Regardless of the etiologic factor or type of seizure, the basic mechanism is the same. The electric discharges (1) may arise form central areas in the brain that affect consciousness immediately; (2) may be restricted to one area of the cerebral cortex, producing manifestations characteristic of that particular anatomic focus; or (3) may begin in a localized area of the cortex and spread to other portions of the brain, which if sufficiently extensive, produce generalized neurologic manifestations.
Seizure activity is believed to be caused by a spontaneous electric discharge initiated by a group of hyperexcitable celled referred to as epileptogenic focus. Normally these discharges are restrained from spreading beyond the focal area by normal inhibitory mechanisms.
In response to any of a variety of stimuli, such as cellular dehydration, abnormal blood sugar levels, electrolyte imbalance, fatigue, emotional stress, temperature elevation, and endocrine changes, these hyperexcitable cells activate normal cells in surrounding areas and in distant, synaptically related cells. A seizure develops when the neuronal excitation from the epileptogenic focus spreads to the brainstem (particularly the midbrain and reticular formation) or to other portions of the brain. These centers within the brainstem, known as the centrocephalic system, are responsible for the spread of the epileptic potentials. The discharges originate spontaneously in the centrencephalic system or be triggered by a focal area in the cortex.
Manifestations depend on the type of seizure, which may be classified as partial or generalized. In partial seizures, the excess neuronal discharge is contained within one region of the cerebral cortex. In generalized seizures, the discharge bilaterally and diffusely involves the entire cortex. Sometimes a focal lesion of one part of the hemisphere activates the entire cerebrum bilaterally so rapidly that it produces a generalized tonic-clonic seizure before a focal sign appears.
1) Simple Partial Seizures
n Consists of motor, sensory, or psychomotor phenomena without loss of consciousness. Patient may have chewing movements, smacking lips, localized numbness or tingling, localized twitching of muscles, olfactory hallucinations, visual hallucinations (flashes of light or formed images).
2) Complex Partial Seizures
n Consists of the patient losing contact with surroundings for 1 to 2
minutes. Patient may stare, perform automatic purposeless movements,
aid, and have mental confusion.
3) Generalized Seizures
n Consists of loss of consciousness and motor function from the onset.
A) Infantile Spasms
the trunk, and extension of the legs. Last a few seconds. Poor
prognosis and hard to treat.
B) Absence Seizures (petit mal)
? Characterized by brief, primarily generalized attacks manifested
by a 10 to 30 sec lapse of consciousness and eyelid flutterings
at a rate of 3/sec, with or without loss of axial muscle tone.
Abruptly stop activity and pick it back up as if nothing
C) Generalized Tonic-Clonic Seizures
? Typically begin with an outcry; they continue with loss of
consciousness and falling, followed by tonic, then clonic
Urinary and fecal incontinence may occur. Seizures last 1 to 2
minutes. May be aura. (Postictal = drousy, sleepy)
D) Atonic Seizures
? Primarily generalized seizures. They are characteristic of loss of
muscle tone and consciousness. The child falls or pitches to the
E) Myoclonic Seizures
? Brief, lightning jerks of a limb, several limbs, or the trunk.
They may be repetitive.
F) Febrile Seizures
? Associated with fever (temperature increases rapidly without evidence of intracranial infection. They are brief, solitary, and generalized tonic-clonic in form.