Epilepsy and Seizures Workup

  • Author: Jose E Cavazos, MD, PhD, FAAN; Chief Editor: Selim R Benbadis, MD   more...
 
Updated: Dec 2, 2011
 

Approach Considerations

Two imaging studies must be performed after a seizure. They are neuroimaging evaluation (eg, brain magnetic resonance imaging [MRI], head computed tomography [CT] scanning) and electroencephalography (EEG).

Lumbar puncture for cerebrospinal fluid (CSF) examination has a role in the patient with obtundation or in patients in whom meningitis or encephalitis is suspected.

Epileptic seizures have many causes, and some epileptic syndromes have specific histopathologic abnormalities. Discussion of these abnormalities are beyond the scope of this article. For more information, see the articles about specific epileptic syndromes listed in the Background section.

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Prolactin Study

Prolactin levels obtained shortly after a seizure have been used to assess the etiology (epileptic or nonepileptic) of a spell. However, the considerable variability of prolactin levels has precluded routine clinical use of such testing. levels are typically elevated 3- or 4-fold and more likely to occur with generalized tonic-clonic seizures than with other seizure types.

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Serum Studies of Anticonvulsant Agents

Obtaining serum levels of anticonvulsants may help to improve the care for patients with seizures and epilepsy and to answer a clinical question. In practice, some authors do not advise routine measurement of serum levels. The following situations are 5 recommended indications for the use of serum levels.

  • Baseline: After seizures are controlled, determine the drug levels needed to achieve seizure-free effectiveness.
  • Toxicity: Determine the maximal anticonvulsant dose that the patient can tolerate without toxic effects.
  • Lack of efficacy: Before an anticonvulsant agent is deemed a failure, knowing whether the patient has achieved an adequate drug level is imperative.
  • Noncompliance: Approximately 30% of patients miss at least 1 dose of their medication every month.
  • Autoinduction or pharmacokinetic change: After an anticonvulsant is used for several weeks, the baseline trough serum concentration slowly decreases because of hepatic autoinduction. This phenomenon is most often seen with carbamazepine, oxcarbazepine, and lamotrigine. Adding medications might substantially change the clearance of some anticonvulsants.

Like any medical test, serum concentrations of anticonvulsants help in making clinical decisions, but the patient's individual response should be the main consideration. For example, a patient with juvenile myoclonic epilepsy (JME) might be seizure free with a valproic acid level of 30 mcg/mL, which is typically considered subtherapeutic. Therefore, clinical judgment regarding how well the patient is doing (ie, no seizures, no adverse effects) should prevail over a laboratory reading.

The usual therapeutic ranges include peak and trough levels of a group of adult patients. If the problem under study is toxicity, a peak level is desirable. However, in most circumstances, a trough level is the best indication of efficacy.

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Neuroimaging Studies

A neuroimaging study, such as brain magnetic resonance imaging (MRI) or head computed tomography (CT) scanning, provides evidence about structural abnormalities that could be the cause for a seizure.

If the patient has normal findings on neurologic examination and his or her condition (eg, cognitive, motor) returns to the usual baseline level, the preferred study is a brain MRI because of its resolution to depict subtle abnormalities.

Brain MRIs obtained with thin coronal sections by using fast spin-echo (FSE) or inversion recovery (IR) sequences from the presumed region of epileptogenic aura are useful for assessing cortical lesions, which may be amenable to potentially curative surgery.

Not every brain MRI study provides the same quality of information. Studies obtained at 3.0 Tesla scanners might show better resolution than conventional 1.5 T scanners, or the "open-sided" scanners of 0.5 T.

For more information, see Presurgical Evaluation of Medically Intractable Epilepsy regarding imaging studies.

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Electroencephalography

Interictal epileptiform discharges or focal abnormalities on electroencephalogram (EEG) strengthen the diagnosis and provide some help in determining the prognosis. Although the criterion standard for diagnosis and classification of epileptic seizures includes the interpretation of sleep-deprived EEG, the clinical history remains the cornerstone for the diagnosis of epileptic seizures.

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Video-Electroencephalography

Video-electroencephalographic (EEG) monitoring is the criterion standard for classifying the type of seizure or syndrome or to diagnose pseudoseizures; that is to establish a definitive diagnosis of spells with impairment of consciousness. This study can be performed to rule out an epileptic etiology with a high degree of confidence if the patient has demonstrable impairment of consciousness during the spell in question. Video-EEG is also used to characterize the type of seizure and epileptic syndrome to optimize pharmacologic treatment and for presurgical workup.

However, video-EEG monitoring is an expensive and laborious study; therefore, monitoring all patients is impractical. Only those whose condition does not respond to treatment should undergo video-EEG. Referral to an epilepsy center should be reserved for patients whose seizures are refractory to treatment. Some frontal-lobe seizures are considered pseudoseizures for many years until appropriate diagnosis is made by means of video-EEG.

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Contributor Information and Disclosures
Author

Jose E Cavazos, MD, PhD, FAAN  Associate Professor with Tenure, Departments of Neurology, Pharmacology, and Physiology, Program Director of the Clinical Neurophysiology Fellowship, University of Texas School of Medicine at San Antonio; Co-Director, South Texas Comprehensive Epilepsy Center, University Hospital System; Director of the San Antonio Veterans Affairs Epilepsy Center of Excellence and Neurodiagnostic Centers, Audie L Murphy Veterans Affairs Medical Center

Jose E Cavazos, MD, PhD, FAAN is a member of the following medical societies: American Academy of Neurology, American Clinical Neurophysiology Society, American Epilepsy Society, and American Neurological Association

Disclosure: GXC Global, Inc. Intellectual property rights Medical Director - company is to develop a seizure detecting device. No conflict with any of the eMedicine articles that I wrote or edited.

Coauthor(s)

Mark Spitz, MD  Professor, Department of Neurology, University of Colorado Health Sciences Center

Mark Spitz, MD is a member of the following medical societies: American Academy of Neurology, American Clinical Neurophysiology Society, and American Epilepsy Society

Disclosure: pfizer Honoraria Speaking and teaching; ucb Honoraria Speaking and teaching; lumdbeck Honoraria Consulting

Chief Editor

Selim R Benbadis, MD  Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, Tampa General Hospital, University of South Florida College of Medicine

Selim R Benbadis, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, American Clinical Neurophysiology Society, American Epilepsy Society, and American Medical Association

Disclosure: UCB Pharma Honoraria Speaking, consulting; Lundbeck Honoraria Speaking, consulting; Cyberonics Honoraria Speaking, consulting; Glaxo Smith Kline Honoraria Speaking, consulting; Pfizer Honoraria Speaking, consulting; Sleepmed/DigiTrace Honoraria Speaking, consulting

Additional Contributors

Ramon Diaz-Arrastia, MD, PhD Professor, Department of Neurology, University of Texas Southwestern Medical Center at Dallas, Southwestern Medical School; Director, North Texas TBI Research Center, Comprehensive Epilepsy Center, Parkland Memorial Hospital

Ramon Diaz-Arrastia, MD, PhD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Neurology, New York Academy of Sciences, and Phi Beta Kappa

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

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