Neuropsychiatric Symptoms of Epilepsy

14 Dementia
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An age- accelerated atherosclerosis with increased carotid artery intima media thickness
is discussed as an independent risk factor in patients with epilepsy [ 70 ]. In fact,
the following risk factors are shared between epilepsy and age-related cognitive
disorders: increased carotid artery intima media thickness (CA-IMT), Hcy, lipid
abnormalities, weight gain and obesity, IR, high levels of inflammatory and oxidative
stresses, as well as the brain structural and pathological abnormalities including
decreased volume of the hippocampus, increased cortical thinning of the frontal
lobe, ventricular expansion and increased white matter ischemic disease, total brain
atrophy, and β-amyloid protein deposition in the brain [ 42 , 72 , 73 ].
Depression and hypertension have been also identified as the risk factors for
unprovoked seizures [ 15 , 16 , 74 ], which constitute an additional risk in patients
with VaD. Some other investigators report that cholinesterase inhibitors itself may
increase risk of seizures in dementias of different etiology [ 52 ].
Interestingly, Imfeld et al. found out that the role of disease duration as a risk
factor for seizures/epilepsy seems to differ between AD and VaD [ 43 ]. Patients with
longer than 3 years standing AD had a higher risk of developing seizures than those
with a shorter disease duration; whereas in patients with VaD the contrary was
observed.
The association between vascular dementia and epilepsy, especially risk factors
for seizures, requires further investigations, as there are many controversies in the
literature. For instance, Conrad et al. reported that no patients with dementia developed
seizures in his study [ 75 ], in contrast to the study by Cordonnier et al. who
found dementia to be an independent risk factor for seizures [ 68 ].
Mechanisms
There are several hypotheses of co-occurrence of dementia and seizures epilepsy.
Some authors view dementia and seizures as on two fundamentally independent
disorders, with the unfortunate co-occurrence of two disease genes or acquired
encephalopathies; this hypothesis is supported by relatively low occurrence of seizures
in dementia, compared to some other neurological disorders [ 17 , 41 , 76 ].
However, the vast majority of authors [ 53 , 76 – 78 ] tend to explain comorbidity of
epilepsy and dementia by the number of mechanisms underlying both conditions.
As many risk factors are shared between VaD and AD, and the importance of
mixed vascular-degenerative dementia has been recognized [ 79 – 81 ], the mechanisms
of their association with seizures and epilepsy will be discussed together.
There are a number of studies looking at the association between amnestic episodes
in patients with AD; in these patients epileptiform EEG discharges such as
spikes and sharp waves [ 82 , 83 ] were found. It was confirmed by the fact that both
conditions (specific cognitive disturbances and the associated epileptiform EEG
discharges) could be prevented by antiepileptic treatment. On the other hand, epileptiform
discharges in patients with temporal lobe epilepsy can also lead to transient
amnesia and even simulate similar to AD memory disturbances [ 46 , 84 ]. Palop