(Tonic-Clonic, Grand Mal)
In the common primary type of seizure, most often a convulsion starts with little or no warning. Sometimes the patient senses the approach of a seizure by several subjective phenomena (prodrome) even prior to an epileptic aura, which represents a focal seizure. For some hours, the patient may feel apathetic, depressed, irritable, or, rarely, the opposite—ecstatic. In a patient with generalized epilepsy (juvenile myoclonic epilepsy being one typical type), one or more myoclonic jerks of the trunk or limbs on awakening may herald a seizure later in the day. Abdominal pains or cramps, a sinking, rising, or gripping feeling in the epigastrium, pallor or redness of the face, throbbing headache, constipation, or diarrhea have been given prodromal status, but they do not occur consistently enough to be predictive of an oncoming seizure.
Most often, generalized seizure strikes without warning, beginning with a sudden loss of consciousness and a fall to the ground that may lead to facial and other injuries. In some cases of generalized seizure there may be momentary movement of one part of the body before consciousness is lost (turning of the head and eyes or whole body or intermittent jerking of a limb), although the patient often fails to form a memory of this and such information is obtained only from an observer. At times, this movement represents a focal onset of a seizure and, as has already been pointed out, it is useful to distinguish between a primary (generalized) type of seizure with widespread EEG abnormalities at the onset, and a secondarily generalized type. The secondary generalized type implicates a focal brain lesion.
The initial motor signs are typically a brief flexion of the trunk, an opening of the mouth and eyelids, and upward deviation of the eyes. The arms are elevated and abducted, the elbows semiflexed, and the hands pronated. These are followed by a more protracted extension (tonic) phase, involving first the back and neck, then the arms and legs. There may be a piercing cry as the whole musculature is seized in a spasm with biting of the lateral margin of the tongue, and air is forcibly emitted through the closed vocal cords. Because the respiratory muscles are caught up in the tonic spasm, breathing is suspended and after some seconds the skin and lips may become cyanotic. The pupils are dilated and unreactive to light. The bladder may empty at this stage or later, during the postictal coma. This is the tonic phase of the seizure and lasts for 10 to 20 s.
There then occurs a transition from the tonic to the clonic phase of the convulsion. At first, there is a mild generalized tremor, which is, in effect, a repetitive relaxation of the tonic contraction. It begins at a rate of approximately 8 per second and coarsens to 4 per second; then it rapidly gives way to brief, violent flexor spasms that come in rhythmic salvos and agitate the entire body. If prolonged, the face becomes violaceous and contorted by a series of grimaces. Autonomic signs are prominent: the pulse is rapid, blood pressure is elevated, pupils are dilated, and salivation and sweating are prominent; bladder pressure may increase sixfold during this phase. The clonic jerks decrease in amplitude and frequency over a period of about 30 s. The patient remains apneic until the end of the clonic phase, which is often marked by a deep inspiration. Instead of the whole dramatic sequence described above, the seizures may be abbreviated or limited in scope by medications.