Serial transcranial Doppler study in meningitis

Transcranial Doppler Sonography in Pediatric Neurocritical Care: A Review of Clinical Applications and Case Illustrations in the Pediatric Intensive Care Unit

Transcranial Doppler sonography is a noninvasive, real-time physiologic monitor that can detect altered cerebral hemodynamics during catastrophic brain injury. Recent data suggest that transcranial Doppler sonography may provide important information about cerebrovascular hemodynamics in children with traumatic brain injury, intracranial hypertension, vasospasm, stroke, cerebrovascular disorders, central nervous system infections, and brain death. Information derived from transcranial Doppler sonography in these disorders may elucidate underlying pathophysiologic characteristics, predict outcomes, monitor responses to treatment, and prompt a change in management. We review emerging applications for transcranial Doppler sonography in the pediatric intensive care unit with case illustrations from our own experience.

The transsylvian approach is "minimally invasive" but not "atraumatic"

OBJECTIVE

In light of the competition between microneurosurgery and alternative methods such as stereotactic radiosurgery, we tested the hypothesis that changes in the cerebral circulation after microneurosurgery are common among patients without evidence of cerebrovascular or neoplastic disease.

METHODS

Blood flow velocities (BFVs) were recorded with transcranial Doppler ultrasonography, before surgery and every other day after surgery, for a group of 50 patients who underwent transsylvian selective amygdalohippocampectomies for treatment of hippocampal sclerosis. Hexamethylpropylene amine oxime-single-photon emission computed tomographic testing, including acetazolamide testing of cerebrovascular reactivity, was performed during the second postoperative week for 20 of the 50 patients.

RESULTS

BFVs in basal arteries ipsilateral to the surgical approach increased significantly (P < 0.001) from preoperative baseline values of approximately 52 +/- 13 cm/s (mean +/- standard deviation) to values of approximately 86 +/- 27 cm/s on postoperative Day 3 and reached their maximal values of approximately 115 +/- 37 cm/s after a median of 7 days. BFVs in contralateral vessels exhibited a similar but somewhat attenuated pattern. Hexamethylpropylene amine oxime-single-photon emission computed tomography demonstrated ipsilateral regions of hypoperfusion in 100.0% of the cases and contralateral hypoperfusion in 80.0%. Cerebrovascular reactivity was impaired in 83.3% of the cases ipsilaterally and in 33.3% contralaterally.

CONCLUSION

A significant proportion of patients who undergo microneurosurgical procedures develop bilateral alterations of their cerebral circulation. The elevations in mean BFV values represent cerebral vasospasm. Because these changes remain asymptomatic for the majority of patients, the transsylvian approach can be considered "minimally invasive" but not "atraumatic." Alternative surgical routes and alternative treatment modalities should be investigated in a similar manner.

Cranial Doppler ultrasonography as a predictor of neurologic sequelae in infants with bacterial meningitis

OBJECTIVE

To perform transcranial Doppler sonography in newborns and infants with bacterial meningitis to evaluate predictive value of neurologic sequelae.

MATERIALS AND METHODS

Thirty-three patients (15 newborn, 18 infant patients) with bacterial meningitis underwent cranial Doppler ultrasonography during acute phase and 3rd and 6th months after disease. Patients were examined regularly for neurologic outcome with electroencephalography and magnetic resonance imaging. The age-matched control group consisted of 20 healthy children underwent cranial Doppler sonography only.

RESULTS

To compare with the healthy controls, the mean blood flow velocity was significantly increased (P < 0.001), and pulsatility index was higher than those control group (P < 0.05) during acute bacterial meningitis. None of the patients were diagnosed with stenosis of cerebral artery. According to neurologic outcome, 14 of 33 patients had neurologic sequelae. The mean cerebral blood flow was significantly higher (P < 0.01) in patients without neurologic sequelae; pulsatility index was significantly higher (P < 0.05) in patients with neurologic sequelae when compared with the healthy controls. There was no significant difference between mean cerebral blood flow velocities and mean pulsatility index values of newborn and infant patients, regarding to neurologic outcome (P < 0.05).

CONCLUSION

Cranial Doppler ultrasonography is useful for prediction of neurologic sequelae in infants with bacterial meningitis.

[Nosocomial meningitis in the adult]

Cerebrospinal fluid (CSF) has anti-infectious defense abilities similar to those of the serum of a neutropenic patient. A septic inoculation as in case of nosocomial meningitis (NM), results rapidly in microbial proliferation with major alterations to the blood brain barrier, cerebral oedema and loss of autoregulation of the cerebral blood flow. Arterial hypotension during NM may induce focal or global cerebral ischaemia. The incidence of NM is increasing, staphylococci and Gram negative bacilli being the most frequent pathological agents. Clinical symptoms are not specific in this postoperative and post-traumatic context. In this context, the analysis of pleocytosis and the increased protein content of CSF is disturbing. Numerous clinical conditions may cause NM. Among them, NM from spinal puncture is an important issue for anaesthetists, while combined epidural and spinal anaesthesia carry the highest risks. Cutaneous contamination plays a major role. Half of the post-operative infections after neurosurgery are due to NM, and CSF leakage, iterative operations and surgery in contaminated conditions are the main risk factors. Antibioprophylaxis for postoperative NM is validated for clean and clean-contaminated surgery. Some consider that only procedures of more than two hours require this prophylaxis. Prophylaxis is targeted on staphylococci. Other preventive measures (drainage of less than 24 h, head shaving and prevention of CSF leakage) are of major importance. Antibiotherapy should be guided by the same considerations as for community acquired meningitis, associated with specific issues in the surgical context (presence of foreign material and CSF blockage).

Vasospastic reactions in response to the transsylvian approach

BACKGROUND

Cerebral vasospasm may occur with various neurosurgical procedures such as the treatment of intracranial aneurysms or of skull base tumors. This study was designed to provide more insight into the nature of vasospastic reactions in response to surgical manipulation alone.

METHODS

Twenty patients who underwent selective amygdalohippocampectomy for medically intractable epilepsy using the transsylvian approach were studied prospectively. Transcranial Doppler ultrasound (TCD) was used for examination of blood flow velocities within the basal cerebral arteries before and after the operation.

RESULTS

Three types of vascular reactions were observed: 1) No or only minimal reaction with increase of the blood flow velocities less than 50% as compared with the preoperative baseline values (N = 4); 2) Ipsilateral/bilateral increase of the blood flow velocities more than 50% of the baselines (N = 14); 3) Paradoxic reactions such as early postoperative resistance flow and contralateral rise of the blood flow velocities (N = 2). There was no morbidity or mortality in this series.

CONCLUSIONS

The transsylvian approach is associated with significant changes in hemodynamics--partially caused by mechanical manipulation and partially by the degradation of blood--although the risk of neurological deterioration seems to be low.