INTERESTING IMAGE
Subclinical Seizures as a Pitfall in 18F-FDG PET Imaging of Temporal Lobe Epilepsy Bashir Akhavan Tafti, MD, Mark Mandelkern, MD, PhD, and Gholam Reza Berenji, MD Abstract: A 61-year-old man with history of heroin abuse, hepatitis B, hepatitis C, and hypertension was evaluated for seizures. MRI findings were concerning for temporal epilepsy. A brain 18F-FDG PET study showed a hypermetabolic focus in the left temporal lobe, although the patient was asymptomatic during the scan. Later review of electroencephalography recordings revealed a subclinical seizure during imaging. A whole-body 18F-FDG PET scan performed 4 days later for cancer screening purposes, during which the electroencephalography tracings were normal, showed no abnormal metabolic activity in the brain. Key Words: PET, epilepsy, subclinical seizure, MRI, electroencephalography (Clin Nucl Med 2014;39: 819Y821)
Received for publication June 17, 2013; revision accepted February 21, 2014. From the Department of Nuclear Medicine, Veterans Administration Greater Los Angeles Health Care System, Los Angeles, CA. Conflicts of interest and sources of funding: none declared. Reprints: Gholam Reza Berenji, MD, Department of Nuclear Medicine, Veterans Administration Greater Los Angeles Health Care System, 11301 Wilshire Blvd, Los Angeles, CA. E-mail: [email protected]. Copyright * 2014 by Lippincott Williams & Wilkins ISSN: 0363-9762/14/3909Y0819
Clinical Nuclear Medicine
REFERENCES 1. la Fouge`re C, Rominger A, Forster S, et al. PET and SPECT in epilepsy: a critical review. Epilepsy Behav. 2009;15:50Y55. 2. Kumar A, Juhasz C, Asano E, et al. Objective detection of epileptic foci by 18 F-FDG PET in children undergoing epilepsy surgery. J Nucl Med. 2010;51: 1901Y1907. 3. Kumar A, Chugani HT. The role of radionuclide imaging in epilepsy, Part 1: sporadic temporal and extratemporal lobe epilepsy. J Nucl Med. 2013;54: 1775Y1781. 4. Goffin K, Dedeurwaerdere S, Van Laere K, et al. Neuronuclear assessment of patients with epilepsy. Semin Nucl Med. 2008;38:227Y239. 5. Siclari F, Prior JO, Rossetti AO. Ictal cerebral positron emission tomography (PET) in focal status epilepticus. Epilepsy Res. 2013;105:356Y361. 6. Stayman A, Abou-Khalil B. FDG-PET in the diagnosis of complex partial status epilepticus originating from the frontal lobe. Epilepsy Behav. 2011;20:721Y724. 7. Bilo L, Meo R, de Leva MF, et al. Thalamic activation and cortical deactivation during typical absence status monitored using [18F]FDG-PET: a case report. Seizure. 2010;19:198Y201. 8. Sperling MR, Alavi A, Reivich M, et al. False lateralization of temporal lobe epilepsy with FDG positron emission tomography. Epilepsia. 1995;36:722Y727.
& Volume 39, Number 9, September 2014
www.nuclearmed.com
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
819
Clinical Nuclear Medicine
Tafti et al
& Volume 39, Number 9, September 2014
FIGURE 1. Mildly motion-degraded axial T2 fluid-attenuated inversion recovery images demonstrate hyperintensity involving the left anterior medial temporal lobe and nearly the entire left hippocampus. No definite abnormal enhancements were noted after contrast administration. Differential diagnosis included changes secondary to recent seizure, underlying inflammatory/ infectious etiology such as herpes encephalitis, unusual appearance of recent ischemic injury, and less likely, an underlying neoplastic process such as glioma.
FIGURE 2. Axial 18F-FDG PET images demonstrating a focus of intense FDG uptake in the left temporal lobe, corresponding to the area of abnormality noted in MRI examination. Approximately, 20% to 30% of patients with epilepsy do not respond to antiepileptic medications, and surgery has proved to be an acceptable alternative for treating patients with intractable focal seizures.1,2 Accurate identification of the epileptogenic focus is of utmost importance for maximizing the chance of operational success and minimizing the risk of complications.1,2 Functional imaging modalities such as PET play an important role in this context.1,2 18F-FDG is the most widely used radiopharmaceutical in PET imaging with good sensitivity and specificity for detection of epileptogenic foci in temporal lobe seizures.1,2 Nevertheless, application of 18F-FDG PET in epilepsy is associated with certain limitations. Most notably, it cannot be routinely performed for imaging in the ictal state because of the relative short half-life of the 18 F label and the unpredictability of seizures.1 In fact, potential epileptogenic zones are usually defined as cortical areas of hypometabolism in interictal 18F-FDG PET images,3,4 although direct visualization of hypermetabolic epileptic foci has been reported in a few cases of focal status epilepticus,5 complex partial status epilepticus,6 and absence status.7 Another rare but important pitfall in visual interpretation of interictal 18F-FDG PET images is the presence of asymptomatic subclinical seizure activity, which may result in false lateralization of an epileptic focus, as previously reported by Sperling et al.8 Here we present another case of a completely asymptomatic patient, whose concurrent electroencephalography (EEG) tracings revealed subclinical epileptic activity during imaging. These cases emphasize the importance of correlating 18F-FDG PET findings on other diagnostic modalities such as EEG and MRI. 820
www.nuclearmed.com
* 2014 Lippincott Williams & Wilkins
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Clinical Nuclear Medicine
& Volume 39, Number 9, September 2014
Seizures in Temporal Epilepsy PET Imaging
FIGURE 3. Tomographic images obtained 4 days later demonstrated interval resolution of the previously noted focus of avid FDG uptake in the left anterior mesial temporal lobe and hippocampus, further confirming a subclinical seizure as the underlying cause for transient focal intense 18F-FDG uptake. There was no evidence of abnormal electrical activity in the EEG recordings during the latter examination. No new regions of abnormal FDG activity were identified within the brain parenchyma. Of note, interval laboratory workup was not suggestive of an active inflammatory/infectious process, and the patient had not received anti-inflammatory treatment (eg, steroids) between the 2 studies.
* 2014 Lippincott Williams & Wilkins
www.nuclearmed.com
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
821
Subclinical Seizures as a Pitfall in 18F-FDG PET Imaging of Temporal Lobe Epilepsy Bashir Akhavan Tafti, MD, Mark Mandelkern, MD, PhD, and Gholam Reza Berenji, MD Abstract: A 61-year-old man with history of heroin abuse, hepatitis B, hepatitis C, and hypertension was evaluated for seizures. MRI findings were concerning for temporal epilepsy. A brain 18F-FDG PET study showed a hypermetabolic focus in the left temporal lobe, although the patient was asymptomatic during the scan. Later review of electroencephalography recordings revealed a subclinical seizure during imaging. A whole-body 18F-FDG PET scan performed 4 days later for cancer screening purposes, during which the electroencephalography tracings were normal, showed no abnormal metabolic activity in the brain. Key Words: PET, epilepsy, subclinical seizure, MRI, electroencephalography (Clin Nucl Med 2014;39: 819Y821)
Received for publication June 17, 2013; revision accepted February 21, 2014. From the Department of Nuclear Medicine, Veterans Administration Greater Los Angeles Health Care System, Los Angeles, CA. Conflicts of interest and sources of funding: none declared. Reprints: Gholam Reza Berenji, MD, Department of Nuclear Medicine, Veterans Administration Greater Los Angeles Health Care System, 11301 Wilshire Blvd, Los Angeles, CA. E-mail: [email protected]. Copyright * 2014 by Lippincott Williams & Wilkins ISSN: 0363-9762/14/3909Y0819
Clinical Nuclear Medicine
REFERENCES 1. la Fouge`re C, Rominger A, Forster S, et al. PET and SPECT in epilepsy: a critical review. Epilepsy Behav. 2009;15:50Y55. 2. Kumar A, Juhasz C, Asano E, et al. Objective detection of epileptic foci by 18 F-FDG PET in children undergoing epilepsy surgery. J Nucl Med. 2010;51: 1901Y1907. 3. Kumar A, Chugani HT. The role of radionuclide imaging in epilepsy, Part 1: sporadic temporal and extratemporal lobe epilepsy. J Nucl Med. 2013;54: 1775Y1781. 4. Goffin K, Dedeurwaerdere S, Van Laere K, et al. Neuronuclear assessment of patients with epilepsy. Semin Nucl Med. 2008;38:227Y239. 5. Siclari F, Prior JO, Rossetti AO. Ictal cerebral positron emission tomography (PET) in focal status epilepticus. Epilepsy Res. 2013;105:356Y361. 6. Stayman A, Abou-Khalil B. FDG-PET in the diagnosis of complex partial status epilepticus originating from the frontal lobe. Epilepsy Behav. 2011;20:721Y724. 7. Bilo L, Meo R, de Leva MF, et al. Thalamic activation and cortical deactivation during typical absence status monitored using [18F]FDG-PET: a case report. Seizure. 2010;19:198Y201. 8. Sperling MR, Alavi A, Reivich M, et al. False lateralization of temporal lobe epilepsy with FDG positron emission tomography. Epilepsia. 1995;36:722Y727.
& Volume 39, Number 9, September 2014
www.nuclearmed.com
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
819
Clinical Nuclear Medicine
Tafti et al
& Volume 39, Number 9, September 2014
FIGURE 1. Mildly motion-degraded axial T2 fluid-attenuated inversion recovery images demonstrate hyperintensity involving the left anterior medial temporal lobe and nearly the entire left hippocampus. No definite abnormal enhancements were noted after contrast administration. Differential diagnosis included changes secondary to recent seizure, underlying inflammatory/ infectious etiology such as herpes encephalitis, unusual appearance of recent ischemic injury, and less likely, an underlying neoplastic process such as glioma.
FIGURE 2. Axial 18F-FDG PET images demonstrating a focus of intense FDG uptake in the left temporal lobe, corresponding to the area of abnormality noted in MRI examination. Approximately, 20% to 30% of patients with epilepsy do not respond to antiepileptic medications, and surgery has proved to be an acceptable alternative for treating patients with intractable focal seizures.1,2 Accurate identification of the epileptogenic focus is of utmost importance for maximizing the chance of operational success and minimizing the risk of complications.1,2 Functional imaging modalities such as PET play an important role in this context.1,2 18F-FDG is the most widely used radiopharmaceutical in PET imaging with good sensitivity and specificity for detection of epileptogenic foci in temporal lobe seizures.1,2 Nevertheless, application of 18F-FDG PET in epilepsy is associated with certain limitations. Most notably, it cannot be routinely performed for imaging in the ictal state because of the relative short half-life of the 18 F label and the unpredictability of seizures.1 In fact, potential epileptogenic zones are usually defined as cortical areas of hypometabolism in interictal 18F-FDG PET images,3,4 although direct visualization of hypermetabolic epileptic foci has been reported in a few cases of focal status epilepticus,5 complex partial status epilepticus,6 and absence status.7 Another rare but important pitfall in visual interpretation of interictal 18F-FDG PET images is the presence of asymptomatic subclinical seizure activity, which may result in false lateralization of an epileptic focus, as previously reported by Sperling et al.8 Here we present another case of a completely asymptomatic patient, whose concurrent electroencephalography (EEG) tracings revealed subclinical epileptic activity during imaging. These cases emphasize the importance of correlating 18F-FDG PET findings on other diagnostic modalities such as EEG and MRI. 820
www.nuclearmed.com
* 2014 Lippincott Williams & Wilkins
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Clinical Nuclear Medicine
& Volume 39, Number 9, September 2014
Seizures in Temporal Epilepsy PET Imaging
FIGURE 3. Tomographic images obtained 4 days later demonstrated interval resolution of the previously noted focus of avid FDG uptake in the left anterior mesial temporal lobe and hippocampus, further confirming a subclinical seizure as the underlying cause for transient focal intense 18F-FDG uptake. There was no evidence of abnormal electrical activity in the EEG recordings during the latter examination. No new regions of abnormal FDG activity were identified within the brain parenchyma. Of note, interval laboratory workup was not suggestive of an active inflammatory/infectious process, and the patient had not received anti-inflammatory treatment (eg, steroids) between the 2 studies.
* 2014 Lippincott Williams & Wilkins
www.nuclearmed.com
Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
821
