Effects of a single mannitol bolus on cerebral hemodynamics in intracerebral hemorrhage: a transcranial Doppler study.

BACKGROUND: Mannitol infusion is widely used in clinical practice to reduce perilesional edema in intracerebral hemorrhage (ICH), though no controlled studies have yet provided evidence of its effects on clinical outcome or on cerebral blood flow impairment following the event. The aim of our study was to evaluate blood flow velocity changes in the middle cerebral arteries (MCA) after a mannitol bolus in patients with ICH. METHODS: Transcranial Doppler bilateral monitoring was performed for 90 min in 20 patients with ICH, during 100 ml mannitol bolus i.v. administration. The MCA mean flow velocities (MFVs) and pulsatility index (PI) were recorded. RESULTS: When the 'healthy' and the 'affected' hemispheres were compared, we observed higher MCA MFV and lower PI on the affected side than on the contralateral side, both at baseline and during the experiment. After the mannitol bolus, we observed a significant MFV increase, starting at the end of the infusion and lasting longer than 60 min in the MCA on the affected side alone. The PI increased after mannitol administration on the healthy side alone. CONCLUSIONS: A single bolus of mannitol modified cerebral hemodynamics in our patients with ICH, increasing flow velocities on the affected MCA. This effect may be a consequence of reduced edema in the perilesional areas. The increased PI on the unaffected side may be indicative of preserved pulsatility in the healthy hemisphere.

Advantages and pitfalls of three-dimensional ultrasound imaging of carotid bifurcation.

OBJECTIVES: Several specialists use three-dimensional (3D) ultrasound as adjuvant imaging technique in their clinical practice. It has been applied to study carotid plaque morphology, surface and volume during atherosclerosis progression. Nonetheless, no papers have so far described the use of this technique in conditions different than carotid stenosis, such as bifurcation anatomy changes of the caliber and vessel course modifications. METHODS: Patients admitted to our ultrasound laboratory for vascular screening were submitted to standard carotid duplex and to 3D ultrasound reconstruction of the carotid bifurcation. RESULTS: Forty normal subjects, 7 patients with caliber alterations (4 carotid bulb ectasia and 3 internal carotid lumen narrowing), 45 patients with course variations (tortuosities and kinking) and 35 patients with internal carotid artery stenosis of various degrees have been investigated. CONCLUSIONS: 3D ultrasound is a feasible technique. It can improve carotid axis imaging through a better presentation of caliber variations and vessel course 'at a glance'. 3D ultrasound from the inward flow can provide imaging of the stenosis, but stenosis quantification should always take into account the assessment of plaque morphology and vessel wall.

Transcranial Doppler for brain death in infants: the role of the fontanelles.

OBJECTIVE: Transcranial Doppler (TCD) is a sensitive technique for circulatory arrest diagnosis in brain death when patterns such as reverberant flow and short systolic spikes are observed. In infants, the nonossified fontanelles compensate for intracranial hypertension. We describe TCD patterns in infants with brain death, different from adults, with the hemodynamic modifications induced by anterior fontanelle compression. METHOD: TCD was performed in 2 infants with diagnosed brain death admitted to the neonatal intensive care unit. RESULTS: TCD showed a large peak 'reverberant' flow, with a high peak systolic velocity and a consistent retrograde component, away from the brain. Compression of the anterior fontanelle induced, at first, a reduction in systolic flow with the subsequent appearance of the characteristic short systolic spikes. Upon compression removal, a brief increase in the systolic flow was observed before the prompt reappearance of the reverberant flow. CONCLUSION: TCD for brain death diagnosis should be done cautiously in infants. In these cases, reverberating flow may be indicative of circulatory arrest even if with a large peak and with a high peak systolic velocity. Heavy fontanelle compression may reproduce the classical adult TCD patterns of brain death, thus supporting the diagnosis of cerebral circulatory arrest.

Contrast carotid ultrasound for the detection of unstable plaques with neoangiogenesis: a pilot study.

OBJECTIVES: To evaluate whether contrast ultrasonography can be used to distinguish asymptomatic from symptomatic carotid plaques and provide insight into underlying pathophysiological differences. DESIGN: Contrast carotid ultrasound was performed in both symptomatic and asymptomatic patients referred for carotid endarterectomy. MATERIALS AND METHODS: Of 77 consecutive patients referred for carotid artery evaluation, 64 underwent carotid endarterectomy for asymptomatic cerebrovascular disease and 9 underwent urgent surgery for acute neurological deficits with hemiparesis. The endarterectomy specimens were assessed immunohistologically. RESULTS: In all 9 patients undergoing urgent surgery, contrast ultrasonography showed the accumulation of diffuse microbubble contrast at the base of the carotid plaque. This pattern was observed only in 1/64 of the patients undergoing surgery for asymptomatic carotid disease. Immunohistologically staining of the endarterectomy specimens showed that the area of microbubble contrast at the base of the symptomatic plaques was associated with an increased number of small diameter (20-30 microm) microvessels staining for vascular endothelial growth factor (VEGF). CONCLUSIONS: Contrast carotid ultrasonography may allow the identification of microvessels with neoangiogenesis at the base of carotid plaques, and differentiate symptomatic from asymptomatic plaques.

Functional MRI, drugs, and poststroke recovery.

Stroke is the first cause of disability in industrialized countries. Thus, understanding the mechanisms of poststroke recovery appears to be crucial in improving motor performance and reducing disability in stroke patients. Strategies through which brain restores lost functions after ischemic lesions are numerous. The mechanisms underlying poststroke recovery, known as cerebral plasticity, are so far hypothetical. However, functional magnetic resonance imaging (fMRI) studies recently have provided new insights in to stroke recovery. This article sketches out the mechanisms that are thought to underly recovery and focuses on fMRI experimental studies that have investigated the influence of a number of drugs on functional recovery. Functional MRI is a valuable tool in understanding functional recovery and may help to disclose new therapeutical approaches.