Frontal lobe epilepsy (FLE) is a neurological disorder that is characterized by brief, recurring seizures arising in the frontal lobes of the brain, that often occur during sleep. It is the second most common type of epilepsy after temporal lobe epilepsy (TLE), and is related to the temporal form in that both forms are characterized by partial (focal) seizures.
Partial seizures occurring in the frontal lobes can occur in one of two different forms: either "focal aware", the old term was simple partial seizures (that do not affect awareness or memory) "focal unaware" the old term was complex partial seizures (that affect awareness or memory either before, during or after a seizure). The symptoms and clinical manifestations of frontal lobe epilepsy can differ depending on which specific area of the frontal lobe is affected.
The onset of a seizure may be hard to detect since the frontal lobes contain and regulate many structures and functions about which relatively little is known. Due to the lack of knowledge surrounding the functions associated with the frontal lobes, seizures occurring in these regions of the brain may produce unusual symptoms which can often be misdiagnosed as a psychiatric disorder, non-epileptic seizure or a sleep disorder.
During the onset of a seizure, the patient may exhibit abnormal body posturing, sensorimotor tics, or other abnormalities in motor skills. In some cases, uncontrollable laughing or crying may occur during a seizure. Affected persons may or may not be aware that they are behaving in an abnormal manner, depending on the patient and type of seizure. A brief period of confusion known as a postictal state may sometimes follow a seizure occurring in the frontal lobes. However, these postictal states are often undetectable and generally do not last as long as the periods of confusion following seizures that occur in the temporal lobes.
There are many different causes of frontal lobe epilepsy ranging from genetics to head trauma that result in lesions in the frontal lobes. Although frontal lobe epilepsy is often misdiagnosed, tests such as prolonged EEG monitoring, video EEG and/or an MRI scan of the frontal lobes can be administered in order to reveal the presence of a tumor or vascular malformation. Unlike most epileptic EEGs, the abnormalities in FLE EEGs precede the physical onset of the seizure and aid in localization of the seizure's origin. Medications such as anti-epileptic drugs can typically control the onset of seizures. However, if medications are ineffective the patient may undergo surgery to have focal areas of the frontal lobe removed.
Signs and symptoms Signs and symptoms of frontal lobe seizures may include Head and eye movements to one side Complete or partial unresponsiveness or difficulty speaking Explosive screams, including profanities, or laughter Abnormal body posturing, especially fencing position Repetitive movements, such as rocking, bicycle pedaling or pelvic thrusting
Epileptic symptoms are frequently the product of the spread of overactivation occurring within one central foci that travels to lateral brain regions thereby causing an array of symptoms. Due to the massive amount of diversity in both the cognitive and motor functions that occur within the frontal lobes, there is an immense variety in the types of symptoms that can arise from epileptic seizures based on the side and topography of the focal origin. In general these symptoms can range anywhere from asymmetric and abnormal body positioning to repetitive vocal outbursts and repetitive jerking movements. The symptoms typically come in short bursts that last less than a minute and often occur while a patient is sleeping. In most cases, a patient will experience a physical or emotional aura of tingling, numbness or tension prior to a seizure occurring. Fear is associated with temporal and frontal lobe epilepsies, but in FLE the fear is predominantly expressed on the person's face whereas in TLE the fear is subjective and internal, not perceptible to the observer.
Tonic posture and clonic movements are common symptoms among most of the areas of the frontal lobe, therefore the type of seizures associated with frontal lobe epilepsy are commonly called tonic-clonic seizures. Dystonic motor movements are common to both TLE and FLE, but are usually the first symptom in FLE episodes where they are quite brief and do not affect consciousness. The seizures are complex partial, simple partial, secondarily generalized or a combination of the three. These partial seizures are often misdiagnosed as psychogenic seizures.
Symptomatology A wide range of more specific symptoms arise when different parts of the frontal cortex are affected.
Supplementary motor area (SMA) The onset and relief of the seizure are quite abrupt. The tonic posturing in this area is unilateral or asymmetric between the left and right hemispheres. A somatosensory aura frequently precedes many large motor and vocal symptoms and most often the affected person is responsive. Motor symptoms: Facial grimacing and complex automatisms like kicking and pelvic thrusting Vocal symptoms: Laughing, yelling, or speech arrest. Primary motor cortex The primary motor cortex has jacksonian seizures that spread to adjacent areas of the lobe which often trigger a second round of seizures originating in another cortical area. The seizures are much simpler than those that originate in the SMA and are usually clonic or myoclonic movements with speech arrest. Some dystonic or contralateral adversive posturing may also be present. Medial frontal, cingulate gyrus, orbitofrontal, or frontopolar regions Motor symptoms of seizures in this area are accompanied by emotional feelings and viscerosensory symptoms. Motor and vocal agitation are similar to that of the SMA with short repetitive thrashing, pedaling, thrusting, laughing, screaming and/or crying. This is some of what can cause the misdiagnosis of a psychological disorder. Dorsolateral cortex This area does not seem to have many motor symptoms beyond tonic posturing or clonic movements. Contralateral or less commonly ipsilateral head turn and eye deviation are commonly associated with this area as well. Operculum Many of the symptoms associated with this area involve the head and digestive tract: swallowing, salivation, mastication and possibly gustatory hallucinations. Preceding the seizure the person is fearful and often has an epigastric aura. There is not much physical movement except clonic facial movements. Speech is often arrested.
Diagnosis Neuroimaging for diagnosis Advancements in technology, has given rise to newer, more efficient methods of diagnosis, most prominent being in the domain of neuroimaging. The high spatial resolution from fMRI has implications on certain brain regions contributing to memory. The usage of task fMRI for examination of memory or other higher cognitive networks may also be used to predict ictal onset zone(s) in patients with FLE, giving the advantage of refinement of patient-specific analyses. The use of multi-modal approaches in association with neuroimaging techniques like fMRI and MEG or EEG will be informative in characterizing atypical functional brain networks in FLE. But, difficulty remains in the evaluation of potential compensatory mechanisms between patients with FLE with normal and impaired memory, without properly characterizing transfer of information during memory tasks.
Common misdiagnoses Episodes that include complex hyperactivity of the proximal portions of the limbs that lead to increased overall motor activity are called hypermotor seizures. When associated with bizarre movements and vocalizations these seizures are often misdiagnosed as psychogenic or functional sezures or other episodic movement disorders such as psychogenic movement disorders, familial paroxysmal dystonic choreoathetosis, paroxysmal kinesogenic choreoathetosis, or episodic ataxia type 1. Hypermotor seizure in children are often confused with pavor nocturnus (night terrors). Paroxysmal nocturnal dystonia or hypnogenic paroxysmal dystonia are other names given to describe FLE symptoms but are simply just FLE.
Autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) is the best understood form of frontal lobe epilepsy but is often misdiagnosed as sleep apnea. Both disorders are characterized by awakening during the night which leads to daytime sleepiness. Some symptoms of sleep apnea overlap with those of ADNFLE, such as sudden awakening accompanied by a feeling of choking and on occasion motor activity which makes diagnosis difficult based on symptoms alone. Video surveillance as well as EEG is occasionally needed to differentiate between the two disorders. It has been reported that sleep apnea might be associated with epilepsy which would account for some of the misdiagnoses.
Causes
The origins of frontal lobe seizures can be different deviations. One of the major reasons for FLE is abnormal cognitive development or sometimes congenital abnormal brain development. Other causes are tumors, head trauma, and genetics.
Tumors Tumors account for about one-third of all frontal lobe epilepsy cases.
Head Trauma Seizures originating directly from head trauma usually occur within a few months, but occasionally they can take years to manifest.
Mechanism
Due to the difference in brain processing and function as well as various surface anatomy landmarks, the frontal lobes have traditionally been divided into two major areas known as the precentral cortex and prefrontal cortex.
Precentral cortex The precentral cortex (Brodmann area 6) is an area of the frontal cortex that is located directly anterior to the central sulcus and includes both the primary motor cortex and the supplementary motor area. Inputs that project to both of these areas arise from a variety of locations in the brain that integrate sensory stimuli including the primary motor cortex, the thalamus and corticospinal projections. These two areas along with several other main functional areas control both the preparation of motor movement as well as the execution of movements. These main functional areas are crucial to the development of the motor related symptoms associated with frontal lobe epilepsy focally when seizures are located within these defined areas. The major functional areas include: Primary motor cortex Contains large neurons that project axons down to the spinal cord where they synapse onto alpha motor neurons. These neurons are involved in the planning of motor movements and the refining of motor movements based on sensory inputs that are received from the cerebellum. Supplementary motor area Area anterior to the primary motor cortex that is involved in planning complex motor movements and coordinating movements along both hands. The main inputs for this area are received from the thalamus. Frontal eye field The frontal eye field is a posterior part of the middle frontal gyrus and is involved in the control of saccadic, contralateral and conjugate eye movement. This area receives its main inputs from both the occipital cortex and dorsal thalamus. Broca's area Controls the motor movements of both the tongue and larynx that enables speech formation. This area receives direct inputs from the primary motor area as well as Wernicke's area located in the temporal lobe.
Prefrontal cortex The prefrontal cortex, the most anterior region of the brain, comprises several key areas that are particularly important for higher mental functions that control various aspects of human personality including anticipation and planning, initiative/judgement, memory and the control of decision making. Damage or lesions to this region of the brain can result in major changes in personality.