Is there a neuropsychology of hysterectomy, ovariectomy or menopause ?

Read Also

  A woman's ovaries partially shut down at menopause,  resulting in a massive drop in circulating estrogen and progesterone,  far below the lowest levels of the pre-menopausal menstrual cycle.   Though there is a reduction in luteinizing and folliculostimulant hormones,   it is estrogen and progesterone concentrations that drop the most  at menopause.  So,  if estrogen truly has a "physiological" on-line brain-mediated effect on the neuropsychological profile,  i.e., on cognitive sex differences,   then women's neuropsychological profile should change dramatically shortly after menopause.   Unfortunately,  as I explained in the preamble to the present chapter,  this has not been studied in depth.   Low estrogen would predict a drop in mood,  in verbal ability,  and a shift of hemispheric "specialization"  or priming to the right hemisphere (relative left field and left ear advantages).    Only the first prediction has been unequivocally tested.    Not only does mood swing downwards (though not in all women) at menopause,  but depression is more frequently encountered.    Several investigations have documented a drop in "general cognitive abilities"  incommensurate with a smooth continuation of the pre-menopausal trajectory.  One such investigation found that post-menopausal women with estrogen-replacement therapy performed significantly better than untreated controls on a battery of cognitive tests including tests of perceptual speed, articulatory skill and verbal fluency  -all tasks believed to be favored by circulating estrogen.  A similar effect has also been observed as a result of hysterectomy,  an operation which has a hormonal effect resembling  menopause.  Interestingly,  this "general cognitive effect" seems to be reversible by estrogen-replacement therapy.  If you believe menopause is biologically benign, that the cognitive decline is trivial,  and that estrogen is irrelevant,  consider this.  Researchers have found that ovariectomized rats suffer a significant memory loss,  which can be countered by cyclical estrogen injections.  Furthermore,  ovariectomized rats without estrogen-replacement have significant degeneration of one type of neuron (granular) in the main memory structure of the brain  -namely the hippocampus.   In one study, estrogen-treated ovariectomized rats had 40% more dendritic spines (synaptic connections) on these neurons than did the untreated ovariectomized rats.  By the way,  this finding has triggered a recent rash of studies investigating efficacy of estrogen therapy in Alzheimer's disease.  I have not been able to find documentation of whether verbal or visuospatial functions show a different pattern of decline.   Absolutely nothing seems to have been published on perceptual asymmetry (hemispheric dominance using either dichotic listening or tachistoscopic techniques) in post-menopausal women.   This would be an easy project to carry out  -an excellent PhD thesis in the giving. 

Finally,  a piece of evidence is indirectly germane to the issue of the effect of menopause on the brain.   Are there sex differences in the brain that seem to emerge late in life ?   The answer seems to be yes.  One investigation assessed effects of age and sex on regional brain structure in humans, focusing on the frontal and temporal lobes. Hemispheric volumes were obtained from magnetic resonance images of 96 young (53 men and 43 women; aged 18-40 years) and 34 older (17 men and 17 women; aged 41-80 years) healthy volunteers. An age  by sex by hemisphere by region interaction indicated that age-related reductions in brain volume were sexually dimorphic, lateralized, and region specific. Greater decrements in brain volume occurred with age in the frontal lobe than in the temporal lobe. Age-related reductions in both regions were greater in men than in women, demonstrating that sexual dimorphisms in human neuroanatomy are not fixed, but continue to change throughout adulthood. The authors proposed that this late-onset sex difference could be hormonally mediated.   I have come across a report of an even greater sex difference which emerges in the brain in old age. The mediobasal hypothalamus   of 33 men (mean age, 77 +/- 10 years) and 31 women (mean age, 78 +/- 10.3 years) was investigated for neurofibrillary pathology associated with abnormally phosphorylated tau protein. A conspicuous pathology was identified, characterized by terminal-like processes contacting the neurohemal vasculature of the posterior median eminence and the adjacent infundibular nucleus. This pathology revealed a striking sex difference: it was identified in 79% of the males, but observed in only 6% of the females. The vessel-associated neurofibrillary lesions of the mediobasal hypothalamus develop independently of Alzheimer's disease-related neocortical pathology. The sex-dependent neurofibrillary degeneration was suggested as an explanation for an impairment in neuroendocrine function previously reported in elderly men.   A caveat deserves mention here.   After the age of menopause,  men and women become very similar in terms of circulating sex hormones.   In fact,  men of this age have slightly more estrogen and progesterone than women do !