Expanded applications of CT. Helical scanning in five common acute conditions.

Helical CT has become a valuable imaging tool for detection of pulmonary embolism, deep venous thrombosis, ureteral colic, acute small-bowel obstruction, and acute appendicitis. Generally, helical CT has good sensitivity and specificity values, and scans can be performed more quickly than previous gold standard diagnostic examinations for the conditions mentioned. In some cases, helical CT can also identify other findings that may be responsible for a patient's symptoms. One notable disadvantage of helical CT is the charge for the procedure, which in some circumstances can be considerably more costly than diagnostic examinations preferred previously. However, because helical CT can often obviate the need for other tests--and may consequently reduce hospital stays--this technology may have the ability to reduce overall expenditures. Cost of helical CT is therefore a multifaceted issue and requires further study before conclusions can be drawn.

Cerebral visual impairment in children.

Much of the brain is devoted to vision. Damage causes visual problems ranging from profound impairment, to cognitive visual problems only. A child with cerebral blindness may have intact perception of movement. The principal cognitive visual pathways comprise the dorsal and the ventral streams. The dorsal stream runs between the occipital lobes (which process incoming visual data), the posterior parietal lobes (which process the whole visual scene and give attention to component parts), the motor cortex (which facilitates movement through the visual scene) and the frontal cortex (which directs attention to chosen parts of the visual scene). The ventral stream runs between the occipital lobes and the temporal lobes (which enable recognition of people and objects, facilitate route finding and serve visual memory). Damage to these pathways disrupts these functions in a variety of combinations. This paper reviews cerebral visual impairment in children, the differential diagnosis and the management.

Periventricular leukomalacia: an important cause of visual and ocular motility dysfunction in children.

The immature visual system in infants born preterm is vulnerable to adverse events during the perinatal period. Periventricular leukomalacia affecting the optic radiation has now become the principal cause of visual impairment and dysfunction in children born prematurely. Visual dysfunction is characterized by delayed visual maturation, subnormal visual acuity, crowding, visual field defects, and visual perceptual-cognitive problems. Magnetic resonance imaging is the method of choice for diagnosing this brain lesion, which is associated with optic disk abnormalities, strabismus, nystagmus, and deficient visually guided eye movements. Children with periventricular leukomalacia may present to the ophthalmologist within a clinical spectrum from severe cerebral visual impairment in combination with cerebral palsy and mental retardation to only early-onset esotropia, normal intellectual level, and no cerebral palsy. Optimal educational and habilitational strategies need to be developed to meet the needs of this group of visually impaired children.