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Atypical absence
by Olivier Dulac Date of submission: August 23, 1999 Date of update: August 15, 2003
Medline SEARCH DATE: August 22, 2003 |
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Acknowledgements
and disclosures Please disclose any financial or other conflicts of interest that might bias your contributions, or give rise to the perception of such bias. Relevant financial ties can include consultantships, memberships in speaker's bureaus, grants, research support, salaries, royalties, ownership, equity positions, stock options, or other financial arrangements wherein you stand to gain substantially from an increase of stock value or corporate revenues. Disclosures and acknowledgements will be linked to the author name(s) and will display along with appointments and affiliations. Disclosures, acknowledgements, and affiliations can be entered and updated via the "Update My Profile" link in the Online Submission System. Alternatively, you may send such information along with your updated manuscript. Thumbnail So that MedLink Corporation can highlight your clinical summary and your authorship on the MedLink Neurology home page and in our weekly email to subscribers, we ask that you provide here a brief overview of your subject (about 50 to 100 words) aimed at enticing readers to view this clinical summary. For updates, please include a sentence that refers to something new you have added. Refer to yourself in the 3rd person (eg, Dr. Doe of Superior Institution explains the basics…). For more information and examples of thumbnails, please see the Instructions to Authors, which can be downloaded from your "My Writing Assignments" page in the Online Submission System (http://www.medlinkoss.com). HISTORICAL NOTE AND NOMENCLATURE Atypical absences are
associated with a high incidence of changes in postural tone. The
beginning and end are usually difficult to identify because they are more
progressive and because this type of seizure affects children whose mental
function is altered. It is, therefore, difficult to determine the duration
that ranges from 5 seconds to 20 seconds. The axial tone is affected, and
this may cause the patient to fall. Eyelid clonus, mild tonic or autonomic
features, or automatisms may also be observed. There is, therefore, a
whole spectrum of clinical manifestations varying from typical absence to
mild manifestations. Because the clinical features may be mild in an
intellectually impaired child, it is often difficult to count such
seizures, even with video EEG monitoring. Attention may decrease seizure
frequency, whereas drowsiness may increase it. The frequency of atypical
absences varies from a few a day to nearly continuous. The frequency of generalized spike-and-waves discharge on EEG is less
than 3Hz. Only an EEG can identify this type of seizure. Many patients
have, in addition to clinical seizures, subclinical discharges. Counting
the seizures is, therefore, an unresolved challenge since isolated
clinical observation omits subclinical discharges that can affect
cognition. Counting EEG discharges would ignore differences in the impact
of clinical versus subclinical discharges, and video EEG is reliable only
if permanent clinical observation is also used to determine whether the
discharge is clinical or subclinical. Such observation would alter the
frequency of seizures, though, since it would raise the vigilance of the
child and, therefore, prevent the occurrence of absences and discharges.
However, the practical implications of this difficulty are moderate
because the aim of treatment, including those used in clinical trials,
should be the disappearance of seizures and of spikes on EEG. Atypical absences may be combined with tonic seizures and slow spike
waves, and this combination defines the Lennox-Gastaut syndrome, which is
usually symptomatic and may follow West syndrome in 40% of the cases.
Atypical absences may be atonic or tonic. They may occur as the only type
of seizure in a patient who exhibits continuous spike waves in slow sleep.
In such patients, the absences are mainly atonic. Atypical absences may be
combined with generalized tonic-clonic and myoclonic seizures in
myoclonic-astatic epilepsy. In this condition, the absences are also
mainly atonic. A seven-year-old child without any history of brain damage but who had
mild speech delay and hyperkinesia started having brief episodes of fixed
gaze and falls. In sleep, the parents observed tonic fits. The awake EEG
showed slow spike waves, and the sleep recording showed generalized bursts
of polyspikes and tonic seizures. This is a frequent mode of onset of
Lennox-Gastuat syndrome in patient without previous evidence of brain
damage. The diagnosis may be more difficult at the beginning when there is
no tonic seizure. A three-year-old boy suffered a few nonfebrile generalized tonic-clonic
seizures for 2 months, and he began to fall. In the morning, his parents
noticed generalized jerks, and there were brief episodes of staring during
which the child’s head suffered from mild atonia. An EEG showed irregular
slow spike-and-waves, and the basic activity was slow with a high
amplitude and brief bursts of polyspikes in sleep. The diagnosis of
myclonic astatic epilepsy was likely. The presence of rare tonic seizures
did not exclude the diagnosis or indicate poor prognosis (Kaminska et al
1999). A five-year-old child suffered from major hyperkinesia and progressive
deterioration of cognitive functions, mainly consisting of repetitive
activity with loss of the ability to anticipate. Episodes of atonia with
loss of contact were observed. An EEG showed generalized bursts of slow
spike waves and a frontal spike wave focus when awake and continuous slow
spike waves in sleep. A four-year-old child with congenital hemiplegia suffered several focal
motor seizures from the age of 3 years. EEG showed slow basic activity on
the contralateral side with bursts of spike waves on the same area and
diffusion to the contralateral side. The first automated external
defibrillator failed to control the fits, and 2 months after switching to
a second drug, the child started to fall; however, the first type of
seizures had not recurred. The EEG showed a considerable increase of
“interictal” spike wave activity that became nearly continuous in slow
sleep. This is a typical case of symptomatic epilepsy switching to
continuous slow spike waves in sleep, possibly with iatrogenic
contribution due to an inappropriate choice of medication. For Lennox-Gastaut syndrome, the combination of valproate with lamotrigine and phenytoin (Dulac and Kaminska 1997) and, more rarely, with felbamate (Siegel et al 1999) have greatly modified the outcome of cases that are not preceded by West syndrome. The latter are most resistant to drug treatment. Steroid treatment and ketogenic diet may be useful, provided they are administered early enough. Callosotomy has been performed with clinically relevant, but usually incomplete, success. In cases beginning after the age of 3, callosotomy is usually sufficient, but for cases following West syndrome, callosotomy must be complete in order to be effective. However, this requires that the operation be performed before the age of 10 years in order to avoid deterioration of speech (Pinard et al 1999). In any case, carbamazepine, vigabatrin, phenobarbital, and tiagabin may worsen the condition. For myoclonic-astatic epilepsy, the combination of valproate with lamotrigine and either ethosuximide or a benzodiazepine has considerably modified the course of the disorder (Dulac and Kaminska 1997). Levetriacetam may be effective. Carbamazepine, vigabatrin, tiagabin, oxcarbazepine, phenobarbital, and phenytoin may worsen the condition. For continuous spike waves in slow sleep, benzodiazepine, ethosuximide,
or sultiam rarely suffice, and combining them with steroids is most
useful, provided that the steroids are given for more than 1 year in
decreasing doses to prevent major side effects (Marescaux et al 1990).
Carbamazepine, phenobarbital, phenytoin, oxcarbazepine, lamotrigine, and
vigabatrin tiagabin may worsen the condition. Blume WT. Pathogenesis of Lennox-Gastaut syndrome: considerations and hypotheses. Epileptic Disord. 2001;3:183-96. Doose H, Gerken H, Leonhardt R, Volzke E, Volz C. Centrencephalic myoclonic-astatic petit mal. Clinical and genetic investigation. Neuropadiatrie 1970;2:59-78. Dulac O, Kaminska A. Use of lamotrigine in Lennox-Gastaut and related epilepsy syndromes. J Child Neurol 1997;12 Suppl 1:S23-8 Gastaut H, Roger J, Soulayrol R, Tassinari CA, Regis H, Dravet C. Childhood epileptic encephalopathy with diffuse slow spike-waves (otherwise known as “petit mal variant”) or Lennox syndrome. Epilepsia 1966;7:139-79. Gibbs FA, Gibbs EL. Atlas of electroencephalography, II. Cambridg, MA: Addison-Wesley, 1935:9-10. 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;36:15-29. Lennox WG, Davis JP. Clinical correlates of the fast and slow spike wave elecctroencephalogram. Pediatrics 1950;5:626-44. Marescaux C, Hirsch E, Finck S, et al. Landau-Kleffner syndrome: a pharmacologic study of five cases. Epilepsia 1990;31(6):768-77 Patry G, Lyagoubi S, Tassinari CA. Subclinical "electrical status epilepticus" induced by sleep in children. A clinical and electroencephalographic study of six cases. Arch Neurol 1971;24:242-52. Pinard JM, Delalande O, Chiron C, et al. Callosotomy for epilepsy after West syndrome. Epilepsia 1999;40(12):1727-34. Siegel H, Kelley K, Stertz B, et al. The efficacy of felbamate as add-on therapy to valproic acid in the Lennox-Gastaut syndrome. Epilepsy Res 1999;34(2-3):91-7 ILAE Major keyword descriptors absences epilepsy myoclonic-astatic epilepsy spike-wave pattern spike waves Minor keyword descriptors seizures Age of presentation 01-23 months 02-05 years Age of typical presentation 01-23 months 02-05 years Permuted topics, synonyms, variants Atypical absences absences, Atypical Related topics Absence status epilepticus Epilepsy Lennox-Gastaut syndrome Myoclonic-astatic epilepsy of childhood
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