in refractory temporal lobe epilepsy ( tle ) , it is important to be able to determine which hemisphere is dominant and hosts the majority of the language areas . when a patient is evaluated as a potential candidate for resective surgery
, language mapping should be able to indicate which hemisphere is dominant and precisely identify where the language areas are situated within the brain . while the general principle of mapping language for tle in children might be the same as for adults , many challenges are encountered in the mapping process because children are not small adults but differ from adults in many aspects . to understand some of the differences between children and adults in tle features , a brief overview of tle
then , a brief summary of language development and lateralization differences between normal children and children with epilepsy is provided .
the semiology of temporal lobe originating seizures is not as well characterized in children compared to adults and is dependent on age .
for example , infants have a predominance of behavioral arrests , they also tend to have more prominent convulsive activity than adults , and their seizures appear clinically generalized . in younger patients ,
the automatisms are first discrete and mostly orofacial , but the complexity of hand automatisms increases with age .
after the age of 3 years , tonic or myoclonic spasms decrease , as do other motor phenomena , which might have been reminiscent of frontal lobe seizures , and the overall semiology becomes closer to that observed in adults [ 1 , 2 ] .
mesial temporal sclerosis ( mts ) is the most common adult etiology , while in children it is relatively rare . in the pediatric population , when mts is present , it is often accompanied by a neocortical pathology ( dual pathology ) [ 36 ] , and curative surgery therefore necessitates a temporal lobectomy instead of a selective amygdalohippocampectomy to maximize the chances of being seizure - free .
other pathologies , such as focal malformation of cortical development , tumors ( such as gangliogliomas and dysembryoplastic neuroepithelial tumors ) , are frequent and also necessitate a neocortical resection . because language is not only affected by interindividual differences but also variably modified by epilepsy , exact language mapping is required before any neocortical resection to minimize postoperative neurological deficit .
epilepsy surgery has been shown to lead to better cognitive development [ 8 , 9 ] if the epileptogenic zone can be completely resected , but it also carries a higher risk of some language deficit ( up to 50% in a series ) .
language is progressively acquired over the years , and its development might be affected by seizures themselves , age at the onset of seizures , seizure severity , and the underlying pathology .
surgery also has a different impact depending on the age at which it is performed .
the general population , independent of handedness , has a 1018% chance of having a right or bilateral dominant hemisphere ( 5% in a right - handed population and 22% in a left - handed population [ 1114 ] ) the majority of them are left handed . by contrast , among the epilepsy population , 77% have an atypical pattern for language ( right or bilateral ) as determined by the wada test or functional mri ( fmri ) [ 1517 ] .
language might be displaced to the contralateral hemisphere or be reorganized within the same hemisphere , either a different location in that hemisphere , or compensated with additional areas recruited [ 14 , 15 , 1825 ] .
it has also been shown that more children with epilepsy have an atypical language network than adults with epilepsy ; whether these findings are correlated with the age of onset of the seizures is a matter of debate .
some studies have shown a difference in language pattern with early - onset seizures [ 17 , 19 , 26 ] , while other studies have not been able to show that correlation [ 16 , 2730 ] .
in addition , the percentage of atypical language seems even higher when the epilepsy is probably symptomatic ( formerly known as cryptogenic , i.e. , : no lesion detected on the mri ) .
however , even if language could be influenced by seizures and might be shifted to the contralateral side in some patients , it could also remain in the  normal  anatomical location on the left even when the seizures are arising from that area , which is important to remember when considering surgery to treat epilepsy .
while it was initially thought that language lateralization was acquired later in life , recent functional magnetic resonance imaging ( fmri ) and magnetoencephalography ( meg ) studies have shown signs of lateralization in infants , with the left frontal region being implicated in the discrimination of speech sounds , for example , [ 3235 ] .
however , there seems to be an increase in lateralization with age as shown by fmri and meg studies in normal children [ 36 , 37 ] , which could explain the better potential outcome in language reorganization following surgery before the age of 5 - 6 years [ 3840 ] .
for example , verb - generation and story - processing tasks demonstrate more changes in lateralization over time than word - picture matching tasks [ 36 , 4143 ] .
all of the tools to assess language were developed in adults and then adapted for pediatric populations . while new technologies allow us to move away from invasive techniques , these technologies still carry challenges when applied to children . when considering all these methods , there are general constraints based on the age of the patient , which will be the same for all .
currently , language assessment is not performed in infants and toddlers , except in specific research settings ; therefore , the following will focus on children who have developed enough language skills to communicate and be tested by visual and/or oral questions . because all of the techniques require cooperation of the subject
, it is important to keep age - specific abilities in mind when developing the tests .
in addition , antiepileptic drugs as well as cognitive delay resulting from epilepsy might affect attention span .
cognitive psychologists have made us quite aware of the timeline of language development , which should be considered when developing tests of language function .
development of phonological , semantic , grammatical , and pragmatic components of language during childhood influences the design of the studies . to obtain satisfactory results and map the language accurately ,
it is essential to use tasks that are appropriate for the age of the patient .
in addition , processes occurring during brain development ( such as the formation of synaptic contacts and myelination ) also affect most of the imaging and mapping techniques and may thus influence the results .
the last point to consider when interpreting the results of a patient compared to a study is that many imaging studies have a relatively small number of subjects , and the subject population is heterogeneous .
for the same type of study , a pediatric study should have a larger number of subjects than an adult study because there is significantly more variability among children due to development , yielding an even more heterogeneous population .
the various mapping techniques are described below , beginning with neuropsychological assessment , moving to more invasive tests , such as cortical stimulation , sodium amobarbital ( wada ) test , and nuclear medicine ( single - photon emission computed tomography  spect  and positron emission tomography 
pet ) , then to contemporary tools , which are being used increasingly more in the clinic ( fmri and meg ) , and finally to newer tools that are currently being assessed , such as functional near - infrared spectroscopy ( fnirs ) and diffusion tensor imaging ( dti ) . in the context of epilepsy ,
clinical language assessment begins with a neuropsychological assessment that helps to determine lateralization and guides the decision as to whether more in - depth assessment is needed ( i.e. , if language is thought to be on the left and the surgery is a right temporal lobectomy , it is not generally necessary to investigate further ) .
the neuropsychological assessment includes a battery of standardized , age - appropriate tests for language and memory , among other cognitive domains , such as attention , visual - spatial skills , motor skills , and executive functions , interpreted in the context of developmental milestones , academic skills , psychosocial functioning , and so forth .
this global assessment helps determine assets and deficits and detect whether the pattern is consistent with dysfunction in a specific region of the brain or with a known neurological syndrome . as part of the neuropsychological test battery ,
fused dichotic word listening tests ( fdwlts ) have proven to be cost - effective , noninvasive methods for identifying language dominance as left , right , or bilateral in adults , children , and adolescents [ 4547 ] . during this behavioral test ,
different words are presented to both ears simultaneously , and the subject reports which one they heard .
the number of correct answers for each ear is counted , and the value indicates a right or left ear advantage .
the rationale behind this test is that contralateral projections from the ear to the brain are stronger than ipsilateral projections .
it is well known that ongoing seizures in refractory epilepsy can affect development therefore by reducing the number of seizures , surgery does help in ameliorating learning and general development deficits .
however , studies show that temporal lobectomy of the dominant hemisphere , even in children , leads to some degree of postoperative deficit in language .
a study of 24 children with complex partial seizures , aged 5.815.7 years , showed a preoperative left - language dominance in 65% of subjects , with an estimated language delay of 1.73.5 years .
postoperatively , these same children had an increase in language delay in all areas except for receptive syntax .
while language lateralization is important , it is not the only factor when considering surgery .
the traditional notion of two areas well demarcated anatomically within the frontal and temporal lobes  broca and wernicke  has been replaced by the knowledge of a language network that has some interindividual variability .
when further information beyond laterality alone is required , imaging or further investigations with more language specificity are undertaken .
the wada test consists of an injection of intracarotid sodium amobarbital to freeze half of the brain to lateralize function .
the procedure consists of a dose of 40125  mg ( depending on the body weight ) of sodium amobarbital into the internal carotid through a femoral catheter .
once the patient has returned to a normal baseline after anesthesia , the side where the seizure focus is present is tested first followed by the opposite side .
the contralateral injection is typically performed 3045 minutes after the first using the same procedure as for the first .
hemiplegia is first examined , and then language is tested either by a pediatric epileptologist or neuropsychologist .
this is subject to variation from one centre to the next and is sometimes even performed on different days .
the sodium amobarbital test requires full cooperation of the child , who has been subjected to a stressful situation because the injection also causes transient hemiplegia .
while the situation can be explained and tolerated by older children ( teenagers ) [ 52 , 53 ] or adults , it is extremely difficult in younger children .
nonetheless , successful sodium amobarbital testing has been reported in children as young as 2 years old [ 53 , 54 ] . in a study that tested 22 patients between the ages of 5 and 12 years ( median 10 ) ,
language lateralization was clearly identified in 50% of patients ; ten children had left hemispheric language while one had a right hemispheric dominance .
furthermore , the percentage of successful sodium amobarbital procedures was higher among children with higher iqs ( 100% over iq 70 , 57% of iq < 70 ) . a later study from the same group reported a 62.5% success rate in 42 children ; 7.5% failed because of inconclusive results from the test ( intact language after both injections , or a mix of intact language after one injection and then noncooperation ) , and 30% failed because of inadequate cooperation .
similarly , schevon reported a successful sodium amobarbital test in 57% of patients younger than 10 years but as high as 93% in patients older than 10 years of age .
however , the information obtained during the sodium amobarbital test is whether language is impaired after injecting sodium amobarbital into a particular side and therefore determines the dominant side .
it might help to detect some bilateral patterns and predict language deficit after a proposed surgery ; however , a cortical map of the language network can not be created based on this procedure .
another useful function of the sodium amobarbital test , which will not be discussed here , is to assess memory , which can be performed in the same setting .
nuclear imaging , such as single - photon emission computed tomography ( spect ) and positron emission tomography ( pet ) , has been used in the past to map eloquent cortex , including language areas . however , even though studies have shown good correlation between nuclear imaging and intraoperative language mapping   or sodium amobarbital tests , such imaging exposes children to radiation .
furthermore , these imaging methods are limited by the lack of spatial and temporal resolution [ 5759 ] .
the subtraction of the ictal and interictal spect then registering to the mri ) and pet are still used to find the epileptogenic zone , but , currently , they are not as commonly used to map language [ 60 , 61 ] .
cortical stimulation to map eloquent cortex was described by penfield in the early 1950s . however , because the procedure required a cooperative patient in the operating room , until the advent of implanted subdural or depth electrodes , it was only amenable to older children or adults .
leaving subdural electrodes in place allows the use of cortical stimulation in the perioperative period .
it also allows distribution of the language tests and mapping on different days , which is more suitable to children 's shorter attention spans .
however , because it is invasive and carries some surgical risks , subdural electrodes , grids , or depth electrodes would not only be implanted for language mapping , but might also be used when invasive recording is otherwise necessary to determinate the epileptogenic zone .
of note , only a restrictive part of the brain is exposed and , therefore , available for testing .
another drawback of this method is the fact that , especially with strips and grids , only the gyri are recorded and the activity in the depth of the sulci is not . the main difference between cortical stimulation mapping ( and the sodium amobarbital test ) and the other mapping techniques is the fact that stimulation directly interferes with the language task under examination .
therefore , cortical stimulation identifies areas that are critical to language instead of highlighting active areas that are part of the language network for a given task but might not be essential ( such as seen with nuclear medicine or fmri ) .
even though perioperative testing made stimulation more amenable to children and can now be performed by the bedside without restricting the child 's movements significantly , it has again proved to be more difficult in children than in adults [ 54 , 6365 ] .
standard stimulation protocols used in adults had to be modified to obtain some response from the stimulation in children .
protocol   using rectangular biphasic pulses of current on two adjacent contacts , starting the stimulation at 1  ma with a 0.3  ms pulse of alternating polarity and a train duration of 35 seconds .
the stimulation intensity is then increased by steps of 1  ma and pulse duration by steps of 0.10.2  ms until after - discharges are seen , a seizure occurs , or there is a physiological response ( speech arrest , motor , or sensory response ) .
the various protocols use frequencies in the 2050  hz range , an intensity between 1 and 20  ma , a pulse train 325 seconds in duration , and a pulse width between 0.14 and 0.2  ms [ 54 , 6668 ] .
while intensities as low as 24  ma in adults generally evoke a response , in children , those intensities might have to be as high as 16 - 17  ma to be effective [ 67 , 6971 ] .
the possible reasons for the difficulties encountered include incomplete myelination and the greater proportion of small fibers .
the chronaxie , which is the pulse duration needed for stimulation to evoke a response , is directly affected by the myelin deposition , and increasing myelination leads to a decrease in time of chronaxie . 

schevon et al . found that 10.2 years was a cut - off age for successfully mapping cortex .
he studied children with both the sodium amobarbital test and cortical stimulations and found that , before the age of 10 , 19% of children had positive cortical stimulation versus 87% for children older than 10 . while a positive response is in general synonymous with critical language areas ,
the tasks administered during the stimulation are important , and , for example , expressive tasks show a better correlation with the sodium amobarbital test than receptive tasks .
however , within the expressive tasks , the generation of sentences might generate a larger perisylvian network of expressive and receptive language [ 73 , 74 ] than a verb - generation task .
various studies have used cortical stimulation to study intrahemispheric reorganization of language in epileptic patients .
for example , kadis et al .   demonstrated anterior reorganization of language in expressive language in the left frontal lobe .
the basics of fmri will not be discussed here because they are explained in another chapter of this issue ( wang et al.functional magnetic resonance imaging for language mapping in tle ) . once again , pediatric fmri studies are more challenging than most adult fmri studies .
first , the cognitive level of the child is dependent on his age ; therefore , the battery of tests should be age dependent .
in addition , it is more difficult for a child than an adult to stay perfectly still in an mri during acquisition of the task .
yuan showed a difference in age and gender in the motion of the head during acquisition ; younger ( 5- to 9-year - old ) male children moved the most .
all groups moved less when engaged visually instead of just with an auditory stimuli ( picture - word matching versus syntactic prosody , story processing , and verb generation ) .
another study showed a similar trend and demonstrated better results in children with normal developmental milestones as well as older children .
in addition , because children have smaller heads , the head coil should be adjusted for younger age groups .
this modification is especially important for younger patients who , in addition to a small head have a shorter neck , would have their head in the lower quadrant of the coil if using an adult coil .
in addition , the thickness of the skull changes with age , which influences the quality of the image . to adjust for
all ages would require an institution to have different head size coils and to avoid surface coils that increase heterogeneity due to the thinner skull ( signal is enhanced in thinner skulls of younger compared to older people ) [ 77 , 78 ] .
thinner skulls also produce increased physiological noise due to the increased heart and breathing frequency in children .
first , the addition of videos for viewing at the beginning of the acquisition , during the anatomical mri as well as in between runs , would likely reduce motion artifact .
second , the buttons subjects push to answer questions should be adapted to smaller children 's hands .
third , the child should be brought into the room and the magnet before the task without being rushed to acclimatize to the environment ; he / she should be fully prepared for the task and the environment before beginning the session . despite the above - mentioned problems , fmri is starting to replace sodium amobarbital tests and cortical stimulation as a clinical tool for language mapping in some comprehensive epilepsy centres because it is less invasive , has a good spatial resolution ( 13  mm ) , and shows a good correlation with more invasive techniques [ 15 , 72 , 8082 ] .
fmri can be used to investigate lateralization of language ( laterality indexes are calculated based on the number of voxels activated on each side ) as well as to show a more precise localization of language areas .
as previously stated , there are various types of tasks that can be used , some active ( verb generation , semantic decision , sentence completion , etc . ) and some involving passive listening .
the activations can be analyzed by contrasting any of these tasks with a resting state , during which the patient is instructed to do nothing , or between any of the conditions .
the language map ( pattern and lateralization ) resulting from the analysis should differ depending on which tasks have been studied and contrasted .
language protocols have to be developed especially for children and according to their age groups .
in addition , delay in language development is common among epileptic children , which should be taken into account and tested before putting the child in the scanner .
fmri shows the entire network of areas involved in the specific task ( figures 1 and 2 ) . because it is important to be as sensitive as possible to decrease the risk of postoperative deficit , paradigms capturing a wider network are usually preferred in pediatric populations ( i.e. , verb generation ) .
while some studies have shown the possibility of performing 3 - 4 language tasks during image acquisition , so many tasks might be difficult in a clinical setting where the available time to train the child on the task and to remove him / her from the magnet in between tasks is less .
however , one must be aware that only one language task might not be enough .
the authors illustrated with two case reports that hemispheric dissociation in language function is possible , which can only be detected when administering different types of language tasks ( i.e. , vowel identification tasks and  beep  story ) .
the design of the study must be carefully developed to adequately capture the language network .
verb - generation tasks , in which the subject is asked to generate a maximum number of verbs related to a noun that is being presented ( i.e. , horse : jump , ride , etc . ) , seem to have a good reliability in determining hemispheric dominance [ 41 , 82 , 85 ] .
story - processing tasks , in which the subject listens to a story with the instructions of listening carefully enough to be able to answer questions on each story after the mri , seem to produce wider bilateral activation and show some asymmetries in pathological subjects [ 86 , 87 ] .
another task commonly used in settings is a picture - word matching , in which the subject sees one or a couple of images and must decide whether it matches the name that is presented orally . in younger children , a passive language ( listening ) task can also be used for patients between the ages of 2 and 4 years .
however , it is difficult to control whether the subject is actually listening to the story as opposed to dreaming or sleeping . in each task
, different designs for each age group must be developed to provide an appropriate level of difficulty for the patient .
all tasks should include resting states or control tasks , such as button press , sensory test , or a finger - tapping task , to compare the task data to .
the fmri signal uses the hemodynamic response and the changes in oxyhemoglobin and deoxyhemoglobin to determine which areas of the brain are activated . because cerebral blood flow varies across ages , should it be corrected for age when doing a group study ? does the immaturity of the brain affect the bold signal ?
the grey / white matter ratio also varies greatly until the age of 7 years then continues to change over time .
the major fiber pathways are in place by the age of 3 , but the average density of neurons and synapses changes until the age of 16 , when it stabilizes until the late 60s . at the age of 7 ,
the average synaptic density of the frontal lobe is approximately 1.4-fold greater than that of an adult [ 77 , 90 ] .
do these developmental variations provide a stable enough environment to use the same methods of analysis when investigating a pediatric population ?
while most pediatric studies that have analyzed correlations with other modalities have found a good correlation , which indicates that fmri seems to yield valid data even in children , those questions have to be considered .
the pediatric brain differs from an adult one , so group studies should not be normalized to an adult atlas , such as the talairach atlas [ 88 , 91 , 92 ] .
this problem does not occur in a clinical setting in which the images of the patient are directly coregistered to his / her own anatomical mri .
careful analysis of the data is of paramount importance , keeping in mind that misused statistics can show anything
. one should be sure of how the analysis has been performed and of the statistical value of the results before interpreting the data .
similar to other functional imaging modalities , fmri can be used to assess verbal and non - verbal memory . while in adults , memory mapping by fmri is sometimes used as a clinical tool , it is usually part of a research protocol in the pediatric population .
because the hippocampus represents only a small area , the motion artifact and the difficulty of the tasks ( without real - time feedback to know if the child is actually doing the task ) , it is difficult to have a valid study in a child .
while it is not as evident as using meg , some studies have attempted to use fmri to detect interictal spikes ( spike - triggered fmri ) [ 94 , 95 ] .
the creation of superconducting quantum interference devices ( squids ) in the late 1960s / early 1970s allowed a different method of recording of brain electrical activity .
meg captures neuronal activity by recording the net current of the flow of ions , leading to an intracellular electrical current generating a magnetic flux .
repetitive events generate event - related potentials leading to evoked magnetic fields , which can then be recorded by the 248 channels positioned around the head . because magnetic fields are less deformed than electrical fields on the scalp , the spatial resolution of the meg ( 24  mm ) is better than the eeg , and the images can be coregistered with an anatomical mri to visualize them . in addition , because meg measures neuronal activity , its temporal resolution is excellent ( 10  sec ) . in epileptic patients ,
meg allows the recording of interictal spikes , sometimes seizures , and eloquent cortex . 

breier et al . demonstrated a good correlation between an meg study and sodium amobarbital test in the pediatric population   such results have been reproduced in adults too ; papanicolaou et al
.   showed no differences in language pattern with age , but other studies on normal subjects comparing meg to fmri for receptive language mapping showed significant differences in language patterns between the two methods , and another study showed good concordance between meg and fmri lateralization in normal teenagers for picture verb - generation , but only 75% concordance for the word verb generation task , and even lower when looking at precise localization ( voxel overlap 50% ) . in patients requiring surgery near language - related eloquent brain areas ( mostly for tumors ) ,
a german group combined meg and fmri and showed a good congruence between the two modalities ( 96% ) ; however for some patient language activation was only seen in one of the modality .
meg is still in its infancy when considering language mapping in epileptic patients , and more studies are required to see how it can be used in presurgical planning .
the national institute of neurological disorders and stroke is currently recruiting patients for a large trial ( nct00706160 ) .
near - infrared spectroscopy is a noninvasive technique used to measure hemodynamic changes using the different light absorption spectra of oxyhemoglobin ( hbo ) and deoxyhemoglobin ( hbr ) .
it necessitates a light - emitting source ( at two different wavelengths , usually between 680 and 1000  nm ) , a detector , and a dispersive element .
this method is also called optical tomography because it uses an exogenous optical tracer to extrapolate the blood flow , blood volume , or oxygenation of a specific region of the brain .
for example , it can be used in conjunction with a bolus injection of indocyanine green to measure cerebral blood flow .
it is also used to detect changes produced by neuronal activity ( similarly to fmri ) .
when there is regional activation during a task , there is an  initial dip  with a reduction of hbo and an increase of hbr , then a large increase of hbo and a decrease of hbr ( focal arterial blood flow ) . because of the shallow penetration of photons ( 35  cm below the scalp ) ,
the advantage of fnirs is that it does not restrict the child to a small space such as an mri scanner does , and because the device is directly on the head of the child , motion artifacts are not a problem .
the other advantage of fnirs is that the child can actually speak during the task ; therefore , his understanding and involvement in the task are actively monitored .
fnirs seems to be more sensitive to bilateral speech pattern , which is sometimes more difficult to analyze with fmri , as shown by benke et al .
, when there is a dissociation between frontal and temporal activations [ 104 , 106 , 107 ] .
diffusion tensor imaging is a technique that enables tracing of neuronal tracts in the brain . because of the tubular nature of neurons , water can move freely in the direction of the axis but is restricted transversally by the membrane .
when applying various field gradients to the brain in the mr scanner , the difference between the diffusivity in the two axes can be represented by a tensor and subsequently mapped to the brain by coregistering it with an anatomical image to obtain mean diffusivity and fractional anisotropy maps .
these maps can aid in the understanding of functional connectivity of the brain by displaying fibers connecting two regions [ 108 , 109 ] .
there are currently no pediatric studies investigating the use of dti and fmri together for language mapping .
however , in adults , a few groups have tried to predict language lateralization by studying the arcuate fasciculus , inferior longitudinal fasciculus , or uncinate fasciculus and their asymmetry reflected by the anisotropy value , the association between anisotropic or mean diffusivity values and language deficits in patients with tle , or finally with dti and cortical mapping to assess colocalization of language areas in the anterior and posterior part of the arcuate fasciculus .
a number of studies have shown that increased mean diffusivity and decreased fractional anisotropy , interpreted as structural compromise of the white matter tracts , are associated with language deficits in patients with epilepsy [ 111114 ] .
transcranial magnetic stimulation ( tms ) is a noninvasive technique , which uses focal magnetic field generated by a rapidly changing current within a conducting coil .
the coil can be applied to the scalp , so the magnetic field has a direct effect on the brain by depolarizing or hyperpolarizing neurons .
experiments have shown that tms can induce a transient change in behavior by interfering in a manner similar to cortical stimulation .
there are several methods for delivering the magnetic field , including single - pulse , paired pulse , and repetitive pulses .
a first study on language and tms was performed in adults by pascual - leone et al .
, who was able to induce speech arrest when stimulating the perisylvian cortex with 10-s trains of repetitive tms ( rtms ) applied at rates of 825  hz .
variations in the frequency of the stimulation were tried , and speech was also disrupted at 4  hz in another study .
the same group showed a good correlation between sodium amobarbital test and tms in 12/16 epilepsy patients , while other studies showed better even better correlations [ 115 , 118 ] .
while some studies have been performed in children and one review article described the safety of tms in children ( including a potential for increased risk of seizures in children younger than 5 years ) , there are no language studies in this group of patients .
some motor studies have shown that it is feasible ; however , recommendations state that tms should be avoided in young children .
language mapping in children requires a specialized multidisciplinary team with specific protocols designed from a developmental perspective .
however , an increasing number of noninvasive techniques have been shown to be reliable and are being implemented clinically in preoperative investigation for epileptic children .
 temporal lobe epilepsy ( tle ) in children is a slightly different entity than tle in adults not only because of its semiology and pathology but also because of the different approach to surgical treatment . 
 presurgical investigations for eloquent cortex , especially language , must take these differences into account . 
 most diagnostic tests were created for adults , and many of the assessment tools need to be adapted for children because they are not just small adults . 
 this paper will highlight the specific challenges and solutions in mapping language in a pediatric population with tle . 
1. Introduction
2. Temporal Lobe Epilepsy in Children
3. Language and TLE
4. Tools to Map Language
5. Emerging Techniques
6. Conclusion