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Historical note and nomenclature

The first clinical description of falling seizures was given by Hunt in 1922 (Hunt 1922). In 1945 Lennox called it “akinetic” (Lennox 1945), but he rebaptized it “astatic” in 1951 (Lennox 1951), and included it into the “petit mal triade,” together with absences and myoclonus. However, it is not before Gastaut and Regis’ polygraphic description that a specific type of seizure with a combination of myoclonus preceding atonia was reported (Gastaut and Regis 1961). Kruse introduced the term “myoclonic-astatic” seizure (Kruse 1968), and Doose and colleagues introduced the concept of a specific clinical entity with this type of seizure being the core of the disorder (Doose et al 1970). Clearly, in addition to myoclonic-astatic epilepsy, there are patients with myoclonic-atonic seizures who have prior mental retardation and lack the characteristics of myoclonic-astatic epilepsy. However, this group of patients has never been addressed specifically.

Clinical manifestations

The major feature is a sudden fall to the ground. It is preceded by a jerk of the axial muscles. Polygraphic recording demonstrates that there is a spike wave complex, and that the spike is usually associated with the myoclonic jerk and the slow wave with the loss of tone. The result is that the patient, usually a child, is suddenly precipitated frontward and, because of the atonia, no protection movement is possible. There is no announcing sign, and the child is literally seized by the phenomenon. For this reason, these children experience bad injuries of the forehead and face.

A 3-year-old child had three generalized tonic clonic seizures. EEG showed generalized spike waves and slow background activity. When given carbamazepine, seizure frequency decreased slightly but soon seizures recurred and the child started falling. When he fell, parents clearly noticed that the child was projected forwards and then became atonic. He was severely hyperkinetic, and falling seizures occurred several times a day. Both contributed to determine bad injuries to the face. Two cousins suffered from idiopathic generalized epilepsy. This is a case of myoclonic astatic epilepsy.

Localization

As for most brief generalized seizures, the relative responsibility of brainstem and cortex remains a matter of strong discussion. The predominance of the contraction in the axial and flexor muscles is considered as an argument in favor of an archaic pattern, therefore, of brainstem origin. Velasco and colleagues (Velasco et al 1991) found either simultaneous activation in the thalamus and cortex or lack of activation in both, thus suggesting that the triggering zone was neither in the thalamus or the cortex. Although he suspected that it was the brainstem, the most likely site of onset is the thalamo-cortico-thalamic loop.

Pathophysiology

Rolandic involvement is highly suggested, and maturation phenomena play a great contribution (Dulac et al 1998). The correlation of myoclonus with the spike and the slow wave with the atonia is consistent with the established significance of both these events: the spike corresponds to an excitatory event, and the slow wave to an inhibitory phenomenon. Thus, the cortex and thalamus may both be involved, within a loop characteristic of seizures of idiopathic generalized epilepsy, namely absences and myoclonus. In addition, the hyperexcitability determined by maturation would be counterbalanced by excess of inhibition, the combination of which would produce the sequence of jerk and atonia. The main difference with massive myoclonus of juvenile myoclonic epilepsy is the intensity of the jerk that also involves the lower limbs, and the inhibitory component. Both could result from overexcitability of the developing cortex, balanced by excess of inhibition. In one study with video-polygraphy study, there was a correlation between intensity of the atonia and depth of the positive component of the spike-wave complex (Oguni et al 2001).

Differential diagnosis

Young children may fall for other reasons than epileptic seizures: clumsiness when walking, syncope, cataplexy, vestibular disorders, and psychogenic seizures may cause the child to fall. Other types of falling seizures, tonic, myoclonic, atonic and partial seizures, and epileptic spasms have to be distinguished. Although the clinical context and the interictal EEG may be helpful, it is only the video polygraphic recording that permits to conclude. However, there is at present no evidence that partial and generalized falling seizures are distinct from the pathophysiological point of view.

Diagnostic workup

The diagnosis can only be established on the basis of video polygraphic recording. However, in the context of typical features of myoclonic-astatic epilepsy, it may not be necessary to perform such a recording. The latter is mainly needed when the clinical evidence is lacking, or when a major therapeutic decision needs to be taken.

Syndromes and diseases in which the seizure type occurs.

Myoclonic-atonic seizures mainly affect patients with myoclonic-astatic epilepsy.

Prognosis and complications

The prognosis is difficult to determine at the onset, although male sex and late onset, after the age of 4 years are 2 features of poor prognosis (Kaminska et al 1999). It is the occurrence of myoclonic status with tonic seizures that is the major factor of poor prognosis.

Management

Treatment is that of the syndrome, the most appropriate combination being valproate and lamotrigine with ethosuximide, eventually a benzodiazepine (Dulac and Kaminska 1997). Patients should not receive carbamazepine, oxcarbazepine, vigabatrin, phenytoin, or phenobarbital that increase seizure frequency in a majority of patients.

In practice, carbamazepine, phenobarbital, phenytoin, and oxcarbazepine should not be given to a 2- to 5-year-old child who begins with tonic-clonic seizures, before myoclonic-astatic epilepsy has been ruled out.

References cited

Doose H, Gerken H, Leonhardt R, Volzke E, Volz C. Centrencephalic myoclonic-astatic petit mal. Clinical and genetic investigation. Neuropadiatrie 1970;2(1):59-78.

Dulac O, Kaminska A. Use of lamotrigine in Lennox-Gastaut and related epilepsy syndromes. J Child Neurol 1997;12 Suppl 1:S23-8.

Dulac O, Plouin P, Shewmon A. Myoclonus and epilepsy in childhood: 1996 Royaumont meeting. Epilepsy Res 1998;30(2):91-106.

Gastaut H, Regis H. On the subject of Lennox's "akinetic" petit mal. Epilepsia 1961;2:298-305.

Hunt JR. On the occurrence of static seizures in epilepsy. J Nerv Ment Dis 1922;56:351.

Kaminska A, Ickowicz A, Plouin P, Bru MF, Dellatolas G, Dulac O. Delineation of cryptogenic Lennox-Gastaut syndrome and myoclonic astatic epilepsy using multiple correspondence analysis. Epilepsy Res 1999:36(1):15-29.

Kruse R. Das Myoclonische-astatische Petit Mal. Berlin: Springer, 1968.

Lennox WG. The petit mal epilepsies: their treatment with Tridione. JAMA 1945;129:1069-73.

Lennox WG. Phenomena and correlates of the psychomotor triad. Neurology 1951;1:357-71.

Oguni H, Fukuyama Y, Tanaka T, et al. Myoclonic-astatic epilepsy of early childhood--clinical and EEG analysis of myoclonic-astatic seizures, and discussions on the nosology of the syndrome. Brain Dev 2001;23(7):757-64.

Velasco M, Velasco F, Alcala H, Davila G, Diaz-de-Leon AE. Epileptiform EEG activity of the centromedian thalamic nuclei in children with intractable generalized seizures of the Lennox-Gastaut syndrome. Epilepsia 1991;32(3):310-21.

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Abbreviations

EEG:electroencephalography

Synonyms

Falling seizures

Major keyword descriptors

akinetic seizures

astatic seizures

atonia

axial muscle jerk

falling seizures

maturation phenomena

myoclonic-astatic epilepsy

myoclonus

rolandic involvement

thalamo-cortico-thalamic loop

Minor keyword descriptors

absences

drop attack

polygraphy

sudden falls

Age of presentation

02-05 years

Age of typical presentation

02-05 years

Permutation

Myoclonic-atonia seizures

atonia seizures, Myoclonic-

seizures, Myoclonic-atonia

seizures, Falling

Related topics

Benign myoclonic epilepsy in infancy

Dravet syndrome (severe myoclonic epilepsy in infancy)

Epilepsy

Myoclonic absences

Myoclonic-astatic epilepsy of childhood

Psychogenic seizures

West syndrome

Differential diagnosis

other reasons for falls

clumsiness when walking

syncope

cataplexy

vestibular disorders

psychogenic seizures

other types of falling seizures

tonic seizures

myoclonic seizures

atonic seizures

partial seizures

epileptic spasms