Morphological evaluation of the human pyramidal tract: Gender and age differences

Abstract

In the past, morphometric research on the nervous system had tended to focus on neuronal somata. Recently, however, research has started on the evaluation of the nervous pathways, especially of the nerve fibers [1][2][3][4][5][6][7][8] . Out of the reasons for this delay may be the lack of reliable methods for the staining of axons with minimum shrinkage. For example, conventional silver impregnation methods may result in extensive axonal shrinkage. It is therefore indispensable to adopt one of the discriminative staining methods developed recently for the evaluation of nerve fibers 8,9) , as it is very important to take into account the shrinkage ratio for the morphometric evaluation of human nerve tissue 8,9) . Such shrinkage should be avoided, or at least be as low as possible and have the narrowest range possible for the purpose. Although there are a few reports on the lateral corticospinal tract (LCST) at L1 level 1, 2) concerning aging or gender differences, no data can be found regarding the cervical levels. In the present report, we will describe the differnces due to gender and aging in nerve fiber axons in the LCST at the C5 level. Material and methodsSpinal cords, including the dura mater coverings and the proximal parts of the spinal nerves after checking the level of spinal nerve roots were removed from the cadavers of 43 human subjects consisting of 31 males (age ranging from 41 to 97 years) and 12 females (age ranging from 59 to 92 years), after injection of a 10% formalin (3.7-4.0% formaldehyde) solution through the femoral artery by a pulsation pump, with the jugular and femoral veins open for drainage of the blood. The subjects showed no evidence, either clinical or pathological, of suffering from diseases affecting the nervous system. We excluded cadavers with a past history of nervous diseases or pathological findings in the nervous system such as cerebrovascular disorders, intracranial tumors, infections, neurodegenerative conditions, etc. The spinal cords prepared for the study were therefore considered to be normal. After making the transverse sections, the selected segments were confirmed to be the fifth cervical segment according to Goto's criteria 10) . Blocks of the spinal cord segments were fixed in a two-step process according to the method given in the reference section 9) . For primary fixation, a 10% solution of formalin for general purposes was used. The blocks were first immersed in the solution over a week, and were then transferred, without washing, into the secondary fixative composed of 5% potassium dichromate and 5% potassium chromate (1:4 in volume) and kept at room temperature for two weeks, followed by an additional week at 37°C. After washing with running water using a pipet-washer with siphon mechanism Okajimas Folia Anat. Jpn., 85(3): 107-109, November, 2008 Morphological evaluation of the human pyramidal tract:Gender and age differences Summary: Using a preparation method composed of secondary chromic acid fixation, nitrocellulose embedding and Luxol fast blue-PAS...

Sex-specific reference values for total, central, and peripheral latency of motor evoked potentials from a large cohort

“…In early adolescence, female motor tracts seem to reflect more widespread changes, while males may undergo relatively more microstructural changes in projective and associative fibers (Hervé et al, 2009;Bava et al, 2011;Pangelinan et al, 2016). Histopathologically, an elegant research study showed that in the human lateral pyramidal tract at the cervical level (C5), large-size myelinated axons are more dominant in number in males, while smallsize myelinated axons are found in relatively lager numbers in females, thus possibly suggesting a sex-difference in the transmission of the responses along this tract (Souma et al, 2008). In line with this finding, neurophysiological nomograms differentiated by sex would be needed to detect even subtle changes.…”