Tag Archives: temporal lobe

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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Autonomic system, Neuroanatomy, Spidey senses

Do your spidey senses tingle, better listen up

Virginia Thornley, M.D., Neurologist, Epileptologist

March 24, 2018

Have you ever walked down a quiet lonely corridor of a building where almost everyone has gone home for the day and your spidey senses started to tingle? Or perhaps, you were caught up at work in a facility and it is now 8pm with not a soul in sight and you have a long desolate walk to the parking lot to your car. Your spidey senses tingle as you place your first step out the door leaving the brightly fluorescent-lit building to go out in the cold darkness. Your heart races, your eyes widen checking out your surroundings in front, on the sides and behind you. That is your fight or flight response kicking in in high gear. This is a common scenario where your senses tell you instinctively that you are not in the best situation and you need to be hyperalert to survive a situation should something adverse were to occur.

How about a less straightforward situation where you waltz into a bank minding your own business, you just needed quarters to do your laundry because you live in an apartment building with no washer or dryer. As the teller is getting you a roll of coins, someone comes in from your peripheral vision. You think how rude, I was here first why is this guy cutting my line? He has sunglasses, a hat and holds up a note to the teller while telling you to be chill, be chill. Then it dawns on you that you are suddenly in the middle of a bank heist. Do you a) scream and ask for assistance from the security guard standing 2 feet away? b) run for your life because the man beside you has his hand in his pocket and you could turn into smithereens in the next few seconds c) stay frozen as your life passes through your mind thinking hmm, what should I do scream for assistance or be chill like the guy reassuringly told me to be. Your mind instinctively tells you it is prudent to do the latter. This is another situation where you are on edge, your systems are overloaded with information and your mind is racing like a marathon on what was the best case scenario to get yourself out of that situation.

 

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Many times in our life we are faced with situations when we feel potential threat or fear of the unknown and lightning speed logic and actions are required. Our bodies are designed to react quickly to situations. The amygdala has an emotional function in our brain that directs our reactions when the unnerving situation is detected. Signals are sent to the hypothalamus in the brain that connects with the adrenal medulla which lies on top of the kidneys and from where epinephrine and norepinephrine are released  The sympathetic nervous system is the system that allows our pupils to dilate, our heart to pump quickly and our palms to sweat. It is part of the autonomic nervous system that controls and regulates the cardiac muscles, muscles, and glands. During fight or flight response to stress, there is an adrenergic rush when epinephrine is released and is available for immediate reuptake by the post-ganglionic nerve endings in order to kick our bodies into high gear to react rapidly if need be. The heart is pumping to ensure the body gets adequate blood flow. In primitive times, you will need your muscles to outrun that cougar. The blood vessels constrict within the organs to make blood flow more available to the muscles necessary for running. Blood flow is shunted to the liver to make energy stores more available. The pupils dilate so they widen allowing more light and you can see your surroundings better in dark light. The breathing becomes heavier because you will need more oxygen when you try to outrun that crouching cheetah in the jungle.

It is a primitive response so engrained in our system that we cannot ignore or control it.  The palms sweat, well, because that’s part of the sympathetic nervous system. Sweating allows you to cool off in hot temperature. If you run hard and fast you become hot, you need sweat to cool down. It is essentially a primitive response entrenched within our systems that help you react towards an untoward situation. By the same token, animals must sometimes freeze in the jungle so they are not seen and eaten by large predators. This is similar to the evolutionary freezing we feel when we are involved in a potentially dangerous situation and suddenly stop and do not know what to do.

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However, everything is interrelated. It is not just the fear of the unknown or being in an unusual situation that can trigger this response. Our memories and emotions may trigger the sympathetic nervous system. Say you walk into a business deal that is supposed to be mutually beneficial. You have high hopes for a great outcome. You walk into the conference room, look your interviewer in the eye and shake his hand. This person is unusually cheerful and accommodating.  You are just happy to have someone interview you in the location of your choice. However, as you start to listen to the situation your mind is triggered by statements that harken back to a situation in a previous job from which you suffered burnout. They are way too accommodating but little statements are voiced making you wonder about the real situation and why they are being a little too nice and too happy about an overburdened schedule. This is where the hippocampal cells in the temporal lobe come in to subserve their function with learned memory.  Your amygdala is processing everything emotionally connecting the dots. While logic is saying take the job it is an ideal location, the salary is great, your amygdala is dissecting emotional content in the discourse and on facial features. It picks up on any fallacy when emotions and statements do not coincide. You detect a disconnect between the sunny disposition and the weight of the job. The intuition many people opine about is really the primitive amygdala telling you when something is not quite right. It detects the unsaid component of a situation and ultimately determines your next course of action. While you are about to start the job your amygdala is screaming out to you releasing hormones producing a milder version of the fight or flight response veering you away from a potentially stressful situation and giving you a completely different reaction from what logic would determine. You feel stressed every time you think about your first day at work. The heart beats a little more quickly, it is a milder version of the sympathetic response found in fight or flight but essentially your amygdala is activating your system to respond as you do in an adverse situation.

The same is true when encountering the threatening looking person. You have an idea they are up to no good, looking shiftily away darting their eyes back and forth. Your brain registers something adverse is about to go down. It’s not paranoia, it’s your primitive brain the amygdala picking up on suspicious activities steering you towards a reaction towards a  potentially adverse event.

Therefore, when your spidey senses tingle, it’s not intuition, it’s not a sixth sense or premonition. It is cerebrally mediated with your primitive brain steering your emotional component to wind your body up about to react to a stressful situation. At one end of the spectrum, it is the fight or flight response at the milder end of the spectrum it is the stress you feel when you are about to make a big mistake. The axiom is true, listen to your gut, to be more apt listen to your amygdala masquerading as your spidey senses.

When the hair on the back of your neck tingles, listen to those spidey senses.

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