monitoring method to detect intraoperative insults to the spinal cord is unsatisfactory in spite of the reproducible wave forms. We conclude that SCEP monitoring can be used as an alternative method or in combination with other types of evoked potentials in patients with severe spinal cord lesions who show abnormal somatosensory evoked potentials preoperatively.
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This study examined the effect of nimodipine or methylprednisolone on spinal cord blood flow (SCBF) and electrophysiological function after spinal cord injury in rats. Three groups of male rats (n = 10 per group) were injured by compression of the cord at T1 for 1 minute with a 52-g clip. The hydrogen clearance technique was used to measure SCBF at the T1 segment. ⋯ The infusions were continued for approximately 3 hours after spinal cord injury. SCBF was not significantly different between the experimental groups at either 1 or 2.5 hours postinjury (P = 0.16 and 0.71, respectively), and evoked potential responses did not return in any rat at any time after injury. Thus, this experiment failed to demonstrate an improvement in SCBF or electrophysiological function with either drug.(ABSTRACT TRUNCATED AT 250 WORDS)
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Comparative Study
The distribution of medication along the spinal canal after chronic intrathecal administration.
Chronic intrathecal drug infusion for the treatment of neurological diseases, such as spasticity and chronic pain, has become an accepted method of therapy in recent years. Concurrent pharmacokinetic studies have shown that the cisternal cerebrospinal fluid (CSF) drug level is considerably lower than the lumbar CSF level during continuous infusion into the lumbar subarachnoid space. One factor that makes analysis of this decline in drug level difficult to quantify is that it is only feasible to sample CSF at the two extremes of the spinal subarachnoid space. ⋯ Over a 20-cm distance of the thoracic cord, radionuclide counts decreased gradually so that the indium-111 diethylenetriamine pentaacetic acid concentration surrounding the cord at the T2 vertebral level was 43% of that at the T12 level in four patients. Therefore, it appears that even with a hydrophilic compound, which minimizes spinal cord capillary losses, there is still a considerable reduction of CSF drug concentration along the spinal canal. The clinical implication of this gradual decline in drug level is that for intrathecal infusion of relatively hydrophilic compounds there may not be any advantage in placing the catheter tip at more rostral locations, such as at the midthoracic or cervical cord.
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Rapid presurgical neuromagnetic localization of the somatosensory cortex was performed successfully on five patients with a large-array biomagnetometer by a protocol called magnetic source imaging (MSI). Determination of the location of the central sulcus is important in assessing operative risk and determining the optimal operative approach to structural lesions in the vicinity of the motor strip. The use of magnetic resonance imaging anatomical methods and intraoperative visual identification can be imprecise, whereas invasive localization prolongs operative time, adds cost, and entails added risk. ⋯ In this study, the validity of MSI localizations was confirmed intraoperatively by direct cortical recording of somatosensory evoked potentials and/or direct motor stimulation. Complete agreement was found between MSI and intraoperative mapping in locating the central sulcus. Objective confirmations considered together with the speed and reliability of the procedure and with the presurgical availability of the results suggests the potential utility of MSI for routine surgical planning.