Daniel G. Nehls

A Comparison of the Cerebral Protective Effects of Isoflurane and Barbiturates during Temporary Focal Ischemia in Primates

Isoflurane has protective properties during experimental global brain ischemia or hypoxia. However, this has not been evaluated in the more common case of focal ischemia, e.g., as caused by middle cerebral artery occlusion (MCAO). The authors therefore compared the effects of isoflurane, thiopental, and N2O/fentanyl anesthesia on neurologic and neuropathologic outcome in baboons subjected to 6 h of transorbital left MCAO. Prior to MCAO, animals were assigned to one of three groups: Group 1 (n = 7) received isoflurane (in O2/air) in concentrations sufficient to maintain deep burst suppression on the EEG (2.0% ± 0.5% inspired, mean ± SD); group 2 (n = 6) received thiopental (O2/air) in doses adequate to maintain similar EEG suppression (3.6 ± 0.7 g total); and group 3 (n = 6) received 60% N2O/40% O2 and fentanyl (25 μg/kg load, 3 μg · kg−1 · h−1 infusion). Efforts were made to keep mean arterial pressure (MABP) between ≈80 and 100 mmHg, using nitroprusside/hydralazine or phenylephrine/metaraminol, with PaCO2 at ≈30 mmHg. The selected anesthetic was established 45 min before MCAO, was maintained until 1 h after clip removal, and in decreasing concentrations for 5 h. Neurologic status was scored for 7 days and formalin-fixed brains were later sectioned for determination of infarction volume. Six of seven group 1 (isoflurane) animals were hemiplegic, and 7/7 had verified infarctions. By contrast, 4 of 6 group 2 (thiopental) animals were normal, with 2/6 having infarctions. Outcome in group 3 (N2O/fentanyl) was intermediate between groups 1 and 2 (3/6 hemiplegic, 4/6 with infarctions). Differences in the infarction rates between groups 1 and 2 was significant (P < 0.05), while a similar comparison of neurologic outcome scores achieved a P value of 0.055. Infarctions in group 1 were more hemorrhagic in character than in group 3 (groups 1 and 2 could not be meaningfully compared). These results must be considered in light of differences in MABP during the occlusion period; MABP in group 1 was ≈80 mmHg in spite of vasopressor use, while that in group 2 was ≈100 mmHg (in spite of vasodilators). Nevertheless, they fail to demonstrate any protective value of isoflurane anesthesia, at least when compared with thiopental.

Synovial cyst of a cervical facet joint: case report.

Intraspinal synovial cysts are rare. Those reported have occurred in the lumbar region. We report a case of an extradural true synovial cyst of the cervical spine causing spastic paraparesis. The cyst occurred after a cervical spine fracture and, hence, was probably related to trauma. Surgical therapy resulted in a satisfactory recovery.

Spontaneous regression of arteriovenous malformations.

Spontaneous regression of an arteriovenous malformation (AVM) is quite rare. When a regression does occur, there is usually an associated factor, such as intracranial hemorrhage, operation, radiation therapy, or new neurological deficit. Twenty-one cases of AVM regression identified in the literature are reviewed. An additional case in which the resolution was totally spontaneous is presented. Regressions occurred over intervals ranging from 7 months to 21 years. Several mechanisms for regression are discussed.

Chronic spinal epidural hematoma presenting as lumbar stenosis: clinical, myelographic, and computed tomographic features. A case report.

The case of a patient with a chronic spinal epidural hematoma presenting as lumbar stenosis is described. There was no history of major trauma to the lumbar spine, anticoagulant use, or coagulopathy. The clinical, myelographic, and CT findings are presented and discussed.

Effect of Naloxone on Experimental Stroke in Awake Monkeys

Naloxone has recently been reported to be of benefit in the treatment of central nervous system ischemia. To study the effect of naloxone in an experimental stroke model, we subjected 40 awake monkeys to middle cerebral artery (MCA) occlusion 2 weeks after the placement of a MCA ligature by a transorbital technique. Cerebral blood flow (CBF) was monitored with stereotactically placed H2 electrodes, and the neurological course was serially recorded. Infarct size was determined 2 weeks after MCA occlusion. Twenty animals served as control and received no naloxone; 10 of these underwent permanent occlusion, and 10 underwent 4-hour MCA occlusion. In 25 treatment animals, naloxone was administered in three different intravenous dosages: (a) naloxone, 2-mg/kg bolus 20 minutes postocclusion and 2 mg/kg/hour X 4 hours, in 10 animals with permanent MCA occlusion; (b) naloxone, 10-mg/kg bolus 20 minutes postocclusion and 10 mg/kg/hour X 4 hours, in 10 animals with 4-hour MCA occlusion; and (c) naloxone, 20-mg/kg bolus, in 5 animals with various neurological deficits. MCA occlusion typically produced a moderate deficit: hemiparesis, hemianopsia, and facial paresis. In most instances, naloxone in the 2- and 10-mg/kg dose regimens produced little or no change in the neurological function. CBF decreased after MCA occlusion and was unaffected by naloxone in most cases. Infarct size was not significantly different between the control and treated groups. However, the 20-mg/kg dose consistently produced a nonfunctional, transient increase in total body motor tone in normal and hemiparetic animals. Naloxone did not significantly improve useful neurological function, CBF, or infarct size in an experimental primate stroke model.

Multiple Unusual Aneurysms and Arteriovenous Malformation in a Single Patient: A Case Report

A patient with multiple unusual aneurysms and an arteriovenous malformation (AVM) is presented. Aneurysms involving the meningohypophyseal trunk and the feeding vessel of the AVM were observed. Two additional aneurysms assumed a pantaloon appearance. The largest aneurysm was responsible for the patients subarachnoid hemorrhage. This aneurysm and two adjacent aneurysms were clipped successfully, and the patient made an uneventful recovery. Subsequent angiography revealed a stable appearance of the remaining aneurysms and AVM.

Air embolism through a ventriculoatrial shunt during posterior fossa operation: case report.

An unusual complication of air embolism through a ventriculoatrial shunt occurred in a patient undergoing posterior fossa operation in the sitting position. Because ventriculoatrial shunts are uncommon, this potential complication may not be widely recognized. A case is presented and the clinical aspects are discussed.

Overview of Cerebral Ischemia: Rationale for Cerebral Protection

With the onset of profound cerebral ischemia, a complex chain of events is set into motion. If there is no intervention, irreversible damage occurs within several minutes. Although the primary insult of cerebral ischemia is a reduction in the supply of major nutrients, the depletion of cellular energy stores soon triggers a series of secondary events known as the “ischemic cascade.” However, numerous factors influence the course of cerebral ischemia, and cell death is not necessarily the inevitable outcome. A simplified scheme of the progression of cerebral ischemia, with identification of possible sites for treatment, is presented in Figs. 1–3.

Current Therapy of Brain Abscess

Brain abscesses present a spectrum of challenging problems in diagnosis and management. Significant advances have provided the clinician with a wide armamentarium of diagnostic and therapeutic modalities, and recent reports have noted a downward trend in mortality.1