Chapter 22. Epilepsy

Questions

Define the following terms:

epilepsy, primary generalized seizure, complex partial seizure, myoclonic seizure, petit mal seizure, simple partial seizure, focal seizure, secondary generalization, status epilepticus, postictal period, interictal, Todd's paralysis, hippocampal sclerosis, temporal lobe epilepsy, seizure focus.
Epilepsy is the tendency to have seizures in the absence of provocations that would cause the normal brain to have a seizure.
A primary generalized seizure is a seizure that involves the entire brain at the same time. Consciousness is necessarily lost.
A complex partial seizure is a seizure of focal onset that involves areas that impair consciousness. The patient often appears dazed or confused and remembers only a part of the seizure (if at all).
Myoclonic seizure is a brief generalized seizure that may be so brief as to produce a motor jerk (myoclonus) but no actual loss of consciousness.
Petit mal seizure is a brief generalized seizure that interrupts consciousness but which does not result in motor symptoms (outside of, possibly, some eyelid fluttering). It may happen hundreds of times a day.
Simple partial seizure is a seizure from portions of the cerebral cortex having very specific functions (i.e., motor, sensory, visual, olfactory, auditory), such that the auras are easily explained.
Focal seizure is another name for a partial seizure. It arises from a specific seizure focus in the cerebral cortex. This may be a scar or an irritated area around a tumor or other cortical lesion.
Secondary generalization is the spread of a focal seizure to involve the entire brain.
Status epilepticus is a medical emergency that consists of continuous or recurrent seizures over at least 30 minutes without waking up in between.
The postictal period is a period of cortical depression following a seizure.
Interictal refers to the period between seizures.
Todd's paralysis is a period of focal weakness after a seizure due to a prolonged postictal period in a region of cerebral cortex. This may give clues to the side and location of a seizure focus.
Hippocampal sclerosis is scarring of the hippocampus. This is a common cause of temporal lobe epilepsy and occurs early in life. It is often associated with prolonged febrile convulsions in early childhood.
Temporal lobe epilepsy indicates an epilepsy with a seizure focus in the temporal lobe.
A seizure focus is an area of abnormal electrical excitability in the cerebral cortex.

22-1. What is epilepsy?

22-1. Epilepsy is the tendency to have seizures in the absence of provocations that would cause the normal brain to have a seizure.

22-2. What are primarily generalized seizures?

22-2. In primary generalized seizures, seizure activity is visible in all areas of cortex simultaneously (there is no clinical warning - aura).

22-3. What are potential causes of primary generalized seizures?

22-3. They may be genetic and are commonly provoked by severe metabolic upset (electrolyte disturbance, organ failure, hypoglycemia, hypoxia, sedative/alcohol withdrawal, etc).

22-4. Does epilepsy last a lifetime?

22-4. Some of the primary epilepsies presenting in childhood may be outgrown.

22-5. What is the usual description of a generalized seizure?

22-5. A common pattern is for tonic-clonic seizures with tonic extension (usually) followed by clonic (alternating jerks of synchronous activity of flexors and extensors and grunting respirations). There is usually autonomic upset - pupils large, hyperthermia, tachycardia, salivation, often emptying of bladder. It is terminated by inhibitory transmitters that result in postictal period of dense stupor or coma.

22-6. What is a petit mal (absence) seizure?

22-6. A petit mal (absence) seizure is a specific pattern of generalized convulsion - brief (usually seconds); no movement (except maybe eye blink or lip movement), no loss of tone; no memory for time; no postictal period; it is most common in children and may be "outgrown."

22-7. What is a myoclonic seizure?

22-7. A myoclonic seizure is a brief, generalized seizure often resulting in myoclonic jerks. It may secondarily generalize and may be part of epileptic syndrome (juvenile myoclonic epilepsy)

22-8. What are partial seizures?

22-8. Focal (partial) seizures - a part of localization-related epilepsy with a focus of onset of seizures.

22-9. What is a simple partial seizure?

22-9. Simple partial seizures are seizures of focal onset with preserved consciousness. They begin in an abnormally excitable portion of the cortex and will have an aura if they don't spread too quickly; aura depends on location.

22-10. What is a complex partial seizure?

22-10. Complex partial seizures are seizures of focal onset with clouded consciousness. These also often have an aura but may not be remembered.

22-11. What are common auras of complex partial seizures arising in the temporal lobes?

22-11. Fear and a rising abdominal sensation is a common temporal lobe aura. A (usually) bad smell may be perceived, as well.

22-12. What is secondary generalization?

22-12. Secondary generalization is a spread to involve surrounding areas of brain; may secondarily generalize by unclear mechanisms that can involve the corpus callosum and brain stem or thalamic levels. The secondary generalization usually results in a tonic-clonic seizure.

22-13. What is status epilepticus?

22-13. Status epilepticus is a medical emergency that consists of continuous or recurrent seizures over 30 minutes without waking up in between.

22-14. What are common causes of status epilepticus?

22-14. Status epilepticus is often due to sedative withdrawal or discontinuation of anticonvulsants by patients with known epilepsy. It may also result from severe metabolic upset.

22-15. Why is status epilepticus an emergency?

22-15. Status epilepticus may result in respiratory failure, lactic acidosis, aspiration, erratic changes in blood pressure, hyperthermia and death.

22-16. What can be done in order to evaluate epilepsy?

22-16. The EEG may be helpful but is often normal in the interictal period. An MRI scan is particularly good at demonstrating abnormal seizure foci (such as hippocampal sclerosis, small tumors, developmental abnormalities, arteriovenous malformations, etc).

22-17. What are "non-epileptic" seizures?

22-17. A significant number of patients diagnosed with epilepsy do not have epileptic seizures - many of these are psychiatric in nature though other causes of loss of consciousness (such as syncope) must be considered. They may be hysterical, conversion reactions or voluntary.

22-18. What are the available therapies for epilepsy?

22-18. Anticonvulsants are the mainstay of therapy for epilepsy. These give good control in 80% and excellent control in 50%. Some anticonvulsants are particular good at treating specific epileptic syndromes. Surgery may help when focus is identified. Callosotomy may cut down on generalization in hard to control cases.