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Biomedical subjects
K R Krishnan
Publications and source records attributed to K R Krishnan.
Morphometric changes of the human midbrain with normal aging: MR and stereologic findings.
PURPOSE: To determine the effects of age on estimated midbrain volume. PATIENTS AND METHODS: T2-weighted MR imaging and an unbiased stereologic method were used in 75 volunteers; the subjects ranged in age from 21 to 82 years and were without any significant neurologic or psychiatric disorders. RESULTS: Age was negatively correlated with estimated midbrain volume (R = -.39, P less than .0005), with the anteroposterior diameter through the substantia nigra (R = -.33, P less than .004) and with the interpeduncular distance (R = -.24, P less than .04). The linear measurements for the right and left side were almost identical. These findings are consistent with prior reports of nigrostriatal degeneration with increasing age. Furthermore, they suggest a close symmetry of age-related changes between the right and left side in normal subjects. CONCLUSIONS: Volumetric and linear measurements of midbrain morphology with MR may prove useful in the investigation of neurologic disorders such as Parkinson disease.
Adult↗
In vivo stereological assessment of human cerebellar volume: effects of gender and age.
Intermediate T2-weighted MR images and a systematic sampling stereological method were used in 37 normal volunteers, 24 to 79 years old, to assess the effects of age and sex on cerebellar volume. Female subjects (n = 21) had significantly smaller cerebellar volumes compared with males (n = 16) of similar age (t = -3.9, p less than .0008, two-tail t test). Using straight-line, univariate regression, we determined that age was not a significant predictor of cerebellar volume (R2 = 0.07, t = -1.66, p = 0.11), whereas gender did appear to account for a significant amount of variability in cerebellar volume (R2 = 0.33, t = -4.13, p = .0002). The mean absolute cerebellar volume in this study was 112 ml (SD +/- 16) for all subjects, 104 ml (SD +/- 10) for females, and 122 ml (SD +/- 16) for males. This study demonstrates the feasibility of using MR images along with a systematic stereological method to assess in vivo human cerebellar volume, thereby providing a research tool to correlate cerebellar morphology with cognitive and neuromotor function.
Adult↗
Bicaudate index on magnetic resonance imaging: effects of normal aging.
The bicaudate and bifrontal indices have been used in prior computed tomographic studies to investigate atrophy of the caudate nuclei in patients with Huntington's chorea and cerebral atrophy. However, the relationship between these indices and caudate volume has not been documented previously. In this study, we used high-field magnetic resonance imaging (MRI) to determine the effects of normal aging on the bicaudate and bifrontal indices and to study the relationship between these indices and caudate volume. The subjects were 49 normal volunteers, aged 22 to 82 years, who were without any significant neurologic or psychiatric disorders. Age was positively correlated with bicaudate index (r = .59; P < .0001) and bifrontal index (r = .40; P < .0047). Age was negatively correlated with caudate nuclei volume (r = -.47; P < .0005). Caudate volume was negatively correlated with bicaudate (r = -.27; P < .06) and bifrontal (r = -.31; P < .03) indices. These findings are consistent with prior reports of caudate nuclei degeneration with increasing age. Linear and volumetric caudate measurements with MRI may prove useful in the investigation of caudate nuclei function in the neuromotor decline with normal aging and in disorders such as Huntington's chorea.
Adult↗
Interuncal distance measurements in healthy volunteers and in patients with Alzheimer disease.
PURPOSE: To evaluate further the clinical utility of the interuncal distance (IUD) measured from axial MR scans as a reflection of hippocampal atrophy. METHODS: The IUD measured from the axial MR scans of 17 healthy control subjects was correlated with the volume of the amygdala hippocampal complex obtained from coronal MR images. The IUD was also measured on axial MR scans in 12 patients with possible or probable Alzheimer disease. RESULTS: The correlation between the total amygdala hippocampal volume and the IUD was insignificant for control subjects (r = -0.38, P = .13). When analysis of covariance was performed with the IUD as the dependent variable and age and diagnosis as the independent variables, overall R2 was 0.25. Age (F = 5.02, df = 1, P = .034), but not diagnosis (F = 0.02, df = 2, P = .88), had a significant effect. CONCLUSIONS: The IUD has no significant correlation with the amygdala hippocampal volume. The IUD appears to be a better measure of overall brain volume, which changes with age. In our patient population diagnosed with mild to moderate Alzheimer disease, the IUD measurement was not found to be useful in distinguishing their scans from those of the volunteers.
Adult↗
Interuncal distance as a measure of hippocampal atrophy: normative data on axial MR imaging.
PURPOSE: To assess the effects of age and gender on the interuncal distance measured from MR images. METHODS: High-field strength MR images (axial) of 75 volunteers, 21-82 years old and free of neurologic disorders, were used to measure the interuncal distance. RESULTS: The interuncal distance increased with age (r = 0.66, P < .0001). The mean (SD) interuncal distance for all subjects was 21.4 (4) mm with a range of 12 to 29 mm. CONCLUSIONS: The interuncal distance in healthy subjects is unlikely to exceed 30 mm. Our data may be of clinical significance in view of a previous report stating that the interuncal distance may be enlarged in pathologic hippocampal degeneration, such as in patients with Alzheimer disease.
Adult↗