History
Although approximately 20-30% of children with Lennox-Gastaut syndrome (LGS) are free from neurologic and neuropsychologic deficits prior to onset of symptoms (ie, idiopathic LGS), these problems inevitably appear during the evolution of LGS. Factors associated with more common or more severe mental retardation include the following:
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An identifiable etiology (ie, symptomatic LGS)
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A history of West syndrome (infantile spasm)
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Onset of symptoms before age 12-24 months
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More frequent seizures
Average intelligence quotient (IQ) score is significantly lower in patients with symptomatic LGS than in those with cryptogenic LGS (ie, patients for whom no cause of LGS can be identified but a cause is suspected). In one study, IQ testing showed variable degrees of mental retardation in 66% of the cryptogenic group and in 76% of the symptomatic group at first examination. At the last examination, mental retardation was found in 95% of the cryptogenic group and in 100% of the symptomatic group.
A significant correlation exists between age of onset of seizures and mental deterioration. In one study, almost 98% of the patients who had an onset of seizures before age 2 years had definite cognitive impairment, compared with 63% of those with onset after age 2 years.
Young children with LGS may exhibit mood instability, personality disturbances, or slowing and/or arrest of psychomotor development and educational progress. In contrast, older children with LGS experience character problems, acute psychotic episodes, or chronic forms of psychosis with aggressiveness, irritability, or social isolation.
The most impaired of the cognitive functions are reaction time and information processing, which are prolonged. The main characteristics of mental deterioration are reported as apathy, memory disorders, impaired visuomotor speed, and perseverance.
Ictal clinical manifestations
Tonic seizures have a frequency of 17-95%. These seizures can occur during wakefulness or sleep but are more frequent during non–rapid eye movement (REM) sleep. Duration is from a few seconds to a minute.
Tonic seizures can be axial, axorhizomelic, or global. Axial tonic seizures involve the head and trunk with head and neck flexion, contraction of masticatory muscles, and eventual vocalizations. Axorhizomelic tonic seizures feature tonic involvement of the proximal upper limbs with elevation of the shoulders and abduction of the arms. Global tonic seizures are marked by contraction of the distal part of the extremities, occasionally leading to a sudden fall and at other times mimicking infantile spasms.
Tonic seizures can be asymmetric. Some patients may show gestural automatisms after the tonic phase. The tonic seizure may end in a vibratory component if prolonged.
Atypical absence seizures range in frequency from 17-100%. This wide range results from parental inability to correctly recognize and identify atypical absences. 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.
Atypical absences may be difficult to diagnose because their onset may be gradual and loss of consciousness may be incomplete, allowing the patient to continue activities to some degree. Patients may have associated eyelid myoclonias, which are not as rhythmic as in typical absences but often are associated with perioral myoclonias or progressive flexion of the head secondary to a loss of tone. Automatisms may be observed. Seizures may end gradually in some patients and abruptly in others.
Atonic seizures, massive myoclonic seizures, and myoclonic-atonic seizures have a frequency of 10-56% in LGS. These seizures are difficult to differentiate by clinical observation only. Considerable discrepancies exist in the use of these terms. All 3 types can produce a sudden fall, producing injuries (drop attacks, Sturzanfälle) or may be limited to the head falling on the chest (head drop, head nod, nictatio capitis). Pure atonic seizures are exceptional; most have a tonic or myoclonic component.
Other types of seizures are noted. Generalized tonic-clonic seizures are reported in 15% of patients, while complex partial seizures occur in 5%. Absence status epilepticus, tonic status epilepticus, and nonconvulsive status epilepticus all can occur and can be resistant to therapy.
Physical Examination
Findings on general physical examination are normal in many patients with LGS. There are no physical findings pathognomonic for LGS.
Nevertheless, the general physical examination can be important in helping to identify specific etiologies that have both systemic and neurologic manifestations (eg, adenoma sebaceum or ash leaf macules in tuberous sclerosis). Use a Wood lamp to examine the skin. Patients may exhibit moderately severe to severe growth delay, a nonspecific finding that is more a reflection of the underlying brain injury than of a specific epilepsy syndrome.
Neurologic examination
Neurologic examination in patients with LGS demonstrates abnormalities in mental status function, specifically deficits in higher cognitive function consistent with intellectual disability.
Abnormalities in level of consciousness, cranial nerve function, motor/sensory/reflex examination, cerebellar testing, or gait are nonspecific findings and more a reflection of the underlying brain injury or effect of anticonvulsant medications. No neurologic examination findings are pathognomonic for LGS.
Complications
Potential complications of LGS include death (either sudden unexplained death in epilepsy or related to an accident involving a seizure) and injuries (especially facial) from seizures resulting in falls.
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Patient with Lennox-Gastaut syndrome wearing a helmet with face guard to protect against facial injury from atonic seizures
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Slow spike wave pattern in a 24-year-old awake male with Lennox-Gastaut syndrome. The slow posterior background rhythm has frequent periods of 2- to 2.5-Hz discharges, maximal in the bifrontocentral areas, occurring in trains as long as 8 seconds without any clinical accompaniment.
