Epilepsy

Vagal nerve stimulation device: its role in medically refractory partial epilepsy and reports of weight loss

 

Virginia Thornley, Neurologist, Epileptologist

@VThornleyMD

April 15, 2018

Introduction

The vagal nerve stimulation device is an implanted device that exerts its effort by pulses of electrical activity that stimulates the vagal nerve or cranial nerve X. It had initially been found to work in animal studies in the 1990’s then later applied in clinical studies.

Mechanism of action 

For years, the mechanism was unknown and was used rather effectively in the clinical realm. The elucidated mechanisms were thought to be that the vagal nerve stimulator modifies the highly synchronized electrical activity that occurs in epilepsy through desynchronization via the vagal nerve. In addition, there is increased regional cerebral perfusion, and there is increased GABA neurotransmitters which are inhibitory towards electrical activity causing seizures and a decrease in glutamate which is known to increase excitation with the brain. There are GABA-A receptor increases, an increase in locus ceruleus produced noradrenergic substances which are released through the vagal nerve and an increase in serotonin transmissions through the raphe nucleus.

Role in controlling seizures

In the original open-label trial in 5 clinical trials, the vagal nerve stimulation device was found to be effective in reducing seizures by 50%. 454 patients had the implanted device and clinical information was obtained from 440. A cardiac stimulation device was implanted along with a coil in the ipsilateral vagal nerve. At 1 year of implantation, more than 50% of reduction of seizures occurred in 36.8% of patients at year 1, 43.2% year 2, and 42.7% at year 3.  The most common side effect at year 2 was hoarseness of about 9.8% and headache in 4.5% and at 3 years there was shortness of breath in 3% (4).

In one retrospective study from 1997 to 2008, 436 patients were found with implanted vagal nerve stimulation devices from ages 1-76, 220 were women and 216 were men. 33 had poor follow-up and 3 had removal due to infection. The mean frequency of seizures was better at 50% reduction.  There was 90% better control on 90 patients, >75% control in 162 patients and 50% control in 255 patients, <50% control in 145 patients. Permanent damage to the vagal nerve happened in 2.8% or 11 patients out of the 400 patients (after the removal of the ones lost to follow-up and infected) (5).

Long-term value of vagal nerve stimulating device, effectiveness after 5 years

There have been many studies reported that it may be effective short-term. But there was one pediatric study that reported success in seizure control in longer than 5 years. In a study of 56 pediatric patients ages 4-17, >9.8% were seizure free after 9 months, 24% after 2 years, 46.4% after 3 years and 54% after 5 years.11 out of the 56 patients became seizure free. After 5 years 62% of the patients had fewer seizures after 5 years.

What happens from diagnosis to implantation to use

A patient is identified as medically refractory, meaning a patient who has already failed 2 or more agents. Once control is failed after 2 anti-epileptic drugs after an adequate dosage and trial,  the likelihood of being seizure free becomes significantly less.  It is usually applied to patients with partial seizures, the most common being temporal lobe epilepsy. After appropriate identification is done, the patient undergoes a procedure where a cardiac device is implanted under the skin which generates an electrical impulse. A wire or coil is attached to the vagal nerve which reacts to this signal and emits an electrical pulse which inhibits the seizure which is electrical activity in the brain by disrupting this through various mechanisms. The device can be programmed to have a set frequency, amount of power and can be set to automatic with features where the patient can apply a magnet to inhibit the seizure when it is about to occur. The magnet is typically swiped over the cardiac device which was implanted over the left side of the chest. The settings can be changed in the doctor’s office adjusting according to the number and frequency of seizures.

Common side effects

Some of the most common side effects reported include hoarseness, cough, throat irritation, dyspnea, insomnia, dyspepsia, and vomiting. The symptoms are related to the location of the device near the nerve causing local irritation and likely due to the functions subserved by the vagal nerve.

Incidental weight loss effect

Vagal nerve stimulation device was applied to treatment-resistant patients with depression where an incidental effect on weight loss was found. One study in 33 patients showed that the vagal nerve stimulator implanted in patients seemed to alter cravings for sweet food which may play a part in weight loss (2). There have been some conflicting studies proving that there is no weight loss in vagal nerve stimulating device at the settings recommended in epilepsy in 21 patients (3). In a large study of 503 patients from 15 study centers, vagal nerve blockade was applied intrabdominally. 294 patients were randomized to treated (192) and to control groups (102). Therapy involved electrical stimulation through an external power source to the vagal nerves in the subdiaphragm which inhibits afferent and efferent vagal transmission. At 12 months, the excess weight loss in the treated group was 17% and in the control group, it was 16%. There was no statistic difference between the two groups, however, the post-study analysis demonstrated a possible result in weight loss related to the system check of the devices using low charges which may have caused weight loss in the control group (6).

In conclusion

There is strong evidence that the vagal nerve stimulation device is effective at reducing seizures of >50% of the medication-resistant epilepsy patient. It is effective even after 5 years of implantation. There are very little side effects which are mild to moderate. In addition, it can cause weight loss.

References:

  1. Serdaroglu, et al, “Long-term effect of vagus nerve stimulation in pediatric intractable epilepsy: an extended follow-up,” Child’s Nervous System, 2016, 32 (4):641-646.
  2. Bodenlos, “Vagus nerve stimulation acutely alters food craving in adults with depression,” Appetite, 2007, 48: 145-153.
  3. Koren, et al, “Vagus nerve stimulation does not lead to significant changes in body weight in patients with epilepsy,” Epilepsy Behav. 2006;8:246–249.
  4. Morris, et al, “Long-term treatment with vagus nerve stimulation with refractory epilepsy,” Neurology, 1999, 53 (8):1731-1735.
  5. Elliot, et al, “Vagus nerve stimulation in 436 consecutive patients with treatment-resistant epilepsy: long-term outcomes and predictors of response,” Epilepsy Behavior, 2011, Jan., 20(1):57-83.
  6. Sarr, et al, “The EMPOWER study:randomized, prospective, double-blind, multicenter trial of vagal blockade to induce weight loss in morbid obesity,” Obes. Surg., 2012, Nov., 22 (11):1771-82.

 

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medical marijuana

Cannabinoids: the other side of the coin, side effects, drug-drug interaction and possible problems of cannabidiol and tetrahydrocannabinol

Virginia Thornley, M.D., Board-Certified Neurologist, Epileptologist

@VThornleyMD

April 6, 2018

 

Introduction

Medical marijuana seems like the shining breakthrough drug the shining pill in armor, the magic pill that seems to cure everything. However, there are always two sides to every coin. One must still proceed with caution. The phytocannabinoids, cannabidiol, and tetrahydrocannabinol exert their effects through the endocannabinoid pathway, the CB1 receptor is most abundantly found in the nervous system. Cannabidiol which has no euphoria acts weakly with the CB1 receptor almost as a reverse agonist blocking the THC from exerting its effect offsetting potent side effects of tetrahydrocannabinol.

The medical benefits are overwhelmingly numerous including ameliorating seizures, spasms from multiple sclerosis, peripheral neuropathy in HIV patients, chronic debilitating pain, post-traumatic stress disorder symptoms and other associated diseases. Despite the stigma of using it, the delay in clinical trials and marked hesitation of the medical community, medical marijuana has landed and there is no going back. Yet even with its numerous health benefits, it is always prudent to take a step back and examine any flaws as with any other new kid on the block or any new agent that comes along even though it’s been around for thousands of years.

Is marijuana safe for medical use? The take on medical marijuana by the FDA

So far from the FDA official website, the FDA does not recognize medical marijuana coming from the botanical plant with any medical indication. The FDA does not recognize it to be safe or beneficial for any type of disease or condition. The FDA will facilitate any companies interested in bringing quality products including science-based research. The full take of the FDA on marijuana can be found here https://www.fda.gov/NewsEvents/PublicHealthFocus/ucm421168.htm#use

Long-term effects on the brain

Perusing the scientific literature, it is difficult to find any long-term damage to the brain. There was a report in a heavy marijuana user where there was damage to the corpus callosum, possibly worse with young users (1). This is a small study of 11 heavy marijuana users with 11 age-matched cohorts. Diffusion tensor imaging was used. Previous reports alluded towards poor cognition with heavy marijuana use. This study is aligned with that. It was suggested that there may be increased diffusibility within the white matter tracts of the corpus callosum. Young age is thought to make the corpus more susceptible to white matter damage. The only caveat is this is with heavy use and the substance found in recreational marijuana is going to be a different form compared to medical marijuana extracted from the marijuana plant used for medicinal purposes. It is not clear if this report would carry over to medical marijuana users where the preparation of the product is much different(1).

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Effect on schizophrenia spectrum diseases

In a large study of 171 patients, it was found that with heavy use of cannabis, the age of onset of schizophrenia spectrum disorders seems to occur earlier (6). This is one of the reasons why in some dispensaries, it is not sold to patients with a history of schizophrenia. There are some anecdotal reports of some patients having a paranoia with medical marijuana that is reversible once taken off.

Effect on the heart, reports of myocardial infarcts and ST elevations

While the literature suggests low toxicity and most side effects are related to cognition and gastrointestinal problems, there are several cannabis-associated myocardial infarcts in the literature. The dispensaries in the state of Florida use a previous history of a previous myocardial infarct as a contraindication in using medical marijuana. These were synthetic drugs used recreationally. There was one case report where a heavy user suffered from an ST elevation and subsequent myocardial infarct after becoming toxic to marijuana used recreationally.  In one study, synthetic cannabis was used, the myocardial happened to a young patient where an atheromatous plaque was excluded as the source. Etiology and mechanism are unclear why infarcts should occur. It is quite possible that because it works on the 5HT receptor for anxiety which can cause vasoconstriction, this may be one mechanism. Other studies are needed to elucidate the mechanism of action.

Drug-drug interactions

Because medical marijuana is used as an adjunctive agent for epilepsy, perhaps off-label since it has not been approved through FDA as an anti-epileptic agent yet, it was found that medical marijuana used in conjunction with Clobazam (Onfi) tended to elevate Onfi at higher levels.

In one small clinical study, in 13 patients, 9 had an increase of about 60 in the Clobazam level and by 300 in Norclobazam level. There was, however, a tremendous reduction of seizures by >50% but Onfi (Clobazam and Norclobazam levels) should be monitored (3) on a routine basis to avoid any untoward toxicity.

Other milder symptoms

In one large study on Lennox-Gastaut syndrome where cannabidiol was titrated to a 20mg/kg over a course of 14 weeks, mild to moderate symptoms were noted including pyrexia, sedation, dizziness, and diarrhea. However, the titration rate was very rapid and the patents who were 50kg were quickly at 1000mg within 14 weeks which does not usually happen in the real world. Medications are usually increased over a longer period of time in slower increments.

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In summary

While everybody is touting the horn of medical marijuana it is always prudent to stand back and ensure there are no possible risk factors for adverse side effects. The most serious and common seen in the literature appear to be related to schizophrenia spectrum disorders and cannabis associated myocardial infarct. The only caveat is that the literature is peppered with these reports, however, the quality of the recreational drugs are vastly different from medical marijuana which tends to be organic and all natural extracted from the plant in licensed medical dispensaries. The extraction of the medical components is vastly different from the smoked synthetic version of tetrahydrocannabinol. So, is difficult to know if these reports would actually corroborate with use in medical marijuana. The ones with side effects were heavy users of recreational smoked types of marijuana, it is unclear if it was synthetic or organic. As the popularity of medical marijuana progresses, more information will be available regarding the side effect profile.

References

  1. Arnone, et al, “Corpus callosum damage in heavy use: preliminary evidence from diffusion tensor tractography and tract-based spatial statistics,” Neuroimage, 2008, Jul., 1, 41 (3): 1067-74.  “J Addict Med. 2017 Sep/Oct;11(5):405-407. doi: 10.1097/ADM.0000000000000326.
  2. Volpon, et al, “Multiple cerebral infarcts in a young patient associated with marijuana use, ” Journ. Addic. Med, 2017, Sep./Oct., 11(5):405-407.
  3. Geffrey, Drug-drug interaction between clobazam and cannabidiol in children with refractory epilepsy,” Epilepsia, 2015, Aug., 58 (8):1246-1251.
  4. Stewart, et al, “Obstructive sleep apnea due to laryngospasm links ictal to postictal events in SUDEP cases and offers practical biomarkers for review of past cases and prevention of new ones,” Epilepsia, 2017, Jun., 58(6): e87-90
  5. https://www.fda.gov/NewsEvents/PublicHealthFocus/ucm421168.htm#use
  6. Shahzade, et al, “Patterns in adolescent cannabis use predict the onset and symptom structure of schizophrenia-spectrum disorder,” Schizophrenia Research, 2018, Feb., 2 pii S090-9964 doi:10. 1016/j. schres. 2018.01.008 (Epub ahead of print)
  7. Orsini, et al, “Prolonged cardiac arrest complicating massive ST-segment elevation myocardial infarct associated with myocardial consumption,” J. Community Hosp. Intern. Med. Perspect, 2016, Sep., 7. 6 (4):31695
  8. Thiele, et al, “Cannabidiol in patients with seizures from Lennox-Gastaut Syndrome (GWPCARE4): a randomized, double-blind placebo-controlled phase 3 trial,” Lancet, 2018, Jan., 390 (10125):1085-1096

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Uncategorized

Cannabidiol: a large study in the U.S., Netherlands, and Poland shows its efficacy in patients with the epileptic disorder Lennox-Gastaut Syndrome

Virginia Thornley, M.D., Neurologist, Epileptologist

@VThornleyMD

March 31, 2018

Introduction

Lennox-Gastaut Syndrome is an epileptic syndrome starting in childhood characterized by a wide spectrum of seizures and slow spike and wave on EEG. The seizures are characterized by the classic mnemonic “a fall, a jerk and a stare” or atonic seizures, myoclonus and complex partial seizures, although there are many other different types. Slow spike and wave generalized epileptiform discharges of 2.5 Hertz or less on electroencephalogram clinch the diagnosis. Patients are often delayed in development. Controlling seizures, because of the sheer complexity, of the different types is often a medical challenge.

Methods of the study

A new study using cannabidiol, which is the non-psychoactive medical component of the cannabis sativa plant, was carried out with the results recently demonstrating value. It covered 24 sites from the U.S., the Netherlands and Poland and studied seizures in patients medically refractory to medications using cannabidiol as an adjunctive add-on agent.  171 patients were enrolled from April 28, 2015, to October 15, 2015, and were randomly assigned to either the placebo control or the group with cannabidiol. 86 received cannabidiol and 85 were in the placebo group. 14 discontinued treatment in the cannabidiol group and 1 in the placebo group. All patients had at least one dose of treatment. Eligible patients ranged from 2-55 years old. Cannabidiol was given at a dose of 20mg/kg.

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Seizure reduction

The results were startling, there was a reduction of seizures by 43.9% in the cannabidiol group and 21% in the control group. 86% patients had side effects in the cannabidiol group and 69% in the control group on placebo. These included somnolence, pyrexia, diarrhea, reduced appetite, and vomiting. 12 stopped in the cannabidiol group due to adverse reactions considered mild to moderate while 1 withdrew from the placebo group. 1 died due to unrelated causes from the cannabidiol group.

Conclusion

Reviewing this study, perhaps one of my critiques of this study is that the dosage was 20mg/kg in a 14-week study which means that within 14 weeks a patient of 50 kg. would have been ramped up to about 1000mg. In real life practice, medications are titrated more gradually over a period of months before maximum efficacy may be seen and in such a gradual way in order to avoid side effects. Although a large percentage of patients had side effects which were mild to moderate, it is quite possible they may have needed a smaller dose and the dosages were increased more than it was necessary to achieve the beneficial effects seen in the study within a short period of time. Nevertheless, the bottom line is that cannabidiol, a product of the Cannabis sativa plant, shows a reduction in seizures in a patient with Lennox-Gastaut syndrome.

This study concluded that there is some efficacy of cannabidiol in Lennox-Gastaut syndrome, one of the most difficult epileptic syndromes to treat, and was found with only very mild to moderate side effects. An open-label study as an extension to this study is currently ongoing.

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Reference

  1. Thiele, et al,. “Cannabidiol in patients with seizures from Lennox Gastaut Syndrome (GWPCARE4): a randomized, double-blind placebo-controlled phase 3 trial,” Lancet, 2018, Jan., 390 (10125):1085-1096.
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ketogenic diet, Uncategorized

Ketogenic diet, modified Atkins diet and what is in them: used in seizure control, can these be a weight loss solution to morbid obesity, a risk factor for cerebrovascular and cardiovascular disease?

Virginia Thornley, M.D., Neurologist, Epileptologist

@VThornleyMD

March 29, 2018

Introduction

Ketogenic diet has been used for seizure control when physicians started to notice a reduction of seizures in patients with a high ketone laden diet. This fell out of favor in the 1920’s with the onset of newer agents. As a side note, weight loss has been noted in those on a ketogenic diet.

Previously, guidelines have recommended a reduction in saturated fat which was thought to be the cause of the growing morbid obesity epidemic. Currently, it has been found that carbohydrates which are rich and refined may contribute towards the obesity epidemic. Sugar-laden sodas, the white bread which has refined flour, pizza batter made out of refined flour, all these food which are popular in theIt is no Western culture contribute to the morbid obesity as it is looming today.

How current culture sets the perfect stage for morbid obesity

The current western diet is about 50% carbohydrates. In addition, physical activity is at an all-time low compared to other eras. The current culture is designed as a sedentary and carbohydrate-rich eating culture. Everything nowadays is rapid pace. There are drive-through banks, drive-through pharmacies. Rather than having to physically go to a shop or order things in person,  many things can be done online or by phone reducing the daily need to exert physical activity. There is less time spent on physical activity compared to 100 years ago. If you go to neighborhoods, sidewalks no longer exist. Unless one lives in an urban environment where you are forced to walk to the bus station or live in cities amenable to walking or biking, the car is the mode of transport. Food is rich in carbohydrate, such hamburger buns, pizza dough, white bread or rolls. It is little wonder that morbid obesity abounds.  Food rich in sugar is abundant in grocery store aisles including donuts, cookies, baking packets. The colorful rich in anti-oxidant fresh fruits and vegetables are usually on the sides of the grocery shops, the food that is actually good for you and you need to take time out of your schedule to cook.

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Living a healthy diet is not just staying active but also eating the proper diet. Food that is closest to their original source are richest in nutrients. In short, the colorful vegetables you have to cook without any of the processing that takes place are the food richest in nutrients and have high anti-oxidant properties. Anti-oxidation is important in helping to combat a wide variety of diseases. Colorful fruits and vegetables are rich in fiber and more difficult to digest, hence, uses up more calories. Those which are high in refined carbohydrates are easily digested and contributes more towards obesity.

Components of the ketogenic diet and ketogenic diet variants

Ketogenic diet variants include modified Atkins diet, low glycemic index treatment, and medium chain diet. The ketogenic diet consists of 4:1 ratio of fat to carbohydrates shifting metabolism to the use of ketone bodies as a source of energy. A lower ratio is sometimes employed called the modified ketogenic diet with a 3:1 or 2:1 ratio of fat to carbohydrates. In the modified ketogenic diet, the palatability is improved and avoids the gastrointestinal symptoms associated with the ketogenic diet such as nausea. With the modified Atkins diet, carbohydrates are restricted to 10-20 grams a day, or a 1-2:1 ratio of protein to fat plus carbohydrates. In the low glycemic index treatment, carbohydrates are limited to 40-60 grams while 50-60% of the diet is fat and 20-30% is from protein. The medium-chain triglyceride diet employs oils as a supplement such as coconut oil. The palatability of these diets improve patient compliance and lessen the side effects of the ketogenic diet. Some patients also used the diets to incidentally lose weight in addition to treating seizures.

Ketogenic diet and evidence it works in losing weight

The ketogenic diet has a carbohydrate component of about 20-50 grams a day. It is not so much the restriction of the carbohydrates but the quality of carbohydrates that are ingested that causes people to shed pounds. High fiber, wheat, and whole grain carbohydrates portend a healthier diet as opposed to just restricting carbohydrates in general. In some clinical studies, it was found that weight loss was higher in those with a low carbohydrate diet compared to a low-fat diet (1).

Will the high fat cause me to have heart disease?

In one study where ketogenic diet was used in glucose transporter deficiency, a pediatric epileptic syndrome with encephalopathy, 10 patients were followed for 10 years. After 10 years on ketogenic therapies, there was no evidence of increased cardiovascular risk. While it is a small study, it shows evidence that eating a low carbohydrate diet did not appear to contribute towards heart disease. Larger clinical trials are needed (3).

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How obesity relates to other diseases

It is not uncommon to see patients who come into the ER or the doctor’s office with a history of hypertension, diabetes mellitus type II, hypercholesterolemia and obesity all related to one common denominator-obesity. Take away the obesity, the bad cholesterol or the LDL values go down, glucose goes down and hypertension resolves. When these risk factors are reduced early enough in your life, the odds of cerebrovascular disease or strokes and cardiovascular diseases or heart attacks vastly diminish. If, however, obesity is long-standing, while it is definitely good to reduce risk factors, once atherosclerosis is present in the blood vessels, there is no magic pill to reverse that.

Early identification and reduction of obesity as a contributor towards many health problems is key. Ketogenic diet may play a role in weight reduction. A small case series did not show any risk of heart disease while on the ketogenic diet long-term, over a span of 10 years. Larger clinical trials are needed to support this.

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Reference

  1. Giugliano, et al, “More sugar? No thank you! The elusive nature of low carbohydrate diets,” Endocrine, 2018, Mar, 19. doi: 10.1007/s12020-018-1580-X (Epub ahead of print)
  2. McDonald, et al, “Ketogenic diets for adults with highly refractory epilepsy,” Epilepsy Currents, 2017, Nov.-Dec., 17 (6):346-350.
  3. Heussinger, et al, “10 patients, 10 years-Long-term follow-up of cardiovascular risk factors in Glut1 deficiency treared with ketogenic diet therapies: a prospective , multicenter case series,” Clin. Nut., 2017, Nov, pil:S0261-5614 (17)31399-7.

 

 

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Epilepsy

Epilepsy surgery in temporal lobe epilepsy due to mesial temporal sclerosis: the timeline in investigative work-up from the neurologist’s office to the O.R.

Virginia Thornley, M.D. Neurologist, Epileptologist

March 27, 2018

Introduction

Temporal lobe epilepsy is one of the most common types of seizures. The most common cause and one of the most successfully treated causes of temporal lobe epilepsy treated through surgery is mesial temporal sclerosis. This article focuses on mesial temporal sclerosis and does not include discussions of other types of temporal lobe epilepsy due to other causes such as tumors, cystic lesions or head injury or non-lesional temporal lobe epilepsy.  In order to identify a patient, the symptoms are generally stereotypical which suggest localizing towards one focus.  An early age of identification may portend a better outcome since frequent temporal lobe seizures may cause the development of circuitry to the opposite side causing another focus to develop on the opposite temporal lobe. In addition, it is important to control temporal lobe epilepsy because of the location of the seizures are in the hippocampus which is important in memory. Many patients complain of poor memory which will continue to progress should seizures remain poorly controlled. Epilepsy surgery is the definitive treatment for temporal lobe epilepsy in mesial temporal sclerosis.

Identification

To identify an appropriate candidate for surgery, the patient should have stereotypical seizures which localize towards one focus. While the focus may cause contralateral clinical symptoms, automatisms of the limb are generally ipsilateral to the focus.  Once a patient has been identified, further diagnostics tests are needed in order to confirm this focus including a routine electroencephalogram and an ambulatory 48-72 hour EEG which can be performed out-patient. The only downfall with an ambulatory EEG is that it is subject to the artifact, since the electrodes may be displaced causing poor adherence of the electrode to the scalp causing resistance manifested as artifact and a poor recording. However, it is still a good screening test to determine whether there may be a single focus versus multiple regions affected. Temporal lobe epilepsy may be seen with high voltage epileptiform spike and wave. It may be accompanied by focal delta slowing within the temporal lobe, suggesting temporal lobe dysfunction due to recurring seizures. If a patient is deemed an appropriate candidate, a referral may be made to an epilepsy center where more in-depth investigations are performed.

 

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Admission to an epilepsy center

Expect to stay at least 1 week or more in order to allow the capture of typical seizures and to obtain an adequate sampling of ictal periods and pinter-ictal periods during wakefulness and sleep. A team of specialists is involved with the work-up including a clinical epileptologist who manages the medications and clinical aspect, a clinical neurophysiologist who interprets the video EEG monitoring and correlates it with the clinical symptoms, a neuropsychologist who performs the WADA testing and a slew of clinical EEG technicians who ensure that the electrodes are properly attached throughout the hospital stay. In-depth conferences are held to review the studies of the patients and evaluate which patients are suitable epilepsy candidates. Sometimes, multiple admissions are necessary before seizures can be captured.

Hospitalization

During admission, seizures are captured and correlated with the electroencephalographic recordings to determine the focus. More than one focus correlates with a poor outcome, a single focus is necessary. The clinician may provoke seizures by tapering medications safely in the hospital setting. Other techniques include sleep deprivation and encouraging any triggers. The full spectrum of clinical seizures must be captured in order to ensure adequate localization. Bitemporal foci portend a poor outcome.

Neuroimaging

A high-quality MRI of the brain using epilepsy protocol with thin cuts through the temporal lobes of 1.5mm to 2mm is essential. Coronal views are the best way to visualize the hippocampi to evaluate for hippocampal sclerosis which characterizes temporal lobe epilepsy. Usually, the hippocampus affected is much smaller than the contralateral one with hyperintensity on T2. As a result of excessive seizures, burning off of the cells in the hippocampus occurs so that is it is now atrophic. Although an MRI of the brain may have already been obtained pre-work-up, a higher resolution and exceptional quality brain MRI is likely to be repeated. This will serve as the visual point on which the neurosurgeon operates. Seeing a sclerotic hippocampus gives a high correlation with mesial temporal sclerosis.

 

Ictal SPECT

Spectroscopy is obtained in-house, where hexamethylpropylenamine oxime (HMPAO) injection is done 30 minutes before an ictus. When the patient has a seizure, the HMPAO perfuses to the area of interest showing where the seizure localizes. Images are obtained. This test has an added value of further localizing the focus. The drawbacks, however, include not being able to predict when a seizure is about to occur and missing the ictus. It is not unusual for this test to be repeated for it to be meaningful. In addition, it can only be done during office hours so that nocturnal seizure will be missed due to lack of adequate staff.

Magnetoencephalography

This is a costly examination which may not be available in some epilepsy centers. It uses a 3-dimensional modality for localizing the focus. The MEG dipoles are superimposed on the MRI images.

WADA testing

A neuropsychologist examines the patient’s memory and language by temporarily putting the opposite side of the brain to sleep through injection of amobarbital into the internal carotid artery. Short-term memory and language are examined. The neuropsychologist must determine that there is adequate memory on the contralateral temporal lobe for temporal lobe surgery to be successful. If both temporal lobes are impaired in terms of memory, the patient will suffer from poor memory following the surgery. Other tests are done by the neuropsychologist to check for cognition, any personality disorders and assess for evidence of mood disorders.

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Electrocorticography

This is one of the final steps in the investigation where the cranium over the temporal lobe of interest is removed and electrodes are placed directly on top of the cerebrum. Depth electrodes are placed in order to capture epileptiform discharges buried deep inside the hippocampus which cannot be adequately detected by electrodes laying on top of the temporal lobe. The seizures are recorded and a more accurate mapping of the seizure focus is obtained.

Discussions

Once all the appropriate investigations are obtained, if all the data points towards a single focus then the patient is deemed an appropriate candidate. Epilepsy conferences are usually held and reviewed by all the specialists involved in the care. Some patients may proceed directly into surgery after mapping. Others may need to go home and return back for another admission to undergo epilepsy surgery. A patient who is still questionable may need to return for more in-depth recording, this may occur in non-lesional epilepsy where the information is not strong enough to justify surgery. The goal of epilepsy surgery is to resect the dysfunctional epileptogenic zone while preserving the functioning surrounding cortex.

After care

Once the surgery is performed, the patient will need to be on anti-epileptic agents for at least 2 years of seizure freedom. In appropriately investigated patients, a favorable outcome of seizure freedom may reach as high as 60%.

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