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Structural and Genetic Frontal Lobe Epilepsy Syndromes
Seizure Types in Frontal Lobe Epilepsy – Autosomal Dominant Nocturnal Frontal Lobe Epilepsy – Structural Frontal Lobe Epilepsy – Rolandic Epilepsy
Structural and Genetic Frontal Lobe Epilepsy
Structural (former secondary) Frontal Lobe Epilepsy is relatively uncommon compared to structural temporal lobe epilepsy.
There is no specific age of onset. Frequency is equal in both sexes.
The majority is caused by developmental abnormalities of the frontal lobe. The rest are caused by tumors, strokes, vascular anomalies, or other lesions and traumas.
Clinical presentations of structural and genetic forms are similar. Nocturnal predominance of some seizures, typical for genetic form, is present in structural frontal epilepsy as well. Genetic form is described at the bottom of this page.
Symptoms of Frontal Lobe Epilepsy
There is a wide range of seizure types arising from the frontal lobe. Seizures depend on the epileptic focus location. Any of the described below types of focal seizures may be followed by generalized tonic-clonic seizures.
Focal motor seizures (primary motor cortex) are more common in the hand, thumb and face. Epileptic focus in the brain causes seizures on the opposite side of the body. The seizure may stay local (face, arm, leg), spread to the neighboring area, or involve the whole body side. The type of movement can be clonic, tonic, tonic-clonic, limb posturing, or myoclonic.
Focal seizures generated by supplementary motor area are usually tonic. Common presentation is “fencing” posturing (versive seizures). The head and eyes turn away from the brain side involved, the arm extends on the side of the gaze and the opposite arm flexes.
Hypermotor seizures (large amplitude body part movements) are typical for this area as well.
Seizures are often brief with sudden onset and termination. They are typically nocturnal and often run in series.
Consciousness is often preserved even when both sides of the body are involved. No postictal confusion. Sensory aura, speech arrest, or vocalizations may occur.
Other Parts of the Frontal Lobe
Automatisms of the frontal lobe origin are sometimes very bizarre, such as pelvic thrusting or other sexual automatisms, bicycling. This presentation often leads to the diagnosis of pseudoseizure due to hysteria, conversion disorder or malingering. Vocalizations are common in frontal lobe epilepsy.
“Frontal absences” may last from several minutes to even days. The patient is staring and is detached from reality in a trance-like state. Focus is usually in the frontal pole or in the medial frontal lobe.
Cingulate Gyrus Seizures
Gelastic (laughter), mood change, gestures, autonomic symptoms
Dorsolateral Frontal Lobe
Forced thinking and forced acts, versive seizures
Gustatory hallucinations, autonomic, focal clonic seizures that may be on the same side and commonly includes face. The most typical opercular seizures are variable oral movements, such as swallowing, chewing, lip smacking, as well as fear, abdominal discomfort (epigastric discomfort), drooling, speech arrest.
Orbitofrontal Frontal Lobe
Simple partial seizures of hallucinations of smell, gestural automatisms, autonomic; often progress into complex partial seizures
Frontal Pole Area
“Frontal absences”, forced thinking, versive seizures, falls, clonic seizures in the torso
Diagnosis of Frontal Lobe Epilepsy
It is not possible to differentiate genetic form of frontal lobe epilepsy from structural on clinical grounds alone. Brain imaging is essential (better MRI). PET CT may also be helpful in evaluation.
EEG, both ictal and inter-ictal, is often normal. Abnormalities, when detected, are variable epileptic discharges, which may be focal, bilateral and may involve neighboring lobes.
Frontal lobe epilepsy is often misdiagnosed as some movement disorder, hysteria, or conversion disorder.
Prognosis and Treatment of Structural Frontal Lobe Epilepsy
Antiepileptic drugs for structural and genetic forms of frontal lobe epilepsy are the same: Carbamazepine, Oxcarbazepine, Pregabalin, Gabapentin, Lamotrigine, Levetiracetam, Tiagabine, Topiramate, and Zonisamide
Prognosis in structural frontal lobe epilepsy is often poor, considering suboptimal response to medications. Medications are effective for secondary generalized seizures but not for the focal ones.
For this reason about 30% of patients undergoing epilepsy surgery have frontal lobe epilepsy, but success is limited.
Autosomal Dominant Nocturnal Frontal Lobe Epilepsy
Sudden movements (hypermotor seizures), stiffening or bizarre posturing of the limbs or the whole body occur while falling asleep or before/upon awakening.
These convulsions are called hypermotor because they produce large amplitude movements, which can literally throw the person out of bed causing injuries.
The attack lasts less than a minute. An aura of fear and shivering is common. The seizure may or may not cause loss of consciousness. The attacks have tendency to run in clusters.
Symptoms in this epileptic syndrome are similar to arising from supplementary motor area, which is known to cause whole body convulsions without loss of consciousness. It is often confusing and may lead to diagnosis of pseudo-seizures.
Symptoms onset is variable, ranging from infancy to late adulthood with peak of 11 years. Majority develops seizures before age 20. No gender preferences.
Mode of inheritance is autosomal dominant with 70% penetrance. Multiple mutations for nicotinic receptors encoding genes are identified: CHRNA4 on chromosome 20q and on 15p CHRNB2 and some others.
The clinical picture is remarkably universal independently of the type of genetic anomaly.
No abnormalities on brain imaging. Both ictal and interictal EEG may be normal.
This is one more reason for pseudoseizure misdiagnosis or labeling it as nocturnal dystonia.
EEG in sleep and during seizure may demonstrate frontal sharp or rhythmic theta waves.
No neurological or mental abnormalities. Seizures is the only symptom. Severity is variable from occasional and brief to frequent and running in series.
This syndrome is a lifelong condition with remissions and relapses. There is a tendency for easing up in fifties.
Two thirds respond well to Carbamazepine.
Depending on the individual circumstance, Oxcarbazepine, Pregabalin, Gabapentin, Lamotrigine, Levetiracetam, Tiagabine, Topiramate, and Zonisamide are other treatment alternatives.
Benign Childhood Epilepsy with Centrotemporal Spikes (Rolandic Epilepsy)
Benign Rolandic Epilepsy is the most common genetic partial epilepsy (15% of children with non-febrile seizures. The most typical age of onset is between of 4 and 10 years with the range from 1 to 16 years. Benign Rolandic Epilepsy is a genetic syndrome linked to 15q14.
The interesting fact about this syndrome is that the age related EEG abnormalities (but not the epilepsy syndrome) are inherited as an autosomal-dominant trait. Inheritance pattern of the seizures appear to be more complex. Parents or siblings with the same type of seizures are not the rule. Febrile seizures are common (10% to 20%).
Seventy five percent of seizures happen in sleep. Parents are typically awakened by strange throaty sounds made by the child. The attack starts with tingling and myoclonic or clonic movements on one side of the mouth, cheek, and tongue. Excessive salivation, speech arrest as well as gargling, death rattle, guttural sounds are very typical.
Clonic or tonic convulsions may further spread to the arm on the same side or turn into a generalized tonic-clonic seizure. Close to 60% do not experience loss of consciousness.
The seizure lasts for 1 to 2 minutes or longer, if loss of conscience is present. Status epilepticus was reported only in 5% of children with Benign Rolandic Epilepsy.
EEG in Rolandic Epilepsy
EEG: high amplitude, centrotemporal spikes with dramatic activation during sleep. This EEG pattern is inherited as an autosomal-dominant trait and, actually, present in 2% to 3% normal school-aged children.
Prognosis of benign rolandic epilepsy is very favorable in the majority of cases. Less than 2% will develop epilepsy later. Between 10% and 20% have a single seizure and the same percentage of patients suffer from frequent seizures.
Seizures remit by the age of 16 years or sooner. Considering that abnormal discharges are coming from the neighborhood of the brain speech area (rolandic), it is not surprising that some children experience language deficits; which are sometimes significant.
Language and cognitive abnormalities are temporary and they resolve by the same age as the seizures.
Treatment is often not required and reserved for frequent seizures. Commonly employed Carbamazepine may aggravate seizures in some children. Levetiracetam is another possible option. Considering favorable side effect profile, Sulthiame (not available in the US) is a good alternative.