NATALIA SHNAYDER,
NATALIA SHNAYDER, DIANA DMITRENKO, ANNA SADYKOVA, LADA SHARAVII, ANDREY SHULMIN, EVGENIA SHAPOVALOVA, MARINA PILUGINA, OLGA DARSAVELIDZE
Krasnoyarsk State Medical University,
Russia
The research observes epidemiology of epilepsy and epileptic
syndromes and risk factors at the population of the middle Siberia
(Krasnoyarsk region and the Tuva Republic, Russian Federation).
The analysis concludes that Siberia (on example the Krasnoyarsk
region and the Tuva Republic) is region with high prevalence of
epilepsy (comparable with the occurrence of epilepsy in the
Europe countries). Though it s lower when comparing the
epilepsy prevalence in developing countries. Prevalence of all
forms of epilepsy was higher at children and teenagers. High
prevalence of idiopathic epilepsy was in childhood populations in
the Krasnoyarsk region and the Tuva Republic. Post-stroke
epilepsy dominated in structure epilepsy with late onset in
Krasnoyarsk region, including Krasnoyarsk city.
Key words: Epilepsy, Epidemiology, Siberia, Russian Federation.
UDC: 616-009.24
Introduction
Epilepsy is a neurological disorder that affects people in every country throughout the
world. Epilepsy is also one of the oldest conditions known to mankind. It is characterized
by a tendency to recurrent seizures and it defined by two or more unprovoked seizures.
The clinical manifestations of seizures will therefore vary and depend on where in the
brain the disturbance first starts and how far it spreads. Transient symptoms can occur,
such as loss of awareness or consciousness and disturbances of movement, sensation
(including vision, hearing and taste), mood or mental function.
Localization-related epilepsies, sometimes termed partial or focal epilepsies, arise from an
epileptic focus, a small portion of the brain that serves as the irritant driving the epileptic
response. Generalized epilepsies, in contrast, arise from many independent foci
(multifocal epilepsies) or from epileptic circuits that involve the whole brain. Epilepsies of
unknown localization remain unclear whether they arise from a portion of the brain or
from circuits that are more widespread. Epilepsy syndromes are further divided by
presumptive cause: idiopathic, symptomatic, and cryptogenic. Idiopathic epilepsies are
generally thought to arise from genetic abnormalities that lead to alteration of basic
neuronal regulation. Symptomatic epilepsies arise from the effects of an epileptic lesion,
whether that lesion is focal, such as a tumor, or a defect in metabolism causing widespread
injury to the brain. Cryptogenic epilepsies involve a presumptive lesion that is otherwise
difficult or impossible to uncover during evaluation (ILAE, 1993).
The risk factors and epileptogenic mechanisms for the different types of epilepsy have
been correlated with their prognosis, thus making it possible to establish therapeutic
strategies based on pharmacological agents or surgical procedures. Nevertheless, in 30-
40% of cases, epilepsy is not satisfactorily controlled by the available remedies, and a nonnegligible proportion has a poor prognosis in terms of both the severity of the epilepsy
and its psychosocial outcome.
There are different causes of epilepsy that are common in certain age groups. During the
neonatal period and early infancy the most common causes include hypoxic-ischemic
encephalopathy, infections of central neural system (CNS), trauma, congenital CNS
abnormalities, and metabolic disorders. During late infancy and early childhood, febrile
seizures are fairly common. These may be caused by many different things, some thought
to be things such as CNS infections and trauma. During childhood, well-defined epilepsy
syndromes are generally seen. During adolescence and adulthood, the causes are more likely to be secondary to any CNS lesion. Further, idiopathic epilepsy is less common.
Other causes associated with these age groups are stress, trauma, CNS infections, brain
tumors, drug use and alcohol withdrawal. In older adults, cerebrovascular disease is a very
common cause. Other causes are CNS tumors, head trauma, and other degenerative
diseases which are common in the older age group, such as dementia (Harrison's
Principles of Medicine. 15th edition).
Epidemiology is the medical discipline which studies the dynamics of a medical condition
in the general population. It is concerned about the numbers of people with the condition,
who are at risk and what is the outcome of the condition. It allows for the rational
planning of health delivery. It is very important because around 50 million people in the
world have epilepsy at any one time. The lifetime prevalence of epilepsy (i.e. the number
of people presently in the world who have epilepsy now or have had it in the past or will
experience it in the future) is approximately 100 million people (WHO, 2001). The
researchers who are engaged in epilepsy in the countries of the Europe and the USA have
come to a conclusion that 7-10 % of all population at least time transfer to lives afebrile
paroxysm, and febrile spasms are marked at 3-5 % of the population of Europe (Hopkins
and Shorvon, 1995).
The prevalence of epilepsy is the proportion of a population with that disorder at a given
point in time. From many studies around the world it has been estimated that the mean
prevalence of active epilepsy (i.e. continuing seizures or the need for treatment) is
approximately 8.2 per 1000 of the general population of the Europe. However, this may
be an underestimate as some studies in developing countries suggest a prevalence of more
than 10 per 1000 (WHO, 2007).
The incidence of epilepsy is the number of new cases at a given time. Studies in developed
countries suggest an annual incidence of epilepsy of approximately 50 per 100000 of the
general population. However, studies in developing countries suggest that this figure is
nearly double that at 100 per 100000 (WHO, 2007). Incidence data are particularly limited,
especially from low and lower middle income countries. They are usually divided into
those of recurrent unprovoked seizures and those that include first seizures, acute
symptomatic seizures or isolated seizures.
Morbidity of epilepsy in the different countries of the world varies from 20 to 120 cases in
a year on 100000 at population.
Better understanding of the epidemiology of epilepsy is a prerequisite for improving
epilepsy care. However, the epidemiological study of epilepsy remains difficult for a
number of reasons. When suspected, epilepsy is not always easy to diagnose. Many
epidemiological studies on epilepsy have been published, but the lack of rigorous
definitions of the disease, differences in the methods of case ascertainment, classifications
of seizures or epileptic syndromes and evaluation of risk factors hamper meaningful
comparisons. The incidence rates of epilepsy in the Europe vary between 28.9 and 47 per
100000 (ILAE, 2005).
The age distribution of the incidence of epileptic seizures and epilepsy is bimodal, with
two peaks of frequency: in childhood and in the elderly.
Data on prevalence are available from the Russian Federation although differences in
methodology and study populations make comparisons difficult. An epidemiological study
of active epilepsy in people over 14 years is being performed in eight European and
(Asian) sites of the Russian Federation in people over 14 years. It has been completed in
the Moscow and in the Irkutsk city and the Ulan-Ude city in the eastern Siberia (Kabakov
and Shprakh, 2002). The crude prevalence rate of epilepsy increased from the western to
the eastern regions, from 2.2 in the Moscow to 4.2 per 1000 in the Irkutsk. The prevalence
was relatively consistent within the European part (2.2-3.4 per 1000) and within Asian
(4.1-5.0 per 1000). Late-onset epilepsy was more frequent in the European than in the
Asian region (Guekht et al., 1999; Guekht, 2005).
The age-adjusted incidence rates of first epileptic seizures or newly diagnosed epileptic
seizures in Europe range from 18.9 to 69.5 per 100000 (ILAE, 2005). The crude incidence
rates for adolescents and adults (aged > 14 years) in several areas of the eastern Siberia,
the Russian Federation, were similar: 25-30 per 100 000 (Kabakov and Shprakh, 2002;
Guekht et al., 2004).
However, before our studies epidemiology of epilepsy in big territory of the middle Siberia
(the Krasnoyarsk region and the Tuva Republic) was not studied.
The Krasnoyarsk region (Russian: Krasnoyarsky kray) is second largest federal subject of
Russia, occupying an area of 2,339,700 km2 (903,400 sq mi), which is 13% of the
country's total territory of Russia (for example, the size of Algeria). The Krasnoyarsk
region lies in the middle of Siberia, and belongs to the Siberian Federal District, stretching
3,000 km from the Sayan Mountains on the south along the Yenisei River to the Taymyr
Peninsula in the north. Over 95% of the cities, a majority of the industrial enterprises, and
all of the agriculture are concentrated in the south of the region including Krasnoyarsk
city. Population (Census, 2002) was 3,023,525 (including Taymyr and Evenk Autonomous
Okrugs). Population of Krasnoyarsk region mostly consists of Russians (88.38%), and
some other peoples of the former Soviet Union. The indigenous Siberian peoples make up
no more than 1% of the population. Krasnoyarsk is a city and the administrative center of
Krasnoyarsk region It is the third largest city in Siberia, with population of 948,500 (2009
est.). BUT Zheleznogorsk is a closed administrative territory of Krasnoyarsk region
Population of BUT Zheleznogorsk mostly consists of Russians. Population of
Zhelesnogorsk town was 93,875 (Census, 2002), population of BUT Zheleznogorsk -
more 110,000 (Sadikova et al., 2010).
The Tuva Republic is federal subject of Russia also. The republic is situated in the far
south of the middle Siberia. The capital city is Kyzyl. Area is 170,427 km2 (65,802 sq mi)
(for example, territories of 2 x Austria or 1 x Florida). The area of the Tuva Republic is a
mountain basin, ca. 600 m high, encircled by the Sayan and Tannu-Ola ranges. Mountains
and hills cover over 80% of the republic's territory. Population was 305.510 (Census,
2002). Childhood population was 105.547 in 2007 (Sharavii, 2010). Tuvans, a Turkis
people, make up 77.0% of the republic's population. Other groups include Russians
(20.1%), Khakas (0.4%), and a host of smaller groups, each accounting for less than 0.5%
of the total population of the Tuva Republic. During the period 1959-2002 there has been
more than a doubling of ethnic Tuvans. The Russian population growth slowed by the
1980s and has now begun to shrink.
The purpose of the research is studying of epidemiology of epilepsy and epileptic
syndromes and its risk factors in population the middle Siberia (the Krasnoyarsk region
and the Tuva Republic)
Materials and methods
Work is executed within the limits of complex theme of federal scientific project
“Epidemiological, clinical and genetics aspects of diseases of central, peripheral and
autonomic neural systems and preventive health care” (the supervisor of the studies -
Prof. Natalia Shnayder). The Register of epilepsy and epileptic syndromes which has been
introduced in practical public health services on the basis of Krasnoyarsk region’s clinics
and Tuva Republic clinics is created (Shnayder et al., 2010).
All patients passed careful preliminary anamnestic and clinical selection. The research
volume includes clinical neurologic inspection, research of the somatic status,
psychological testing of higher cortical functions, neurophysiologic inspection (multiple
parameter analysis computer electroencephalography (EEG), including three-dimensional
localization «Brain Loc» of sources epileptiform activity, video-EEG-monitoring),
laboratory techniques (clinical analysis of blood, blood biochemistry, analysis of the
immune status), functional methods (electrocardiogram - ECG, echocardiography, Holter
monitoring - under indications), neuroradiology methods (magnetic resonance imaging - MRI, computer tomography - CT, magnetic resonance angiography - MRA or spiral
computer cerebral angiography).
Selection of patients was carried out by a method of the stratified randomization with
using of criteria of inclusion and an exception. Criteria of inclusion in the Register:
inhabitants of the Krasnoyarsk, inhabitants of BUT Zheleznogorsk of the Krasnoyarsk
region, inhabitants of the Tuva Republic, adults and children who suffer from epileptic
attacks at the moment of the reference in polyclinic, at the moment of hospitalization or
in the anamnesis. Criteria of an exception: inhabitants of other regions of the Russian
Federation, non-epileptic attacks, psychogenic reactions, conversion attacks (hysteria).
Terms of carrying out of research are 2004-2009. Statistical data processing of the Register
is spent with using the standard parametrical and nonparametric methods of comparison.
The parametrical data was represented in the form of average sizes with an average
quadratic error and 95% a confidential interval (CI). Reliability of statistical distinctions
was estimated with using of Student’s criteria, Uilkokson’s and the Mann-Witney’s criteria.
Distinctions were considered authentic at a significance value not less than 95%. Statistical
processing is made by means of a package of applied programs for processing of
biomedical data STATISTICA v.7.0 (StatSoft, USA, 2001).
Results of research
The mean standardized prevalence of epilepsy in general population of the Krasnoyarsk
region (on example BUT Zheleznogorsk) was 2.8 on 1000, including idiopathic epilepsy -
0.21 per 1000, symptomatic epilepsy - 1.24 per 1000 (post-stroke epilepsy - 0.47 per 1000;
posttraumatic epilepsy - 0.24 per 1000; epilepsy from the effects of congenital CNS
abnormalities - 0.21 per 1000; epilepsy from the effects of CNS tumors - 0.17 per 1000),
cryptogenic epilepsy - 1.35 per 1000 population. The incidence of epilepsy in general
population of Krasnoyarsk region increased from 31 per 100000 in 2006 to 59 in 2008
(during our research) (Figure 1).
Prevalence of epilepsy at children from newborn till 15 years in the Krasnoyarsk region
(mean age of patients - 9.8 ± 1.1 [95 % CI: 8 - 13] years old; mean age of seizures onset -
6.1 ± 0.6 [95 % CI: 3 - 9] years old) was 5.04 per 1000, including idiopathic epilepsy - 0.65
per 1000, symptomatic epilepsy - 2.52 per 1000, cryptogenic epilepsy - 1.87 per 1000. The epilepsies in childhood that remit in adolescence are benign myoclonic epilepsy in infancy,
childhood absence epilepsy (pure), early onset occipital epilepsy (Panayiotopoulos
syndrome), benign epilepsy with centrotemporal spikes, Landau-Kleffner syndrome,
epilepsy with continuous spike and wave during slow sleep and some generalized and
focal epilepsies.
Prevalence of epilepsy at teenagers from 15 till 18 years in the Krasnoyarsk region (mean
age - 15.9±1.5 [95% CI: 15 - 17] years old, mean age of seizures onset - 11.5±1.1 [95 %
CI: 9 - 15] years old) was 5.75 per 1000, including idiopathic epilepsy - 1.27 per 1000,
symptomatic epilepsy - 2.21 per 1000, cryptogenic epilepsy - 2.7 per 1000. Epilepsies with
onset in adolescence included juvenile absence epilepsy, juvenile myoclonic epilepsy,
generalized tonic-clonic seizures on awakening, photosensitive epilepsy, mesial temporal
lobe epilepsy, progressive myoclonic epilepsy and other partial or generalized epilepsies.
Prevalence of epilepsy at adults in the Krasnoyarsk region (mean age of patients -
44.5±4.6 [95% CI: 29 - 56] years old, mean age of seizures onset - 34.5±3.1 [95% CI: 18 -
50] years old) was 2.31 per 1000, including idiopathic epilepsy - 0.10 per 1000,
symptomatic epilepsy - 1.0 per 1000, cryptogenic epilepsy - 1.21 per 1000 (Sadikova et al.,
2010).
Prevalence of epilepsy among adult of the Krasnoyarsk city (mean age - 48.6±17.2 [95%
CI: 35-60] years old; mean age of seizures onset - 43.69±20.7 [95% CI: 28-59] years old)
was 0.44 per 1000, including idiopathic epilepsy - 0.017 per 1000, symptomatic epilepsy -
0.29 per 1000 (post-stroke epilepsy - 0.11 per 1000; posttraumatic epilepsy - 0.093 per
1000; epilepsy from the effects of CNS infections - 0.05 per 1000; epilepsy from the
effects of congenital CNS abnormalities - 0.008 per 1000; epilepsy from the effects of
hereditary diseases of CNS - 0.008 per 1000; epilepsy from the effects of CNS tumors -
0.025 per 1000); cryptogenic epilepsy - 0.13 per 1000 (Dmitrenko et al., 2007).
Prevalence of epilepsy with a late onset (mean age of patients - 59.1±10.47 [95% CI: 55 -
67] years old; mean age of seizures onset - 52.3±15.14 [95% CI: 43 - 65] years old) was
0.31 per 1000 among senior adults (age - more 40 years old), including idiopathic epilepsy
- 0.008 per 1000; symptomatic epilepsy - 0.22 per 1000; cryptogenic epilepsy - 0.008 per
1000 (Dmitrenko et al., 2007). The clinical manifestations of epilepsy in the elderly are different from those in younger adults and children. The most common seizure types in
the elderly are complex partial seizures, which may be shorter and less impressive than
those seen in younger patients. However, the elderly often have more severe, prolonged
postictal symptoms, including postictal confusion with disorientation, hyperactivity,
wandering and incontinence can persist for up to one week.
The mean standardized prevalence of epilepsy at childhood population of the Tuva
Republic with age from newborn till 18 years old (mean age of patients - 10.9±4.4 [95%
CI: 7 - 14] years old, mean age of seizures onset - 4.9±0.4 [95% CI: 1.5 - 5.3] years old)
was 3.19±0.3 [95% CI: 0.96 - 4.63] per 1000 (Table 1), including idiopathic epilepsy - 0.37
per 1000, symptomatic epilepsy - 1.25 per 1000 (epilepsy from the effects of CNS
infections - 0.44 per 1000; epilepsy from the effects of hypoxic-ischemic encephalopathy -
0.35 per 1000, posttraumatic epilepsy - 0.33 per 1000, epilepsy from effects of congenital
CNS abnormalities - 10.42 per 1000), cryptogenic epilepsy - 1.31 per 1000. Prevalence of
epilepsy in Kyzyl city was 0.36 per 1000 at childhood population. The incidence of
childhood epilepsy increased from 41 per 100000 in 2005 to 109 per 100000 in 2007
during our study (Figure 2) (Sharavii, 2010).
Conclusion
The studies had shown that the epidemiological characteristics of epilepsy in different
region in the Russian Federation, including the middle Siberia, are similar. Our data has
shown trends similar to those in eastern and western countries of Europe, although the
studies in the European part of the Russian Federation, the western and middle Siberia
indicated a lower prevalence than in the Europe. For instance, prevalence in the
Krasnoyarsk region is 2.8 on 1000 in general population versus 8.2 (ranges from 3.5 to
10.7) per 1000 in general population of the Europe.
The rates are higher in rural areas compared to urban areas in different countries of world.
Also, our studies had shown that prevalence of epilepsy in adults population in the
Krasnoyarsk region (2.31 per 1000) was higher that prevalence in the Krasnoyarsk city
(0.44 per 1000). It could be caused higher level diagnostic and medical aid, presence
specialized epileptological centers and the early reference of patients with an epilepsy
behind medical aid in the Krasnoyarsk. On contrary, in rural and remote territories of the
Krasnoyarsk region diagnostic equipment (video-EEG-monitoring, MRI/CT and other modern diagnostics methods of epilepsy) is absent, the specialized medical help
(epileptologists) is absent also. Post-stroke epilepsy (Silverman et al., 2002) without gender
distinctions dominated in structure epilepsy with late onset in the Krasnoyarsk region,
including the Krasnoyarsk city (Figure 3). (Dmitrenko et al., 2007; Shnayder et al., 2010;
Sadikova et al., 2010).
The lifetime prevalence in children of the middle Siberia (5.04 per 1000 in the
Krasnoyarsk region, 3.19 per 1000 in the Tuva Rebublic) correlated with lifetime
prevalence in the European countries. For instance, the lifetime prevalence in the Norway
(aged 0-15 years) was ranges from 4.4 to 6.8 (Forsgren et al., 2005), and in children of the
Lithuania (aged 0-15 years) was 4.2 (3.4 when age-standardized) per 1000 (Endziniene et
al., 1997).
Our studies had shown the prevalence of childhood epilepsy was higher in the
Krasnoyarsk region (5,04 per 1000) versus in the Tuva Republic (3.19 per 1000). It could
be caused difficulties of inspection of children during exit medical inspections of the
children's population in remote mountain areas of republic where the message is possible
by an air transport, and children from in deserted-steppe areas republic, where Tuvans
have a nomadic way of life (cattle breeding).
Now, our epidemiological, genetics and clinical studies of epilepsy in the middle Siberia
regions are continuing.
Summary
1. Our epidemiological studies suggest the middle Siberia (on example the Krasnoyarsk
region and the Tuva Republic) is region with high prevalence of epilepsy (as prevalence
of epilepsy in Europe countries). However, prevalence of epilepsy in the middle Siberia
was lower, that in the European countries and in developing countries.
2. Prevalence of all forms of epilepsy in the middle Siberia was higher at children and
teenagers. Prevalence of idiopathic epilepsy was high in childhood populations of the
Krasnoyarsk region and the Tuva Republic.
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