Fearing possible sequels after seizure patients may seek a thorough medical examination. During the consult, a patient may ask “Do I have epilepsy?”. A question that requires extensive clinical knowledge and experience on diagnosing epilepsy. Usually, through a diagnosis, this question will be answered. However, the physician is responsible for determining if the patient suffered a true epileptic seizure, and later categorizing the findings into a diagnosis.
It is important to recall that the underlying processes in the group of epileptic illnesses are not completely understood therefore definite answers are hard to obtain. Nevertheless, satisfactory treatment can follow a correct diagnosis of epilepsy based upon precise clinical definitions, the clinical examination through both clinical manifestations and testing technologies for disease, and its classification according to current guidelines.
The first step in diagnosing epilepsy is comprehending the correct clinical definitions related to the task at hand. In the first place, one must consider the conceptual and operational definitions of epilepsy. The conceptual definition of epilepsy according to the 2005 Taskforce of the International League against Epilepsy is quoted.
Epilepsy is a disorder of the brain characterized by an enduring predisposition to generate epileptic seizures, and by the neurobiological, cognitive, psychological, and social consequences of this condition. The deﬁnition of epilepsy requires the occurrence of at least one epileptic seizure.
Additionally, the conceptual definition requires the discussion of the definition of epileptic seizures as described by the same paper.
An epileptic seizure is a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain.
The conceptual definition summarizes the current understanding of the disease along with a general description of both clinical and testing. In the clinical setting the practical definition, derived from the conceptual definition of 2005, defined epilepsy as having two unprovoked seizures with at least 24 hours apart. Even though useful, the practical definition had some shortcomings associated with increased risk associated with some patients with a possible diagnosis of epilepsy. Additionally, patients with a diagnosis of epilepsy, who had not experienced symptoms for several years.
For this reason, an official practical definition of epilepsy was created and expanded to be defined by three conditions in 2013 by a task force designated by the League against epilepsy.
At least two unprovoked (or reﬂex) seizures occurring>24 h apart.
One unprovoked (or reﬂex) seizure and a probability of further seizures similar to the general recurrence risk (at least 60%) after two unprovoked seizures, occurring over the next 10 years.
Diagnosis of an epilepsy syndrome.
These new definitions, through the second condition, allowed the patient with increased risk of a second seizure to be identified as an epileptic patient. Also, the third condition incorporated the concept of epilepsy syndromes. This was beneficial because patients could experience a seizure along with numerous other signs associated with a specific epilepsy syndrome, and with the previous definition, in some cases, would not be identified as an epileptic patient.
Additionally, to adequately categorize patients whose symptoms had significantly improved the term resolved epilepsy was created.
Epilepsy is considered to be resolved for individuals who had an age-dependent epilepsy syndrome but are now past the applicable age or those who have remained seizure-free for the last 10 years, with no seizure medicines for the last 5 years.
It is important to emphasize that it is described as resolved, contrasting with cured. This can be explained because regardless of the clinical improvement the patient did suffer from epilepsy and does not have the same condition as other patients. It must be pointed out that patients with epilepsy are not limited in functions provided they are adequately treated and/or their epilepsy has resolved.
Another aspect that was modified was the previous definition of epilepsy as a disorder rather than a disease. Usually, disorders are characterized by a temporal loss of function, in contrast to entities defined as a disease where the loss of function can be identified as long lasting. It also important point out that in both definitions epilepsy was mentioned a disorder or a disease. In general, scientist and physicians when describing epilepsy sometimes can describe in in the singular sense. However, epilepsy is characterized by having a great diversity of presentation and therefore is recognized as a group of diseases, not a single entity.
It is important to recognize that the new working definition a perfect one as pointed out by task for itself. A particular aspect that needs to be further developed is the distinction from unprovoked and provoked seizures. If a patient suffers head trauma or an infection experiences a seizure, in some of these cases it can be evident that the seizure was provoked. However, in absence of a provocative factor does not mean these do not exist rather in some case could be missed. Additionally, the presence of provocative factors does not mean that patient could have a predisposition for developing epilepsy and the provocative factor acted as a trigger.
Regardless of the impreciseness of the term, it is necessary to discuss the differences found across the distinct types of seizure. First of all, concerning epileptic seizures and non-epileptic seizures. These differences are associated with the first system created to classify which was made with an essential test for epilepsy¸ the electroencephalogram along with the clinical manifestation. In epileptic seizures, there are abnormalities that are always associated with the manifestation of seizures. This is not the case for non-epileptic seizures, where no evidence of abnormalities in the electroencephalogram is found. Another term used to describe non-epileptic seizures are psychogenic seizures.
Additionally, epileptic seizures have been classified into three major groups, partial, generalized and unclassified seizures. The distinction is thought derives from the signs and symptoms that are thought to derive from specific electrophysiological dysfunctions in the brain, which can be observed by the electroencephalogram. Partial seizures are well described by their alternate names, focal or focal seizures. In which, electrophysiological and clinical signs show affection of either one hemisphere or a specific nervous functional system. Generalized, as implied by their name show affection of diffuse areas of the brain.
Partial seizures are further subdivided into simple partial seizures, complex partial seizures and partial seizures evolving to secondarily generalized. The difference between each is the degree of consciousness found in the patient during the seizure. During simple seizures, some degree of consciousness remains in the patient, whereas during complex seizures the patient loses consciousness. Practically, consciousness is defined as the degree of awareness (described as the contact a patient has with the surroundings) along with responsiveness (described as the ability of the patient to carry out simple commands from willed movements).
Simple partial seizures additionally have additional descriptors of additional signs and symptoms in four categories, minor signs, sensorial symptoms (somatosensory or special sensory), autonomic symptoms or signs, and psychic symptoms. These do not alter the original identification of partial epilepsy but rather presents additional signs and symptoms that describe the patient’s clinical presentation. Complex partial seizures have further subdivisions, which divides the seizures into a group, those whose loss of consciousness began after an initial simple partial seizure and seizures with loss of consciousness from the moment the seizure began.
The last category is one describing the progression of partial seizures to generalized seizures. These are classified according to the type of seizures presented into three subgroups. The first group is including initial simple partial seizures that are progressing into generalized seizures. The second group progresses into generalized seizures from complex partial seizures. The third group includes seizures who progress into a complex partial seizure from simple partial seizures, which later progress into generalized seizures.
Generalized seizures are classified into six groups, absence, myoclonic, clonic, tonic, tonic-clonic and atonic seizures. This classification is also arranged around the association of clinical findings associated with specific electroencephalogram results. Clinical findings describe the type of movement or absence of, found in the moment of the seizure.
Currently, to aid the diagnosis of epilepsy, seizures are classified into a semiological classification, which can be parallel to the first classification or used independently. The semiological seizure classification divides seizures into four main groups sensation, cognition, autonomic and motor. This classification helps in the description of the clinical presentation because witnesses can be interrogated and these can provide relatively consistent information. Additionally, it does not constrain the division according to specific electroencephalogram finds, as the associations are not always exact.
This classification of seizures is essential when studying the clinical presentation to diagnose epilepsy. Additional to characteristics of the seizure itself, it important to put the seizure into the context of the phases. Which in epileptic patients include a prodromal, aural, ictal and postictal phase.
The prodromal phase represents the phase previous to the initiation of the ictus (or seizure episode). It can last for many hours and is characterized by alteration in a patient’s mood, behavior or cognition. Usually, this presents as anxiety, depression or inability to think or concentrate. The essential characteristic of this phase is the lack of findings in the electroencephalogram.
When initial finding on the electroencephalogram begins, the aural phase begins. It can last from several seconds with minutes. Usually, the findings associated with either simple partial seizures or complex partial seizures appear. Commonly the aura can help the physician identify the epileptogenic area in the brain. However, in primary generalized seizure patients do not experience aura.
Afterward, the ictal phase begins, which can vary in duration according to the type of seizure. (15-30 seconds for absence seizures, 2 – 5 minutes for major motor seizures, and 1 – 5 minutes in simple or complex features. The product of the loss of consciousness, the patient is amnesic during this phase if it is a generalized seizure or a partial complex seizure, contrasting with simple partial seizures which do not have loss of consciousness.
Finally, after the seizure the post-ictal phase begins. This phase varies according to the type of seizure experienced. If an absence seizure occurs the patient may continue their task at hand without any alterations. Seizures involving major motor manifestations tend to be confused and disoriented after the seizure. During this phase, the patient must be subjected to a full neurological exam due to the possibility of the appearance of post-ictal Todd state. (Common neurological signs include hemiparesis, aphasia, anesthesia, reflex asymmetry, Babinski sign and visual defect.).
The normal progression of seizures has been studied throughout years and the phases along with the components can be easily detected. However, in most cases, the physician is not present and the complete clinical presentation is not easily recreated from the witness of the seizure. Therefore, the physician must rely upon several tests for epilepsy to help them diagnose epilepsy. The test for epilepsy includes an electroencephalogram along with image studies.
The electroencephalogram is essential in studying patients with epilepsy. This test involves the placing of electrodes in specific places in the patient’s head. These electrodes will measure the patient´s electrophysiological activity. Even though essential, between seizures only 50% of patients will present with abnormal epileptic brain activity. In the other hand, during sleep patients will present abnormal finding in 80-90% of electroencephalogram results. Additionally, the abnormal finding resulting from this test are not specific to the different types of epilepsy.
Image testing for epilepsy are regularly performed after an episode, either to identify the cause of the episode (this would identify the seizure as being provoked) or abnormal finding associated to epileptic patients. In computerized tomography studies, findings in provoked seizures include cerebrovascular events, cerebral absences, and certain tumors. In contrast, findings associated with epileptic diseases include sclerosis in the hippocampus and cortical development abnormalities. Additionally, function test like single photon emission computerized tomography or positron emission tomography can reveal abnormalities in diverse function of neurotransmitters.
The diagnosis of epilepsy is not complete without the identification of the type and characteristics of each case of epilepsy. This part is done through the evaluation of the 5 dimensions of the epileptic diseases epileptogenic zone, seizure classification, etiology, seizure frequency and related medical information. These 5 dimensions are studied indecently and in parallel and will provide a physician with a complete description of patient´s epileptic disease.
The 5 dimensions of epileptic disease are also useful in summarizing the details concerning the diagnosis of epilepsy. The first two dimensions, dimensions aid the physician when studying the characteristics of the seizure episodes and the possible underlying pathophysiologic mechanism which caused them. Additionally, it helps both patient and physicians identify these characteristics and remember that there are numerous types of epilepsy. The third, recalls that the conceptual definition of the disease points out that epileptic patients suffer unprovoked seizures. If a physician finds a specific cause of the seizure, this means the patient does not suffer epilepsy. In contrast, epileptic patients have several factors that lead to the disease. Also, it is important to point out that febrile seizure and neonatal seizures have their diagnosis procedures due to differences with epilepsy. The last two aid the physician to recognized that epilepsy can have detrimental effects on some patient’s quality of life. However, in some patients, they will be able to lead a normal life. Even in patients with active disease, through a proper diagnosis of epilepsy can be adequate management of the disease.