Cerebral Doppler Sonography

Abstract

The open fontanelles are excellent acoustic windows for the image of the intracranial structures and for Doppler sonographic flow measurement in all major intracranial arteries and veins. Normal values are essential for the judgement of pathologic flow. Major indications for cerebral Doppler sonography are intracranial hemorrhage and hydrocephalus. Low flow velocities in intracranial arteries of infants are a major risk factor for the deve-lopment of intracranial bleeding. Retrograde diastolic blood flow in patients with subdural, epidural or subarachnoid hemorrhage, caused by increased intracranial pressure, is prognostic unfavorable. Progressive ventricular dilatation in infantile hydrocephalus may cause an increase of the intracranial pressure characterized by a decrease of diastolic flow and flow velocities. The most sensitive Doppler sonographic method for an increased intracranial pressure is the comparison of the flow in the petrosal and cerebral part of the internal carotid artery. In contrast to healthy infants flow intracranially increase simultaneously with intracranial pressure. Meningoencephalitis is characterized by an increase of all flow velocities. If ventriculitis is present cerebro-spinal fluid flow can be displayed with color Doppler. Hypoxemic-ischemic encephalopathy is often associated with brain edema which may cause an increase of diastolic flow in intracranial arteries. In severe cases diastolic flow may be reduced, sometimes retrograde with a bad prognosis. Neonatal stroke may be caused be arterial (ischemic stroke) or venous (hemorrhagic stroke) occlusion. Neonatal stroke can be diagnosed by Doppler sonography by a thorough investigation of all major intracranial arteries and veins. Rare indications for cerebral Doppler sonography are space occupying lesions such as cysts, tumors, arterio-venous malformations and cerebral angiomas. In cystic lesions no flow can be detected. Tumors and vascular malformations are characterized by internal vessels. Doppler sonography can detect patients with position dependent hypo perfusion of the brain stem, who have a greater risk to die from sudden infant death. Doppler sonography is helpful in the diagnosis of intra vital brain death characterized by undulating or zero flow in all intracranial arteries. Different therapeutic interventions and medications, frequently used in neonatology, may influence cerebral blood flow velocities.