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The ILAE 2010 report does not classify focal seizures and instead uses “descriptors” to distinguish focal seizures with versus without impaired consciousness. Below, we recall a recent informal conversation that took place while traveling a back road in Australia (true story), discussing problems with the old terms as well as new biological and practical evidence separating events formerly known as complex partial versus simple partial seizures. Impaired level of consciousness is a core distinguishing feature of focal seizures, which arises from established physiological mechanisms and can be readily determined based on behavior in most cases. After some debate, we arrive at succinct terms compatible with the old as well as the new ILAE classification report: Focal Impaired Consciousness Seizures (FICS), and Focal Aware Conscious Seizures (FACS). We hope that this discussion will bring impaired consciousness off the back roads of epilepsy classification, and provide useful names for these two very common seizure types.
“There is no turning back,” we both agreed. We would not return over the dark winding mountain road behind us to the point where we had left the main highway. As we drove, our conversation had strayed and in the process we did not notice where we were going. Somewhere past the 12 Apostles on the south coast of Victoria, we hoped to find our way to Lorne through a tangle of overgrowth and mist. No other cars had passed in some time and the road ahead twisted precariously upward.
Graeme: “Look… there are plenty of good things about this.”
Graeme: “Well no one has found much use for terms like ‘idiopathic’ or ‘cryptogenic’ anyway, at least not recently (Jackson, 2011). We need to embrace the new direction and stop grumbling about the past.”
Hal: “I agree, but what do we do about simple partial and complex partial seizures? Every clinician knows that those terms are very useful. I understand all the arguments about ‘simple’ and ‘complex’ being confusing (Berg et al., 2010). But it seems we've thrown out the baby with the bath water, and now we have no good terms at all for seizures with or without loss of consciousness. I can live with ‘focal’ instead of ‘partial.’ But what am I supposed to do when my patient has a ‘focal’ seizure that causes a motor vehicle accident? Sure, it could be a hemiconvulsive seizure with spared consciousness, but that's pretty rare. Most of the time impaired consciousness is the culprit. Now we're supposed to call that a ‘focal seizure with impairment of consciousness or awareness’ (Berg et al., 2010; Table 1). That's eight words instead of three. Doesn't exactly roll off the tip of your tongue….”
Table 1. Terminology for focal or partial seizures
|ILAE 1981 Classification (ILAE, 1981)||ILAE 2010 Commission Report (Berg et al., 2010)|
|Complex partial seizure||Focal seizure with impairment of consciousness or awareness|
|Simple partial seizure||Focal seizure without impairment of consciousness or awareness|
As if to emphasize the last point the car lurched over a branch in the road and then moved forward in the darkness.
Graeme: “But how would you define consciousness? The whole goal of the new classification is to move toward biological mechanisms and that's why consciousness was left out. Gloor (1986) pointed out back in the 1980s that there is no easy way to test consciousness. For instance someone can be fully conscious during a seizure, but if they can't speak or move, they can't show it. And if they have amnesia after the seizure is over they won't be able to report their consciousness, even in hindsight.”
It looked like there were thousands of eyes peering at us from the dark trees surrounding the car on the sides of the road. We took a right turn, hoping it would lead us back down toward the coast.
Hal: “I'm sure you didn't bring Anne Berg up this road when she visited here a few years back.”
Graeme: “They say there are more species of deadly spiders and snakes in Australia than the whole rest of the world together.”
Hal: “That's comforting….”
Graeme: “Well speaking of biology, maybe we can be helped out by neuroimaging and other methods they couldn't do very well back when Pierre Gloor was writing about consciousness.”
Hal: “You're right! You know there are differences in SPECT (single photon emission computed tomography) imaging and intracranial EEG (electroencephalography) between seizures with or without impaired consciousness. Temporal lobe seizures with impaired consciousness show abnormal brainstem and thalamic activity, and depressed function in the frontoparietal cortex, which looks like deep sleep or coma (Blumenfeld, 2012; Figs. 1 and 2). On the other hand temporal lobe seizures without impaired consciousness show abnormal activity that stays confined to the temporal lobe.”
Graeme: “Yes, and fMRI (functional magnetic resonance imaging) is a pretty powerful way to study seizure networks even at rest (Jackson et al., 2012). I'll bet we'll be seeing much more progress along those lines. But as a clinician, when I see a patient with seizures, the behavior is what counts most. We can argue like Gloor did about consciousness, but in the end it's usually pretty obvious if a patient can respond normally during seizures or if they are globally impaired. The imaging studies suggest that when they don't respond it's not that they are frozen but awake. Their brain arousal networks are in a very abnormal state (Blumenfeld, 2012; Table 2). So as clinicians we need a way to name seizures that will cause our patients to crash their car or have other serious problems.”
Hal: “There is some recent work showing that focal seizures are not so hard to classify after all based on behavior. Plum and Posner (1982) originally distinguished the level of consciousness—like the brightness knob on a TV; from the content of consciousness—all the stuff that's on the TV screen. As Andrea Cavanna likes to point out, when the level of consciousness is impaired, multiple specific behaviors are affected (Cavanna et al., 2011). It turns out that impaired behavior during focal seizures is bimodally distributed (Yang et al., 2012; Bauerschmidt et al., 2013; Fig. 3). Most of the time multiple behaviors are either impaired together because the level of consciousness has been affected, or they are mostly spared.”
Table 2. Differences between focal seizures with versus without impaired level of consciousness
| ||With impaired consciousness||Without impaired consciousness||References|
|Practical differences||Greater risk of accidental injury or work/school disruption||Less risk of accidental injury or work/school disruption||Berkovic (2000), Gastaut & Zifkin (1987), Yang et al. (2010)|
|Physiologic differences||Decreased cerebral blood flow in frontoparietal association cortex (see Fig. 1)||Few changes in neocortical blood flow||Blumenfeld et al. (2004)|
|Increased blood flow in thalamus and upper brainstem (see Fig. 1)||Few changes in thalamus and upper brainstem||Blumenfeld et al. (2004), Lee et al. (2002)|
|Slow wave activity in frontoparietal association cortex (see Fig. 2)||Few changes in neocortex||Englot et al. (2010)|
|Increased thalamocortical synchrony||Few changes in thalamocortical synchrony||Arthuis et al. (2009), Guye et al. (2006), Lambert et al. (2012)|
|Bilateral temporal lobe involvement more common||Bilateral temporal lobe involvement less common||Englot et al. (2010), Gloor et al. (1980)|
|Decreased activity in brainstem arousal neurons (animal model)||No data yet||Motelow et al. (2012)|
|Behavioral differences||Most cognitive functions severely impaired (see Fig. 3); resembles encephalopathy, minimally conscious state, or deep sleep parasomnias||Little or no cognitive impairment (see Fig. 3)||Bauerschmidt et al. (2013), Yang et al. (2012)|
Figure 1. Cortical and subcortical changes in focal seizures with impaired level of consciousness. Temporal lobe seizures with impaired consciousness are associated with significant cerebral blood flow increases and decreases in widespread brain regions. Statistical parametric maps depict single photon emission computed tomography (SPECT) increases in red and decreases in green. Changes ipsilateral to seizure onset are shown on the left side of the brain, and contralateral changes on the right side of the brain (combining patients with left and right onset seizures, n = 10). Data are from >90s after seizure onset, when consciousness was markedly impaired. Note that at earlier times there were SPECT increases in the ipsilateral mesial temporal lobe (not shown). Also, focal seizures without impairment of consciousness showed only localized SPECT increases in the temporal lobe without widespread cortical and subcortical changes (not shown, see Blumenfeld et al., 2004). (A–D) Horizontal sections progressing from inferior to superior, and (E, F) coronal sections progressing from anterior to posterior. The images show blood flow increases in the bilateral midbrain, hypothalamus, medial thalamus, and midbrain. Decreases are seen in the bilateral association cortex. (G) Three-dimensional surface renderings show increases mainly in the bilateral medial diencephalon, upper brainstem, and medial cerebellum, whereas decreases occur in the ipsilateral >contralateral frontal and parietal association cortex (same data as A-F). Extent threshold, k = 125 voxels (voxel size = 2 × 2 × 2 mm). Height threshold, p = 0.01. Reproduced with permission from Blumenfeld et al. (2004).
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Figure 2. Impaired consciousness in focal temporal lobe seizures is associated with cortical slow wave activity. (A–D) Time course of intracranial EEG changes during typical temporal lobe seizure with impaired consciousness. Only ipsilateral contacts are shown. Bars along left margin indicate electrode contacts from different strips, rows, or depth electrodes in the indicated brain regions. A subset of representative electrodes are shown of the 128 studied in this patient. Calibration bar on right is 3 mV. Montage is referential to mastoid. (A) Seizure onset with low-voltage fast activity emerging from periodic spiking in the mesial temporal contacts. (B) Sample of EEG from early seizure. Rhythmic polyspike and sharp wave activity develops in the mesial temporal lobe, whereas the frontal and parietal contacts show large-amplitude irregular slow activity. (C) Sample of EEG from midseizure. Polyspike and wave activity is present in the mesial and lateral temporal lobe contacts, with ongoing slow waves in the association cortex. Paracentral rolandic and occipital contacts are relatively spared. (D) Postictal suppression is seen in temporal lobe contacts, with continued irregular slowing in the frontoparietal neocortex. (E–H) Group data. Focal temporal lobe seizures with impaired consciousness have bilateral increases in temporal beta frequency and frontoparietal delta frequency activity, whereas seizures without impaired consciousness show mainly increases in ipsilateral temporal lobe beta. Mean fractional changes (± standard error of the mean [SEM]) in intracranial EEG power compared to 60 s preseizure baseline. (E) Temporal lobe beta in seizures with impaired consciousness. (F) Neocortical delta in seizures with impaired consciousness. (G) Temporal lobe beta in seizures without impaired consciousness. (H) Neocortical delta in seizures without impaired consciousness. Bilateral temporal lobe beta activity and frontoparietal delta activity were significantly higher in seizures with versus without impaired consciousness (p < 0.05, Mann-Whitney U test; n = 38 seizures with impaired consciousness and 25 seizures without impaired consciousness in 26 patients). Mes T, mesial temporal; Lat T, lateral temporal; OF, orbital frontal; Lat F, lateral frontal; Med F, medial frontal; Lat P, lateral parietal; C, perirolandic pre- and postcentral gyri.; O, occipital. Reproduced with permission from Englot et al. (2010).
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Figure 3. Impairment on behavioral tasks is bimodally distributed, suggesting that most focal seizures can readily be separated into those with overall impairment (left cluster in the histogram) versus those without overall impairment (right cluster). Multiple standardized behavioral tasks, including both verbal and nonverbal items (items 1–10) were administered prospectively during focal seizures and scored based on video-EEG review. Scores show a bimodal distribution, with the large majority receiving a score of either “0” (no response whatsoever) or “4” (normal, unimpaired response). Data are from 33 focal seizures in 11 patients: 4 with temporal lobe epilepsy and 7 with neocortical or unlocalized focal epilepsy. A bimodal pattern of behavioral test scores was also seen in 35 focal seizures from 14 patients using an earlier prospective testing battery (Yang et al., 2012). A bimodal pattern has not been observed with similar testing items in other disorders of consciousness (Giacino et al., 2004). Reproduced with permission from Bauerschmidt et al. (2013).
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“So focal seizures can usually be separated into those with or without globally impaired level of consciousness, and this has a sound biologic basis (Table 2). Now where does this leave us in the new ILAE classification?”
The road was becoming more difficult to travel and the very real possibility of a large tree coming down loomed large. It was easy at that moment to imagine how they would discover us later. Two cleanly polished skeletons left behind in the car by a voracious colony of man-eating ants.
Graeme: “Maybe there are some terms we could adopt from the new classification to use for focal seizures? Blume and company published a Glossary about 10 years ago that's supposed to be used with the new descriptors (Blume et al., 2001). But the interesting thing is that the words ‘consciousness’ or ‘awareness’ or even ‘responsiveness’ do not appear anywhere in the Glossary. Plenty of other specific cognitive deficits like aphasia and amnesia or even anger and depersonalization are mentioned. But there are no terms in the Glossary for globally impaired level of consciousness affecting all cognitive functions like we often see in our patients.”
Hal: “Luckily, the 2010 ILAE Commission Report at least suggests that we can describe focal seizures as either with or without impairment of consciousness or awareness. But again, we're back to these long-winded descriptions that aren't going to catch on in the clinic.”
Graeme: “‘Dyscognitive’ is also offered as an option for focal seizures with impaired consciousness.”
Hal: “Personally, I think that confuses matters even more, since cognition is not the same thing as consciousness. Ictal aphasia can cause cognitive impairment without impaired level of consciousness. The core dysfunction is impaired level of arousal, not a bunch of isolated cognitive deficits. Come on—can't we come up with some snappy acronym or nickname? Those SISCOM guys really got it right…can't we think up with something almost as cool sounding as SISCOM?”
It was Graeme's phone. Sam and Ingrid and the others were wondering where the hell we were. They were waiting to have dinner with us in Lorne, which seemed very inviting, if only we could find our way back to the civilized world.
Graeme: “Great, ok so let's play around a bit with the descriptive terms the ILAE Commission gave us. We could have Focal Impaired Consciousness Seizures, or FICS. Hey, that's kind of catchy! And then Focal Unimpaired Consciousness Seizures, or FU… um, uh… maybe that won't work afterall.”
Hal: “I think we're really close though! Maybe three letters will do it. Let's see… Focal Unconscious Seizures—that's FUS. Pretty good, but seems oversimplified Most of the time people aren't 100% unconscious, as in a coma, just severely impaired (McPherson et al., 2012). Maybe we should stick with FICS but use a different vowel in the partner term… how about FACS, for Focal Aware Conscious Seizures? Could also be Alert Responsive Seizures, but we might get in trouble again there with the acronym…
Graeme: “I like FICS and FACS! They are worth running up the flagpole. Let's see… I'm in a fix if my patient has a FICS, but can fax that driving form if they have a FACS. Or with case presentations… A 15-year-old male with a history of febrile seizures developed frequent FICS… Or a 39-year-old female had onset of FACS 2 years after a head injury…”
Hal: “Wait, are FICS and FACS singular or plural?”
Graeme: “Could be both. Kind of like fish or scissors. I don't really like the sound of ‘FICS-es’ or ‘FICS-en’ ”
Hal: “OK. FICS and FACS. Focal Impaired Consciousness Seizures and Focal Aware Conscious Seizures. Four words each, a bit longer than the old terms but still snappy, new, and much more clear. But I hope we live long enough to share this with some other people. Y'know I'm really getting hungry.”
Miraculously, the car now seemed to be moving slightly downhill toward the coast rather than further up the mountain. Faint lights appeared in the distance through the trees. Hope glimmered that we might soon join our colleagues in Lorne and get back to trying to cure epilepsy.