Late-onset Childhood Occipital Epilepsy (Gastaut Type)



Late-onset Childhood Occipital Epilepsy (Gastaut Type)


Giuseppe Gobbi

Renzo Guerrini

Salvatore Grosso



Introduction

Occipital epilepsies commonly start in childhood or adolescence and include two etiologic groups: Symptomatic and idiopathic epilepsies. Symptomatic occipital epilepsies may be caused by brain malformations (focal cortical dysplasia, polymicrogyria, subcortical band heterotopia, periventricular heterotopia), metabolic disorders (Lafora disease, juvenile neuronal ceroid lipofuscinosis, mitochondrial disorders such as MERRF [syndrome of myoclonus epilepsy and ragged red fibers] and MELAS [syndrome of mitochondrial encephalopathy, lactic acidosis, and strokelike episodes]), and occipital bilateral calcifications (often associated with celiac disease).95 Among the idiopathic group, the new classification system of the International League Against Epilepsy (ILAE) Task Force30 recognizes three epilepsy syndromes: (a) the early-onset benign childhood occipital epilepsy (Panayiotopoulos type), (b) the late-onset childhood occipital epilepsy (Gastaut type), and (c) the idiopathic photosensitive occipital lobe epilepsy. The latter is included among the reflex epilepsies.

The late-onset childhood occipital epilepsy–Gastaut type (LOCOE-Gastaut type) is the topic of this chapter, while the early-onset benign childhood occipital epilepsy (Panayiotopoulos type) and the idiopathic photosensitive occipital lobe epilepsy are described in Chapters 237 and 257.


Historical Perspectives

Benign occipital epilepsy was first described by Gastaut.35 It was considered an epilepsy syndrome with a typical clinical history and interictal electroencephalographic (EEG) pattern. The existence of an idiopathic/cryptogenic benign childhood occipital epilepsy was already evident in the first reports of Gastaut in 195034 and Gibbs and Gibbs in 1952.42 Further observations corroborated the identification of “benign occipital epilepsy,”10,25,68,93 but discussions about a new “benign migraine-epilepsy syndrome” developed among authors.1,16,71,78,90,94 The controversy regarding whether the origin of this syndrome was epileptic or migrainous was resolved by Gastaut,35,36 who critically reviewed the four children reported by Camfield et al.16 and concluded that their benign occipital epilepsy constituted “a primary and independent epileptic disorder.” Gastaut36 and Gastaut and Zifkin39 considered both visual ictal symptoms and the interictal occipital spikes and waves that appeared upon closing the eyes as the main clinical and EEG signs of the benign childhood epilepsy with occipital paroxysms (CEOP). However, it was already known that occipital foci in young children might also be a sign of a “maturational” factor in a variety of cerebral dysfunctions.63 In fact, occipital lobe epileptogenesis with occipital spikes may occur in genetically predisposed children with visual defects at a critical stage of development.67,73 Reactive occipital spikes have been reported in children without epileptic seizures2,11,60,76 as well as in patients having cryptogenic or symptomatic occipital epilepsies2,23,27,36,41,51,76,98 and those having occipital epilepsies associated with progressive disorders.29,49,50,74,89,91 Finally, visual symptoms and reactive occipital paroxysms may be absent in CEOP.41,54 These data cast some doubt on the existence of a true benign and idiopathic occipital epilepsy as defined, using the clinical and EEG criteria proposed by Gastaut.35 Among patients with occipital epilepsy and occipital EEG abnormalities suppressed by eye opening, a series emerged with “nonlesional” epilepsy, remarkable age-dependent seizure onset, familial predisposition, and benign evolution.6,23,98 According to these criteria, CEOP was included in the ILAE classification21 as an idiopathic form having the clinical and EEG findings suggested by Gastaut,35,36 but with an uncertain long-term prognosis. More recently, Panayiotopoulos80,81 described a form of CEOP characterized by early onset, nocturnal seizures with tonic deviation of the eyes, and vomiting,80,81 which has an excellent prognosis with seizure remission occurring within 1 to 2 years. On that basis, Caraballo et al.17 proposed designating this early-onset CEOP as “Panayiotopoulos-type benign childhood occipital epilepsy,” and “Gastaut type of benign childhood occipital epilepsy” the occipital epilepsy described by Gastaut.

Finally, the latest diagnostic scheme for people with epilepsy proposed by the ILAE Task Force on Classification and Terminology30 recognized this syndrome as “late-onset childhood occipital epilepsy–Gastaut type.”


Definition

LOCOE-Gastaut type is an age-related, possibly genetically determined, epilepsy syndrome, with onset ranging from 4 to 13.2 years, and with a peak of incidence at 8 years. Girls and boys are equally affected.85

Epileptic seizures are characterized by brief, frequent, diurnal visual hallucinations; blindness; or both. Although commonly preserved, the consciousness is mainly impaired when seizure progresses toward a hemiclonic or generalized convulsion or automatism. In 25% to 50% of cases, visual seizures are followed by pulsating headache, associated with nausea and vomiting in about 10% of patients.

Interictal EEG features consist of high-voltage spikes-and-wave complexes or sharp waves recurring rhythmically in the occipital and posterior temporal areas of one or both hemispheres, but only when the patient’s eyes are closed. Fixation-off sensitivity is typical. Ictal EEG is characterized by the sudden appearance of an occipital discharge consisting of fast activity and/or spikes, which may spread to the central or temporal regions.85

Since both clinical and EEG findings do not exclude a symptomatic epilepsy, neurophysiologic, neuropsychological, neuroimaging, and laboratory assessment are always indicated. At
present, no definite statement on prognosis is possible,21 even though it seems to be relatively benign, especially using rigid criteria of selection.99


Epidemiology

LOCOE-Gastaut type is a rare condition with a probable prevalence of 0.2% to 0.9% of all epilepsies, and 2% to 7% of benign childhood partial seizures. On average, LOCOE-Gastaut type is considered five times less frequent than Panayiotopoulos type.85 Higher figures have been reported by Gokcay et al.,52 who observed ten patients with LOCOE-Gastaut type among 29 cases presenting with idiopathic occipital epilepsies. A slightly higher frequency of LOCOE-Gastaut type than the Panayiotopoulos type has also been found by Tsai et al.,99 which was attributed to the inclusion of patients with migrainous headache with focal occipital paroxysms and the exclusion of patients with adversive seizure and EEG foci beyond the occipital area.


Etiology and Pathophysiology

Gastaut36,37 stressed the presence of genetic or functional factors, such as a predisposition to epilepsy and febrile convulsions, in 36.6% to 47% of the cases. However, patients with lesional epilepsy related to premature birth, mild perinatal distress, and HHE (hemiconvulsion-hemiplegia-epilepsy) syndrome were also included in LOCOE-Gastaut type.36,37,41 A thalamocortical mechanism, similar to the reticulocortical mechanism of idiopathic generalized epilepsies46 but limited to a localized thalamocortical area, was hypothesized.34 According to the concept of “idiopathic” epilepsy, symptomatic cases are no longer included in this group of patients.

A role of genetic factors as part of the etiology is still presumed, and the recognition of familial cases strongly suggests this hypothesis. A family history of epilepsy varying from 33% to 43% in patients with occipital epilepsy has been reported by several authors.6,60,98 Kuzniecky and Rosenblatt65 suggested “an autosomal dominant pattern for the EEG abnormalities with age-dependent expression and variable penetrance of the seizure disorder.” Nagendran et al.75 reported a family in which two siblings had visual seizures and occipital paroxysms, and another presented with centrotemporal spikes on the EEG. Moreover, there may be an association between idiopathic generalized epilepsies and LOCOE-Gastaut type. In fact, generalized spike-wave discharges in addition to occipital epileptiform activity were noted in this group of patients.36 In turn, in idiopathic generalized epilepsies there may be focal activity, which is typically frontal but may also occur in posterior areas.77 Caraballo et al.18 reported the occurrence of childhood absence epilepsy in 5 out of 35 children with LOCOE-Gastaut type. Patients with both types of epilepsy have also been reported by Sofue et al.92 and by Grosso et al.,53 respectively. Typical absences have mainly been found in patients with LOCOE-Gastaut type (14% of patients) rather than in the much larger group with the Panayiotopoulos type (0.6%). Therefore, it has been suggested that childhood absence epilepsy may have a closer genetic relationship to LOCOE-Gastaut type than to the Panayiotopoulos type.18

From a pathogenetic point of view, mechanisms underlying LOCOE-Gastaut type remain to be established. The primary visual cortex (VI or Brodmann area 17) represents the site where elementary visual hallucinations are generated. Simple visual symptoms can also be evoked by stimulation of extra-striate and prestriate (Brodmann areas 18 and 19) cortical regions. The stimulation of the latter areas can also provoke visual illusions. Recently, it has been confirmed that both the mesial and lateral occipital lobe may be involved in generating elementary visual phenomena, and that there is a wide semiologic overlapping of visual symptoms between seizures originating from these occipital areas.15 In fact, mesial foci rapidly spread to the lateral occipital region and vice versa.20 Occipital epileptogenic activity spreads extensively to the adjacent neocortex and to limbic structures through the projections from the occipital cortex to lateral and mesial temporal areas.15

In particular, reciprocal connections between temporal neocortex and the primary visual cortex have recently been confirmed.3,62 Complex visual seizures have been considered to represent seizure spread to the temporal lobe. Blume et al.15 suggested that structured visual phenomena require the involvement of both neocortical and limbic regions. This is consistent with the clinical occurrence of initial occipital symptoms followed by structured visual hallucinations and other temporal lobe findings.5,102 Actually, the role of the temporal lobe in determining visual symptoms appears to be more complex. Indeed, it should be remembered that simple visual phenomena have also occasionally been reported in temporal (lateral or medial) epilepsy. Motor phenomena of both lateral and mesial occipital epileptogenesis may be explained by their access to supra-Sylvian or to brainstem motor regions.15

The pathophysiologic mechanisms leading to postictal headache remain also to be clarified. Migraine is considered a paroxysmal and unique neurovascular disorder.101 According to Goadsby,47 migraine is a disorder of sensory dysmodulation that involves the trigeminovascular system and central nervous system modulation of the pain-producing structures of the cranial structures. A multitude of factors able to increase neuronal and network hyperexcitability may trigger migraine attack. Thus, it is possible that an occipital ictal discharge triggers a genuine migraine headache through trigeminovascular or brainstem mechanisms.84 It has been pointed out that postictal migraine headache occurs in predisposed children with impaired or labile cerebrovascular autoregulation. On that basis, occipital ictal activity may result in a persistence of vasodilation in the posterior territory of cerebral and basilar arteries with subsequent plasma extravasation and neuropeptide release.101


Clinical Presentation

The mean age at onset ranges from 3 to 4 to 13 to 16 years.85,99 Gastaut and Zifkin41 reported an upper age at onset of 19 years.

The main clinical findings of LOCOE are represented by visual seizures. Usually, they occur in the daytime, but are not invariably present. In some instances, triggering or facilitation stimuli have been reported: Extinction of light,69,79 passage from light to darkness or vice versa,8,37 and darkness.86 In some teenage girls, seizures seem to occur with menstruation.37,41 Elementary visual hallucinations are brief (5 to 20 seconds, rarely more than 3 minutes or even 15 to 20 minutes) seizures, which usually occur as an initial ictal symptom, and may represent the only seizure type (30% of the patients)64,84 or be associated with other occipital symptoms such as illusions of ocular movements, tonic deviation of the eyes, and eyelid fluttering. This type of seizure may also be prolonged, especially when visual symptoms are followed by autonomic-migrainous postictal symptoms, and may progress to hemiconvulsions or generalized tonic–clonic seizures. Positive elementary visual hallucinations may consist of perception of white flashes or colored (bright red, yellow, blue, and green are prominent) unformed or formed phenomena, usually circular, commonly appearing in the periphery of a hemifield, evolving into multicolored circular patterns that multiply and enlarge during seizure progression, flashing or static, with a possible horizontal movement toward
the other side.84 Sometimes the patient may turn his or her head and eyes to look at them.64 In each patient elementary visual hallucinations have a stereotypic appearance regarding morphology, colors, location, and movement. Negative elementary visual seizures6,36,37 are the second most common seizure type. They consist of a sudden ictal blurred vision or amaurosis, lasting up to 5 minutes. Ictal amaurosis may be the sole event in a patient who, during other seizures, has visual hallucinations without blindness. Blindness may involve the whole visual field or be confined to a part of it (quadrantanopia, hemianopia). Hemianopia may be both ictal and postictal. The elementary visual seizures in nontreated patients may be frequent, up to several per day or week. Responsiveness is commonly preserved. Loss of consciousness usually occurs at the onset of other ictal manifestations following visual hallucinations or amaurosis, such as eye deviation or convulsions.85

Complex visual hallucinations and visual illusions are rare in LOCOE-Gastaut type patients, occurring in <10% of the patients. Complex visual hallucinations represent the progress of elementary visual seizures, and consist of hallucinations of animals, people, or scenes, or of numerals or letters, stationary or moving. In complex hallucinations an evident emotional component, such as elements from memory, unfulfilled wishes, or intense affects related to them, which is lacking in simple hallucinations, is experienced by the patient. Ictal visual illusions may be simple with alteration in perception of objects, such as micropsia/macropsia (dysmegalopsia), dyschromatopsia, achromatopsia, metamorphopsia, plagiopsia, kinetopsia, and teichopsia, or may be complex, such as palinopsia, teleopsia, macroproxiopia, and microtlepsia.6,36,37,38,39,41,78,81 Sensory hallucinations of ocular movements and pain without detectable motion usually occur with progression of ictal elementary visual hallucinations

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Aug 1, 2016 | Posted by in NEUROLOGY | Comments Off on Late-onset Childhood Occipital Epilepsy (Gastaut Type)
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