Women with Epilepsy: A Handbook of Health and Treatment Issues (Chapter 10)

Brain differences (Excerpt)

Paula Shear and Rosemary Fama

Studies in men and women with epilepsy

Whereas most people with epilepsy have normal cognitive abilities, some have cognitive difficulties (dysfunction) related to the effects of epilepsy and seizures on the brain and the side effects of treatment. Very few studies have looked at differences in the cognitive abilities of men and women with epilepsy. People who have epilepsy because of a left hemisphere brain injury that occurs early in life (before the age of 1) may show sex differences in cognitive skills. Because the left hemisphere of the brain usually controls speech, damage to the left hemisphere often causes difficulty with language. However, a proportion of individuals who experience early left hemisphere damage go on to transfer their speech functions to the healthy right hemisphere. In the relatively few people who have language function in the right hemisphere, left hemisphere injury causes very little, if any, language problems.

The transfer of speech to the right hemisphere is typically associated with some degree of cognitive loss in areas other than language, probably because the brain regions that usually control these other functions are now forced to support language skills also. Women with epilepsy resulting from early left hemisphere lesions may have difficulties in both language and nonlanguage functions only if speech is transferred to the right hemisphere. However, men show generalized cognitive dysfunction following early left hemisphere injury regardless of whether speech is represented in the left or the right hemisphere. This suggests that women have earlier brain maturation than do men. Men have more widespread cognitive problems due to the greater immaturity of their brains at the time of injury. If injury occurs while brain cells are still developing and forming connections to other brain regions, it is more likely to cause a cascade of abnormalities, even at remote brain sites, than if there is injury to cells that have already matured and established their neural connections.

Several studies have examined whether men and women differ in their cognitive abilities after epilepsy surgery in the anterior temporal lobe. Before surgery, women are better than men at learning word lists (consistent with what is seen in healthy adults), and this sex difference persists following surgery. Men are more likely than women to show a drop in verbal memory after temporal lobe surgery (lobectomy), which is consistent with the literature suggesting that verbal skills are less lateralized in women than in men.

Less is known about sex differences in memory for visual information following temporal lobectomy. One study found that, overall, neither men nor women declined significantly following temporal lobectomy (removal of part of the temporal lobe) in their ability to remember visual material. However, those women who had a relatively larger right than left hippocampus (a temporal lobe brain structure that is critical to memory ability) before surgery had the strongest preoperative visual memory abilities and also showed the greatest memory decline following surgery. This relationship between the hippocampal size and memory loss was not apparent in men. This result may seem to be inconsistent with the data suggesting that women have less lateralized cognitive abilities than men. The authors suggest that perhaps women are more able to recover from left hemisphere lesions and men show a better ability to recover from right hemisphere lesions. This hypothesis will need to be tested in future studies that address visual memory loss following temporal lobe surgery.

-- Excerpted from "Women with Epilepsy: A Handbook for Health and Treatment Issues" edited by Martha J. Morrell, MD and Kerry L. Flynn, M.A. Published by Cambridge University Press, 2003. It is available for purchase in our marketplace.