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Epilepsy

Is a group of disorders characterised by behavioural consequences of recurrent, spontaneous paroxysms of abnormal brain activity. The epileptic attack or seizure, the common denominator of all these conditions, may appear as impaired consciousness, involuntary movement, autonomic disturbance or psychic or sensory disturbance.

Definitions

• Epileptic seizure: An episodic, uncontrollable, abnormal motor, sensory or psychological behavior caused by abnormal electrochemical activity in the cerebrum.
• Epilepsy: A chronic condition characterized by repetitive seizures.

Types of seizures

1. Reactive seizure: Occur in predisposed patients a variety of sensory stimuli can precipitate reflex epilepsy. E.g. video games (valproic acid is most effective).
2. 1ry epilepsy: These usually reflect an underlying genetic predisposition.
3. 2ry acquired epilepsy: Seizures result from a known structural or metabolic disease of the brain.
4. Hysterical seizures: Seizures have no organic cause, they usually occur in the presence of others. They never occur at sleep, the subject never hurts himself, there are never attacks of urinary incontinence. EEG normal, antiepileptic drugs are contraindicated.

Pathophysiology

Most focal seizures are a result of pathologic excitation of specific parts of the cerebral hemisphere. Most often they originate in association with anatomically restricted lesions of gray matter such as scars, tumors, arteriovenous malformations, or focal areas of inflammation.

Generalized seizures by contrast, express themselves with bilateral motor abnormalities, usually accompanied by a brief loss of consciousness. They reflect either a diffuse hyperexcitable propensity of brain cells or the presence of a deeply lying, cryptic epileptogenic abnormality that involves centrally located subcortical activating mechanisms.

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Clinical pictures

Incidence: Recurrent seizures occur in 2-4% of all people in developed and 4-8% in 3rd world. They can occur at any age and the clinical manifestations are related to the seizure pattern.

Classification of epileptic seizure patterns

Partial seizures consist of repetitive attacks of uncontrollable, focal neurologic dysfunction. The attacks are described as simple if only a restricted form of behavior or experience is expressed (equivalent to the aura) and consciousness remains intact. Attacks are complex if the pattern of neurologic symptoms and signs evolves or if the patient's consciousness is impaired or lost. The initiating signs and symptoms offer the best clinical localizing evidence for the brain area that contains the epileptogenic lesions.

I. Partial Seizures

1. Partial Simple Seizures

a. Partial Simple Motor Seizures

1ry motor (Jacksonian- with march / without march). The march presents as a rhythmic, clonic twitching with begins in the opposite thumb and spreads gradually to the hand, arm and face. Occaisionally the spread happens in the opposite direction.

Premotor, supplementary motor, prefrontal partial motor seizure lead to complex focal motor manifestations.

b. Partial Simple Sensory Seizures

They usually present with the following epileptic aura.

c. Partial Simple Psychological Seizures

2. Partial Complex Seizures

Partial complex seizures are focal (simple) seizures above + loss of consciousness. The most common form arises from the limbic system - temporal lobe.

Temporal lobe epilepsy

1. Aura: gives an indication to the origin of focus (see table above).

2. Attack The attack itself can be associated with many manifestations e.g. deja vu; affective manifestations such as laughing, fear, rage; sensory manifestations such as hallucinations; motor manifestations which include lip smacking, chewing, drowsiness.

3. Post-ictal: (Following the attacks) headache or residual neurological manifestations.

4. Inter-ictal: (between attacks) obsessiveness, religiosity, hypersensitivity, hypergraphia and self-absorption.

II. Generalized Seizures

1. Nonconvulsive Generalized Seizures

• Absence (petit mal) epilepsy: Simple petit mal is a childhood disease and is characterized by a blank stare, eye blinking or brief motor jerk / enuresis for just a second. Complex petit mal is a more protracted form but rarely lasts longer than a minute.
• Atypical absence: a childhood disease characterized by atypical EEG and less benign clinical course.
• Atonic epilepsy: a childhood disease, characterized by a sudden brief loss of tone - dropping of head / complete collapse.
• Myoclonic epilepsy: This is characterized by a rapid jerk of the whole body or part of the body. DD from non-epileptic myoclonus (which is asymmetrical - starting with one limb then another ? or induced by motor or sensory stimuli or toxic or metabolic conditions).

2. Convulsive Generalized Seizures

• Tonic - clonic (grand mal): can begin at any age. Most produce a loss of consciousness at onset, although most report a brief rising epigastric sensation as the attack begins. Prodromal warnings (not auras) sometimes precede the attacks by several hours and can include a change in mood, a sense of apprehension, insomnia, or a loss of appetite. As the convulsion begins, patients stiffen tonically in extension, usually with muscles contracted so tightly as to arrest breathing. Deep cyanosis follows before relaxation and the patient starts breathing again. This usually lasts as long as a minute. The hyperextension phase (above) gradually gives way to a series of rapid successive clonic jerks of the neck, trunk, and extremities. Finally a flaccid relaxation ensues.
• Tonic only
• Clonic only

III. Atypical or unclassified Seizures

These usually do not impair consciousness.

• Paroxysmal tonic spasms
• Spinal myoclonus

DD hysterical seizures ask about tongue biting, falling with injury, spontaneous micturition, during sleep and not in front of an audience.

Diagnosis

1.     History: if aura, focal lesion then partial seizures
if only generalized convulsions then generalized

2.     EEG: interictal changes are highly suggestive

EEG is the single most useful investigation showing characteristic spike and wave discharges.

Treatment

Therapeutic goal:

To achieve complete seizure control with complete prevention of recurrence with absent or minimal drug toxicity.

1.     Epilepsy is treated only when it happens more than once or when it is secondary to a cause that suggests future recurrence.

2.     If repeated seizures occur then diagnose the probable type and give the single preferred medication (see table 119-8) in its full recommended dose.

Indications: Ethosuximide is only used in petit mal. Carbamazipine is used as 1st choice in both partial and generalized tonic-clonic. Then valproate and phenytoin are 2nd choice (phenytoin is better in partial epilepsy than valproate) then phenobarbital.

3.     If one drug does not control seizures even at toxic levels then give the next most effective agent.

4.     If still no control then send the patient to a specialized center to treat with combined therapy. As combination therapy is hard to control and may be very toxic.

NEVER STOP ANTIEPILEPTICS FOR GENERALISED SEIZURES ABRUPTLY AS THIS MAY RESULT IN STATUS EPILEPTICUS.

A serum blood level within 3 weeks or when the dose of a drug is changed then is helpful to tell if patient is in the therapeutic range.

On succeeding in controlling seizures a serum blood level is obtained only annually.

When to stop:

Either due to ineffective treatment (rare)

Or complete control for a long time: 2 years in absence and 3 for all others.

20-50% relapse specific risk factors include (difficult control initially or long initial interval of convulsions e.g. 6 months, a moderately abnormal EEG).

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