Page 4 - ILAE_Lectures_2015

a low-income community in New York, the incidence among Hispanics (36.5 per 100,000) was
similar to that of non-Hispanic whites (39.4 per 100,000) and non-Hispanic blacks (37.6 per
100,000). Lower income was, however, associated with a higher incidence of epilepsy in all ethnic
groups33.

The median prevalence of lifetime epilepsy in developing countries has been estimated to be 15.4
per 1000 (range 4.849.6) in rural areas and 10.3 per 1000 in studies in urban areas (range
2.837.7). The corresponding figures for active epilepsy were 12.7 per 1000 (range 3.545.4) and
5.9 per 1000 (range 3.410.2)2.

Characteristics of epilepsy in a general population

Based on a prevalence rate of 6 per 1000, it has been estimated that in the UK there are about 96,000
people with epilepsy who require continuing hospital-based medical treatment. Of those, 15,000
will have more than one major seizure a month and 36,000 more than one seizure a month. Overall
it has been estimated that there are approximately 12,000 patients with severe epilepsy and
additional handicaps who may require institutional care.

In population-based studies the most frequent causes of epilepsy are cryptogenic (presumed
symptomatic) or idiopathic (presumed genetic), ranging from 44.5%34 to 67%35, with the proportion
of identified causes (symptomatic or localisation-related epilepsy – remote or progressive)
increasing with age. The number of cases classified as cryptogenic has remained broadly similar
over the past 20 years despite significant improvements in neuroimaging. In a study in New York33
55% of cases were defined as idiopathic/cryptogenic, similar to the 61% of cases in the NGPSE6
almost 20 years ago. Risk factors or associated factors linked to the subsequent development of
epilepsy such as cerebrovascular disease, head trauma, neurodegenerative disease, CNS infections,
neoplasms and learning disability predominate in identified aetiologies in population-based
incidence studies. Aetiologies tend to be age specific with cerebral palsy, congenital brain damage
and learning disability predominating in the young, while tumours, neurodegenerative disorders
and especially cerebrovascular disease dominate in the elderly. In resource-poor countries, infective
causes (e.g. parasitic infestation, malaria, tuberculosis) are an important risk factor for epilepsy.
However, as in developed countries, cryptogenic cases predominate.

Based on community-based studies6,12,36 proportions (%) of presumed identified causes of epilepsy
are the following: cerebrovascular disease 11−21%, trauma 2−6%, tumours 4−7%, infection 0−3%,
and idiopathic 54−65%.

Partial seizures predominate in most studies from developing countries: NGPSE (59% vs 39%)6,
the Rochester study (57% vs 40%)12, the Umeå study (Sweden) (68% vs 16%)36 and the CAROLE
study (France) (46.2% vs 31.9%)37. A systematic review17 found that partial seizures occurred in
55% of patients compared to 45% with generalised seizures. In the Rochester study age-specific
incidences of generalised and partial seizures were compared; generalised seizures were more
common in the first five years of life, the incidence was similar for both between the ages of 6 and
24, and partial seizures were at least twice as common as generalised onset seizures in adults over
24 years12. Interestingly a predominance of partial seizures has also been demonstrated in a
community-based study of children with newly diagnosed epilepsy (55% had partial seizures
compared to 45% with generalised seizures)38.

In contrast, many studies from the resource-poor countries have found more people with
generalised seizures (80.5% in Pakistan and 65.4% in Turkey)39. The combined use of EEG and