الفهرس 
Anatomical and physiological considerations.Only 14 pages are availabe for public view
 |  | from | 188 |  |  |
| | | from | 188 | | |
Abstract
Improvements in critical care medicine have resulted in the increased survival of premature, low birth weight and asphyxiated infants. Several problems are associated with imaging of critically ill neonates. These include the choice of imaging technique, the timing of the imaging study, and transporting acutely ill neonates, many of whom require ventilatory assistance and multiple indwelling catheters.
Sonography is a neuro-imaging technique that is well established in its use in the neonatal incubator units. It is the accepted initial investigation for the diagnosis of germinal matrix, intraventricular hemorrhage, or both in the premature infant, and hydrocephalus complicating intraventricular hemorrhage.
For a number of other clinical indications, for example, seizures or perinatal asphyxia in full-term infants; MR imaging and CT are established as the imaging modalities of choice. However, CT and MR imaging equipment may not be universally available, and neonates may be too unstable to leave the intensive care unit. Sonography is frequently an essential investigation in such situations until more sophisticated imaging can be arranged and performed.
Representative coronal and sagittal views should be obtained from various angulations of the transducer from its position over the anterior fontanelle.
When scanning through the anterior fontanelle, the most poorly evaluated region is the posterior fossa. Other additional scanning windows, the posterior and posterolateral fontanelles may be used to improve visualization of the posterior fossa.
Transcranial Doppler is used to monitor cerebral hemodynamics in critically ill neonates. Indications of transcranial Doppler in the neonate include asphyxia, hemorrhage, hydrocephalus, brain death, arteriovenous mal-formations, and differentiation of subarachnoid from subdural fluid collections. The most important vessels insonated are the ACA and its pericallosal branches in the sagittal view, and the ICA and MCA in the coronal plane. The transtemporal approach may also be used to insonate the MCA.
Measurement of the resistive index, peak systolic and end diastolic velocities are the most commonly used spectral Doppler measurements for monitoring the cerebral hemodynamics and predicting the extent of ischemic damage.
In cases of suspected CNS infection, diagnosis is almost always made on a clinical basis and the role of imaging is to assess for complications. Ultrasound easily identifies complications, such as calcifications, abscesses, subdural effusions and empyema, ventriculitis, and hydrocephalus.
In the setting of traumatic brain insults, Subdural and epidural hemorrhage can be a difficult on sonography compared with CT or MRI. On sonographic examinations, they appear as unilateral or bilateral hypoechoic or echogenic fluid collection (depending on the nature of the fluid) surrounding the brain parenchyma.
In conclusion, transcranial ultrasound and color Doppler have been a major advance in the study of neonatal brain. It is a portable, safe, non-invasive and highly effective technique of low cost that is of considerable value in diagnosis, evaluation and follow up of neonatal brain insults.