Autoregulative function in the brain in an endotoxic rat shock model

OBJECTIVE AND DESIGN

Autoregulative function in the brain gets relevant in hypodynamic conditions of a sepsis syndrome. We investigated the temporal pattern and dose dependent effects of LPS-induced shock on autoregulative function in rats.

MATERIAL AND SUBJECTS

Chloralose-anesthetized and mechanically ventilated male CD-rats (n = 30).

TREATMENT

Animals were subjected to vehicle, 1 or 5 mg/kg b.w. lipopolysaccharide (LPS) from E. coli given intravenously.

METHODS

Autoregulative function was tested repeatedly with a carotid compression technique assessing the transient hyperemic response ratio (THRR) in the cortex with laser Doppler flowmetry up to 270 min. THRR data from exsanguination experiments served as controls.

RESULTS

Despite lower blood pressure levels in the high dose group (control: 114 +/- 7 mmHg; 1 mg/kg LPS group: 82 +/- 16 mmHg; 5 mg/kg LPS group: 62 +/- 16 mmHg; p < 0.05) progressive cerebral hyperemia occurred similarly in both groups. Compared to exsanguinations experiments autoregulative compensation for lower blood pressure levels was lacking in the high LPS dose group at the end of experiments.

CONCLUSIONS

Cerebral autoregulation was affected by LPS-induced shock supporting the notion of vasoregulative failure in endotoxic shock.

Paraneoplastic neurological syndromes in patients with carcinoid

BACKGROUND

Paraneoplastic neurological syndromes (PNS) are mainly associated with small-cell lung cancer, gynaecological tumours and lymphomas. Few studies report the association of neurological syndromes with a carcinoid, the majority being a serotonin-related myopathy. We report four patients with a PNS associated with carcinoid.

PATIENTS AND RESULTS

The clinical syndromes were sensory neuropathy, limbic encephalitis, myelopathy and brain stem encephalitis. Two patients had antineuronal autoantibodies (one anti-Hu, one anti-Yo), one patient had antinuclear antibodies, and one patient had no autoantibodies. For two of the carcinoids, expression of HuD in the tumour could be demonstrated.

CONCLUSION

This study demonstrates that carcinoids can also be associated with classical antineuronal antibody-associated PNS.

SOX-1 autoantibodies in patients with paraneoplastic neurological syndromes

Paraneoplastic neurological syndromes (PNS) are tumour-associated disorders, which are not caused by the tumour itself or its metastases. Since antineuronal autoantibodies can be detected in these patients, an autoimmune pathogenesis is suspected. Recently, autoantibodies against cerebellar Bergmann glia were found in patients with paraneoplastic Lambert-Eaton myasthenic syndrome and other paraneoplastic neurological syndromes associated with small cell lung cancer, and SOX1 has been identified as the corresponding antigen. SOX1-antibodies have been reported to be highly specific for paraneoplastic neurological disorders. However, increasing evidence exists that they may also be associated with other neuroimmunological disorders without an underlying tumour.

Detrimental effects of 60 kHz sonothrombolysis in rats with middle cerebral artery occlusion

Recent studies have raised concerns about the safety of low frequency ultrasound in transcranial therapeutic application in cerebral ischemia. This study was designed to evaluate safety aspects and potential deleterious effects of low frequency, 60 kHz ultrasound in treatment of experimental middle cerebral artery occlusion (MCAO) in rats. Forty-five male Wistar rats were submitted to either temporary (90 min; groups I and II) or permanent MCAO (groups III and IV) using the suture technique. All animals received recombinant tissue plasminogen activator (rt-PA) starting 90 min after the beginning of occlusion. Groups I and III were additionally treated with 60 kHz ultrasound (time average acoustic intensity 0.14 W/cm(2), duty cycle 50%). Outcome assessment consisted of magnetic resonance imaging (MRI) and clinical evaluation after 5 and 24 h, and histology (perfusion fixation after 24 h). Overall mortality was higher in animals treated with ultrasound (43% versus 29% in controls). Most animals died during the insonation period (25% in group I, 36% in group III, no animals in the corresponding control groups; p < 0.05). Histology revealed disseminated microscopic intracerebral bleeding and subarachnoid hemorrhage as one possible cause of death. After temporary occlusion, the hemispheric ischemic lesion volume was more than doubled in animals treated with ultrasound (20.3% +/- 14.1% versus 8.6% +/- 5.1% in controls; p < 0.05). No difference in lesion volume was seen after permanent MCAO. Neurological assessment showed impairment of hearing as an additional specific side effect in ultrasound treated animals (65%, no impairment in controls). Although the results are not directly transferable to the human setting, this study clearly demonstrates the potential limitations of low frequency therapeutic ultrasound and the importance of pre-clinical safety assessment.

Can early neurosonology predict outcome in acute stroke?: a metaanalysis of prognostic clinical effect sizes related to the vascular status

BACKGROUND AND PURPOSE

Prediction of short- and long-term prognosis is an important issue in acute stroke care. This metaanalysis explores the prognostic value of initial bed-side transcranial ultrasound in acute stroke.

METHODS

All studies prospectively applying TCCS or TCD within 24 hours of symptom onset in acute stroke, with a minimal cohort size of 20 patients, and reporting clinical outcome variables in relation to the vascular findings were included into this metaanalysis. Study quality was assessed by 2 independent reviewers.

RESULTS

Twenty-five studies with 1813 included patients identified by electronic and manual search fulfilled the inclusion criteria. Middle cerebral artery (MCA) occlusion was associated with a significantly increased risk for a fatal course of stroke (OR 2.46, 95% CI 1.33 to 4.52). Patients with patent MCA were more likely to clinically improve within 4 days than patients with MCA occlusion (OR 11.11, 95% CI 5.44 to 22.69). Full recanalization within 6 hours after symptom onset was highly significantly associated with clinical improvement within 48 hours (OR 5.64, 95% CI 3.82 to 8.31) and functional independence after 3 months (OR 6.07, 95% CI 3.94 to 9.35).

CONCLUSIONS

Transcranial ultrasound provides important information on prognosis in patients with acute stroke.

Cranial venous outflow under lower body positive and negative pressure conditions and head-up and -down tilts

BACKGROUND

Although there exists a large body of knowledge on the regulation of arterial cerebral hemodynamics, little is known about the cerebral venous outflow (CVO).

METHODS

In 19 healthy volunteers, the middle cerebral artery and the straight sinus were examined using transcranial Doppler sonography. Arterial and venous mean flow velocities (aFV(mean), vFV(mean), respectively) were registered continuously while applying lower body positive (LBPP) or negative (LBNP) pressure of 30 mmHg and performing head-down (-20 degrees , HDT) and -up (+30 degrees , HUT) tilt manoeuvres. The arterial blood pressure was registered simultaneously with a noninvasive finger blood pressure monitor. Relative changes in parameters compared to the proceeding no-pressure, no-tilt baseline were used for analysis.

RESULTS

While aFV(mean) did not change significantly, vFV(mean) inc reased during LBPP by 10.5 +/- 2.9% and decreased during LBNP by 15.1 +/- 3.5% (mean +/- standard error of mean [SEM], P < .01). HUT resulted in a decrease in vFV(mean) by 25.5 +/- 3.3% and HDT, in an increase by 7.8 +/- 3.2% (P < .01) without alteration in aFV(mean). This may imply a decrease of cerebral blood volume (CBV) during LBPP and HDT and an increase during LBNP and HUT.

CONCLUSIONS

CVO cannot be neglected when studying cerebral hemodynamics because it might affect the CBV.

Neurovascular coupling in Alzheimer patients: effect of acetylcholine-esterase inhibitors

Dualistic effects of acetylcholine-esterase inhibitors on neuronal as well as vasoregulative function have been debated. This study investigated for the first time effects of medication on both components. Visually evoked potentials and resultant hemodynamic responses were assessed in Alzheimer patients (n=31) without vascular lesions in a MRI scan and compared to controls (n=20). After baseline recordings (AD0) tests were repeated under 2x1.5 to 2x3mg (AD1) and 2x4.5 to 2x6mg (AD2) rivastigmine/d. Long-term effects were investigated under 6 months of medication (AD2L). The ADAS, MMSE and DEMTECT were used to assess cognitive function at AD0, AD2 and AD2L. Improvement in vasoregulative function was independent from changes in evoked potentials. Acetylcholine-esterase inhibitors demonstrate substantial vascular effects in humans, which are independent from changes in neuronal function.

Prognostic value of transcranial sonography in acute stroke patients

Accurate assessment of stroke is critical for patient prognosis and selection of appropriate treatment regimens in order to optimize patient outcomes. Advanced neurosonologic techniques are straightforward, portable, and cost-effective, representing significant advantages over other noninvasive imaging modalities for monitoring of the hemodynamic status of acute ischemic stroke. Ultrasound findings acquired both early (<3 h from onset of stroke) and later (6-24 h after stroke) have demonstrated feasibility and validity for the detection of stenosis/occlusion of key intracranial structures, such as the middle cerebral artery, and for immediate and unambiguous indication of flow velocities, particularly when contrast enhancement is used. In addition, the target of thrombolysis can be identified and localized, and the success of therapy monitored, by transcranial ultrasound. Finally, transcranial ultrasound can be used to gauge the appropriateness of more complex and costly imaging studies, thereby optimizing utilization of health care resources.