Epilepsy - Diagnosis

The most informative method of diagnosis in epilepsy is a thorough collection of anamnesis and detailed information about the manifestations of seizures. During physical and neurological examination, special attention should be paid to identifying neurological symptoms that may indicate the etiology and localization of the epileptic focus. However, in epilepsy, anamnesis is more important than physical examination.

Laboratory blood testing is performed to determine infectious or biochemical causes of seizures, as well as baseline white and red blood cell counts, platelet counts, and blood and kidney function before prescribing antiepileptic drugs. A lumbar puncture may be required to rule out meningitis.

Neuroimaging may be needed to detect structural changes in the brain that may be the cause of seizures, such as tumors, hematomas, cavernous angiomas, arteriovenous malformations, abscesses, dysplasia, or old stroke. MRI is more useful for seizures than CT because it can detect subtle structural changes, including mesotemporal sclerosis, which manifests as hippocampal atrophy and increased signal intensity on T2-weighted images.

Mesotemporal sclerosis (MTS) is frequently found in patients with temporal lobe epilepsy. In this regard, the question of whether it is a cause or a consequence of seizures is widely debated. Although in laboratory animals, MTS develops after repeated temporal lobe seizures, there are only isolated observations in humans with dynamic MRI confirming the possibility of the appearance and development of MTS signs during repeated seizures. On the other hand, hypoxia and ischemia can cause changes in the hippocampus similar to those observed in MTS before the onset of seizures. In any case, MTS is a very useful neuroimaging marker of temporal lobe epilepsy, allowing to localize the epileptic focus. However, this cannot serve as proof that all epileptic seizures in a given patient are generated in this area.

EEG is of particular diagnostic importance in epilepsy. EEG is a recording of fluctuations in time of electrical potentials between two points. Typically, EEG is recorded using 8-32 pairs of electrodes placed over different areas of the head. Electrical activity is usually recorded for 15-30 minutes. Ideally, EEG should be recorded both during wakefulness and during sleep, since epileptic activity may only manifest itself in a state of drowsiness or light sleep. EEG specialists interpret its data, paying attention to the overall voltage, symmetry of activity in the corresponding areas of the brain, frequency spectrum, the presence of certain rhythms, for example, the alpha rhythm with a frequency of 8-12/s in the posterior parts of the brain, the presence of focal or paroxysmal changes. Focal changes may appear as slow waves (e.g., delta activity at 0-3/s or theta activity at 4-7/s) or as decreased EEG voltage. Paroxysmal activity may appear as spikes, sharp waves, spike-wave complexes, and changes that accompany epileptic seizures.

Usually, it is rarely possible to record an EEG during a seizure. Therefore, in cases where a seizure must be recorded to clarify the localization of the epileptic focus when planning a surgical intervention, long-term EEG recording is necessary. Video and audio recording can be synchronized with EEG in order to identify the correspondence between behavioral phenomena and electrical activity. In some cases, invasive EEG recording using intracranial electrodes must be used before surgical intervention.

EEG data taken by themselves cannot serve as a basis for diagnosing epilepsy. EEG is only an additional study confirming the anamnesis data. It should be taken into account that some people have abnormal peaks on the EEG, but never have seizures, and therefore cannot be diagnosed with epilepsy. On the contrary, in patients with epilepsy, the EEG may be normal in the interictal period.

Simulation of epilepsy

Some conditions may involve abnormal movements, sensations, and loss of reactivity, but they are not associated with abnormal electrical discharge in the brain. Thus, syncope may be incorrectly assessed as an epileptic seizure, although in a typical case it is not accompanied by such a prolonged period of convulsions. A sharp decrease in cerebral perfusion may cause symptoms similar to epilepsy. Hypoglycemia or hypoxia can cause confusion as in an epileptic seizure, and in some patients there may be difficulties in differential diagnosis of seizures from severe migraine attacks accompanied by confusion. Transient global amnesia is a sudden and spontaneously passing loss of the ability to remember new information. It can be distinguished from complex partial seizures by its duration (several hours) or by the preservation of all other cognitive functions. Sleep disorders such as narcolepsy, cataplexy, or excessive daytime sleepiness may also resemble epileptic seizures. Extrapyramidal disorders such as tremors, tics, dystonic postures, and chorea are sometimes mistaken for simple motor partial seizures.

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Conditions that mimic epilepsy

There are many clinical pictures and classifications, but they cannot be considered satisfactory. In particular, it has been shown that schizophrenia is more common among patients with epilepsy than among patients suffering from other chronic neurological disorders, such as migraine. Theoretically, all of them can be associated with the commission of crimes. The following conditions are described in the literature:

1. Hallucinations and/or severe emotional disturbances occurring in connection with the seizure: during the aura or during one of the other disturbances of consciousness.
2. Paranoid hallucinatory states following grand mal attacks, lasting two to three weeks and accompanied by clouding of consciousness.
3. Transient schizophrenia-like episodes that end on their own and occur between seizures. They can vary greatly from case to case: some patients remain fully conscious, while others are "clouded." Some have amnesia, while others remember everything perfectly. Some have an abnormal EEG, while in others the EEG normalizes (and becomes abnormal as the psychosis resolves). Some effects are treatment-related.
4. Chronic schizophrenia-like psychoses, identical to paranoid schizophrenia. Described in connection with a long history of epilepsy (usually temporal), lasting more than 14 years.
5. Affective disorders. It seems that these disorders are more common in people with temporal lobe epilepsy. They are usually short-lived and self-limiting. Affective and schizoaffective psychoses also occur. However, it is important to remember that the suicide rate is higher among people with epilepsy.
6. Fainting
7. Sleep disorders (narcolepsy, cataplexy, excessive daytime sleepiness)
8. Ischemic attacks
9. Heart rhythm disturbances
10. Hypoglycemia
11. Fluxion
12. Migraine attacks with confusion
13. Transient global amnesia
14. Vestibulopathies
15. Trembling hyperkinesis, tics, dystonia
16. Panic attacks
17. Nonepileptic seizures (psychogenic seizures, pseudoseizures)

Psychogenic conditions are also difficult to distinguish from epileptic seizures. These conditions include panic attacks, hyperventilation, episodic loss of control syndrome (rage attacks, intermittent explosive disorder), and psychogenic seizures, which can be especially difficult to distinguish from true epileptic seizures. In breath-holding attacks (affective-respiratory seizures), the child, in a state of anger or fear, holds his breath, turns blue, loses consciousness, after which twitching is possible. Night terrors are characterized by a sudden, incomplete awakening from sleep with a piercing scream and confusion. Although breath-holding attacks and night terrors cause concern in parents, these are benign conditions. Psychogenic seizures are also called psychosomatic seizures, pseudo-seizures, or nonepileptic seizures. They are provoked by a subconscious conflict. In most cases, a nonepileptic seizure is not a conscious simulation of a seizure but a subconscious psychosomatic reaction to stress. Treatment of psychogenic seizures consists of psychological counseling and behavioral therapy, not the use of antiepileptic drugs. Videoelectroencephalographic monitoring is usually necessary to confirm the diagnosis of psychogenic seizures, since the changes usually observed in an epileptic seizure are not present in a psychogenic seizure. Since seizures that mimic epileptic seizures can be difficult to distinguish from true epileptic seizures, some patients misdiagnosed with epilepsy are inadequately treated with antiepileptic drugs for many years. Obtaining detailed information about the nature of the seizure is of key importance for the diagnosis of pseudoseizures. Particular attention should be paid to the nature of the prodrome, stereotypy, duration of seizures, the situation in which they occur, provoking factors, and the patient's behavior during seizures.

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