eMedicine Specialties > Neurology > Seizures and Epilepsy

Frontal Lobe Epilepsy: Differential Diagnoses & Workup

Author: Sheryl Haut, MD, Director, Adult Epilepsy, Associate Professor of Clinical Neurology, Departments of Neurology, Comprehensive Epilepsy Management Center, Montefiore Medical Center, Albert Einstein College of Medicine
Contributor Information and Disclosures

Updated: May 7, 2009

Differential Diagnoses

Absence Seizures
Periodic Limb Movement Disorder
Psychogenic Nonepileptic Seizures
REM Sleep Behavior Disorder
Somnambulism (Sleep Walking)
Temporal Lobe Epilepsy

Other Problems to Be Considered

Nocturnal paroxysmal dystonia (unclear if this represents an independent entity)

Workup

Laboratory Studies

Blood tests should be performed to rule out a metabolic cause of new-onset seizures, eg, hypoglycemia or hypomagnesemia. Once the diagnosis of epilepsy is established, blood testing remains important in the management of patients who are taking anticonvulsants. Blood monitoring should be guided by the likely complications of a given anticonvulsant and, more importantly, by patient risk factors and symptoms.

  • Complete blood cell count: Monitor for neutropenia and thrombocytopenia.
  • Liver function tests
  • Anticonvulsant levels: Most anticonvulsants have a typical therapeutic window, although these levels should be used only as a guide; levels are less frequently monitored for the newer anticonvulsant agents.

Imaging Studies

  • MRI
    • The imaging modality of choice in patients with frontal lobe seizures is MRI. Recent advances in MRI have improved the identification of underlying lesions, which are reported to be present in up to 50% of patients with frontal lobe epilepsy.
    • Optimally, MRI with gadolinium should be obtained with high resolution, 1 mm thick slices, and multiple sequences. If EEG or other testing indicates a potential epileptogenic zone, thin slices through the area of interest should be requested. A field strength of 3 Tessla (3T) can further increase the identification of lesions.11
  • Position emission tomography
    • Position emission tomography is being used increasingly in the presurgical evaluation of patients with extratemporal epilepsy.
    • Interictal hypometabolism, reflective of focal dysfunction, may be seen in areas that were normal on MRI, although this finding is better established for temporal than for frontal lobe epilepsy. The role of tracer-imaging functions other than glucose metabolism, such as benzodiazepine receptors, still is being defined.
    • Decreased thalamic metabolism ipsilateral to the seizure focus may be seen in nonlesional frontal lobe epilepsy, particularly in association with a long duration of intractability.
  • Single-photon emission computed tomography
    • Ictal single-photon emission computed tomography (SPECT) scan may be obtained during prolonged video-EEG monitoring.
    • Hyperperfusion seen on ictal SPECT scan is suggestive of an area of seizure onset. Sensitivity of ictal SPECT hyperperfusion is reported to be higher in frontal lobe epilepsy than in temporal lobe epilepsy.
    • As seizures in patients with frontal lobe epilepsy are often brief and may generalize rapidly, obtaining an ictal SPECT scan is difficult.
  • Magnetic resonance spectroscopy
    • Magnetic resonance spectroscopy (MRS), while still mainly an experimental testing modality, is being increasingly used in the presurgical evaluation of intractable epilepsy.
    • MRS may demonstrate decreased NA/Cr ratios in the frontal epileptogenic zone, consistent with abnormalities of energy metabolism.

Other Tests

  • Scalp EEG and prolonged video-EEG monitoring: All patients with frontal lobe epilepsy should undergo EEG evaluation. Patients with intractable epilepsy, or in whom the diagnosis is doubtful, should undergo prolonged video-EEG monitoring. If the events are primarily or exclusively nocturnal, polysomnography should be considered, with extended EEG montages if available.
    • Interictal EEG
      • Findings may be normal.
      • Spikes or sharp waves may be absent; may appear maximal unilaterally, bilaterally, or in the midline; or may appear generalized due to secondary bilateral synchrony.
      • Background rhythm abnormalities with or without focal slowing may be present.
    • Ictal EEG
      • Closely spaced frontal electrodes can enhance localization.
      • Ictal onset often is seen poorly from the scalp and is highly variable in appearance.
      • Muscle artifact may obscure EEG.
      • Lack of ictal discharge in the temporal lobes suggests a frontal onset.
      • Video analysis of seizure semiology may suggest frontal epilepsy. Fencing posturing and lack of postictal confusion are highly suggestive.1
      • Postictal slowing also can be confirmatory, and at times, localizing or lateralizing.
      • Clinical semiology can provide lateralization information, with many unilateral movements or postures predicting a contralateral seizure onset.12
  • Intracranial EEG: Patients with suspected frontal lobe epilepsy frequently require invasive EEG monitoring. Intracranial EEG is used for localizing the epileptogenic region and for functional mapping prior to resection. Electrode coverage of both frontal and temporal (and/or parietal) lobes may be needed.
    • Stereotactically placed depth electrodes have the greatest accuracy if the area of interest is well defined, but records from a small anatomic area.
    • Subdural strips and grids have less hemorrhagic risk, sample more broadly, and can be used to perform cortical mapping, but have higher infection risk and less anatomic specificity. Epidural pegs and screws are used less often than either depth or subdural electrodes.
    • Ictal onset most often appears as a low-voltage, high-frequency discharge (ie, buzz), although rhythmic activity at alpha, theta, or delta frequencies may be seen. Because of rapid bilateral synchrony, discharge on scalp recording may appear bilateral.

Histologic Findings

Tissue from surgical resections for intractable frontal lobe epilepsy may demonstrate evidence of a developmental lesion, tumor, gliosis, or vascular malformation.

More on Frontal Lobe Epilepsy

Overview: Frontal Lobe Epilepsy
Differential Diagnoses & Workup: Frontal Lobe Epilepsy
Treatment & Medication: Frontal Lobe Epilepsy
Follow-up: Frontal Lobe Epilepsy
References
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References

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  4. So NK. Mesial frontal epilepsy. Epilepsia. 1998;39 Suppl 4:S49-61. [Medline].

  5. Kotagal P, Arunkumar GS. Lateral frontal lobe seizures. Epilepsia. 1998;39 Suppl 4:S62-8. [Medline].

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  12. Bonelli SB, Lurger S, Zimprich F, Stogmann E, Assem-Hilger E, Baumgartner C. Clinical seizure lateralization in frontal lobe epilepsy. Epilepsia. Mar 2007;48(3):517-23. [Medline].

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Further Reading

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Keywords

frontal lobe epilepsy, supplementary motor area seizures, primary motor cortex seizures, medial frontal seizures, cingulate gyrus seizures, orbitofrontal seizures, frontopolar seizures, dorsolateral cortex seizures, operculum seizures, seizure treatment, epilepsy treatment

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Contributor Information and Disclosures

Author

Sheryl Haut, MD, Director, Adult Epilepsy, Associate Professor of Clinical Neurology, Departments of Neurology, Comprehensive Epilepsy Management Center, Montefiore Medical Center, Albert Einstein College of Medicine
Sheryl Haut, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Neurology, American Clinical Neurophysiology Society, American Epilepsy Society, and American Neurological Association
Disclosure: UCB Honoraria Speaking and teaching; King Consulting fee Consulting; Jazz Consulting fee Consulting; Endo Grant/research funds Research

Medical Editor

Edward B Bromfield, MD, Associate Professor of Neurology, Faculty Member, Division of Sleep Medicine, Harvard Medical School; Chief, Division of EEG, Epilepsy and Sleep Neurology, Consulting Neurologist, Brigham and Women's Hospital
Edward B Bromfield, MD is a member of the following medical societies: American Academy of Neurology, American Clinical Neurophysiology Society, American Epilepsy Society, American Neurological Association, and Massachusetts Medical Society
Disclosure: Nothing to disclose.

Pharmacy Editor

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

Managing Editor

Jose E Cavazos, MD, PhD, FAAN, 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, FAAN 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

CME 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.

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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