I Subependymal hemorrhage into one or both germinal matrices
II Germinal matrix hemorrhage with intraventricular extension, no hydrocephalus
III Germinal matrix hemorrhage with intraventricular extension and hydrocephalus
IV Germinal matrix hemorrhage with intraparenchymal extension infants are evaluated for neurological disorders secondary to prematurity. This coupled with primary neurological diseases has led to wide use of US as a leading diagnostic imaging tool in the neurological evaluation of children.  Regions of the brain hemorrhage can be readily diagnosed and graded, typically on a scale of 1 to 4 (lable^B.) . Hemorrhages can range in size from a small, solitary petechial hemorrhage to multiple large parenchymal hemorrhages with associated ventricular changes. Noninvasive follow-up imaging of these hemorrhages can be repeated as necessary without concern for radiation exposure. Small, germinal matrix hemorrhages, common in premature infants, carry the best long-term neurological prognosis (Fig...2.3-24) . In contrast, intraventricular hemorrhages may be seen in premature infants, representing a higher-grade hemorrhage. Larger parenchymal hemorrhages represent the more severe spectrum of premature brain injury and typically result in long-term neurological deficits. Hydrocephalus may complicate brain hemorrhage, which can be readily diagnosed and followed with US.
Congenital and Acquired Neonatal Disorders. US can provide useful information regarding other intracranial pediatric abnormalities, particularly in the newborn period.
Figure 23-24 Cranial ultrasound of infant demonstrating left germinal matrix hdmorrhagarrow).
For example, congenital abnormalities such as Chiari malformations, agenesis of the corpus callosum, anencephaly, aqueductal stenosis, holoprosencephaly, and encephaloceles can be evaluated. Congenital pediatric neoplasms that occur in the first year of life such as choroid plexus papilloma and carcinoma, gliomas, primitive neuroectodermal tumors, and vascular disorders (e.g., the vein of Galen malformation) can be elucidated. Infectious diseases of the brain may result in abnormal intracranial fluid collections, complicating meningitis or encephalitis. US can be useful in providing guidance for needle aspirations of these collections.
Limitations of US include decreased detection rates of convexity lesions, such as extra-axial hemorrhages or masses (i.e., subarachnoid hemorrhage). Periventricular leukomalacia, or the effects of perinatal asphyxia can be imaged but can also be challenging to recognize. As necessary, US information can be supplemented by other imaging tests, such as CT or MRI to improve detection of conditions not recognized by US.
The indications for TCD continue to evolve but primarily focus on stroke prevention. TCD is useful in inferring the presence of intracranial stenosis or occlusions of major intracranial arteries and may further document routes of collateral circulation. One important role for TCD is for screening and follow-up of intracranial vasospasm complicating subarachnoid hemorrhage. Vasospasm typically peaks on days 3 through 7 after SAH. TCD is useful in screening these patients for the onset of vasospasm, before clinical symptomatology (. Fig 2.3.-2.5.). This allows for early treatment planning, before the patient becomes symptomatic. TCD can be useful intraoperatively, for example, providing continuous intraoperative recording of the middle cerebral artery during carotid endarterectomy, and, therefore, can help identify patients needing an indwelling shunt. Other developing indications of TCD include screening patients for intracranial stenosis that complicates sickle cell disease, identification of flow disturbances in migraine, and identification of AVM. In the latter instance, the nidus of AVM can be analyzed showing routes of supply and drainage and may further show flow reductions in AVMs after interventions. Lastly, TCD may be useful in accessing venous diseases such as sagittal sinus thrombosis and may play a future role in brain death determination.
The prevalence of stroke in the United States has led to development of screening modalities aimed toward recognition and correction of stroke risk factors. Increasingly, atherosclerotic disease involving the cervical carotid and vertebral arteries is recognized for its inherent risk in stroke. The Asymptomatic Carotid Atherosclerosis Study demonstrated benefit in ipsilateral stroke reduction with carotid endarterectomy for patients with asymptomatic stenoses of extracranial carotid artery greater than or equal to 60 percent. y The North American Symptomatic Carotid Endarterectomy Trial demonstrated strong benefit with carotid endarterectomy in symptomatic patients with ipsilateral carotid stenosis greater than or equal to 70 percent. y Therefore, because the majority of strokes are currently believed to be embolic in etiology, carotid screening becomes justified. The presence of significant stenosis of the carotid bifurcation is now generally accepted as an indication for intervention in both asymptomatic and symptomatic patients.
US of the cervical vasculature has several key advantages compared with other imaging modalities as a screening study. y y y These include patient comfort, lack of procedure risk, and high sensitivity and specificity in detecting cervical stenosis. Information regarding surface contour and internal characteristics of plaque can be routinely obtained. US limitations include operator dependency and possible error,
Figure 23-25 Transcranial Doppler image of left middle cerebral artery showing elevated flow velocities in the left middle cerebral artery status post subarachnoid hemorrhage consistent with vasospasm.
field of view limitations (thorax inferiorly and the mandible superiorly), technical problems related to vessel tortuosity, and kinking, dense calcifications, and the potential to miss a trickle of blood in cases of high-grade, 99 percent stenosis. The latter, in particular, continues to justify the need for additional imaging studies in cases of suspected complete carotid occlusion and in cases in which information beyond the US field of view is needed. Indications for cervical US include evaluation of cervical bruit, transient ischemic attack, and stroke. Figure. 23-2.6 demonstrates an example of a severe cervical carotid bifurcation plaque with angiographic correlation. US is also useful in following progression of atherosclerosis in cases of known plaque or in detecting other cervical pathologies, such as arterial dissection (. .Fig 23-27 ).
At many institutions, carotid stenosis is graded based on a sliding scale developed by Bluth. y Mild carotid stenosis results in broadening of the normal ultrasonic spectral waveform with mild elevation of PSV due to turbulent flow from small plaques. In contrast, higher degrees of stenosis results in higher flow velocities, which can be seen in both systole and diastole. Generally, PSV greater than 130 cm/ sec indicates moderate stenosis whereas PSV greater than 250 cm/sec indicates severe stenosis. Systolic and diastolic ratios between the stenotic internal carotid artery and the common carotid artery are also calculated and, if increased, may further indicate regions of carotid narrowing. Ratio analysis can aid in identifying false-positive and false-negative results in conditions such as systemic hypertension. Routinely, all high-flow jets are also recorded. A point can be reached in which flow velocities can diminish. These areas can further define abnormal regions of critical carotid stenosis.
Imaging of spinal abnormalities is useful in children up to 3 to 6 months of age as the posterior elements are membranous not bony. Beyond this age, these elements calcify and generally US would then need to be complemented with another imaging modality. Early evaluation and differentiation of neural tube defects, such as lipomas, meningoceles, myelomeningoceles, and tethered spinal cord, is possible. US can evaluate the subcutaneous structures and allow for recognition of abnormal spinal canal development, including spinal cord abnormalities. Even in older children, the presence of abnormal skull dimples, pores, or hair tufts can be evaluated for underlying spinal dysraphism. Rarely, US can be useful in evaluating spinal neoplasm or syrinx development.
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