[WEB SITE] Epilepsy and Seizures: Practice Essentials, Background, Pathophysiology – Medscape

Epileptic seizures are only one manifestation of neurologic or metabolic diseases. Epileptic seizures have many causes, including a genetic predisposition for certain types of seizures, head trauma, stroke, brain tumors, alcohol or drug withdrawal, repeated episodes of metabolic insults, such as hypoglycemia, and other conditions.

Epilepsy and Seizures

  • Author: David Y Ko, MD; Chief Editor: Selim R Benbadis, MD  more…
Updated: Nov 19, 2015

Practice Essentials

Epilepsy is defined as a brain disorder characterized by an enduring predisposition to generate epileptic seizures and by the neurobiologic, cognitive, psychological, and social consequences of this condition.[1]

Signs and symptoms

The clinical signs and symptoms of seizures depend on the location of the epileptic discharges in the cerebral cortex and the extent and pattern of the propagation of the epileptic discharge in the brain. A key feature of epileptic seizures is their stereotypic nature.

Questions that help clarify the type of seizure include the following:

  • Was any warning noted before the spell? If so, what kind of warning occurred?
  • What did the patient do during the spell?
  • Was the patient able to relate to the environment during the spell and/or does the patient have recollection of the spell?
  • How did the patient feel after the spell? How long did it take for the patient to get back to baseline condition?
  • How long did the spell last?
  • How frequent do the spells occur?
  • Are any precipitants associated with the spells?
  • Has the patient shown any response to therapy for the spells?

See Clinical Presentation for more detail.

Diagnosis

The diagnosis of epileptic seizures is made by analyzing the patient’s detailed clinical history and by performing ancillary tests for confirmation. Physical examination helps in the diagnosis of specific epileptic syndromes that cause abnormal findings, such as dermatologic abnormalities (eg, patients with intractable generalized tonic-clonic seizures for years are likely to have injuries requiring stitches).

Testing

Potentially useful laboratory tests for patients with suspected epileptic seizures include the following:

  • Prolactin levels obtained shortly after a seizure to assess the etiology (epileptic vs nonepileptic) of a spell; levels are typically elevated 3- or 4-fold and more likely to occur with generalized tonic-clonic seizures than with other seizure types; however, the considerable variability of prolactin levels has precluded their routine clinical use
  • Serum levels of anticonvulsant agents to determine baseline levels, potential toxicity, lack of efficacy, treatment noncompliance, and/or autoinduction or pharmacokinetic change
  • CSF examination in patients with obtundation or in patients in whom meningitis or encephalitis is suspected

Imaging studies

The following 2 imaging studies must be performed after a seizure:

  • Neuroimaging evaluation (eg, MRI, CT scanning)
  • EEG

The clinical diagnosis can be confirmed by abnormalities on the interictal EEG, but these abnormalities could be present in otherwise healthy individuals, and their absence does not exclude the diagnosis of epilepsy.

Video-EEG monitoring is the standard test for classifying the type of seizure or syndrome or to diagnose pseudoseizures (ie, to establish a definitive diagnosis of spells with impairment of consciousness). This technique is also used to characterize the type of seizure and epileptic syndrome to optimize pharmacologic treatment and for presurgical workup.

See Workup for more detail.

Management

Pharmacotherapy

The goal of treatment is to achieve a seizure-free status without adverse effects. Monotherapy is important, because it decreases the likelihood of adverse effects and avoids drug interactions.

Standard of care for a single, unprovoked seizure is avoidance of typical precipitants (eg, alcohol, sleep deprivation). No anticonvulsants are recommended unless the patient has risk factors for recurrence.

Special situations that require treatment include the following:

  • Recurrent unprovoked seizures: The mainstay of therapy is an anticonvulsant; if a patient has had more than 1 seizure, administration of an anticonvulsant is recommended
  • Having an abnormal sleep-deprived EEG that includes epileptiform abnormalities and focal slowing, diffuse background slowing, and intermittent diffuse intermixed slowing

Selection of an anticonvulsant medication depends on an accurate diagnosis of the epileptic syndrome. Although some anticonvulsants (eg, lamotrigine, topiramate, valproic acid, zonisamide) have multiple mechanisms of action, and some (eg, phenytoin, carbamazepine, ethosuximide) have only one known mechanism of action, anticonvulsant agents can be divided into large groups based on their mechanisms, as follows:

  • Blockers of repetitive activation of the sodium channel: Phenytoin, carbamazepine, oxcarbazepine, lamotrigine, topiramate
  • Enhancer of slow inactivation of the sodium channel: Lacosamide, rufinamide
  • Gamma aminobutyric acid (GABA)–A receptor enhancers: Phenobarbital, benzodiazepines, clobazam
  • NMDA receptor blockers: Felbamate
  • AMPA receptor blockers: Perampanel, topiramate
  • T-calcium channel blockers: Ethosuximide, valproate
  • N- and L-calcium channel blockers: Lamotrigine, topiramate, zonisamide, valproate
  • H-current modulators: Gabapentin, lamotrigine
  • Blockers of unique binding sites: Gabapentin, levetiracetam
  • Carbonic anhydrase inhibitors: Topiramate, zonisamide
  • Neuronal potassium channel (KCNQ [Kv7]) opener: Ezogabine

Nonpharmacologic therapy

The following are 2 nonpharmacologic methods in managing patients with seizures:

  • A ketogenic diet
  • Vagal nerve stimulation

Surgical options

The 2 major kinds of brain surgery for epilepsy are palliative and potentially curative. The use of a vagal nerve stimulator (VNS) for palliative therapy in patients with intractable atonic seizures has reduced the need for anterior callosotomy. Lobectomy and lesionectomy are among several possible curative surgeries.

See Treatment and Medication for more detail.

Source: Epilepsy and Seizures: Practice Essentials, Background, Pathophysiology

 

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