'Phantom' typical absences, absence status and experiential phenomena

Idiopathic generalized epilepsy with phantom absences, absence status, and generalized tonic-clonic seizures: A case report

RATIONALE

Phantom absences refer to mild and short-lasting absence seizures, which are usually accompanied by infrequent generalized tonic-clonic seizures and absence status. Generally, phantom absences do not impair the individual neurological functions. Herein, we report the case of a young woman with idiopathic generalized epilepsy, phantom absences, absence status, and generalized tonic-clonic seizures.

PATIENT CONCERNS

A 31-year-old woman presented with a 16-year history of paroxysmal convulsions.

DIAGNOSES

Electroencephalogram (EEG) showed recurrent universal and synchronized 3~4 Hz spike waves and spike-slow waves in the interictal phase with normal background activity. During the ictal phases, EEG revealed bursts of 3~4 Hz spike waves and spike-slow waves that were universal, synchronized, and symmetrical. Additionally, there was 1 seizure episode induced by a 3-Hz flash in the current case. Based on these findings, a diagnosis of idiopathic generalized epilepsy was made.

INTERVENTIONS

The patient was treated with oral sodium valproate, and the epileptic seizures were controlled.

OUTCOMES

The frequency of absence seizures was significantly reduced and there were no generalized tonic-clonic seizures.

LESSONS

Idiopathic generalized epilepsy with phantom absences, absence status, and generalized tonic-clonic seizures is an extremely rare condition. EEG is the exclusive method for diagnosis. Antiepileptic drugs are effective for controlling epileptic seizures in this disease.

Idiopathic generalized epilepsies imitating focal epilepsies

Classification of epileptic seizures and epilepsy syndromes as either focal or generalized is a fundamental and early part in the diagnostic process and is generally fairly easily accomplished. However, in patients with idiopathic generalized epilepsies, seizure and EEG features may suggest, particularly to the unwary, the occurrence of focal rather than generalized seizures. Misinterpretation of typical absence seizures as focal seizures, especially as temporal lobe seizures and of myoclonic seizures as focal clonic seizures, is a relatively common error and focal features during generalized tonic-clonic seizures may also be quite common. Sequences of seizures in idiopathic generalized epilepsies (such as absences or jerks followed by generalized tonic-clonic seizures) may also cause confusion. Versive and circling seizures are seizure types whose ictal semiology is clearly focal; nevertheless such seizures are described in idiopathic generalized epilepsies accompanied by generalized EEG discharges. The occurrence of focal EEG abnormalities in certain idiopathic generalized epilepsy syndromes is common. This is best known in juvenile myoclonic epilepsy.

Distinct behavioral and EEG topographic correlates of loss of consciousness in absences

PURPOSE

To describe the behavioral and EEG topographic correlates of absences with 3-Hz generalized spike-waves and partitioned impairment of consciousness.

METHODS

Two adult women had so-called "phantom" absences, characterized by brief and mild impairments of consciousness that were previously inconspicuous to both patient and physician. Neuropsychological examination was performed under video-EEG monitoring during absence status. EEG topographic mapping of spike-wave discharges was obtained in the two cases.

RESULTS

Only mild attentional and executive disturbances were observed during absence status despite prolonged discharges. Spike-wave bursts were associated with selective impairment in the initiation of response and self-generated action, whereas short-term storage of external information during discharges was fully preserved. This is consistent with a predominant involvement of frontomesial cortex demonstrated by topographic mapping of spike-wave discharges in the two cases. By contrast, in two other patients with typical absences and a complete lack of retention for information given during the discharges, topographic mapping found a more lateral frontal involvement by spike-wave activity.

CONCLUSIONS

Different types of absence seizures may impair distinct components of conscious behavior. A predominant involvement of frontomesial thalamocortical circuitry may underlie an "inconspicuous" disorder of consciousness as seen in phantom absences with selective loss of initiation and goal-oriented behavior, whereas involvement of more lateral frontal areas in typical absences may additionally disrupt working memory processes.

Typical absence status in adults: diagnostic and syndromic considerations

PURPOSE

To study the electroclinical features of typical absence status (TAS) in adults with syndromes of idiopathic generalized epilepsies (IGEs).

METHODS

Twenty-one patients with one or more spells of TAS were identified among 136 consecutive adult patients with IGEs. All patients with TAS had comprehensive electroclinical investigations and EEG or video-EEG recorded absences.

RESULTS

TAS occurred in 24.4% of 86 patients who had IGEs with typical absences alone or in combination with other seizures presisting in adult life. The prevalence of TAS appeared to be syndrome related, ranging from as high as 57.1% in perioral myoclonia with absences and 46.2% in "phantom" absences with GTCS to as low as 6.7% in juvenile myoclonic epilepsy. A varying degree of impairment of cognition was the cardinal clinical symptom shared in all TAS, but corresponding syndromes of IGE were often betrayed by other symptoms such as eyelid or perioral myoclonia. In phantom absences with GTCS, TAS was more numerous (p < or = 0.05) and more frequently the first overt seizure type (p = 0.006) than in any other IGE. Only in the syndrome of eyelid myoclonia with absences, TAS was always situation related, mainly as a result of antiepileptic drug discontinuation.

CONCLUSIONS

The clinical EEG semiology and prevalence of TAS appear to be syndrome related with the highest prevalence in the syndromes of perioral myoclonia with absences and phantom absences with GTCS (p = 0.0024).

Idiopathic generalised epilepsy in adults manifested by phantom absences, generalised tonic-clonic seizures, and frequent absence status

OBJECTIVES

To describe the clinical and EEG features of adult patients with very mild absences, late onset generalised tonic clonic seizures, and frequent absence status.

METHODS

Patients were referrals to a clinic for epilepsies. They all had clinical assessment and EEG, video EEG, or both for documentation of absences.

RESULTS

Of 86 adults with idiopathic generalised epilepsies and EEG/video-EEG documented absences, 13 patients showed similar clinico-EEG features with: (a) "phantom absences" consisting of mild ictal impairment of cognition associated with brief (3-4 s), generalised 3-4 Hz spike/multiple spike and slow wave discharges; (b) infrequent, mainly late onset, generalised tonic clonic seizures, and (c), absence status which occurred in six of them either in isolation or terminating with generalised tonic clonic seizures. None of the patients had myoclonic jerks or photosensitivity. Two patients were father and daughter and another patient had a family history of infrequent generalised tonic clonic seizures.

CONCLUSION

It seems that this is an idiopathic generalised epilepsy syndrome in adults which has not been previously recognised.

Consistent EEG focalities detected in subjects with primary generalized epilepsies monitored for two decades

PURPOSE

To describe the evolution of interictal findings in serial EEGs from patients with primary generalized epilepsy.

METHODS

A cohort of 89 subjects with various primary generalized epilepsies were reviewed. Thirty-one did not meet a priori criteria. Of the 58 patients analyzed, 12 had only absence seizures, 28 had absence seizures followed by one or more generalized tonic-clonic seizures, 9 had generalized tonic-clonic seizures followed by absence and/or myoclonic seizures. and 9 had juvenile myoclonic epilepsy. Patients were followed for a mean of 16 years. An average of 39 EEGs were obtained on each patient.

RESULTS

Thirty-two patients (56%) had focal features present in up to 65% of the EEGs in each of the patients. Accepted focalities were only those that were consistent in lateralization, location and, often, morphology across the span of the study. Focal findings were most often temporal or frontal.

CONCLUSIONS

Patients with typical primary generalized epilepsies show a high incidence of focal EEG features that cannot be explained on the basis of structural lesions, coincidental factors, or to artifacts of the selection criteria. Although the data do not allow a definitive explanation, possible mechanisms include associated focal cortical pathology such as microdysgenesis, and development over time of localized, self-sustaining hyperexcitability in low-threshold cortical structures subjected to repeated generalized spike-wave activity. Either hypothesis implies the participation and interaction of genetic, ontogenic, and environmental factors.