Spectral properties of EEG fast activity ictal discharges associated with infantile spasms.

OBJECTIVE: The aim of this study was to evaluate the characteristics of the ictal EEG event accompanying infantile spasms. METHODS: Quantitative analysis was used, based on the application of a bivariate autoregressive (AR) parametric model; autospectra, coherence, phase functions and inter-hemispheric time differences were estimated on homologous EEG channels in 18 infants presenting with either cryptogenic or symptomatic West syndrome. RESULTS: The AR analysis of the 500 ms EEG epochs preceding spasm onset revealed the presence of a short discharge of fast activity restricted to a narrow frequency band in 13 of the 18 cases included in the study. The fast discharge peaked at 17.5+/-2.1 Hz, with rather low inter-hemispheric coherence values (0.52+/-0.17) and asymmetric amplitude on homologous EEG derivations. It persisted briefly after spasm onset, reaching a higher coherence value (0.71+/-0.16). The inter-hemispheric time difference, estimated in those cases with the coherence values significantly different from zero, ranged from 9.1 to 14.3 ms (11.4+/-1.9) in the epoch preceding spasm onset. CONCLUSION: The data obtained from the analysis of the ictal EEG events, compared with clinical and interictal EEG features, indicate that an asymmetric EEG pattern (mainly consisting of a rhythmic burst of fast activity) consistently preceded both symmetric and asymmetric spasms, thus suggesting a localized cortical origin of the ictal discharge giving rise to the spasms.     

Very fast rhythmic activity on scalp EEG associated with epileptic spasms

PURPOSE: Very fast activity was investigated on the ictal EEGs of epileptic spasms to elucidate the pathophysiology of West syndrome (WS) and related disorders from a novel point of view. METHODS: The traces of scalp ictal EEG of spasms temporally were expanded in 11 patients whose clinical diagnosis was symptomatic WS in six, cryptogenic WS in two, Aicardi syndrome in one, and symptomatic generalized epilepsy after WS in the remaining two. Time evolution of averaged power spectra of the ictal fast activity also was analyzed in each patient. RESULTS: Rhythmic gamma activity with frequency ranging from 50 to 100 Hz was detected in a total of 345 of 537 spasms. Fast activity was seen bilaterally in nine patients, was lateralized to one hemisphere in another, and appeared independently on each hemisphere in the remaining infant with Aicardi syndrome. Power spectra showed a clear peak corresponding to spasm-associated gamma rhythm, with frequency centering approximately 65 Hz and ranging from 51 to 98 Hz. The morphology and spectral characteristics of ictal gamma rhythm were completely different from those of muscle activity or alternating current (AC) artifacts. CONCLUSIONS: Spasm-associated gamma activity was clearly detected on the scalp. This observation may provide a clue to the pathophysiology of spasms.     

EEG findings in West syndrome a follow-up of 20 patients.

Clinical and EEG findings of 36 patients with West syndrome (WS) were reported. Twenty patients (7 males, 13 females; mean age 7.4 months at the first EEG examination) were followed for a mean period of 19.3 months. Fifty per cent of the 8 cases with cryptogenic SW showed a full recovery, 2 cases showed persistence of psychomotor retardation or seizures and 2 of both these features. At the end of follow-up period, 92% of the 12 patients with symptomatic WS showed a psychomotor retardation and 75% a persistence of seizures. EEG pattern was a typical hypsarrhythmic one in 11 patients and atypical in the remaining cases. The typical pattern correlated with a better outcome with full recovery in 27.3% compared with 11.1% in the group with atypical EEG. Moreover EEG monitoring was useful for the evaluation of therapeutic response and in the follow-up of the disease, showing a correlation with clinical course, incidence of spasms and outcome.     

Patients with West syndrome whose ictal SPECT showed focal cortical hyperperfusion

To clarify the mechanism of clustered spasms in West syndrome (WS), we examined ictal SPECT and EEG, as well as those during the interictal period, in three patients with symptomatic WS who had apparent focal cerebral lesions. For ictal SPECT and EEG, we monitored the patients with EEG, and as soon as we noticed the occurrence of clustered spasms clinically and electroencephalographically, [(99m)Tc]ECD was injected intravenously and flushed thoroughly with saline. In these three patients, regional cerebral blood flow (rCBF) increased during ictus and decreased during the interictal period in the area that coincided with the focal cerebral lesion recognized by CT/MRI. The ictal hyperperfusion of bilateral basal ganglia was also detected in two of the three patients. The ictal EEG showed a diffuse slow wave complex corresponding to a clinical spasm. The sharp waves that preceded the diffuse slow wave complex and the spasm appeared in the same area in which rCBF increased during ictus. None of the patients showed partial seizure before or after clustered spasms clinically or electroencephalographically during the ictal SPECT study. Secondary generalization from a cerebral focus may explain the mechanism of spasms in these patients with WS: focal cortical discharge may primarily generate clustered spasms and trigger the brainstem and basal ganglia structures to produce spasms.     

The Idiopathic Form of West Syndrome

Summary: The clinical and electroencephalographic data of 31 children with cryptogenic West syndrome (WS), selected from a series of 103 WS patients, with a follow-up between 4 and 12 years, were studied retrospectively to verify whether this group included patients who fulfilled the criteria for an idiopathic etiology. The results identified a possible idiopathic etiology in 17 patients (55%), who had a family history of other forms of idiopathic epilepsy or febrile convulsions, or who developed, during the follow-up, an EEG genetic trait such as a photoconvulsive response or spike-and-wave discharges, or rolandic spikes. All 17 children had a favorable outcome and all had normal neuropsychological development. Four children (13%) fulfilled the criteria for a true cryptogenic etiology, a causative lesion being suspected, but never proved. At the end of the follow-up all four had seizures, or developmental delay or both, all signs that suggest an underlying cerebral lesion. The other 10 children, representing 32% of the cryptogenic cases, had a good prognosis, with early disappearance of spasms and hypsarrhythmia, and normal neurological development, but none had an EEG epileptic trait or family history of epilepsy or febrile convulsions; although they could have had an idiopathic WS, this was not proved. We conclude that among the children classified as having a cryptogenic WS, many—in our series at least 55%—fulfill the criteria for an idiopathic etiology.     

Neurophysiology of spasms.

Spasms are a form of epileptic seizure typical of infancy. From a clinical point of view, the child presents a flexor-extensor movement involving the trunk and limbs and lasting about 1s. Although asymmetry can be present, the seizure involves both sides of the body.The ictal discharge most frequently associated with spasms in West syndrome (WS) is a diffuse triphasic slow high-amplitude wave and less frequently a low-amplitude brief rapid rhythm. The origin of the spasm in WS and classification as either partial or generalized seizure are the subject of much discussion.Factors supporting partial origin include: interictal electroencephalography (EEG) characterized by multifocal anomalies; high incidence of focal cortical lesions and remission of spasms following surgical removal of focal lesions. Factors supporting generalized origin are: clinical involvement of the entire body; mostly generalized ictal EEG pattern; existence of idiopathic cases and possibility of spasms immediately following a partial seizure like a particular form of secondary generalization. In our opinion, the categories of 'partial' and 'generalized' seizures are not applicable to spasms in WS. Sometimes the spasms in WS can be observed together with other types of partial or generalized seizures.Polygraphic recordings have demonstrated that despite being clinically similar, each spasm is different from the other because of a variable sequence in muscular contraction.These data support the peculiar nature of the spasm in WS that could be a subcortical phenomenon that requires a cortical trigger.     

Twenty-Four-Hour Ambulatory EEG Monitoring in Infantile Spasms

Summary: Twenty-four-hour ambulatory EEG (AEEG) recordings were performed in 74 infants with West Syndrome (WS) who had not received corticosteroids before the recording. EEG analysis was performed visually for interictal background activity as well as for ictal events: spasms (isolated or in clusters) and other seizures either generalized or partial. Six hundred fifty-four seizures were recorded in 67 patients. Partial seizures (PS) were noted in 31 infants (51% of symptomatic WS cases, 33% of cryptogenic WS cases). In 14 patients, PS were immediately followed by a cluster of spasms consisting of a single ictal event. Patients with PS had an asymmetrical interictal background activity in 85% of cases, with no return to hypsarrhythmia between spasms in a given cluster. AEEG is a reliable method to detect and analyze ictal events in infants with WS. In this population, patients with unfavorable outcome of both epilepsy and psychomotor development have PS. Therefore, the existence of PS may contribute to etiologic diagnosis and prognostic evaluation.     

Short-term nonhormonal and nonsteroid treatment in West syndrome

PURPOSE: West syndrome (WS) is considered an age-dependent epileptic encephalopathy and also a particular type of electrical epileptic status. Short-term hormonal or steroid treatment of WS with good efficacy is reported in the literature. The aim of this retrospective multiinstitutional study was to evaluate the early discontinuation of nonhormonal and nonsteroid treatment for WS. METHODS: Twenty-two WS cases in which treatment was discontinued after a maximum of 6 months, were collected. Inclusion criteria were the presence of typical EEG hypsarrhythmia (HY) and video-EEG recorded epileptic spasms. Exclusion criteria were the presence of partial seizures or other seizure types before spasm onset. The patients were treated with vigabatrin (VGB) in 19 cases and nitrazepam (NTZ) in three. The dose range was 70-130 mg/kg/day for VGB and 0.7-1.5 mg/kg/day for NTZ. The drug was discontinued if spasms stopped and HY disappeared after a mean treatment period of 5.1 months (range, 3-6 months). All patients underwent repeated and prolonged awake and sleep video-EEG, both before and after drug discontinuation. RESULTS: Cryptogenic (15) and symptomatic (seven) WS patients were included. All the symptomatic cases had neonatal hypoxic-ischemic encephalopathy. The mean age at spasm onset was 5.5 months (range, 3-7 months; median, 6). The interval between spasm onset and drug administration ranged from 7 to 90 days (mean, 23 days; median, 20). The interval between drug administration and spasm disappearance ranged from 2 to 11 days (mean, 6 days; median, 6 days). The interval between drug administration and HY disappearance ranged from 3 to 30 days (mean, 9 days; median, 10 days). Drugs were stopped progressively over a 30- to 60-day period. Follow-up ranged from 13 to 50 months (mean, 26 months; median, 22 months). None of our cases showed spasm recurrence. CONCLUSIONS: Our data show that successful nonhormonal and nonsteroid treatment can be shortened to a few months without spasm recurrence in patients with cryptogenic or postanoxic WS.     

Dynamic cortical activity during spasms in three patients with West syndrome: a multichannel near-infrared spectroscopic topography study

PURPOSE: To investigate spatial and temporal cortical activity during clusters of naturally occurring epileptic spasms in patients with West syndrome (WS) by using multichannel near-infrared spectroscopy (mNIRS). METHODS: Conventional magnetic resonance imaging (MRI) and interictal and ictal single-photon emission computed tomography (SPECT) were carried out in three patients with WS. Thereafter, cortical hemodynamics during naturally occurring epileptic spasms were measured by mNIRS with simultaneous video/electroencephalographic (EEG) monitoring. RESULTS: Ictal SPECT revealed multiple hyperperfused areas within the cortex. With the use of mNIRS, an increase in regional cerebral blood volume (CBV) was observed in these areas, which is representative of cortical activation. The increase in CBV was accompanied by an increase in the concentrations of both oxy- and deoxyhemoglobin. The following heterogeneous regional changes in CBV during ictus were observed: (a) transient increases that were synchronized with spasms; (b) a gradual increase during an ictal event that fluctuated in synchrony with spasms; and (c) a combination of transient and gradual increases. An increase in regional CBV occurred in multiple areas that were activated either simultaneously or sequentially during an ictal event. Topographic changes in CBV were closely correlated with the phenotype of the spasm. CONCLUSIONS: During ictal events, multiple cortical areas were activated simultaneously or sequentially. The pattern of cortical activation closely affected the phenotype of the spasm, which suggested that the cortex was involved in the generation of spasms.     

Epidemiological and clinical studies of West syndrome in Miyagi Prefecture, Japan

We performed a retrospective epidemiological study of West syndrome (WS) in Miyagi prefecture over a 3-year period (2000 -2003). Twenty-two children (6 boys, 16 girls) developed WS. The incidence of WS was 3.4/10,000 live births. It agreed with the incidence of previous report in Japan. The mean age at onset of spasms was 6.5 months (range 1 - 17 months). Thirteen patients (59%) had symptomatic WS; of these, eight patients had prenatal causes and five had perinatal causes. There were no familial cases, although four patients had family history that included neurological diseases. Periventricular leukomalacia was found in four of nine patients with abnormal magnetic resonance imagings (MRI) . Early seizure outcome was good in twenty-one patients (95%). Six patients (29%) had seizure recurrence. There were no significant differences between symptomatic WS and cryptogenic WS in terms of seizure recurrence and persistent EEG abnormalities. The Five patients (20%) with developmental quotients (DQ) more than 70 were all cryptogenic WS, while patients with DQ less than 70 were significantly frequent in symptomatic WS as compared with cryptogenic WS.