eMedicine Specialties > Neurology > Pediatric Neurology

Lennox-Gastaut Syndrome: Differential Diagnoses & Workup

Author: Tracy A Glauser, MD, Professor, Departments of Pediatrics and Neurology, University of Cincinnati College of Medicine, Children's Comprehensive Epilepsy Program, Children's Hospital Medical Center of Cincinnati
Coauthor(s): Diego A Morita, MD, Assistant Professor of Pediatrics and Neurology, Department of Pediatrics, Division of Neurology, Cincinnati Children's Hospital Medical Center, University of Cincinnati
Contributor Information and Disclosures

Updated: Apr 10, 2006

Differential Diagnoses

Epilepsy in Adults with Mental Retardation
Epilepsy in Children with Mental Retardation
Epilepsy, Juvenile Myoclonic
Epileptic and Epileptiform Encephalopathies

Other Problems to Be Considered

Myoclonic-astatic epilepsy (Doose syndrome)

Workup

Imaging Studies

  • Computed axial tomography scan or magnetic resonance imaging
    • In general, an MRI is the preferred neuroimaging study for a patient with LGS, rather than a CT scan. CT scans may be preferred in selected situations (eg, evaluation of suspected intracranial injury and/or hematoma in a patient with head trauma resulting from an atonic and/or tonic seizure).
    • Neuroimaging is an important part of the search for an underlying etiology in a patient with LGS. Abnormalities revealed by neuroimaging associated with LGS include tuberous sclerosis, brain malformations (eg, cortical dysplasias), hypoxia-ischemia injury, or frontal lobe lesions.
  • Positron emission tomography
    • No current indication exists for routine PET scanning in patients with LGS.
    • PET scans may be useful when patients are undergoing evaluation as candidates for epilepsy surgery.
  • Single-photon emission computed tomography
    • No current indication exists for routine single-photon emission computed tomography (SPECT) scanning in patients with LGS.
    • SPECT scans may be useful when patients are undergoing evaluation as candidates for epilepsy surgery.

Other Tests

  • Electroencephalogram: Always perform an EEG in patients with suspected LGS, since the diagnosis depends on the presence of specific EEG findings. If possible, obtain prolonged video/EEG telemetry to perform the following:
    • Record both waking and sleep EEG to assist in confirming a suspected diagnosis. A routine 20-minute EEG may not capture the patient both awake and asleep and thus may miss specific important EEG findings.
    • Capture and classify each of the patient's multiple seizure types.
    • Educate the parents on which of the patient's "events" are seizures and which are nonepileptic behavioral events. Parental ability to correctly recognize and identify atypical absences is poor. In one study using video/EEG monitoring in a cohort of children with LGS, parental recognition was 27% for atypical absences, while the sensitivity was as high as 80% for myoclonic seizures and 100% for tonic, atonic, tonic-clonic, clonic, and complex partial seizures.
  • Interictal EEG
    • Interictal EEG is characterized by a slow background that can be constant or transient. Permanent slowing of the background is associated with poor cognitive prognosis.
    • The hallmark of the awake interictal EEG in patients with LGS is the diffuse slow spike wave (see Image 2). This pattern consists of bursts of irregular and generalized spikes or sharp waves followed by a sinusoidal 35- to 400-millisecond slow wave with an amplitude of 200-800 microvolts, which can be symmetric or asymmetric. The amplitude often is higher in the anterior region or in the frontal or frontocentral areas, but in some patients the activity may dominate in the posterior head regions. The frequency of the slow spike wave activity commonly is found at 1.5-2.5 Hz.
    • Slow spike waves usually are not activated by photic stimulation. Hyperventilation rarely induces slow spike waves, although mental retardation prevents adequate cooperation in many patients. During non-REM sleep, discharges are more generalized, more frequent, and consist of polyspikes and slow waves. In REM sleep, spike waves decrease. During periods of frequent seizures, the total duration of REM sleep is reduced.
  • Ictal EEG
    • During a tonic seizure, the EEG is characterized by a diffuse, rapid (10-13 Hz), low-amplitude activity pattern, mainly in the anterior and vertex areas ("recruiting rhythm") that progressively decreases in frequency and increases in amplitude. A brief generalized discharge of slow spike waves or flattening of the recording may precede this pattern. Diffuse slow waves and slow spike waves may follow it. These fast discharges are common during non-REM sleep. Unlike tonic-clonic seizures, no postictal flattening occurs. Clinical manifestations appear 0.5-1 second after the onset of EEG manifestations and last several seconds longer than the discharge.
    • During an atypical absence seizure, the EEG is characterized by diffuse, slow (2-2.5 Hz), and irregular spike waves, which may be difficult to differentiate from interictal bursts. Occasionally, discharges of rapid rhythms may be observed preceded by flattening of the record for 1-2 seconds, followed by progressive development of irregular fast rhythm in the anterior and central regions, and ending with brief spike waves.
    • During atonic, massive myoclonic, and myoclonic-atonic seizures, the EEG is characterized by slow spike waves, polyspike waves, or rapid diffuse rhythms. Simultaneous video/EEG recording can help differentiate these seizure types. In most patients, these 3 types of seizures coexist.
    • The EEG during absence status epilepticus reveals continuous spike wave discharges, usually at a lower frequency than at baseline, and rapid rhythms during tonic status epilepticus.

More on Lennox-Gastaut Syndrome

Overview: Lennox-Gastaut Syndrome
Differential Diagnoses & Workup: Lennox-Gastaut Syndrome
Treatment & Medication: Lennox-Gastaut Syndrome
Follow-up: Lennox-Gastaut Syndrome
Multimedia: Lennox-Gastaut Syndrome
References
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References

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Further Reading

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Keywords

childhood epileptic encephalopathy with diffuse slow spike waves, Lennox-Gastaut syndrome, LGS, pediatric epilepsy syndrome, childhood epilepsy, seizures, mental retardation

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Contributor Information and Disclosures

Author

Tracy A Glauser, MD, Professor, Departments of Pediatrics and Neurology, University of Cincinnati College of Medicine, Children's Comprehensive Epilepsy Program, Children's Hospital Medical Center of Cincinnati
Tracy A Glauser, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Pediatrics, American Epilepsy Society, and Child Neurology Society
Disclosure: Nothing to disclose.

Coauthor(s)

Diego A Morita, MD, Assistant Professor of Pediatrics and Neurology, Department of Pediatrics, Division of Neurology, Cincinnati Children's Hospital Medical Center, University of Cincinnati
Diego A Morita, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Pediatrics, American Epilepsy Society, and American Medical Association
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

Kenneth J Mack, MD, PhD, Senior Associate Consultant, Department of Child and Adolescent Neurology, Mayo Clinic
Kenneth J Mack, MD, PhD is a member of the following medical societies: American Academy of Neurology, Child Neurology Society, Phi Beta Kappa, and Society for Neuroscience
Disclosure: Nothing to disclose.

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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