6.5. Hippocampal sclerosis and cardiovascular regulation

In the present study, diminished HRV was observed both in patients with or without hippocampal sclerosis. The measures of HRV tended to be smaller in patients with than without hippocampal sclerosis. Overall, the number of patients with hippocampal sclerosis was small. However, the present data suggests that there is no clinically significant difference in the presence of cardioregulatory autonomic dysfunction between TLE patients with or without hippocampal sclerosis. Therefore, epilepsy related functional rather than structural changes may be important in relation to alterations in cardioregulatory functions.

Focal brain lesions are frequently associated with disturbances of the cardioregulatory system (Appenzeller & Goss 1971, Senaratne et al. 1984, Ørskov et al. 1987, Pentland & Ewing 1987, Turkka et al. 1987, Oppenheimer et al. 1990, Korpelainen et al. 1994, Freitas et al. 1996, Korpelainen et al. 1996a, Korpelainen et al. 1996b). The cardioregulatory system can be described as a continuously functioning network widely distributed in the temporal lobes with various ascending and descending connections to other parts of the brain (Cechetto 1990, Oppenheimer 1993, Cechetto 2000). The clinical and experimental data indicate the crucial role of the insula and limbic structures such as amygdala in cerebrogenic cardiovascular disturbances and sudden death (Cheung et al. 2000). For example, electrical stimulation of the insula and amygdala with its adjacent areas produces changes in HR, BP, respiration and increased norepinephrine secretion in various mammals including humans (Oppenheimer et al. 1990). In fact, various changes of HR and cardiovascular regulation has been demonstrated in patients with TLE (Schraeder & Lathers 1989, Oppenheimer et al 1992, Druscky et al. 2001), as also shown in the present study.

Therefore, it is possible that functional imbalance of the ANS in the form of changing biochemical neuromodulation may contribute to cardioregulatory dysfunction in patients with TLE. The presents results agree with this hypothesis, suggesting that dysfunction of the cardioregulatory system is rather associated with functional than structural changes of the inner temporal lobe in patients with TLE.