Presentation and course
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• The typical visual seizures consist of simple visual hallucinations or ictal blindness.
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• Motor seizures and hemiconvulsions can occur.
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• Postictal headache is common and in many cases difficult to distinguish from migraine.
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• Prognosis is variable. Seizure remission will occur in many patients but is not universal. Patients will often have associated deficits in attention, memory, and visuospatial skills.
Visual seizures are the cardinal symptoms of childhood occipital visual epilepsy. They are usually frequent and diurnal, and they usually last from seconds to 1 to 3 minutes. Ictal blindness may last longer than this. The seizures may progress and coexist with other occipital symptoms such as sensory illusions of ocular movements and ocular pain, tonic deviation of the eyes, eyelid fluttering, or repetitive eye closures. Complex visual hallucinations, visual illusions, and other symptoms from more anterior ictal spreading rarely occur. Consciousness is intact during the visual symptoms but may be disturbed or lost if the seizures progress. Postictal headache often occurs.
Simple visual hallucinations. Visual seizures are the most typical and usually the first ictal symptom (27; 28; 10; 09; 50). In a study of 129 patients with childhood occipital visual epilepsy, visual hallucinations were the first symptom in 62% and the only manifestation in 39% of patients (50).
Elementary visual hallucinations are typically brief. They develop quickly, lasting for 5 to 15 seconds, and seldom exceeding 1 to 2 minutes if they occur alone without other occipital or extra-occipital spreading. Rarely, they may last 15 to 20 minutes or longer. They are often multicolored and circular, appearing either in the periphery of a hemifield or centrally; they may multiply in number or size, or both; they may move horizontally to the other side; and they may be flashing or static.
They may be the only ictal manifestations, or progress to other seizure symptoms. They typically have a stereotyped appearance and progression. Patients may know at what stage during their visual hallucinations progression to secondary generalization is likely to occur (38; 10; 36; 39). Consciousness is not affected.
Blindness or partial visual loss. Blindness is probably as common an ictal symptom as elementary visual hallucinations. It can occur alone and can be the only ictal event in patients who may, in other times, have visual hallucinations without blindness (38; 39; 27; 28). Blindness is sudden and total, often lasting several minutes, with preserved consciousness (09; 04). Postictal blindness, hemianopia, and other partial visual loss are well established after visual seizures, with or without secondarily generalization.
Complex visual hallucinations and visual illusions. Complex visual hallucinations are much rarer, probably occurring in less than 10% of the patients and usually emerging from elementary visual hallucinations (28). These patients usually see the form of a face or figures, which may have the same location and movement sequence as that of the elementary visual hallucinations. They do not have the same emotional or other characteristics as those associated with temporal lobe semiology.
Ictal visual illusions such as micropsia, metamorphopsia, and palinopsia are most likely generated from the nondominant parietal regions (28). They are extremely rare and may be associated more with symptomatic occipital seizures (38).
Sensory hallucinations of ocular movements and pain. A sensation of ocular movement in the absence of detectable motion is a rare occurrence and mainly occurs as a progression of elementary visual hallucinations (38; 39).
Nonvisual ictal symptoms
Deviation of the eyes and oculoclonic seizures. Deviation of the eyes, usually following elementary visual hallucinations and often associated with ipsilateral turning of the head, is the most common (around 70%) nonvisual symptom (27; 28; 38; 39; 21; 10). This focal motor seizure usually starts after visual hallucinations, but may also occur while the hallucinations still persist. It may progress to hemiconvulsions and generalized tonic clonic seizures (GTCS) (38; 09; 39).
Ictal clinical symptoms from occipital seizure propagation. Elementary visual hallucinations or other ictal symptoms may progress to hemiconvulsions or generalized convulsions. According to Gastaut and Zifkin, visual seizures are often followed by other nonvisual seizure symptoms such as hemiconvulsions (43%), complex focal seizures (14%), dysphasia, dysesthesia, aversive convulsions (25%), and generalized tonic-clonic seizures (13%) (28). Forced eyelid closure and eyelid blinking occur in approximately 10% of patients, usually at a stage in which consciousness is impaired. They signal impending secondarily generalized convulsions (27; 28; 38; 39).
Headache. Postictal headache is a consistent symptom in about half of patients (28; 09). This occurs immediately, or 5 to 10 minutes after the end of the visual hallucinations. The duration and severity of the headache appears to be proportional to the duration and severity of the preceding seizures. The headache may be diffuse and of mild to moderate intensity, but in some patients it is strong and pulsating and may be associated with nausea, vomiting, photophobia, and phonophobia, which may make it indistinguishable from migraine (28; 04). Ictal headache, mainly orbital, is a rare occurrence.
Circadian distribution. Visual seizures are predominantly diurnal and occur at any time of the day. Longer seizures, with or without secondarily hemiconvulsions or generalized convulsions tend to occur either during sleep, causing the patient to wake, or after awakening.
Frequency of seizures. In untreated patients, brief visual seizures are frequent, occurring at a frequency of several per day or weekly. However, propagation to other seizure manifestations, such as focal or more generalized convulsions is much less frequent, occurring monthly, yearly, or exceptionally (10; 39).
Prognosis and complications
Prognosis is unclear, though available data may indicate that remission occurs in more than 60% of patients (29; 28; 10; 50). Patients whose seizures continue into adulthood may be unlikely to have long-term remission at all (03).
This syndrome is often misdiagnosed as migraine, resulting in the delay of appropriate antiseizure medication, sometimes for years, which may affect prognosis (38; 21; 39). In a study of 19 patients with childhood occipital visual epilepsy, only four patients had remission of seizures before the age of 17 years; seven patients also developed other types of seizures (47). Prognosis was not associated with a specific EEG pattern whether abnormal or normal.
There have been reported cases of childhood occipital visual epilepsy that developed continuous spike-waves during slow-wave sleep with cognitive deterioration, which may be reversible with appropriate medication (37; 22).
Various studies have demonstrated intellectual and neuropsychological abnormalities in children with childhood occipital epilepsy. Gulgonen and colleagues tested intellectual functioning, attention, memory, academic achievement, visual-motor functioning, and executive functioning in 21 patients with childhood occipital epilepsy compared to controls (31). The case patients' performance scores were lower in attention and memory, as well as in intellectual functioning.
Language impairments, and in particular difficulties with semantic function, have also been demonstrated in children with childhood occipital visual epilepsy (45). In neuropsychological assessment with specific visuoperceptual testing of six patients, a deficit in facial discrimination was found in four patients and was associated with a line orientation deficit in three (13). Significant abnormalities have also been found in the domains of visuomotor coordination, memory, and attention (42).
Children with childhood occipital visual epilepsy have been demonstrated to have impairments in visuospatial processing and those who experienced a higher number of seizures or in whom interictal EEG discharges had been present for a longer time demonstrated a higher degree of impairment (07).
Comparative neuropsychological testing between patients with childhood occipital visual epilepsy and Panayiotopoulos syndrome showed impairments in psychomotor speed, writing and arithmetic skills, and verbal memory in both groups whereas children with Panayiotopoulos syndrome showed worse performance in terms of visual memory and reading problems (02).
An otherwise normal 8-year-old boy had onset of weekly episodes of elementary visual hallucinations. These were brief, lasting 5 seconds to 15 seconds, and consisted of three to four concentric spherical rings of red and yellow moving from the left to the right visual field, and repeating the same course again after their disappearance on the right. On other occasions, only one colored ball was moving continuously from left to right. The colors were faint at onset, becoming more intense as the seizure progressed. There was no impairment of consciousness, convulsion, or headache. An initial diagnosis of acephalgic migraine was made.
Beginning at 10 years of age, on four occasions, the same concentric rings were bigger (double in size), followed the same course from left to right, but the duration of the seizure was longer, lasting 1 minute. On three more occasions, visual seizures were longer, lasting 2 to 3 minutes, followed by left sided deviation of the head, and left hemiconvulsions. At this stage, the diagnosis of occipital lobe seizures was suspected. An initial routine EEG was normal in the awake state.
Carbamazepine 600 mg daily was initiated at 11 years of age. The head deviation and hemiconvulsions ceased but he continued to have infrequent, brief, elementary visual hallucinations like those mentioned above, which were more likely to occur after watching television or playing video games for long periods. These were occasionally followed by diffuse headache of moderate intensity for 10 to 15 minutes, and once he felt sick. A follow-up EEG was again normal in the awake state but showed occasional occipital spikes during sleep. A high-resolution MRI was normal.
At 17 years of age, he had three visual seizures lasting for nearly an hour each (focal visual status epilepticus). They started with left sided blurring of vision, “whitish like a fog,” together with “small clouds of colors; mainly red,” and mixed with small colored circles. Symptoms did not progress, but when the blurring of vision and the visual hallucinations cleared, he had left sided throbbing headache, which started 5 to 7 minutes after the cessation of the seizures, and lasted for half an hour. His carbamazepine dose was increased and he has had no further seizures of any type.