eMedicine Specialties > Neurology > Seizures and Epilepsy

Epilepsy in Children with Mental Retardation: Differential Diagnoses & Workup

Author: Norberto Alvarez, MD, Assistant Professor, Department of Neurology, Harvard Medical School; Consulting Staff, Department of Neurology, Boston Children's Hospital
Contributor Information and Disclosures

Updated: Aug 29, 2007

Differential Diagnoses

Absence Seizures
Lennox-Gastaut Syndrome
Anencephaly
Mental Retardation
Cerebral Palsy
Neural Tube Defects
EEG Seizure Monitoring
Neuroacanthocytosis
First Seizure: Pediatric Perspective
Neuroacanthocytosis Syndromes
Hydrocephalus
Neurofibromatosis, Type 1
Identification of Potential Epilepsy Surgery Candidates
Neuroimaging in Epilepsy Surgery
Incontinentia Pigmenti
Seizures and Epilepsy: Overview and Classification
Infantile Spasm (West Syndrome)
Status Epilepticus
Landau-Kleffner Syndrome
Vagus Nerve Stimulation

Other Problems to Be Considered

Pseudoseizure

Workup

Laboratory Studies

  • The following tests are indicated for evaluating children with mental retardation. These usually are requested even in patients who do not have epilepsy.
    • Urine - Amino acids, organic acids, mucopolysaccharides, oligosaccharides, reducing substances, ferric chloride, sodium nitroprusside, and dinitrophenylhydrazine
    • Blood - Amino acids, lactate and pyruvate, ammonia, very-long-chain fatty acids, chromosomal studies
    • Cerebrospinal fluid (CSF) (only in selected individuals) - Lactate and pyruvate quantification

Imaging Studies

  • Neuroimaging studies are indicated in almost every patient with mental retardation. Generally, a routine evaluation with CT scanning or MRI is enough for diagnostic evaluation of the mental retardation. More complex evaluation is indicated in those patients who are candidates for surgery.
  • MRI is probably the best test for evaluating congenital malformations of the brain and deficiencies in white and gray matter. Recent advances in MRI technology, such as the fluid attenuation inversion technique (FLAIR), fat-suppression short T1 inversion recovery technique (STIR), as well as fast and ultrafast MRI technology, have increased the usefulness of MRI for evaluating the causes of mental retardation to diagnose epileptic disorders.
  • CT scanning, which is also useful for the same purposes, is indicated when MRI is not possible.
  • Ultrasonography, which has a limited use in evaluating intracranial abnormalities, plays a role in screening the brain and spinal cord in neonates and young infants. It also may help when MRI and CT scanning are unavailable.
  • Arteriography and magnetic resonance angiography (MRA) have more limited indications, mostly for preoperative evaluation of intractable seizures.
  • Positron emission tomography (PET) scanning and single-photon emission computed tomography (SPECT) studies might be more diagnostically sensitive than MRI in areas of the brain where the metabolic disorder is more important than the structural abnormalities. Such is the case of small cortical dysplasias, which show hypometabolism. These tests are more relevant for presurgical evaluation of patients with intractable seizures.

Other Tests

  • The EEG, combined with the clinical picture, is central to the diagnosis of epilepsy. The EEG findings in epileptic disorders are described in other eMedicine articles. This article aims to describe some of the EEG changes that are seen more often or are specifically relevant to individuals with mental retardation.
    • EEG changes observed in persons with mental retardation and epilepsy are, in general, similar to the ones observed in individuals with epilepsy without mental retardation.
    • Some syndromes, such as hypsarrhythmia and Lennox-Gastaut, which have particular EEG features, are seen more often in individuals with mental retardation.
    • Long-term closed-circuit television videotaping and digitized EEG telemetry (CCTV-EEG) is becoming a standard technique to document the diagnosis and also for presurgical evaluation of patients with intractable seizures.
  • In children with seizures and progressive degenerative disorders, the presence of slowing in the background activities and loss of normal patterns in serial EEGs might help in the recognition that the patient's encephalopathic process is not static.
  • Findings on serial EEGs, which might help confirm the diagnosis in children with Rett syndrome, are usually normal in the first stages of the disease, even when the child has shown some signs of deterioration. As the disease progresses, the background activity deteriorates and the EEG shows spikes and sharp waves in the central and temporal areas; these waves become more frequent during sleep and have the characteristics of benign centrotemporal spikes. As the child's mental condition deteriorates, the discharges become generalized with pseudoperiodic theta and delta patterns as well as marked slowing of the background.
  • In Angelman syndrome, the interictal EEG shows high-voltage theta and delta activity, which is generalized with anterior predominance and, at times, with runs of slow delta activity followed by sharp waves.
    • Spike and slow activity, which is facilitated by eye closure, is seen in the posterior quadrants.
    • In some cases, an almost continuous, myoclonuslike movement involving the face is accompanied by rhythmic 5- to 10-Hz activity.
    • These abnormal activities are exaggerated by drowsiness and sleep.
  • Children and young adults with fragile X syndrome have centrotemporal spikes, which are activated by sleep.
  • In a few cases of children with autism, clinical regression was associated with epilepsy and/or EEG abnormalities. Centrotemporal spikes with no clinical seizures also have been described. Whether these findings have any relationship with the autistic disorder and whether antiepileptic medications might be useful in those patients with EEG abnormalities but without clear clinical seizures is unclear. The most traditional approach is that children with autistic features, abnormal EEG findings, and no clinical seizures would not benefit from antiepileptic medications. Some recent reports, however, showed that children with autism and no clinical seizures might improve with antiepileptic medications.
  • Malformations of cortical development might be associated with defined EEG changes.
    • In some cases of cortical malformations, the EEG background activity might be normal or have minimal changes.
    • The degree of EEG abnormality generally correlates with the severity of the malformation and the severity of the seizure disorder.
    • The EEG findings are not specific or characteristic of any particular condition.
  • In cases with hemimegalencephaly, EEG findings include poorly organized background activities plus frequent focal and multifocal spikes and sharp waves as well as burst-suppression patterns, which are mostly over the malformed hemisphere.
  • In focal cortical dysplasia, the EEG changes, mostly focal slowing and/or epileptiform activity, are primarily localized to the abnormal cortical area.
  • In lissencephaly (and depending on the type of brain abnormality), the EEG might show a hypsarrhythmic type pattern, more often in younger children, or high-voltage continuous diffuse discharges of beta activity in both hemispheres. Generalized discharges at slow frequencies also have been described.

More on Epilepsy in Children with Mental Retardation

Overview: Epilepsy in Children with Mental Retardation
Differential Diagnoses & Workup: Epilepsy in Children with Mental Retardation
Treatment & Medication: Epilepsy in Children with Mental Retardation
Follow-up: Epilepsy in Children with Mental Retardation
References
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Further Reading

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Keywords

antiepileptic medications, anti-epileptic medications, epilepsy in children with mental retardation, epilepsy in MR, epilepsy in mental retardation

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Contributor Information and Disclosures

Author

Norberto Alvarez, MD, Assistant Professor, Department of Neurology, Harvard Medical School; Consulting Staff, Department of Neurology, Boston Children's Hospital
Norberto Alvarez, MD is a member of the following medical societies: American Academy of Neurology, American Epilepsy Society, and Child Neurology Society
Disclosure: Nothing to disclose.

Medical Editor

David A Griesemer, MD, Professor, Departments of Neurology and Pediatrics, Medical University of South Carolina
David A Griesemer, MD is a member of the following medical societies: American Academy of Neurology, American Epilepsy Society, and Child Neurology Society
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Jose E Cavazos, MD, PhD, Assistant Professor, Departments of Medicine (Neurology), Pharmacology, and Physiology, University of Texas Health Science Center at San Antonio
Jose E Cavazos, MD, PhD is a member of the following medical societies: American Academy of Neurology, American Clinical Neurophysiology Society, American Epilepsy Society, and Society for Neuroscience
Disclosure: Glaxo-SmithKline Honoraria Speaking and teaching; Ortho-McNeil Neurologics Honoraria Speaking and teaching; UCB Pharma Honoraria Speaking and teaching

CME Editor

Selim R Benbadis, MD, Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, University of South Florida School of Medicine, Tampa General Hospital
Selim R Benbadis, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, American Clinical Neurophysiology Society, American Epilepsy Society, and American Medical Association
Disclosure: Nothing to disclose.

Chief Editor

Nicholas Y Lorenzo, MD, Chief Editor, eMedicine Neurology; Consulting Staff, Neurology Specialists and Consultants
Nicholas Y Lorenzo, MD is a member of the following medical societies: Alpha Omega Alpha and American Academy of Neurology
Disclosure: Nothing to disclose.

 
 
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