Epilepsiu, 33(6):110f&1114, 1992 Raven Press, Ltd., New York 0 International League Against Epilepsy
Determinants of IQ Profile in Children with Idiopathic Generalized Epilepsy Pratibha D. Singhi, Usha Bansal, Sunit Singhi, and “Dwarka Pershad Department of Pediatrics and “Psychiatry, Postgraduate institute of Medical Education and Research, Chandigarh, India
Summary: To determine the IQ profile of children with epilepsy and the influence of various epilepsy-related variables on IQ scores, we studied 50 children with idiopathic generalized epilepsy of > 1-year duration, 25 of their siblings, and 30 healthy controls. IQ assessments were made with Malin’s Indian modification of the Wechsler IntelligenceScale for Children. The mean SD IQ scores of children with epilepsy (85.6 k 12) and their siblings (93.2 -t 11) were significantly lower than those of the controls (101.6 9). The IQ scores of the children with epilepsy were also significantly lower than those of their siblings (p < 0.05). The IQ scores showed a significant correlation with socioeconomic status (SES) score
(r = 0.33), a history of status epilepticus (r = -0.38), duration of seizure disorder (r = -0.31), and total number of seizures (r = -0.31). On multiple regression analysis, status epilepticus emerged as the most significant variable, accounting for 14% variance, followed by SES score (9% variance), duration of seizure disorder (6% variance), and sex of the child (5% variance). Genetic or environmental factors that probably lead to cognitive deficit in children with epilepsy and their siblings require further study. Key Words: Idiopathic generalized epilepsy-Status epilepticus-Cognitive function-Intelligence-Child.
Impairment of cognitive abilities and a decrease in intellectual function in patients with epilepsy has been described for many years (Lennox, 1942) and discussed in several reviews (Harrison and Taylor, 1976; Brown and Reynolds, 1981; Dodrill, 1983; Lesser et al., 1986; Addy, 1987; Besag, 1989; Cull, 1989). Some investigators believe that most children with epilepsy but with no other disease process are of normal overall intelligence and do not deteriorate with time (Bourgeois et al., 1983; Ellenberg et al., 1986; Addy, 1987). Others have shown that the intelligence scores of children with epilepsy are in the average range but tend to cluster toward the lower side (Rodin, 1978; Farwell et al., 1985). Several epilepsy-related factors, i.e., etiology, type, age at onset, localization, severity and duration of seizure, and heredity are generally believed to affect IQ of patients with epilepsy (Ossetin, 1988; Dodson, 1990). Lower IQ scores have been reported in children with symptomatic epilepsy as compared with those with idiopathic epilepsy or ab-
sence seizures (Bourgeois et al., 1983) and in persons with generalized seizures as compared with those with psychomotor or partial seizures (Klove and Mathews, 1966, 1974; Fedio and Mirsky, 1969). The precise nature of cognitive deficit associated with different locations of epileptic foci on EEG is not clear, however (Fedio and Mirsky, 1969; Camfield et al., 1984; Corbett et al., 1985; Ossetin, 1989). Other variables, such as seizure severity (Aicardi et al., 1986; Lesser et al., 1986), early age of onset (Dikmen et al., 1977; O’Leary et al., 1981; Bourgeois et al., 1983; Lesser et al., 1986), and seizure frequency (Dikmen et al., 1977; Seidenberg et al., 1981) have all been shown to be associated with low IQ scores. However, there is a lack of agreement over the independent effect of these variables and the role of antiepileptic drugs (AEDs) in causing cognitive deficits (Dikmen, 1980; Thompson et al., 1980; Giordani et al., 1983; Trimble and Reynolds, 1984; Smith et al., 1985; Dodrill, 1986; Trimble and Cull, 1988). A literature survey showed that several methodologic problems exist in research on the relationship of intellectual performance and epilepsy, and they have been described (Giordani et al., 1985; Dodrill, 1986). The major issues are inconsistency in diag-
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Received July 1991; revision accepted May 1992. Address correspondence and reprint requests to Dr. S . Singhi at Department of Pediatrics, P.G.I.M.E.R., Chandigarh 160012, India.
1106
I Q AND EPILEPS Y
nosis and classification of seizures, inclusion of populations with different types of seizures, highly variable individual differences among patients, use of normative data provided in the intelligence tests, and an analytic framework that does not control for confounding effects of various epilepsy-related variables. Some previous studies have also failed to control for socioeconomic and family variables, and simultaneous evaluation of matched controls and siblings of epileptic children has not been undertaken except by Ellenberg et al. (1986) and Bourgeois et al. (1983). Socioeconomic status (SES), maternal education and IQ, prenatal care, and associated other illnesses in epileptic children have been shown to account for a variance in IQ scores of 25-28% of white and 15-17% of black children (Dodson, 1990). We wished to examine the profile of IQ scores of children with generalized idiopathic epilepsy and their siblings, compare them with scores of matched controls, and determine the influence of various epilepsy related variables on IQ. MATERIALS AND METHODS We studied three groups of children. Epilepsy group Fifty children aged 6-16 years with generalized tonic-clonic idiopathic epilepsy (Revised International Seizures Classification) (Commission, 1981) of >I-year duration formed the epilepsy group. These patients were attending the general pediatric outpatient clinics of Nehru Hospital of the Postgraduate Institute and were entered in the study consecutively if they were free of clinically evident neurologic deficit, AED toxicity, malnutrition (defined as weight for age
Determinants of IQ Profile in Children with Idiopathic Generalized Epilepsy Pratibha D. Singhi, Usha Bansal, Sunit Singhi, and “Dwarka Pershad Department of Pediatrics and “Psychiatry, Postgraduate institute of Medical Education and Research, Chandigarh, India
Summary: To determine the IQ profile of children with epilepsy and the influence of various epilepsy-related variables on IQ scores, we studied 50 children with idiopathic generalized epilepsy of > 1-year duration, 25 of their siblings, and 30 healthy controls. IQ assessments were made with Malin’s Indian modification of the Wechsler IntelligenceScale for Children. The mean SD IQ scores of children with epilepsy (85.6 k 12) and their siblings (93.2 -t 11) were significantly lower than those of the controls (101.6 9). The IQ scores of the children with epilepsy were also significantly lower than those of their siblings (p < 0.05). The IQ scores showed a significant correlation with socioeconomic status (SES) score
(r = 0.33), a history of status epilepticus (r = -0.38), duration of seizure disorder (r = -0.31), and total number of seizures (r = -0.31). On multiple regression analysis, status epilepticus emerged as the most significant variable, accounting for 14% variance, followed by SES score (9% variance), duration of seizure disorder (6% variance), and sex of the child (5% variance). Genetic or environmental factors that probably lead to cognitive deficit in children with epilepsy and their siblings require further study. Key Words: Idiopathic generalized epilepsy-Status epilepticus-Cognitive function-Intelligence-Child.
Impairment of cognitive abilities and a decrease in intellectual function in patients with epilepsy has been described for many years (Lennox, 1942) and discussed in several reviews (Harrison and Taylor, 1976; Brown and Reynolds, 1981; Dodrill, 1983; Lesser et al., 1986; Addy, 1987; Besag, 1989; Cull, 1989). Some investigators believe that most children with epilepsy but with no other disease process are of normal overall intelligence and do not deteriorate with time (Bourgeois et al., 1983; Ellenberg et al., 1986; Addy, 1987). Others have shown that the intelligence scores of children with epilepsy are in the average range but tend to cluster toward the lower side (Rodin, 1978; Farwell et al., 1985). Several epilepsy-related factors, i.e., etiology, type, age at onset, localization, severity and duration of seizure, and heredity are generally believed to affect IQ of patients with epilepsy (Ossetin, 1988; Dodson, 1990). Lower IQ scores have been reported in children with symptomatic epilepsy as compared with those with idiopathic epilepsy or ab-
sence seizures (Bourgeois et al., 1983) and in persons with generalized seizures as compared with those with psychomotor or partial seizures (Klove and Mathews, 1966, 1974; Fedio and Mirsky, 1969). The precise nature of cognitive deficit associated with different locations of epileptic foci on EEG is not clear, however (Fedio and Mirsky, 1969; Camfield et al., 1984; Corbett et al., 1985; Ossetin, 1989). Other variables, such as seizure severity (Aicardi et al., 1986; Lesser et al., 1986), early age of onset (Dikmen et al., 1977; O’Leary et al., 1981; Bourgeois et al., 1983; Lesser et al., 1986), and seizure frequency (Dikmen et al., 1977; Seidenberg et al., 1981) have all been shown to be associated with low IQ scores. However, there is a lack of agreement over the independent effect of these variables and the role of antiepileptic drugs (AEDs) in causing cognitive deficits (Dikmen, 1980; Thompson et al., 1980; Giordani et al., 1983; Trimble and Reynolds, 1984; Smith et al., 1985; Dodrill, 1986; Trimble and Cull, 1988). A literature survey showed that several methodologic problems exist in research on the relationship of intellectual performance and epilepsy, and they have been described (Giordani et al., 1985; Dodrill, 1986). The major issues are inconsistency in diag-
*
*
Received July 1991; revision accepted May 1992. Address correspondence and reprint requests to Dr. S . Singhi at Department of Pediatrics, P.G.I.M.E.R., Chandigarh 160012, India.
1106
I Q AND EPILEPS Y
nosis and classification of seizures, inclusion of populations with different types of seizures, highly variable individual differences among patients, use of normative data provided in the intelligence tests, and an analytic framework that does not control for confounding effects of various epilepsy-related variables. Some previous studies have also failed to control for socioeconomic and family variables, and simultaneous evaluation of matched controls and siblings of epileptic children has not been undertaken except by Ellenberg et al. (1986) and Bourgeois et al. (1983). Socioeconomic status (SES), maternal education and IQ, prenatal care, and associated other illnesses in epileptic children have been shown to account for a variance in IQ scores of 25-28% of white and 15-17% of black children (Dodson, 1990). We wished to examine the profile of IQ scores of children with generalized idiopathic epilepsy and their siblings, compare them with scores of matched controls, and determine the influence of various epilepsy related variables on IQ. MATERIALS AND METHODS We studied three groups of children. Epilepsy group Fifty children aged 6-16 years with generalized tonic-clonic idiopathic epilepsy (Revised International Seizures Classification) (Commission, 1981) of >I-year duration formed the epilepsy group. These patients were attending the general pediatric outpatient clinics of Nehru Hospital of the Postgraduate Institute and were entered in the study consecutively if they were free of clinically evident neurologic deficit, AED toxicity, malnutrition (defined as weight for age
