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Diagnosing LGS

Lennox-Gastaut syndrome (LGS) is a type of epilepsy that usually appears before the age of 8.1 It occurs more often in boys than girls. It is very rare—LGS only accounts for 4% of all childhood epilepsy cases.2

Even if your child is diagnosed early with epilepsy, it may take more time to diagnose LGS. Some of the features of LGS occur with other forms of epilepsy or seizure conditions, which makes diagnosing LGS difficult. It is likely that you will need to go to a specialized epilepsy center to get a proper diagnosis by an epileptologist.

LGS is usually characterized by:

  • Multiple seizure types
  • An EEG with a slow spike-wave pattern between seizures
  • Cognitive impairment or developmental delays3
Diagnosis of LGS is challenging.

Understanding the EEG
Electroencephalography (EEG) records the electrical activity of the brain. It is an important test for diagnosing epilepsy because it shows patterns of normal or abnormal brain activity.4

When diagnosing LGS, doctors will look for diffused slow spikes and slow waves in cycles of 2-2.5 per second.1 This is between seizures, and while the person is awake.1 An EEG during sleep is also necessary.1 These EEG patterns differentiate LGS from other epilepsy syndromes.1

Causes of LGS
The history and causes of LGS vary. An estimated 20% of children with LGS have a prior history of infantile spasms. (often referred to as West syndrome).1 LGS can be caused by genetic disorders such as tuberous sclerosis.2 Injuries affecting the brain, such as lack of oxygen or diseases like meningitis and encephalitis, can also cause LGS when they happen within a few months of birth.2 Unfortunately, a cause cannot be found for roughly 1 in 3 cases.2

Once a child is diagnosed with LGS, the prognosis varies by individual. The cause associated with the syndrome will likely affect the prognosis, and sometimes the therapeutic strategies. Patients with a prior history of infantile spasms have a significantly worse prognosis.5

Risk factors for a less favorable LGS prognosis include:
  • Symptomatic cause
  • Prior history of infantile spasms
  • Onset before the age of 3
  • High frequency of seizures
  • Worsening periods of long duration
  • Repeated episodes of status epilepticus6
LGS is a type of epilepsy that affects a child’s intellectual functioning and may cause behavioral disturbances.7 Unfortunately, LGS usually persists through childhood and adolescence into adulthood. Unfortunately, there is no cure for LGS, so freedom from seizures and normal development is very unusual.7

While the seizures associated with LGS are difficult to control, there are treatment options that may help.6 It is important for parents and caregivers to understand the different types of seizures associated with LGS. By keeping track of seizure activity and frequency in daily life, parents can give doctors information that may help improve the treatment plan.8

Learn more: Seizures associated with LGS »

1.  Arzimanoglou A, French J, Blume WT, et al. Lennox-Gastaut syndrome: a consensus approach on diagnosis, assessment, management, and trial methodology. Lancet Neurol. 2009;8:82-93.
2.  Crumrine PK. Lennox-Gastaut syndrome. J Child Neurol. 2002;17(suppl 1):S70-75.
3.  Wheless J. Lennox-Gastaut syndrome: characteristics and clinical manifestations. August 7, 2009. Accessed July 31, 2012.
4.  Diagnosis. Epilepsy Foundation Web site. Accessed August 20, 2012.
5.  Etiology/causes. Accessed July 31, 2012.
6.  Epilepsy syndromes. Epilepsy Foundation Web site. Accessed September 23, 2010.
7.  NINDS Lennox-Gastaut information page. National Institute of Neurological Disorders and Stroke Web site. Updated June 15, 2010. Accessed July 31, 2012.
8.  Phillips L. Dear seizure diary: how and why to record your epileptic seizures. Neurology Now. November/December 2009;5(6):35-36.

View a documentary featuring 2 families living with LGS that offers perspectives from physician experts and patient advocates.

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