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.     

Influence of changes in arterial pCO2 on cerebral blood flow and metabolism during high-dose barbiturate therapy in dogs

In 13 dogs the response of the cerebral circulation to changes in PaCO2 ranging from 20 to 60 torr was studied before and after administration of high doses of sodium thiopental. Infusion of sufficient barbiturate to produce 30- to 60-second burst suppression in the electroencephalogram was associated with a profound degree of cerebral vasoconstriction, equivalent to that produced by hypocapnia with PaCO2 = 20 torr. Furthermore, once sodium thiopental was administered, no significant difference in cerebral blood flow (CBF) or vascular resistance (CVR) was noted between PaCO2 of 30 and 20 torr. However, changes of approximately 15% in CBF and 30% in CVR were noted between PaCO2 at 40 and 20 torr. These data suggest that hyperventilation of PaCO2 of less than 30 torr may not effectively increase the degree of cerebral vasoconstriction in these circumstances.     

Brachytherapy for malignant recurrent and untreated gliomas.

Twelve consecutive patients with recurrent malignant glioma were treated with brachytherapy. Thereafter, a prospective randomized study involving 35 patients was undertaken. Although additional study is necessary, preliminary recommendation calls for treatment at diagnosis rather than at recurrence.     

The role of radiation therapy in the management of ependymomas of the spinal cord

Twenty patients with biopsy-proven ependymomas of the spinal cord were treated between 1960 and 1984-7 with surgery only, 3 with radiation therapy only, and 10 with surgery and postoperative radiation therapy. Of these, 2 patients developed recurrent tumor at the primary site, 3 developed a recurrent tumor in the thecal sac, and 1 developed distant metastasis. The absolute 5- and 10-year survival rates were 95% (19/20) and 86% (12/14), respectively. None of 13 patients who were treated with radiation therapy only or combined surgery and postoperative radiation therapy developed recurrent tumor at the primary site, and none of 7 patients who received thecal sac irradiation developed thecal sac recurrences. In contrast, 2 of 7 patients (29%) treated with surgery alone developed recurrent tumor at the primary site, and 3 of 13 patients (23%) who received no thecal sac irradiation developed a recurrent tumor in the thecal sac. The failure rates following surgery were greatest in patients who had tumor removed in a piecemeal fashion (43%, 6/14). The results show that radiation therapy is probably not necessary if the tumor has been removed completely in an en bloc fashion. However, radiation therapy is needed if the tumor has been incompletely removed or removed in a piecemeal fashion. If the tumor has been removed in a piecemeal fashion, the radiation portals should be extended to include the thecal sac. Histologic subtypes influenced the pattern of recurrence. Myxopapillary ependymomas and high grade cellular ependymomas appear to be more likely to recur in the thecal sac. However, no big difference could be detected in local recurrence.     

Magnetic resonance imaging and posttraumatic Lhermitte's sign

Two patients developed Lhermitte's sign after cervical spine fractures. The patients were otherwise without evidence of spinal cord dysfunction. Both patients were studied with magnetic resonance scans of the cervical spine. The magnetic resonance scans were normal. The possible etiology of Lhermitte's sign in these patients is discussed. The differential diagnosis including cervical spondylosis, combined systems degeneration, multiple sclerosis, neoplasm, and radiation myelopathy is reviewed. These patients should be carefully evaluated clinically, and flexion/extension lateral cervical spine films as well as a complete blood count and peripheral smear should be obtained. Magnetic resonance scanning may have an important role in evaluating these patients. Magnetic resonance is exquisitely sensitive in detecting demyelination; therefore, we speculate that subarachnoid scarring may be responsible for this symptom. Gadolinium-enhanced magnetic resonance scanning may confirm the presence of such scarring in the future.     

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.     

Effect of hemorrhagic shock upon spinal cord blood flow and evoked potentials

Although somatosensory evoked potentials are being used in the evaluation of spinal cord injury and the monitoring of cord function during surgical procedures, their limitations in the face of fluctuations in blood pressure await further clarification. To study the effect of hypotension upon spinal cord blood flow (SCBF) and spinal evoked potentials (SEPs), we subjected five anesthetized lambs to graded hypotension to a mean arterial pressure (MAP) of 80, 60, 40, and less than or equal to 30 mm Hg. Five animals served as controls. Maximal hypotension was associated with a significant decrease in renal and sciatic nerve blood flow of 83% and 77%, respectively. SCBF, on the other hand, showed no decrease with hypotension down to a MAP of 40 mm Hg. As hypotension progressed, a gradual but significant slowing in nerve conduction velocity was noted without alteration in the cord conduction velocity from L7 to L1. Control animals demonstrated a decline in sciatic nerve blood flow of 48%, without any change in latency or amplitude of nerve action potentials. These findings suggest that, in hypotension, the peripheral nerve (lacking autoregulation) becomes ischemic, resulting in slowing of nerve conduction velocity with an increase in latency and decrease in amplitude of SEPs. Cord conduction velocity, on the other hand, remains unchanged. Caution is advised in relying upon SEPs generated by peripheral nerve stimulation to monitor cord function in situations where profound hypotension is anticipated. Variations in SEPs may reflect alterations in the peripheral nerve and not the spinal cord.