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Biomedical subjects

J D Acker

Publications and source records attributed to J D Acker.

At least 19 recordsLinked to original sources
PubMed2004

Differential aging of the medial temporal lobe: a study of a five-year change.

OBJECTIVE: To test the hypothesis that entorhinal cortex (EC) volume decreases at a slower rate than the hippocampal (HC) volume in healthy adults, and to examine whether the rate of shrinkage increases with age. METHODS: Volumes of the HC and EC were measured twice on MRI scans of 54 healthy adults (aged 26 to 82 years), with an average interval of 5 years. RESULTS: Markedly different age trends were noted in the examined regions. The EC showed no age-related differences on both occasions and only minimal age-related change (0.33%/y). By contrast, the HC exhibited significant age-related differences at baseline and at follow-up evaluation and decreased at a faster pace of 0.86%/y. Older participants (aged > or = 50 years) showed increased annual shrinkage of the HC (1.18%) and EC shrinkage (0.53%/y). The rate of HC volume loss significantly exceeded that of the EC. No EC shrinkage and modest HC volume reduction were observed in people aged <50 years. CONCLUSIONS: Age-related shrinkage occurs in the medial temporal lobes of healthy adults, with significant hippocampal decline and minimal entorhinal changes. In both regions, the rate of decline accelerates with age, although the role of pathologic factors in age-related increase of volume loss merits further investigation.

Adult↗
PubMed2000

Neuroanatomical and cognitive correlates of adult age differences in acquisition of a perceptual-motor skill.

The objective of this study was to examine age differences in procedural learning and performance in conjunction with differential aging of central nervous system (CNS) structures. Sixty-eight healthy volunteers (age 22-80) performed a pursuit rotor task (four blocks of 20 15-second trials each). Volumes of the cerebellar hemispheres, neostriatum, prefrontal cortex, and hippocampus were measured from Magnetic Resonance (MR) images. Improvement in pursuit rotor performance was indexed by increase in time on target (TOT). A general improvement trend was evident across the blocks of trials. Overall, younger participants showed significantly longer TOT. The rate of improvement was age-invariant during the initial stages of skill acquisition but became greater in middle-aged participants as the practice progressed. When the influences of regional brain volumes were taken into account, the direct age effect on mean TOT measured during the first day of practice disappeared. Instead, reduced volumes of the cerebellar hemispheres and the putamen and poorer performance on nonverbal working memory tasks predicted shorter TOT. In contrast, neither the volume of the caudate and the hippocampus, nor verbal working memory showed association with motor performance. Pursuit rotor performance at the later stages of practice was unrelated to the reduction in putamen volume and was affected directly by age, cerebellar volume, and nonverbal working memory proficiency. We conclude that in a healthy population showing no clinical signs of extrapyramidal disease, age-related declines in procedural learning are associated with reduced volume of the cerebellar hemispheres and lower nonverbal working memory scores. During initial stages of skill acquisition, reduced volume of the putamen is also predictive of poorer performance.

Adult↗
PubMed1998

Neuroanatomical correlates of cognitive aging: evidence from structural magnetic resonance imaging.

To examine putative brain substrates of cognitive functions differentially affected by age the authors measured the volume of cortical regions and performance on tests of executive functions, working memory, explicit memory, and priming in healthy adults (18-77 years old). The results indicate that shrinkage of the prefrontal cortex mediates age-related increases in perseveration. The volume of visual processing areas predicted performance on nonverbal working memory tasks. Contrary to the hypotheses, in the examined age range, the volume of limbic structures was unrelated to any of the cognitive functions; verbal working memory, verbal explicit memory, and verbal priming were independent of cortical volumes. Nevertheless, among the participants aged above 60, reduction in the volume of limbic structures predicted declines in explicit memory. Chronological age adversely influenced all cognitive indices, although its effects on priming were only indirect, mediated by declines in verbal working memory.

Adolescent↗
PubMed1998

Differential effects of age and sex on the cerebellar hemispheres and the vermis: a prospective MR study.

PURPOSE: The purpose of this study was to determine the effects of age and sex on the size of the cerebellar hemispheres, the cerebellar vermis, and the pons in healthy adults. METHODS: We estimated the volumes of the cerebellar hemispheres (excluding the vermis and the peduncles), the cross-sectional area of the vermis, and the cross-sectional area of the ventral pons from MR images obtained in 146 healthy volunteers, 18 to 77 years old. RESULTS: We found a mild but significant age-related reduction in the volume of the cerebellar hemispheres and in the total area of the cerebellar vermis; however, the analysis of age trends in the vermian lobules revealed differential age-related declines. The areas of lobules VI and VII and of the posterior vermian lobules (VIII-X) declined significantly with age, whereas the anterior vermis (I-V) showed no significant age-related shrinkage. The volume of the cerebellar hemispheres (especially the right) and the area of the anterior vermis were greater in men, even after adjustment for height. Neither age nor sex affected the area of the ventral pons. CONCLUSIONS: Normal aging of the cerebellum is associated with selective regional shrinkage. The cerebellar hemispheres and the area of the anterior vermis may be larger in men than in women regardless of differences in body size.

Adolescent↗
PubMed1998

Differential aging of the human striatum: a prospective MR imaging study.

BACKGROUND AND PURPOSE: Advancing age is associated with declines in motor function; understanding age-related changes in the basal ganglia, therefore, is imperative for comprehension of such functional changes. The purpose of this study was to examine the age, sex, and hemispheric differences in volume of the caudate nucleus, the putamen, and the globus pallidus. METHODS: In a sample of 148 healthy right-handed adults (18-77 years old) with no evidence of age-related motor disorders, we estimated the volume of the head of the caudate nucleus, the putamen, and the globus pallidus from MR images. RESULTS: The analyses revealed bilateral age-related shrinkage of the head of the caudate nucleus and the putamen in both sexes. In men, the age-related shrinkage of the caudate was stronger on the left, whereas, in women, the opposite trend was evident. In both sexes, age-related shrinkage of the right putamen was greater than of its left counterpart. The mild bilateral age-related shrinkage of the globus pallidus was observed only in men. In both sexes, we observed significant rightward asymmetry in the putamen, significant leftward asymmetry in the caudate, and no asymmetry in the globus pallidus. CONCLUSIONS: Bilateral age-related shrinkage of the neostriatum is found in healthy adults. The shrinkage of the globus pallidus is less pronounced and may be restricted to men only.

Adolescent↗
PubMed1995

Age, gender, and hemispheric differences in human striatum: a quantitative review and new data from in vivo MRI morphometry.

We reviewed postmortem and neuroimaging studies of striatal neuroanatomy in humans. The quantitative review revealed evidence of moderate age-related shrinkage of the caudate nucleus and the putamen and consistent leftward asymmetry of the globus pallidus. The data on sex differences were very sparse. We examined neostriatal structures in two samples (healthy volunteers and patients with negative radiological findings) using in vivo magnetic resonance imaging. In both samples, bilateral age-related shrinkage of the caudate nucleus was found, although among the patients the effect was significant only for males. The putamen was measured only in the second sample, and age-related reduction in its volume was found also only among males. A trend for rightward asymmetry in the volume of caudate nucleus was observed in both samples, although it reached statistical significance only among the patients. Putative pathological and physiological mechanisms underlying the observed differences in teh neostriatum are discussed.

Adolescent↗
PubMed1995

Selective neuroanatomic abnormalities in Down's syndrome and their cognitive correlates: evidence from MRI morphometry.

We examined the pattern of neuroanatomic abnormalities in adults with Down's syndrome (DS) and the cognitive correlates of these abnormalities. Specifically, we compared this pattern with what would be predicted by the hypotheses attributing DS pathology to either premature aging or Alzheimer's disease. We measured a number of brain regions on MRIs of 25 subjects: 13 persons with the DS phenotype and 12 age- and sex-matched healthy volunteers. Study participants had no history of cardiovascular disease, diabetes, thyroid dysfunction, or seizure disorder. After statistical adjustment for differences in body size, we found that, in comparison with controls, DS subjects had substantially smaller cerebral and cerebellar hemispheres, ventral pons, mammillary bodies, and hippocampal formations. In the cerebellar vermis of DS subjects, we observed smaller lobules VI to VIII without appreciable differences in other regions. In addition, we noted trends for shrinkage of the dorsolateral prefrontal cortex, anterior cingulate gyrus, inferior temporal and parietal cortices, parietal white matter, and pericalcarine cortex in DS subjects compared with normal controls. The parahippocampal gyrus was larger in DS subjects. We found no significant group differences in the volumes of the prefrontal white matter, the orbitofrontal cortex, the pre- and postcentral gyri, or the basal ganglia. We conclude that the pattern of selective cerebral damage in DS does not clearly fit the predictions of the premature aging or Alzheimer's disease hypotheses. To examine the relationship between brain abnormalities and cognitive deficits observed in DS, we correlated the size of brain regions that were significantly reduced in DS with performance on tests of intelligence and language. The correlation analysis suggested age-related decline in the DS subjects in general intelligence and basic linguistic skills. General intelligence and mastery of linguistic concepts correlated negatively with the volume of the parahippocampal gyrus. There was no relationship between total brain size and the cognitive variables.

Adult↗
PubMed1992

Age-related regional differences in cerebellar vermis observed in vivo.

We investigated age-related differences in the cerebellar vermis. The areas of five vermal regions of interest were estimated from digitized midsagittal magnetic resonance imaging scans of 29 healthy volunteers and 30 neurologically intact patients (aged 18 to 78 years) who were free of vestibular symptoms, seizures, psychosis, or alcoholism. The five regions of interest included the following: (1) lingula and centralis, (2) culmen, (3) declive, folium, and tuber, (4) pyramis, and (5) uvula and nodulus. The ventral pons was used as a control region. After covarying skull size, we found a significant age-related reduction in the total area of the cerebellar vermis. The area of the dorsal regions declined with age, whereas the ventral segments of the vermis--lingula-centralis and uvula-nodulus--showed no significant age-related shrinkage. Notably, the area of the most dorsomedial portion, the declive-folium-tuber, tended to be more strongly associated with age than other segments. The pontine area was unaffected by age. No sex differences were found in the area of the vermis or its subdivisions, but the ventral pontine area was larger in male subjects than in female subjects, even after adjustment for skull size. The mechanisms underlying the observed differences are unclear. It appears, however, that phylogenetically more recent vermal regions, which are late to mature and are endowed with more extensive cortical connections, are the most vulnerable to the effects of aging.

Adolescent↗
PubMed1992

Age-related shrinkage of the mamillary bodies: in vivo MRI evidence.

Mamillary body (MB) is a diencephalic structure hypothesized to be involved in memory, a cognitive function that declines with age. In this study, age-related differences in the size of MB were examined in vivo using magnetic resonance (MR) imaging. The cross-sectional area of the MB was estimated from MR images of the brain in healthy volunteers and neurologically intact patients (age 18-78). The cross-sectional area of the tectum was used as a control region of interest. We found a significant age-related reduction in the area of the MB, but not of the tectum. No sex differences were observed in the size of either structure.

Adolescent↗
PubMed1992

Blastomycotic cranial osteomyelitis.

This is the second case report of a temporal bone osteomyelitis caused by Blastomyces dermatitidis, which presented as a chronic serous otitis media. The presenting serous otitis media was refractory to conventional medical and surgical management and progressed to a temporal bone osteomyelitis prior to diagnosis. B. dermatitidis is a rare fungal pathogen that causes a systemic pyogranulomatous disease that primarily manifests itself in the skin, bones, pulmonary, and genitourinary systems. If left untreated it is associated with a high rate of mortality. The otologic presentation of this rare disease is emphasized, while the clinical and therapeutic features are reviewed.

Adult↗
PubMed1988

Infection-related spontaneous atlantoaxial dislocation in an adult. Case report.

This paper reports the third described case of infection-related atlantoaxial subluxation in an adult. Like most of the similar cases seen in the pediatric literature, this case was associated with a parapharyngeal beta-hemolytic streptococcal abscess. Based upon this experience, the authors advocate intravenous antibiotic therapy and 1) immediate reduction followed by application of a halo brace; 2) immobilization in a halo brace for at least 3 months; and 3) a C1-2 wiring and fusion procedure for patients who fail this trial of conservative therapy.

Abscess↗
PubMed1987

Diagnosis of diseases of the lumbar spine: correlation of computerized tomography with myelography and clinical findings.

Data from 339 patients referred for evaluation of suspected lumbar disease were studied retrospectively to correlate findings in the routine clinical evaluation with results of computed tomography and myelography. Clinical features from the patients' history that correlated with an abnormal CT and myelogram included age greater than or equal to 40, a history of previous surgery, and absence of a history of injury. Signs from the physical examination that correlated included reduced lumbar motion, a motor or sensory deficit, abnormal reflexes, and reduced capacity for straight leg-raising or walking. Using a clinical score incorporating these variables, we suggest a diagnostic strategy to promote more efficient and selective use of CT scans and myelograms. We project that the use of this diagnostic approach can reduce the number of myelograms ordered in a similar population by more than 50%.

Adult↗
PubMed1986

Duplex carotid ultrasound.

Technical advances in the field of ultrasound have resulted in the development of a high resolution real-time B-mode imaging system that permits direct Doppler analysis of hemodynamic abnormalities. This system combines both anatomic information and physiological information which permits detailed analysis of the entire spectrum of disease occurring at the carotid bifurcation. Future developments will permit improved management of patients at risk for stroke from carotid vascular disease.

Arteriosclerosis↗
PubMed1986

Reformatted sagittal images in the differential diagnosis of meningiomas and pituitary adenomas with suprasellar extension.

Approximately 3 to 4 times a year, a tumor with suprasellar extension escapes classification on high resolution coronal and transaxial computed tomography. When arteriography failed to determine the diagnosis, the differential choices were usually meningioma or pituitary adenoma. The authors report the use of sagittal reformatted images in this differential diagnosis and conclude that these images may aid in the distinction between pituitary tumors with suprasellar extension and meningiomas located in this area.

Adenoma↗
PubMed1985

Nonsurgical management of small and intracanalicular acoustic tumors.

Although surgical removal is generally regarded as the management strategy of choice for acoustic tumors, there remains a small group of patients usually with small or intracanalicular tumors in whom nonoperative management may be a desirable alternative to operation. The authors present a series of six such cases and discuss criteria that may aid in the selection of patients suitable for initial nonoperative management.

Aged↗
PubMed1985

Presentation of central nervous system sarcoidosis as intracranial tumors.

Five cases of sarcoid presenting as an intracranial tumor are reported. In one instance, the lesion presented as a tumor in the cerebellopontine angle, a site not previously reported for the initial presentation of sarcoid isolated to the central nervous system. The role of computerized tomography, surgery, and steroid therapy is discussed. In the absence of pulmonary involvement, serum angiotensin-converting enzyme levels do not appear to be helpful in predicting steroid response.

Adolescent↗