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Biomedical subjects

N Nieves

Publications and source records attributed to N Nieves.

6 recordsLinked to original sources
PubMed1995

Gadolinium-enhanced magnetic resonance imaging assessment of hydroxyapatite orbital implants.

PURPOSE: Successful prosthesis attachment depends on complete vascularization of porous coralline hydroxyapatite when it is used as an orbital implant. We retrospectively assessed the utility of gadolinium-enhanced magnetic resonance imaging to evaluate and characterize the temporal progression of this fibrovascular process, which has been histologically documented elsewhere. METHODS: Serial T1-weighted gadolinium-enhanced orbital magnetic resonance examinations were performed in five patients receiving hydroxyapatite orbital implants. Retrospective evaluation of the enhancement patterns was performed. Magnetic resonance imaging enhancement patterns guided timing of final drilling for prosthesis fixation. RESULTS: Serial gadolinium-enhanced T1-weighted sequences consistently demonstrated centrally advancing, peripheral enhancement centered on the drilled access channels. Progression over time varied, with the following two patterns demonstrated: (1) rapid peripheral enhancement, which led to diffuse enhancement (three patients); and (2) enhancement limited to the periphery, which failed to advance centrally. CONCLUSIONS: The temporal enhancement seen on magnetic resonance imaging is identical to the histologically proven fibrovascular ingrowth pattern and most likely reflects this process. Magnetic resonance imaging can identify progression of fibrovascular ingrowth into the hydroxyapatite orbital implants and guide surgical planning. It may also identify implants that fail to vascularize, thereby preventing the morbidity encountered by drilling into an avascular hydroxyapatite implant.

Adolescent↗
PubMed1991

Attention deficit disorder without hyperactivity: a distinct behavioral and neurocognitive syndrome.

This study examined the issue as to whether or not children carefully diagnosed as having either attention deficit disorder with hyperactivity (ADDH) or without hyperactivity (ADDnoH) could be distinguished on selected cognitive, academic, rapid naming, and behavioral measures. Employing a previously validated multimodal, multi-informant diagnostic process that results in reliable clinical diagnoses, 10 ADDH and 10 ADDnoH children were examined. While no significant differences in cognitive ability were noted between groups, significant underachievement was found in the children diagnosed as ADDnoH, particularly in mathematics achievement. The ADDnoH children were also significantly slower on rapid naming tasks than the ADDH children. Further, 60% of the ADDnoH children had a codiagnosis of a developmental reading or arithmetic disorder while none of the ADDH children received such a codiagnosis. Conversely, 40% of the ADDH children had a codiagnosis of conduct disorder and were rated by their parent as significantly more motorically active, impulsive, and deviant in the demonstration of age-appropriate social skills. These findings are discussed as they relate to the notion that children with attention deficit disorder may suffer from a right hemispheric syndrome.

Attention Deficit Disorder with Hyperactivity↗
PubMed1989

Attention deficit disorder with and without hyperactivity: reaction time and speed of cognitive processing.

This study addressed the issue as to whether children reliably diagnosed as attention deficit disordered with hyperactivity (ADD/H) and without hyperactivity (ADD/WO) differed significantly from each other and a clinic control (CC) population on speed and efficiency of cognitive processing. From an outpatient clinic population, 43 ADD/H and 22 ADD/WO children were examined. An analysis of mean reaction time and speeded classification task performance revealed significant group effects on both mean reaction time and on a measure of within-subject variability. ADD/H children performed significantly more slowly and variably than the CC children on several of the speeded classification tasks. However, the ADD/WO group was not distinguished on any measure. Thus, while children may be reliably diagnosed as ADD/H or ADD/WO using behavioral measures, it would appear that they cannot be distinguished on these neurocognitive tasks. Issues related to childhood psychopathology and the neuropsychological basis of ADD/H are discussed.

Age Factors↗
PubMed1987

Lateralization of visual hemifield attention across development.

Heilman and Valenstein (Clinical Neuropsychology, 1979, Oxford University Press, New York) have hypothesized a right hemispheric mechanism which mediates attention bilaterally. Shapiro and Hynd ("The development of functional lateralization in visual hemifield attention." Developmental Neuropsychology, Vol. 1, pp 67-80, 1985) examined the developmental validity of this model and their findings did not provide evidence for a lateralized mechanism for visual hemifield attention in 9, 13, and 18 year olds. However, length of foreperiod and gender effects were noted. This study attempted to compare these groups with a group of normal adults (ages 25-35) using the same reaction time paradigm. The study demonstrated support for the length of foreperiod effect found by Shapiro and Hynd. Hand effects were also found. However, these results do not lend support to either the model proposed by Heilman and Valenstein (1979) or Shapiro and Hynd's (1985) notion of developmental differences across age groups with respect to right hemisphere dominance for mediating attention.

Journal Article↗