Summary
Highlights
The initial step in assessing a patient with seizures is differentiating between true seizures and pseudo seizures. If it's a true seizure, determine if it's a new occurrence or a recurrent one, which will affect the further investigations. It's also essential to define whether the seizure is partial or generalized.
Partial seizures originate in one hemisphere, detectable clinically or via EEG. Generalized seizures, however, cannot be traced to a single hemisphere; they often start in the diencephalon, affecting both hemispheres simultaneously. Different types of partial seizures are discussed.
If a seizure is partial, differentiate between simple and complex. Simple partial seizures don't alter consciousness, while complex partial seizures do. This is determined through patient history and observation. EEG evidence then helps confirm electrophysiological disturbances, especially during the seizure itself.
EEG helps identify the focus of the seizure (e.g., frontal, temporal lobe). MRI and CT scans can also aid in anatomical localization. Distinguishing between symptomatic and idiopathic epilepsy is crucial. Symptomatic epilepsy has an underlying cause (tumor, infection), while idiopathic epilepsy doesn't have a clear structural or metabolic origin.
Symptomatic epilepsy is secondary to an underlying condition, like a tumor, where removing the cause can eliminate the seizures. Idiopathic epilepsy is typically inherited and managed with medication.
Key questions to address when managing epilepsy: Is it a true seizure? Partial or generalized? If partial, is it simple or complex, motor, sensory, or psychomotor? Is there evidence of disturbed electrophysiology? What is the anatomical location? What is the cause? Which drug is most appropriate? How to manage the underlying cause?
EEG is crucial during a seizure. A normal EEG during a full-blown attack suggests a pseudo seizure. Interictal EEG (between attacks) might be normal in epilepsy patients or abnormal in individuals without epilepsy, reducing its diagnostic reliability.
Partial seizures are divided into simple and complex, with subdivisions for motor, sensory, and psychomotor manifestations. Motor seizures may be tonic, clonic, atonic, or tonic-clonic. The key differentiator between simple and complex remains the alteration of consciousness.
Motor seizures, depending on the presence and type of movements involves any part of the body, may or may not affect conscious level. Sensory seizures cause abnormal sensations while psychomotor seizures include phenomena like deja vu, hallucinations, or automatisms (automatic behaviors). Disturbed conscious level makes these simple, complex partial seizures. If the seizure begins as partial and progresses to involve the whole body the seizure is generalized.
Generalized seizures include absence (petit mal), tonic-clonic (grand mal), tonic, clonic, myoclonic, and atonic seizures. Absence seizures typically start in childhood, characterized by brief periods of mental absence, often with eye blinking or slight automatisms. EEG typically shows three cycles per second spike and wave pattern. Absence seizures are best treated with ethosuximide (ethosuccimide) which reduces calcium influx in the thalamic neurons.
Tonic-clonic seizures involve distinct phases: prodrome, aura, tonic, colonic, and postictal. The prodrome involves mood or behavioral changes. The aura is a sensory experience perceived only by the patient. The tonic phase features rapid loss of consciousness and stiffening of the body, potentially with cyanosis and crying. The clonic phase involves jerking movements with risk of tongue biting and incontinence. Postictal phase is characterized by drowsiness and confusion/irritability.
During the clonic phase of tonic-clonic seizures, tongue biting and urinary/fecal incontinence can occur. Current recommendations advise against inserting anything into the mouth during a seizure. Postictal care involves close monitoring due to possible status epilepticus.
Various factors can trigger seizures, including bright or flickering lights, sleep deprivation, exhaustion, certain drugs (or their withdrawal), CNS infections, and metabolic disturbances (hypoglycemia, electrolyte imbalances), specific triggers like noise or reading are also possible.
Jacksonian epilepsy, also referred to as Jacksonian March, is a seizure in which the motor activity or sensation progressively spreads across a body part, because the neural firing is marching in a contiguous pattern through the cortex, corresponding to a march of sensation or motor activity of the specific body part. The limb may experience a temporary weakness after the seizure (Todd's paralysis).
Epilepsy is broadly classified as symptomatic or idiopathic. If suspicion for symptomatic epilepsy is high aggressive diagnostic investigation is warranted. Partial seizures, adult-onset epilepsy, and drug-refractory epilepsy have a higher likelihood of identifiable underlying causes.
Partial seizures are mainly symptomatic. Possible etiologies include focal structural lesions, and genetic focal structural lesions such as tuberous sclerosis, and neurofibromatosis type 2. Embryonic problems such as cortical dysgenesis, mesial temporal sclerosis can also be a cause.
Cerebrovascular events, like thrombotic or embolic infarctions, or cerebral vein thrombosis, arteriovenous malformations, and tumors also need to be excluded as potential causes. Vein thrombosis carries a high chance that the patient will present with epilepsy.
Infections like cerebral abscesses (often from otitis media), toxoplasmosis, cysticercosis, tuberculomas, subdural empyema, temporal lobe encephalitis (commonly herpes simplex), and HIV/AIDS if they invade the CNS can cause partial seizures. Inflammatory conditions like sarcoidosis and vasculitis should also be considered. SLE can lead to cerebral vasculitis which has a poor prognosis.
Causes of generalized seizures include genetic conditions, metabolic disorders (storage diseases like Tay-Sachs), cerebral birth injury, hydrocephalus, prolonged cerebral anoxia, and certain drugs.
Various drugs can irritate the CNS and precipitate seizures. e.g. Penicillin, anitemalarials, isoniazid, and cardiac antiarrhythmics (disturb electrical activity in CNS). Psychotropic drugs phenothiazines block stimulation, whereas tricyclic antidepressants block reuptake of monoamines which results in increased concentration of the synaptic cleft, and may cause seizures.