A patient who is being treated for temporal lobe epilepsy (complex partial seizures) and who is having recurrent seizures on his chronic regimen of carbamazepine is given phenobarbital as a second drug. However, the seizures increase in frequency. What is the probable reason for the apparent deleterious effect of adding phenobarbital: (AIIMS Nov 2009)
|A||Intracerebral bleeding from worsening bone marrow suppression|
|B||Decreased carbamazepine level|
|C||Decreased stability of CNS neuronal membranes|
Decreased carbamazepine level
PARTIAL SEIZURES – Seizure activity is restricted to discrete areas of cerebral cortex. Partial seizures are often associated with structural abnormalities of the brain. In such case CT/MRI of brain is mandatory.
1). Simple partial seizure – The consciousness is fully preserved during the seizure simple partial seizure cause motor, sensory autonomic or psychic symptoms.
2). Complex partial seizure (Temporal lobe epilepsy) – Focal seizure activity accompanied by a transient impairment of patient’s ability to maintain normal contact with the environment. Automatism is a feature of CPS.
3). Partial seizures with secondary generalization – Partial seizure can spread to involve both hemisphere and produce generalized seizure. Aura is an important feature. It is frequently observed following simple partial seizure.
Jacksonian march – Movements begin in a very restricted region and gradually progress to include a larger area.
Todd’s paralysis – Localized paresis in the involved region.
Epilepsia partialis continua – Seizure activity continue for hours – days.
1). Generalized Seizures – Arise from both cerebral hemisphere simultaneously. Result from cellular, biochemical or structural abnormalities.
Characteristic features of Absence seizures / Petit mal seizures:
a. Almost always begin in childhood and cease by age of 20.
b. Sudden brief lapses of consciousness without loss of postural control
c. Seizure typically lasts only for seconds. Impairment is so brief that patient may be unaware of it.
d. Consciousness returns as suddenly as it was lost i.e. onset and termination of attack, both are abrupt.
e. Usually accompanied by subtle bilateral motor signs such as
i. Rapid blinking of eye lids
ii. Chewing movements
iii. Small amplitude, clonic movements of hands
f. There is no postictal confusion
g. The seizure can occur hundreds of times per day.
h. First clue to absence seizure is often unexplained 'day dreaming' and a decline in school performance recognized by a teacher.
a. Electrophysiological hallmark of typical absence seizure is a generalized symmetric, 3 Hz spike and wave discharge that begins and ends suddenly superimposed on a normal EEG background.
b. Hyperventilation tends to provoke these electrographic discharges and even the seizures themselves.
2). Atypical absence seizure –Lapse of consciousness is longer duration, less abrupt in onset and cessation.
EEG ≤ 2.5HZ.
Mental retardation positive
3). Atonic seizures – Loss of postural muscle tone lasting 1 to 2 second.
Consciousness is briefly impaired but there is no post ictal confusion.
Ranging from quick head drop to collapse.
EEG → Brief generalized spike and wave discharge followed by diffuse slow waves that correlate with loss of ms. tone.
4). Myoclonic seizures – Sudden and brief muscle contraction that may involve one part of the body or the entire body.
Causes – Metabolic disorders, degenerative CNS disorder, Anoxic brain damage. Creutzfeldt Jacob disease. Myoclonus may occur in normal person also.
EEG → B/L Synchronous spike and wave discharges.
5). GTCS (Generalized Tonic Clonic Seizure)