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Occipital Lobe Epilepsy – Structural vs. Genetic
Occipital Lobe Epilepsy – Symptoms – Prognosis – Treatment – Migraine Headache – Panayiotopoulos Type – Gastaut Type
Occipital Lobe Epilepsy
Occipital epilepsy is not very common (about 5% of neurosurgical cases). Structural causes are similar to epilepsy arising from other regions of the brain, such as strokes, tumors, vascular malformations, trauma, infections, and developmental anomalies. The most common genetic forms of occipital epilepsy are also covered in this article (see below).
Some metabolic disorders have tendency to initially cause focal seizures originating in the occipital lobes. Severe hypertensive encephalopathy in pregnant (eclampsia) has a tendency to predominantly affect the occipital lobes. Seizures originating in the occipital lobes is one of the symptoms of eclampsia. Mitochondrial and some other metabolic disorders (Lafora and coeliac diseases) may present with occipital lobes seizures.
Occipital lobe epilepsy may occur in any age with the exception for the genetic form of late childhood described below. Males and females are equally affected.
Symptoms of Occipital Lobe Epilepsy
Visual aura and focal seizures are the most common symptoms (in 80%). They are simple visual hallucinations of flashing or steady lights, colors, circles or other shapes, which last from several second to a couple of minutes. Complex visual hallucinations are less common. Image distortions like micropsia or macropsia, distorted colors or shapes may occur.
Other visual symptoms are temporary blindness or loss of a part of the visual field, turning eyes to the side as if following some moving object, eye closure of eyelid fluttering.
Epileptic activity spreading to the neighboring lobes leads to more complex seizures and to generalized convulsions. Seizures may be frequent and often run in clusters.
A confusing symptom of occipital epilepsy is the following migraine type of headache in up to half of the patients. The majority of occipital epilepsy seizures tend to happen while being awake.
Diagnosis of Occipital Lobe Epilepsy
Brain MRI (in all patients) to rule out structural lesions and investigation of potential genetic or metabolic disorders (in some patients) are required. Brain MRI is normal in genetic forms of occipital epilepsy.
Inter-ictal EEG: focal spikes are seen in 50 to 80%. Ictal EEG is often nonspecific because of rapid spread of epileptic activity to the surrounding areas.
Due to combination of visual phenomena and headaches in some patients, occipital epilepsy has to be differentiated from migraine. Visual phenomena are strikingly different in these two conditions, however. Migraine visual aura lasts much longer (10 to 30 minutes or so), and usually has a distinct pattern. Complex visual phenomena in migraine (Alice in Wonderland) occur almost exclusively in children.
Prognosis and Treatment
Carbamazepine, Levetiracetam, and Lamotrigine are the drugs of choice. Other antiepileptic medications, indicated for focal epilepsy, can be tried depending on the presence of other medical conditions, age and gender.
Neurosurgery is reserved for intractable occipital epilepsy with identifiable brain lesion. The prognosis and response to treatment in occipital epilepsy largely depend on the underlying cause of seizures.
Childhood Epilepsy with Occipital Paroxysms - Early Onset (Panayiotopoulos syndrome)
Early onset Childhood Epilepsy with Occipital Paroxysms, or Panayiotopoulos syndrome, is probably a genetic epilepsy syndrome because it is reported to be running in families. Some children have siblings with benign rolandic epilepsy. It typically starts in preschool children (74% start between 3 and 6 years of age), but the onset as early as 1 year old or as late as 14 years old is not uncommon. There is no gender predominance.
Seizures are characterized by attacks of autonomic symptoms: nausea, retching, vomiting (70% to 80%), paleness, dilated or constricted pupils, irregular respirations and heart rate, change in body temperature, urinary and fecal incontinence, and excessive salivation with preserved awareness. Some level of confusion may be present in individual cases.
These symptoms may last for prolonged periods of time (in 30 to 50% of patients); then it is called autonomic status epilepticus. Loss of consciousness that is similar to fainting is not uncommon. There could be some behavioral changes, such as irritability, sick appearance, or quietness.
In some patients the attack may then progress to speech arrest, gaze turn to the side (60% to 80%), followed by convulsions (on either one side or both) with loss of consciousness.
Seizures are often long – from 5 to 10 minutes. Autonomic status epilepticus may last for more than 30 minutes.
About 2/3 of seizures occur in sleep.
EEG demonstrates multifocal, high amplitude sharp waves predominantly in the occipital lobes.
Brain MRI is expected to be normal.
Treatment is not required in most cases. For frequent seizures, Carbamazepine is usually the drug of choice.
The prognosis is excellent. Seizures remit in 90% of children within 1 to 2 years after the initial presentation and the rest will have a remission by later adolescence.
Most of the patients have only occasional seizures, but about 25% may experience frequent and hard to control seizures. Thirty present have only one seizure; less than 10% have more than 10 seizures, 20% may develop benign rolandic epilepsy or some other epilepsy syndrome, which will remit by the age of 16 years.
Risk of future epilepsy does not exceed the one of the general population.
Childhood Epilepsy with Occipital Paroxysms - Late Onset (Gastaut type)
Childhood Epilepsy with Occipital Paroxysms of late onset (idiopathic childhood occipital epilepsy of Gastaut) rarely has family members with the same epilepsy syndrome, but there is an increased chance of epilepsy (21% to 37%) and migraine in the relatives.
Age of onset is between 3 and 15 years with first symptoms more common in the school-aged children (mean around 8 years old).
There is no sex predominance.
The hallmark of Childhood Epilepsy with Occipital Paroxysms of late onset is visual hallucinations at the seizure onset. Visual hallucinations initially at are simple geometrical patterns that start in the periphery of the visual field. These hallucinations last from seconds to 3 minutes.
Further progression to more complex and well-formed hallucinatory images or illusions may follow. Spreading of epileptic activity to the larger area leads to convulsions that may be generalized or limited to one side of the body. A sudden temporarily blindness lasting for 3 to 5 minutes is another possible symptom.
Ten percent of patients have headache in the orbital area in association with the seizures. Consciousness is preserved in the beginning of the attack but eventually gets impaired as the seizure progresses.
A confusing symptom, which might lead to misdiagnosis, is a migraine-headache that follows the seizure in half of the patients.
Seizures in this form of epilepsy syndrome are limited to the awake state.
The diagnosis of idiopathic childhood occipital epilepsy of Gastaut requires brain imaging, such as an MRI, because it is clinically indistinguishable from symptomatic focal epilepsy caused by structural brain lesions. Presence of a migraine-like headache complicates the diagnostic process.
EEG interictally may be normal or may demonstrate occipital spikes, as well as centrotemporal, frontal, or generalized discharges in some patients.
Ictal EEG shows fast rhythms and/or fast spikes.
Prognosis is good in 50% to 60% with remission in 2 to 4 years after the onset. The reminder will continue having visual seizures with occasional generalized tonic-clonic seizures.
Treatment is usually required. The drug of choice is Carbamazepine with more than 90% patients responding well to the medication.