Visually sensitive seizures: An updated review by the Epilepsy Foundation.

Light flashes, patterns, or color changes can provoke seizures in up to 1 in 4000 persons. Prevalence may be higher because of selection bias. The Epilepsy Foundation reviewed light-induced seizures in 2005. Since then, images on social media, virtual reality, three-dimensional (3D) movies, and the Internet have proliferated. Hundreds of studies have explored the mechanisms and presentations of photosensitive seizures, justifying an updated review. This literature summary derives from a nonsystematic literature review via PubMed using the terms "photosensitive" and "epilepsy." The photoparoxysmal response (PPR) is an electroencephalography (EEG) phenomenon, and photosensitive seizures (PS) are seizures provoked by visual stimulation. Photosensitivity is more common in the young and in specific forms of generalized epilepsy. PS can coexist with spontaneous seizures. PS are hereditable and linked to recently identified genes. Brain imaging usually is normal, but special studies imaging white matter tracts demonstrate abnormal connectivity. Occipital cortex and connected regions are hyperexcitable in subjects with light-provoked seizures. Mechanisms remain unclear. Video games, social media clips, occasional movies, and natural stimuli can provoke PS. Virtual reality and 3D images so far appear benign unless they contain specific provocative content, for example, flashes. Images with flashes brighter than 20 candelas/m2 at 3-60 (particularly 15-20) Hz occupying at least 10 to 25% of the visual field are a risk, as are red color flashes or oscillating stripes. Equipment to assay for these characteristics is probably underutilized. Prevention of seizures includes avoiding provocative stimuli, covering one eye, wearing dark glasses, sitting at least two meters from screens, reducing contrast, and taking certain antiseizure drugs. Measurement of PPR suppression in a photosensitivity model can screen putative antiseizure drugs. Some countries regulate media to reduce risk. Visually-induced seizures remain significant public health hazards so they warrant ongoing scientific and regulatory efforts and public education.

Lateralized hyperkinetic motor behavior.

Seizures are followed by a post-ictal period, which is characterized by usual slowing of brain activity. This case report describes a 68-year old woman who presented with right-sided rhythmic, non-voluntary, semi-purposeful motor behavior that started 2 days after an episode of generalized seizure. Her initial electroencephalogram (EEG) showed beta activity with no evidence of epileptiform discharges. Computed tomography scan showed hypodensity in the left parieto-occipital region. Magnetic resonance imaging (MRI) showed restricted diffusion/fluid-attenuated inversion recovery hyperintensities in the left precentral and post-central gyrus. Unilateral compulsive motor behavior during the post-ictal state should be considered, and not confused with partial status epilepticus to avoid unnecessary treatment. Abnormal magnetic resonance imaging (MRI) findings, which are reversible, can help with the diagnostic and therapeutic approach.

Neurophysiology of Juvenile and Progressive Myoclonic Epilepsy.

SUMMARY: Myoclonus can be epileptic or nonepileptic. Epileptic myoclonus has been defined in clinical, neurophysiological, and neuroanatomical terms. Juvenile myoclonic epilepsy (JME) is typically considered to be an adolescent-onset idiopathic generalized epilepsy with a combination of myoclonic, generalized tonic-clonic, and absence seizures and normal cognitive status that responds well to anti-seizure medications but requires lifelong treatment. EEG shows generalized epileptiform discharges and photosensitivity. Recent observations indicate that the clinical picture of JME is heterogeneous and a number of neuropsychological and imaging studies have shown structural and functional abnormalities in the frontal lobes and thalamus. Advances in neurophysiology and imaging suggest that JME may not be a truly generalized epilepsy, in that restricted cortical and subcortical networks appear to be involved rather than the entire brain. Some patients with JME may be refractory to anti-seizure medications and attempts have been made to identify neurophysiological biomarkers predicting resistance. Progressive myoclonic epilepsy is a syndrome with multiple specific causes. It is distinct from JME because of the occurrence of progressive neurologic dysfunction in addition to myoclonus and generalized tonic-clonic seizures but may sometimes be difficult to distinguish from JME or misdiagnosed as drug-resistant JME. This article provides an overview of progressive myoclonic epilepsy and focuses on the clinical and neurophysiological findings in the two most commonly recognized forms of progressive myoclonic epilepsy-Unverricht-Lundborg disease (EPM1) and Lafora disease (EPM2). A variety of neurophysiological tests can be used to distinguish between JME and progressive myoclonic epilepsy and between EPM1 and EPM2.

Minimum Technical Requirements for Performing Ambulatory EEG.

SUMMARY: Ambulatory EEG (AEEG) devices offer portable, multichannel, digital EEG recording with or without video in the patient's natural environment. The technology applied for AEEG recording is like the technology for routine EEG and inpatient long-term video-EEG monitoring but designed to be compact and wearable. Computer-based AEEG technology is well-suited to digital recording, signal processing, and visual display. However, acquiring interpretable EEG outside of the hospital setting presents its own technical challenges. Published guidelines have established technical standards for performing routine EEG and inpatient video-EEG monitoring, but technical standards for AEEG are lacking. Therefore, this guideline provides minimal technical standards for the performance of AEEG which are essential to ensure the quality of studies for clinical and research practice. We expect these minimum standards to evolve over time with improved performance and advances in the technology.

The Impact of COVID-19 on Epilepsy Care: A Survey of the American Epilepsy Society Membership.

The COVID-19 pandemic has impacted the delivery of care to people with epilepsy (PWE) in multiple ways including limitations on in-person contact and restrictions on neurophysiological procedures. To better study the effect of the pandemic on PWE, members of the American Epilepsy Society were surveyed between April 30 and June 14, 2020. There were 366 initial responses (9% response rate) and 337 respondents remained for analysis after screening out noncompleters and those not directly involved with clinical care; the majority were physicians from the United States. About a third (30%) of respondents stated that they had patients with COVID-19 and reported no significant change in seizure frequency. Conversely, one-third of respondents reported new onset seizures in patients with COVID-19 who had no prior history of seizures. The majority of respondents felt that there were at least some barriers for PWE in receiving appropriate clinical care, neurophysiologic procedures, and elective surgery. Medication shortages were noted by approximately 30% of respondents, with no clear pattern in types of medication involved. Telehealth was overwhelmingly found to have value. Among the limitation of the survey was that it was administered at a single point in time in a rapidly changing pandemic. The survey showed that almost all respondents were affected by the pandemic in a variety of ways.

Ondansetron and seizures.

Experimental studies suggest that 5-hydroxytryptamine (5-HT) receptors play a role in epileptogenesis and seizure propagation. Ondansetron, a 5-HT(3) receptor antagonist, has been reported to have proconvulsant and anticonvulsant effects in animals. We describe three patients who developed seizures after receiving ondansetron. There were two females and one male. Ages ranged from 38-56 years. None had a previous or family history of seizures. Four milligrams (mg) of ondansetron was given intravenously for severe nausea and vomiting in association with migraine, gastritis, and diabetic ketoacidosis. A generalized tonic-clonic seizure occurred in each patient--12, 15, and 22 min after injection. Brain magnetic resonance imaging (MRI) and electroencephalography (EEG) were normal in all patients. Although no antiepileptic drugs were given, none had seizure recurrence subsequently. The temporal relationship between ondansetron administration and seizures, lack of EEG or MRI abnormalities, and absence of seizure recurrence suggest that the seizures were causally related to ondansetron in our patients.

Overview of EEG Montages and Principles of Localization.

Montages are logical, orderly arrangements of electroencephalographic derivations or channels that are created to display activity over the entire head and to provide lateralizing and localizing information. Most often, bipolar and referential montages are used for routine electroencephalographic recordings. Common average and Laplacian montages can also be helpful in some situations. Because each type of montage has certain strengths and limitations, the ACNS guidelines recommend the use of multiple classes of montages for each electroencephalographic recording. A variety of factors need to be considered for localization by scalp electroencephalogram, but in clinical practice, a three-step approach can be used to localize an interictal epileptiform discharge by visual inspection using a standard set of scalp electrodes and conventional montages. The ACNS guideline provides a number of standard and suggested montages, but, depending on the clinical situation, additional montages can be designed using the electrodes within the 10-20 system or by placing additional electrodes.

Corrigendum to "A revised glossary of terms most commonly used by clinical electroencephalographers and updated proposal for the report format of the EEG findings. Revision 2017" [Clin. Neurophysiol. Practice 2 (2017) 170-185].

[This corrects the article DOI: 10.1016/j.cnp.2017.07.002.].

Neurologic complications of hepatitis C.

BACKGROUND: Hepatitis C virus (HCV) infection is a common and chronic disorder with numerous extrahepatic manifestations. We review the neurologic complications in this article. REVIEW SUMMARY: Neurologic complications can involve the peripheral or the central nervous system. The most frequently reported complication is a subacute, distal, symmetric, sensorimotor polyneuropathy in the presence of mixed cryoglobulinemia (MC). HCV infection is the most common cause of MC. In HCV-infected patients without MC, mononeuropathy or mononeuropathy multiplex is more common. Both ischemic and hemorrhagic strokes, probably related to MC and vasculitis, have been described. More recently, transverse myelopathy and cognitive impairment have been linked to HCV infection, but the association is less certain and needs to be confirmed in larger studies. HCV has also been reported as a possible cause of encephalomyelitis in some cases. Although there are no definite treatment guidelines, immunomodulating agents and antiviral therapy are most often used with favorable outcomes. CONCLUSIONS: HCV infection should be considered in the differential diagnosis of a variety of neurologic disorders. Further studies are necessary to establish the full spectrum of the neurologic complications, identify specific pathophysiologic mechanisms, and provide clear guidelines for management.

Normalized Transfer Entropy as a Tool to Identify Multisource Functional Epileptic Networks.

Epilepsy is a major health problem worldwide. A significant proportion of patients develop medication-refractory epilepsy (MRE); they are of ten evaluated for possible surgery where the focus of epileptogenic zones (EZ) are removed from the brain. Hence, prior to epilepsy surgery, insertion of depth electrodes into the brain is necessary to identify the EZs. These depth electrodes have multiple contacts that monitor the neuronal activity in multiple locations within the brain along each electrode trajectory. In the present study, we show that normalized transfer entropy measurements demonstrate functional connectivity across multiple sites within the brain of an MRE patient who did not demonstrate a clear EZ using conventional EEG criteria. Interestingly, linear measures of functional connectivity were not predictive of such an epileptic network. Our results suggest that routine evaluation of both linear and non-linear functional connectivity including normalized transfer entropy from depth electrode recordings may be useful to identify multisource epileptogenic networks in MRE patients. Identification of networks that contribute to epilepsy in such patients could potentially allow the clinician to avoid resective surgery and adopt alternate therapies such as vagal nerve stimulation or other emergent alternatives.

Composite SISCOM perfusion patterns in right and left temporal seizures.

OBJECTIVE: To compare composite subtraction ictal single-photon emission computed tomography coregistered to magnetic resonance imaging (also known as SISCOM) patterns between right and left medial temporal-onset seizures to document neuroanatomical involvement in perfusion patterns. DESIGN: A retrospective comparative survey. SETTING: Epilepsy monitoring unit in a tertiary care referral center. PARTICIPANTS: Subjects with temporal lobe epilepsy (TLE) who underwent ictal single-photon emission computed tomography studies. MAIN OUTCOME MEASURES: Comparison of ictal perfusion pattern changes in subjects with right and left temporal seizures. RESULTS: Composite subtraction ictal single-photon emission computed tomography coregistered to magnetic resonance images showed similar regions of hyperperfusion change in the ipsilateral anteromedial temporal-corpus striatum-insula region in both groups. In the midbrain reticular formation, there was a significant difference in hyperperfusion between the left and right TLE groups. In addition, the right, but not the left, TLE group shows contralateral hypoperfusion of the temporoparietal junction. CONCLUSIONS: While anteromedial temporal-corpus striatum-insula perfusion patterns are similar, there are brainstem and hemispheric perfusion pattern differences in right and left TLE seizures, confirming pathophysiological differences between the groups. These findings help define neuronal network involvement in TLE seizures, and may explain the differences in clinical symptoms of right and left TLE seizures.

A unique patient with epilepsy with cinematographic visual hallucinations.

PURPOSE: The purpose of this case report is to document a patient with cinematographic hallucinations, with corresponding right temporal lobe seizures on electroencephalogram (EEG). RESULTS: The results showed that the patient's EEG was normal. The patient subsequently reported hallucinations, which had been occurring for the last several months. During monitoring, no interictal EEG abnormalities were identified, but a total of 11 partial seizures were captured originating from the right posterior temporal area. They either were subclinical or corresponded with his visual hallucinations. CONCLUSION: The present study demonstrates focal seizures of temporal lobe origin producing complex visual hallucinations without a corresponding lesion on MRI brain imaging.

American Clinical Neurophysiology Society Guideline 2: Guidelines for Standard Electrode Position Nomenclature.

This revision to the EEG Guidelines is an update incorporating current electroencephalography technology and practice and was previously published as Guideline 5. While the 10-10 system of electrode position nomenclature has been accepted internationally for almost two decades, it has not been used universally. The reasons for this and clinical scenarios when the 10-10 system provides additional localizing information are discussed in this revision. In addition, situations in which AF1/2, AF5/6, PO1/2 and PO5/6 electrode positions may be utilized for EEG recording are discussed.

American Clinical Neurophysiology Society Guideline 3: A Proposal for Standard Montages to Be Used in Clinical EEG.

This revision to the EEG Guidelines is an update incorporating current electroencephalography technology and practice and was previously published as Guideline 6. A discussion of methodology for the appropriate selection of reference electrodes is added. In addition, montages are added to assist with localization of abnormal activity in mesial frontal and anterior temporal regions.

American Clinical Neurophysiology Society Guideline 3: A Proposal for Standard Montages to Be Used in Clinical EEG.

This revision to the EEG Guidelines is an update incorporating current electroencephalography technology and practice and was previously published as Guideline 6. A discussion of methodology for the appropriate selection of reference electrodes is added. In addition, montages are added to assist with localization of abnormal activity in mesial frontal and anterior temporal regions.