Response of spinal cord blood flow and motor and sensory evoked potentials to aortic ligation.

To produce spinal cord ischemia in the lamb, ligation of the thoracic aorta was performed for 15, 30, and 45 minutes in three animals each. Spinal cord blood flow and motor and sensory evoked potentials were measured before, during, and after aortic ligation. Ischemia with a blood flow of zero during ligation was encountered in the thoracic and lumbar cords, followed by hyperemia upon release of the ligature. Both somatosensory and motor evoked potentials were obliterated during aortic ligation and gradually recovered following resumption of flow. Motor and sensory evoked potentials behaved similarly to high aortic ligation.

Spinal cord blood flow in response to focal compression.

Anesthetized sheep were subjected to spinal cord compression to 200 mm Hg at T13 by means of a distensible epidural balloon. Eight animals were subjected to compression for 20 min, 10 animals for 40 min, and 12 animals for 80 min. Spinal cord blood flow (SCBF) and spinal evoked potentials (SEPs) from L7 to C7 and vice versa were measured prior to, during, and 1/2, 1 1/2, 2 1/2, and 3 1/2 h following compression. The traumatized zone manifested a hyperemic response subsequent to balloon withdrawal in the 20-min and 40-min groups. In the 80-min group, SCBF returned to baseline. With compression, SEPs were obliterated in all animals and failed to recover after 3 1/2 h following injury, irrespective of the duration of compression. These results show that reperfusion of the cord following a compressive insult is not accompanied with recovery of SEPs.

Locked facets in the thoracic spine: report of three cases and a review.

Facet dislocation is a rare finding in the thoracic spine. This article presents three cases of bilateral locked facets in the thoracic region. Two were due to car accidents and the third was secondary to a vertical fall. The level of the injury was T2-T3 in two cases and T9-T10 in the third. Two patients were completely paraplegic on admission, whereas the third was neurologically intact. All patients had various associated injuries and fractures. The diagnosis of locked facets was not suspected in any of the cases, but was later made by computerized tomography with parasagittal reconstructions. All patients underwent surgery. The radiological diagnosis was confirmed intraoperatively in two cases. The facets were relocated by manual traction in one case and by Harrington distraction in the other. Fixation and fusion were performed in all three. Stability and vertebral alignment were achieved in all cases postoperatively.

Magnetic resonance imaging and neurobehavioural outcome in traumatic brain injury.

Magnetic resonance (MR) imaging is a sensitive means of detecting haemorrhagic and nonhaemorrhagic forms of brain injury. This study correlates the neurobehavioural (NB) deficits in 49 adult patients with lesions detected by MR imaging. MR imaging was performed 2-19 days following trauma, analyzed for the injury type and graded for severity. A battery of NB tests was performed prior to hospital discharge or at the time of initial follow-up visit (31 patients). 15 patients were so severely impaired that testing could not be done and 3 died prior to discharge. The NB test scores were grouped into 3 levels of impairment. The overall NB scores were compared with MR lesion severity ratings and a positive correlation found (r = 0.47). In addition, lesion severity, type and location resulted in specific NB deficits. We conclude that the lesion location and severity can be accurately identified by acute phase MR are associated with specific types of neurobehavioural deficits in a high percentage of testable patients.

Diagnostic yield in CT-guided stereotactic biopsy of gliomas.

Twenty-seven patients underwent 29 computerized tomography (CT)-guided stereotactic biopsy procedures for untreated or recurrent malignant astrocytomas. Biopsies were obtained from the hypodense center, enhancing margin, and hypodense periphery as seen on contrast-enhanced CT scans, with diagnostic yields of (number of biopsies yielding tumor/number of biopsies obtained): 34/61 (56%), 68/101 (67%), and 8/22 (36%) from these three zones, respectively. Although tumor was identified in all three zones, diagnostic yield was significantly higher in the hypodense center and enhancing margin. Comparison of patients with untreated tumors to those with recurrent tumors demonstrated no statistical difference in tumor distribution, although there was a trend toward a higher yield from the hypodense periphery in the recurrent tumor group. Tumor was found up to 15 mm beyond the CT-enhancing margin, in addition to extending beyond the area of abnormality on T2-weighted magnetic resonance images. These findings suggest that serial stereotactic biopsies should be targeted to the hypodense center and enhancing margin for improved diagnostic yield. Biopsy material obtained from the hypodense periphery that demonstrates tumor also indicates that a tumor volume beyond the confines of the CT-enhancing margin should be considered when calculating dosimetry for interstitial radiation.

Symptomatic Chiari malformations. An analysis of presentation, management, and long-term outcome.

The Chiari malformation is a condition characterized by herniation of the posterior fossa contents below the level of the foramen magnum, and is categorized into three types based on the degree of herniation. The authors review their surgical experience between 1975 and 1985 with 50 patients afflicted with symptomatic Chiari malformations. Any patient with associated myelomeningocele, tethered spinal cord, lipoma, or diastematomyelia was excluded from this series. Forty-one patients had Chiari I malformations, seven were classified as having Chiari II, and two as having Chiari III. The presentation of pediatric and adult patients was identical. Treatment was directed at the posterior fossa pathology. Seven patients with accompanying ventral bone compression underwent transoral decompression of the cervicomedullary junction, 42 had posterior decompressive procedures, and six received ventriculoperitoneal shunts. The posterior decompression included opening the outlet foramina of the fourth ventricle, occluding any communication between the spinal cord central canal and the obex, shunting the fourth ventricle, and placing a dural graft. Postoperatively, 20% of the patients are asymptomatic, 66% improved, and 8% stabilized; in 6% the disease has progressed in spite of multiple procedures. Preoperative signs that are predictive of a less favorable outcome include muscle atrophy, symptoms lasting longer than 24 months, ataxia, nystagmus, trigeminal hypesthesia, and dorsal column dysfunction (p less than 0.05, chi-square test). A model based on the presence or absence of atrophy, ataxia, and scoliosis at the time of the preoperative examination has been generated that allows prediction of long-term outcome at the 95% confidence level.

Effect of hetastarch, mannitol, and phenylephrine on spinal cord blood flow following experimental spinal injury.

Anesthetized lambs were subjected to epidural cord compression at T13 by means of an epidural balloon distended to 200 mmHg for 80 minutes. Determinations of spinal cord blood flow (SCBF) were made by labelled microspheres prior to and during compression, and then 1/2, 1 1/2, and 2 1/2 hours after compression. Twelve control animals received saline (80 ml/h). Nine animals received hetastarch (a 20 ml/kg bolus followed by an 80 ml/h infusion) and 8 animals received mannitol (a 1 g/kg bolus followed by 1 g/kg/hr). An additional 10 animals received phenylephrine to raise mean arterial pressure by 20 to 40%. Somatosensory evoked potentials (SEPs) were recorded following each determination of SCBF. Animals were killed following determination of the 2 1/2 hour postcompressive flow. The animals treated with either hetastarch or phenylephrine had a postcompressive mean arterial pressure that was significantly greater than that of the controls (P less than 0.01). During treatment, cardiac output in the hetastarch and mannitol animals was significantly greater and hematocrit significantly less than in the controls (P less than 0.05). In spite of these changes, postcompressive SCBF was significantly increased only in those animals treated with phenylephrine (P less than 0.05). Statistical analysis of the relationship between mean arterial pressure and postcompressive SCBF revealed that autoregulation is indeed lost with this experimental model of spinal cord injury. Histological examination of the injured site failed to demonstrate any difference in the area of hemorrhagic necrosis among the four groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Nicardipine after spinal cord compression in the lamb.

To study the effects of the calcium channel blocker nicardipine on spinal cord blood flow and spinal evoked potentials, the following study was undertaken. After cord compression, which was productive of paraparesis, nicardipine was administered intravenously in 10 anesthetized lambs. Ten control animals were subjected to compression but received saline instead. Nicardipine produced a significant decrease in mean arterial pressure when compared to the control group. Thirty minutes after compression, spinal cord blood flow also was lower in the nicardipine group compared with controls. Spinal evoked potentials did not recover after compression in either group.

Methylprednisolone in spinal cord compression.

In acute nonsurvival studies, eight anesthetized lambs were subjected to cord compression at T13 by means of an epidural balloon distended to a pressure of 200 mm Hg for 40 minutes. Subsequent to withdrawal of the balloon, each animal received 30 mg/kg of methylprednisolone succinate in an intravenous bolus followed by a continuous infusion of 10 mg/kg/hr for the duration of the experiment. Spinal cord blood flow (SCBF) and spinal evoked potential (SEP) determinations were obtained sequentially prior to, during, and at 1/2, 1 1/2, and 2 1/2 hours following compression. In spite of the absence of ischemia following compression, SEPs failed to recover. Methylprednisolone had no apparent effect on blood flow or on the recovery of SEPs when compared with results in ten control animals that received saline alone.

De novo aneurysm formation following carotid ligation: case report and review of the literature.

The authors report a patient with an aneurysm of the carotid siphon who underwent ligation of the cervical carotid artery. Six years after this procedure, the patient suffered a subarachnoid hemorrhage from an apparent de novo aneurysm. Pertinent literature is reviewed to determine the incidence of this occurrence, and congenital arteriosclerotic and hemodynamic factors causing aneurysm enlargement are discussed.

Presentation and management of pediatric Chiari malformations without myelodysplasia.

Chiari malformations without myelodysplasia are rarely diagnosed in the pediatric age group. With current neurodiagnostic techniques, however, they are being seen more frequently. Unfortunately, the prognosis is not clear because publications have included a number of different entities, used a variety of surgical approaches, and lacked long term follow-up. Sixteen patients younger than 20 years were treated for Chiari malformations (without myelodysplasia) between 1975 and 1985. The average age was 11 years, and the average duration of symptoms was 20 months. The common symptoms were isolated motor weakness (56%), pain (37.5%), and sensory loss (25%). Frequently seen signs were motor deficit (81%), sensory loss (50%), scoliosis (50%), and cranial nerve palsy (50%). The surgical procedures used were foramen magnum decompression (3 transoral clivus odontoid resections and 15 posterior fossa decompressions with dural grafting), alteration of cerebrospinal fluid (CSF) pathways at the cervicomedullary junction (plugging the foramen cecum and a 4th ventricle to subarachnoid shunt with posterior fossa decompression), and ventriculoperitoneal shunting (2 cases). In follow-up, 37.5% of the patients are asymptomatic, 50% are improved, and 12.5% are stable after an average follow-up period of 43 months. The asymptomatic group was younger (9.3 years) and had a shorter symptom duration (7.2 months) than both the improved (11.9 years, 16.4 months) and the stable groups (15 years, 20 months). Optimal outcome depends on complete evaluation of the abnormal CSF pathways and bony abnormalities at the craniovertebral junction. Operation is then directed toward correction of these abnormalities as delineated radiographically. Of our patients, 87.5% have at least shown improvement, which has been long term in all cases.

Stereotaxic surgery in the treatment of multiple brain abscesses.

Controversy exists regarding the optimal treatment for patients with multiple brain abscesses. These lesions are often small and located deep in the brain and close to vital structures, making surgery difficult. With this in mind the authors review their experience in treating multiple abscesses using computerized tomography (CT)-guided stereotaxic aspiration. From 1983 to 1985, 15 patients were treated for multiple brain abscesses, of whom eight underwent stereotaxic aspiration. There were a total of 28 abscesses in these eight patients: 11 abscesses were aspirated and two excised using CT-guided techniques. Most were cortical in location, although there were 12 in the deep white matter, one in the thalamus, and two in the caudate nucleus. All patients received a total of 6 weeks of antibiotic therapy. Follow-up CT showed resolution of the abscesses in all patients. Currently, four are neurologically normal, one has a mild hemiparesis, one has a well-controlled seizure disorder, and one requires supportive care. A single death occurred 5 weeks postoperatively of unrelated causes. Location, size, and age of an abscess all have bearing upon the response to management and outcome of the patient. Stereotaxic surgery is a procedure with minimal morbidity and mortality. Stereotaxic aspiration should be considered in patients with small, multiple, or deep-seated abscesses, in those who are poor operative candidates, and in those who have failed prior therapy.

Distal cervical carotid dissection after carotid endarterectomy: a complication of indwelling shunt?

Technical factors and surgical techniques in carotid endarterectomy remain a controversial subject. The use of an indwelling arterial shunt has theoretical advantages in assuring intraoperative hemispheric perfusion and affording a more relaxed surgical environment. There has been little clinical demonstration, however, of superior results with carotid shunting. Although champions of routine shunting argue that it is a benign protective intervention, the possibilities of distal embolization or intimal disruption exist. The authors report a case of cervical carotid dissection far distal to the operative site that they postulate resulted from intimal disruption after routine shunt placement. This devastating complication from an otherwise benign procedure prompts reconsideration of the benefits and risks of routine shunt placement.