eMedicine Specialties > Neurology > Seizures and Epilepsy

Seizures and Epilepsy, Overview and Classification: Differential Diagnoses & Workup

Author: Jose E Cavazos, MD, PhD, Associate Professor with Tenure, Departments of Neurology, Pharmacology, and Physiology, University of Texas Health Science Center at San Antonio; Co-Director, South Texas Comprehensive Epilepsy Center; Director of the Epilepsy Center, Audie L Murphy Veterans Affairs Medical Center
Coauthor(s): Mark Spitz, MD, Professor, Department of Neurology, University of Colorado Health Sciences Center
Contributor Information and Disclosures

Updated: Jan 29, 2009

Differential Diagnoses

Cardioembolic Stroke
Idiopathic Orthostatic Hypotension and other Autonomic Failure Syndromes
Confusional States and Acute Memory Disorders
Migraine Headache
Febrile Seizures
Somnambulism (Sleep Walking)
First Seizure in Adulthood: Diagnosis and Treatment
Transient Global Amnesia
First Seizure: Pediatric Perspective
Frontal Lobe Epilepsy

Other Problems to Be Considered

Syncope (eg, cardiac arrhythmia, vasovagal syncope, dysautonomia)
Metabolic conditions (eg, hypoglycemia)
Migraine (eg, migrainous aura, migraine equivalent)
Vascular conditions (eg, transient ischemic attacks)
Sleep disorder (eg, cataplexy, narcolepsy, night terror)
Movement disorder (eg, paroxysmal dyskinesia)
GI conditions (eg, esophageal reflux in neonates and infants)
Psychiatric conditions (eg, conversion, panic attacks, breath-holding
spells, malingering, secondary gain)

Workup

Laboratory Studies

  • 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.
  • 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, the present authors do not advise routine measurement of serum levels. Five recommended indications for the use of serum levels are the situations listed below.

     
    1. Baseline: After seizures are controlled, determine the drug levels needed to achieve seizure-free effectiveness.
    2. Toxicity: Determine the maximal anticonvulsant dose that the patient can tolerate without toxic effects.
    3. Lack of efficacy: Before an anticonvulsant is deemed a failure, knowing whether the patient has achieved an adequate drug level is imperative.
    4. Noncompliance: Approximately 30% of patients miss at least 1 dose of their medication every month.
    5. 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 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.

Imaging Studies

  • Two studies must be performed after a seizure: neuroimaging (eg, brain MRI, head CT scan) and EEG.
    • A neuroimaging study, such as brain MRI or head CT scan, 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. Brain MRI studies obtained at 3.0 Tesla scanners might show better resolution that conventional 1.5 T scanners, or the "open-sided" scanners of 0.5 T.
  • See Presurgical Evaluation of Medically Intractable Epilepsy for additional discussion regarding imaging studies.

Other Tests

  • Electroencephalography
    • Interictal epileptiform discharges or focal abnormalities 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.
  • Video-EEG
    • Video-EEG monitoring might be needed to establish a definitive diagnosis of spells with impairment of consciousness.
    • This test 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 monitoring is also used to characterize the type of seizure and epileptic syndrome to optimize pharmacologic treatment and for presurgical workup.

Procedures

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

Histologic Findings

Epileptic seizures have many causes. Some epileptic syndromes have specific histopathologic abnormalities. For further discussion, refer to the articles about specific epileptic syndromes listed in the Introduction.

More on Seizures and Epilepsy, Overview and Classification

Overview: Seizures and Epilepsy, Overview and Classification
Differential Diagnoses & Workup: Seizures and Epilepsy, Overview and Classification
Treatment & Medication: Seizures and Epilepsy, Overview and Classification
Follow-up: Seizures and Epilepsy, Overview and Classification
References
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Further Reading

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Keywords

spells, convulsions, attacks, seizures, epilepsy, epileptic seizures, overview of seizures and epilepsy, classification of seizures, classification of epilepsy, partial-onset seizures, generalized-onset seizures, unclassified seizures, epileptic syndromes

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Contributor Information and Disclosures

Author

Jose E Cavazos, MD, PhD, Associate Professor with Tenure, Departments of Neurology, Pharmacology, and Physiology, University of Texas Health Science Center at San Antonio; Co-Director, South Texas Comprehensive Epilepsy Center; Director of the Epilepsy Center, Audie L Murphy Veterans Affairs Medical Center
Jose E Cavazos, MD, PhD is a member of the following medical societies: American Academy of Neurology, American Clinical Neurophysiology Society, American Epilepsy Society, and Society for Neuroscience
Disclosure: Glaxo-SmithKline Honoraria Consulting; Ortho-McNeil Neurologics Honoraria Consulting; UCB Pharma Honoraria Consulting

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; ortho-mcneil Honoraria Review panel membership

Medical Editor

Ramon Diaz-Arrastia, MD, PhD, Assistant Professor, Department of Neurology, Comprehensive Epilepsy Center, University of Texas Southwestern
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.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.

Managing Editor

Selim R Benbadis, MD, Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, University of South Florida School of Medicine, Tampa General Hospital
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: Nothing to disclose.

CME Editor

Matthew J Baker, MD, Consulting Staff, Collier Neurologic Specialists, Naples Community Hospital
Matthew J Baker, MD is a member of the following medical societies: American Academy of Neurology
Disclosure: Nothing to disclose.

Chief Editor

Selim R Benbadis, MD, Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, University of South Florida School of Medicine, Tampa General Hospital
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: Nothing to disclose.

 
 
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