Deep Brain Stimulation of the Basolateral Amygdala: Targeting Technique and Electrodiagnostic Findings

brain sciences

Article Deep Brain Stimulation of the Basolateral Amygdala: Targeting Technique and Electrodiagnostic Findings

Jean-Philippe Langevin 1,*, James W. Y. Chen 2, Ralph J. Koek 3, David L. Sultzer 3, Mark A. Mandelkern 4, Holly N. Schwartz 3 and Scott E. Krahl 5 1 Neurosurgery Service, VA Greater Los Angeles Healthcare System, Los Angeles, CA 90073, USA 2 Neurology Service, VA Greater Los Angeles Healthcare System, Los Angeles, CA 90073, USA; [email protected] 3 Psychiatry and Mental Health Service, VA Greater Los Angeles Healthcare System, Los Angeles, CA 90073, USA; [email protected] (R.J.K.); [email protected] (D.L.S.); [email protected] (H.N.S.) 4 Radiology Service, Nuclear Medicine VA Greater Los Angeles Healthcare System, Los Angeles, CA 90073, USA; [email protected] 5 Research and Development Service, VA Greater Los Angeles Healthcare System, Los Angeles, CA 90073, USA; [email protected] * Correspondence: [email protected]; Tel.: +1-310-478-3711

Academic Editors: Tipu Aziz and Alex Green Received: 30 June 2016; Accepted: 5 August 2016; Published: 10 August 2016 Abstract: The amygdala plays a critical role in emotion regulation. It could prove to be an effective neuromodulation target in the treatment of psychiatric conditions characterized by failure of extinction. We aim to describe our targeting technique, and intra-operative and post-operative electrodiagnostic findings associated with the placement of deep brain stimulation (DBS) electrodes in the amygdala. We used a transfrontal approach to implant DBS electrodes in the basolateral nucleus of the amygdala (BLn) of a patient suffering from severe post-traumatic stress disorder. We used microelectrode recording (MER) and awake intra-operative neurostimulation to assist with the placement. Post-operatively, the patient underwent monthly surveillance electroencephalograms (EEG). MER predicted the trajectory of the electrode through the amygdala. The right BLn showed a higher spike frequency than the left BLn. Intra-operative neurostimulation of the BLn elicited pleasant memories. The monthly EEG showed the presence of more sleep patterns over time with DBS. BLn DBS electrodes can be placed using a transfrontal approach. MER can predict the trajectory of the electrode in the amygdala and it may reflect the BLn neuronal activity underlying post-traumatic stress disorder PTSD. The EEG findings may underscore the reduction in anxiety.

Keywords: amygdala; basolateral nucleus; deep brain stimulation; microelectrode recording; PTSD; targeting technique

1. Introduction The amygdala is a critical node within a network that regulates emotions. Two functional zones of the amygdala are especially important in this role. The centromedial group is the output of the amygdala: through its efferent connections, it orchestrates the physiological and behavioral components of emotions [1]. The basolateral group receives sensory input and it links emotions to stimuli [2,3]. This function is particularly important because it defines the behavior manifested in response to a stimulus. To fulfill its role, the basolateral amygdala receives modulatory inputs from the medial prefrontal cortex (mPFC) and several other regions, such as the hippocampus and the ventral tegmental area [4,5]. Because it defines the emotional context of behavior, the amygdala has been surgically targeted for intractable psychiatric conditions. Bilateral transfrontal stereotactic amygdalotomies have been

Brain Sci. 2016, 6, 28; doi:10.3390/brainsci6030028 www.mdpi.com/journal/brainsci Brain Sci. 2016, 6, 28 2 of 9 performed for patients suffering from intractable aggressiveness [6]. In these cases, aggression was targeted as a symptom regardless of the specific underlying psychiatric condition. The amygdala was understood as a center of fear and anger. Recent studies have shown that the amygdala links both positive as well as negative emotions to stimuli (for review [3]). The amygdala determines if a stimulus should elicit fear (association) or not (extinction). In fact, the basolateral nucleus of the amygdala BLn contains “fear cells” that are active during fear acquisition and consolidation and “extinction cells” that are active during fear extinction [4]. Emotional extinction is a delicate process by which the basolateral nucleus (BLn) learns to no longer elicit an emotion in response to a stimulus. This learning process likely requires plasticity in the BLn, in part induced by modulation from the mPFC [2], whereby a larger population of extinction cells is activated relative to fear cells. In this sense, the BLn can be seen as an emotional receptive field modulated by the mPFC, the hippocampus and several other regions [7]. The relative population of active fear cells and extinction cells can therefore determine the specific response to a reminder. An intense stimulus, such as a life-threatening event, may overwhelm this learning process by forming a stereotypical neurophysiological response in the BLn. In post-traumatic stress disorder (PTSD), a life-threatening event leads to a state of failure of fear extinction that may be understood as a neuroplasticity failure to re-engage extinction cells. In this context, neuromodulation could be focally applied to the BLn to restore fear extinction by modifying the relative volume of active fear cells compared to extinction cells. Indeed, we have previously shown that BLn deep brain stimulation (DBS) can promote fear extinction in a rodent model of PTSD [8,9]. This effect could translate in patients suffering from PTSD. We are performing an early-phase trial evaluating BLn DBS for treatment-refractory PTSD [10]. In this paper, we aim to describe our targeting technique and intraoperative microelectrode recording (MER) results in a case of bilateral BLn DBS electrode placements. We are aware of only one other human BLn DBS case: a teenage boy was treated successfully for treatment-refractory self-mutilating behavior in the context of severe autism [11].

2. Materials and Methods

2.1. Subject Our subject is a Gulf War veteran who developed PTSD from participation in a military assault and the subsequent exposure to the bodies of enemy combatants. His baseline Clinician Administered PTSD Scale (CAPS) [12] score was 119, classifying him among the most severely ill patients. He suffered from vivid nightmares during which charred corpses would surround him. Upon exposure to trauma reminders, he would enter an unresponsive, hyper-aroused, dissociated state. He often missed workdays after a triggered ﬂashback and lost several jobs due to absenteeism. He remained severely symptomatic despite 20 years of antidepressant, antipsychotic, antiadrenergic (prazosin) and mood stabilizer pharmacotherapy and cognitive-behavioral psychotherapy. The patient met all the criteria for enrollment in our clinical trial [10], and he gave his informed consent for inclusion before participating in the study. The study was conducted in accordance with the Declaration of Helsinki, and the protocol was approved by the institutional review board of the Greater Los Angeles VA Healthcare System (IRB approval code is PCC#2016-040351).

2.2. Targeting The patient underwent a stereotactic 3T MRI with gadolinium. The images were re-oriented along the anterior commissure/posterior commissure (AC/PC) in our planning software (FHC, Bowdoin, ME, USA). Targeting the BLn is complicated due to anatomical variations in this region. Using a stereotactic atlas [13], the inferior limit of the BLn is located 16 mm lateral to the AC, 4 mm posterior to the AC and 18 mm inferior to the AC-PC plane. However, these coordinates would be incorrect for a large number of patients, and targeting has to be performed based on the local mesiotemporal anatomy. Brain Sci. 2016, 6, 28 3 of 9 incorrect for a large number of patients, and targeting has to be performed based on the local mesiotemporal anatomy. The BLn is located in the inferior portion of the amygdala. It is at the center of the amygdala where it is flanked laterally by the lateral nucleus and medially by the basomedial and basolateral ventromedial part [14]. The central and medial nuclei of the amygdala are dorsal to the BLn. When the MRI is oriented along the AC-PC plane, the fornices can be seen crossing the hypothalamus in

Brainthe same Sci. 2016 coronal, 6, 28 plane as the BLn within the amygdala [14]. Within this coronal plane, the BLn3 of is 9 located in the center of the amygdala from a medial-to-lateral perspective. When studying the axial plane at this level, the BLn is located just anterior to the tip of the temporal horn, which thus serves as anotherThe BLn important is located landmark in the inferior [11]. Finally, portion the of infe therior amygdala. border of Itthe is BLn at the is marked center of by the the amygdala presence whereof the head it is ﬂankedof the hippocampus laterally by the(Figure lateral 1). nucleus and medially by the basomedial and basolateral ventromedialThe electrode part [ 14trajectory]. The central must andavoid medial critical nuclei structures of the amygdalato permit area safe dorsal transfrontal to the BLn. approach. When the It MRIshould is orientedbe posterior along to thethe AC-PClenticulostriate plane, the perfor fornicesator canvessels be seen from crossing the first the segment hypothalamus of the middle in the samecerebral coronal artery plane and asit should the BLn remain within lateral the amygdala to the superior [14]. Within aspect this of coronal the ambient plane, cistern the BLn (Figure is located 1). inFinally, the center the trajectory of the amygdala should from be seen a medial-to-lateral traversing just perspective. anterior to Whenthe tip studying of the temporal the axial planehorn to at thisconfirm level, the the location BLn is locatedwithin the just BLn anterior [11]. to The the locati tip ofon the of temporal the entry horn, point which will vary thus depending serves as another on the importantanatomy of landmark the critical [11 structures.]. Finally, theIn general, inferior borderit will have of the a BLnlateral is markedangle of by0–10° the from presence midline of the and head an ofanterior the hippocampus angle of 70–80° (Figure from1). the AC-PC plane.

Figure 1. The figure shows the anatomical position of the BLn electrodes in the coronal plane (A,C,D) Figure 1. The ﬁgure shows the anatomical position of the BLn electrodes in the coronal plane (A,C,D) and sagittal plane (B): (A) The electrode must avoid the superior extent of the ambient cistern and sagittal plane (B): (A) The electrode must avoid the superior extent of the ambient cistern (arrow); (arrow); (B) and the lenticulostriate vessels (arrowhead); (C,D) respectively show the right and left (B) and the lenticulostriate vessels (arrowhead); (C,D) respectively show the right and left Bln electrodes Bln electrodes with segmentation of the nuclei: in yellow, the central nucleus; in red, the basolateral with segmentation of the nuclei: in yellow, the central nucleus; in red, the basolateral nucleus; in blue, thenucleus; lateral in nucleus blue, the and, lateral in white, nucleus the headand, ofin thewhite, hippocampus. the head of The the electrodehippocampus. contact The distribution, electrode fromcontact dorsal distribution, to ventral: from Central dorsal nucleus to ventral: (one contact); Central BLn nucleus (two contacts); (one contact); Hippocampus BLn (two (one contacts); contact). Laterally:Hippocampus Lateral (one nucleus contact). (zero Laterally: contacts). Lateral nucleus (zero contacts).

2.3. Anesthesia and Microelectrode Recording The electrode trajectory must avoid critical structures to permit a safe transfrontal approach. It shouldInduction be posterior was performed to the lenticulostriate with fentanyl perforator and propofol. vessels fromSubsequently, the ﬁrst segment the patient of the received middle cerebralsevoflurane artery until and the it burr should holes remain were lateralcompleted. to the At superior that point, aspect sevoflurane of the ambient was stopped, cistern the (Figure patient1). Finally,was awakened the trajectory and the should laryngeal be seen mask traversing was removed. just anterior The to themicroelectrode tip of the temporal recording horn (MER) to conﬁrm was thestarted location on withinthe right the BLnside, [11 ].once The locationthe patien of thet entryhad pointfully willregained vary dependingconsciousness, on the anatomyusing a ofplatinum-iridium the critical structures. differential In general, electrode it will (DZAP, have aFH lateralC). The angle patient of 0–10 received˝ from midlinefentanyl and (100 an mcg) anterior and anglemidazolam of 70–80 (1 ˝mg)from during the AC-PC the right plane. MER and he received fentanyl (50 mcg) and midazolam (1 mg)

2.3. Anesthesia and Microelectrode Recording Induction was performed with fentanyl and propofol. Subsequently, the patient received sevoflurane until the burr holes were completed. At that point, sevoflurane was stopped, the patient was awakened and the laryngeal mask was removed. The microelectrode recording (MER) was started on the right side, once the patient had fully regained consciousness, using a platinum-iridium Brain Sci. 2016, 6, 28 4 of 9 differential electrode (DZAP, FHC). The patient received fentanyl (100 mcg) and midazolam (1 mg) during the right MER and he received fentanyl (50 mcg) and midazolam (1 mg) during the left MER. This medication was administered in order to assist the patient with symptoms of pain and anxiety that became clinically significant as the patient emerged from anesthesia. The MER was started 20 mm above the target. The microelectrodes were advanced and the signal output was recorded for 30 s at 0.5 mm increments. The unit signals were sampled at 48,000 Hz and were recorded with low- and high-frequency cutoffs of 500 and 5000 Hz, respectively. The spike counts were calculated with a spike threshold set at 150 µvolt (MATLAB, MathWorks, Natick, MA, USA). The spike detection algorithm follows a few rules for automatic spike detection. It only detected spikes in unilateral direction (on the upward deflection) when the signal data point reaches above the threshold of 150 µvolt. It requires the signal data point to decrease below 150 µvolt before a new spike is counted. This algorithm biased toward a low estimate of the actual spike generated because in scenario that multiple discharging units were overlapping one after the other and the waveform stayed above the threshold, the multiple spikes were counted as the same spike. However, this algorithm could avoid a bigger bias by counting every data point above the threshold as a new spike. Spikes were counted per second over the 30 s period, and the mean and standard deviation (n = 30) of spike frequency was calculated per recording site.

2.4. EEG Recording The EEG recording was performed using a clinical EEG machine (Nihon Kohden, Irvine, CA, USA). The electrodes were placed according to the standard international 10–20 system. The EEG tracings were displayed using a double-banana montage. The EEG was studied using conventional clinical analysis techniques.

2.5. Sleep and Nightmares Recording The most distressing PTSD symptom reported by our patient was the occurrence of severe nightmares. Given the clinical relevance of those episodes for our subject, we elected to measure the impact of BLn DBS on sleep and nightmares. Upon enrollment, he was given a table on which he recorded the hours that he slept every night as well as the number and the subjective intensity (0 none, 10 most severe) of these nightmares. This method of measurement is inherently qualitative, subjective and non-validated. Our aim was to obtain a preliminary sense of the impact of our treatment on subjective sleep experience.

3. Results

3.1. Microelectrode and DBS Lead Positions The positions of the DBS leads were conﬁrmed using a stereotactic CT scan fused to the preoperative MRI using our planning software (WayPoint, FHC, Bowdoin, ME, USA). The location of microelectrode recordings in relation to the anatomy was extrapolated based on a stereotactic atlas [14], while taking into account the local anatomy and the AC-PC coordinates at each MER recording point.

3.2. Microelectrode Recording The MER data correlated to the anatomy as predicted by a stereotactic atlas (Figure2). The initial high-frequency signal was in the position of the ventral globus pallidus externa (GPe) (49 ˘ 17 Hz on the left and 114 ˘ 84 Hz on the right). This signal was followed by an area sparse in spikes in the region of the ventroamygdalofugal pathway dorsal to the amygdala. The entry into the amygdala was characterized by an increase in ﬁring frequency in the region of the central nucleus of the amygdala CeA (2 ˘ 3 Hz on the left and 20 ˘ 18 Hz on the right). The BLn was characterized by a similar neuronal ﬁring frequency as the CeA. The dorsal BLn showed 3 ˘ 3 Hz on the left and 29 ˘ 19 Hz on the right. The ventral BLn had a spike frequency of 12 ˘ 13 Hz and 33 ˘ 30 Hz on the left and right, Brain Sci. 2016, 6, 28 5 of 9 respectively.Brain Sci. 2016 The, 6, ventral28 exit from the BLn was characterized with a drop of spikes and background5 of 9 activity consistent with white matter in the region separating the BLn from the hippocampus. The entry hippocampus. The entry into the hippocampus was characterized by high-frequency activity on the into theright hippocampus (85 ± 53 Hz), wasbut characterizednot on the left by(2 high-frequency± 4 Hz). Overall, activity the frequency on the was right higher (85 ˘ in53 the Hz), right but not on thehemisphere left (2 ˘ 4 compared Hz). Overall, to the the left. frequency was higher in the right hemisphere compared to the left.

Figure 2. MER signals at different sites along the trajectory of the microelectrode. The predicted Figure 2. MER signals at different sites along the trajectory of the microelectrode. The predicted trajectory has been superimposed to a stereotactic brain atlas [14]. The MERs match the predicted trajectoryanatomy has with been higher superimposed frequencies tonoted a stereotactic in the GPe, brain the amygdala atlas [14 and]. The the MERshippocampus. match theThe predictedright anatomyside withshows higher a higher frequencies frequencynoted than the in theleft GPe,side. theThe amygdalaentrance and and the the ex hippocampus.it from the amygdala The right are side showsmarked a higher by a frequency drop in background than the leftactivity. side. The entrance and the exit from the amygdala are marked by a drop in background activity. 3.3. Intraoperative Neurostimulation 3.3. IntraoperativeThe patient Neurostimulation was awake and able to correspond with the psychiatry team during testing of DBS Theelectrode patient contacts. was awake The intra-operative and able to correspond neurostimulation with thewas psychiatry conducted teamusing during the implant testing DBS of DBS electrode (3387, Medtronic, Minneapolis, MN, USA). The DBS electrodes were connected to an electrode contacts. The intra-operative neurostimulation was conducted using the implant DBS external neurostimulator (37022, Medtronic, USA) using an alligator clip wire (3550-67, Medtronic, electrode (3387, Medtronic, Minneapolis, MN, USA). The DBS electrodes were connected to an external USA) that allows for each contact to be activated individually. For each electrode contact, we used neurostimulatorthe following (37022, stimulation Medtronic, parameters: USA) 120 using μs of anpulse alligator width, clip160 Hz wire of (3550-67,frequency Medtronic,and an amplitude USA) that allowsof for0–5 eachV increased contact by to increments be activated of 0.5 individually. V. The activation For each of the electrode contacts contact,located in we the used BLn triggered the following stimulationmemories parameters: of places he had 120 been,µs of mainly pulse in width, his childhood. 160 Hz Some of frequency of the scenes and were an experienced amplitude ofas if 0–5 V increasedfrom bya distance. increments These of 0.5were V. generally The activation experienced of the as contacts pleasant located or amusing. in the BLnHe also triggered experienced memories of placesemotions he had of calm. been, Since mainly his in diagnosis his childhood. of PTSD Some, he had of the not scenes had pleasa werent experienced memories and as ifthis from a distance.represented These werea new generally experience experienced for him. The asonly pleasant unpleasant or amusing. experience He was also a transient experienced subjective emotions of calm.sensation Since that his diagnosishe could not of PTSD,picture hethe had examiner’s not had face pleasant when he memories closed his and eyes, this despite represented accurate a new recognition by looking at the examiner in person or on an identification card. There were no other experience for him. The only unpleasant experience was a transient subjective sensation that he could adverse events related to the stimulation at amplitudes up to 5 V. Electrical stimulation of the not picture the examiner’s face when he closed his eyes, despite accurate recognition by looking at mesiotemporal structures has led to similar experiences in epilepsy patients [15]. the examiner in person or on an identification card. There were no other adverse events related to the stimulation3.4. Post-Operative at amplitudes Electroencephalogram up to 5 V. Electrical stimulation of the mesiotemporal structures has led to similar experiences in epilepsy patients [15]. The patient underwent surveillance of a 30 min EEG at baseline and then monthly post-operatively. The predominant muscle artifacts that were noted in awake recordings attenuated 3.4. Post-Operative Electroencephalogram significantly after DBS stimulation. The persistent finding of being able to relax his frontalis muscles Thesuggests patient that underwent the patient surveillancewas less anxious of a or 30 hy minpervigilant. EEG at baseline Over time, and the then EEG monthly has demonstrated post-operatively. a The predominantreduction in musclethe frequency artifacts of thatthe wereposterior noted dominant in awake rhythm recordings (PDR) attenuated from 11 significantlyHz to 9 Hz. after DBS stimulation. The persistent finding of being able to relax his frontalis muscles suggests that the patient was less anxious or hypervigilant. Over time, the EEG has demonstrated a reduction in the Brain Sci. 2016, 6, 28 6 of 9

Brain Sci. 2016, 6, 28 6 of 9 frequency of the posterior dominant rhythm (PDR) from 11 Hz to 9 Hz. Furthermore, the EEG showed progressivelyFurthermore, more the EEG sleep showed patterns progressively and, by month more 10, sl sloweep patterns wave sleep and, wasby month observed 10, slow on all wave subsequent sleep EEGwas studies observed (Figure on all3). subsequent The patient EEG reported studies improved (Figure 3). duration The patient and reported quality ofimproved sleep during duration the and same Brain Sci. 2016, 6, 28 6 of 9 interval.quality In of particular,sleep during he the reported same interval. an average In particul gain ofar, three he reported hours of an sleep average and gain a marked of three reduction hours of in sleep and a marked reduction in nightmare frequency and severity (Figure 4). These nightmares nightmareFurthermore, frequency the andEEG severityshowed progressively (Figure4). These more sl nightmareseep patterns wereand, by reported month 10, to slow the studywave sleep team and were reported to the study team and many previous psychiatrists as horrifying re-experiences of many previouswas observed psychiatrists on all subsequent as horrifying EEG studies re-experiences (Figure 3). The of patient combat reported events improved that woke duration himfrom and sleep combat events that woke him from sleep in an autonomically hyper-aroused state. For years he in an autonomicallyquality of sleep hyper-arousedduring the same state.interval. For In yearsparticul hear, would he reported get out an ofaverage bed after gain theseof three nightmares hours of and would get out of bed after these nightmares and stand in a cold shower for an hour or more, trying stand insleep a cold and showera marked for reduction an hour in or nightmare more, trying freque toncy “wash and severity off” the (Figure residue 4). ofThese charred nightmares ﬂesh he had to “wash off” the residue of charred flesh he had experienced enveloping him during the nightmare. experiencedwere reported enveloping to the him study during team theand nightmare.many previo Uponus psychiatrists enrollment as inhorrifying the study, re-experiences given that of this was Uponcombat enrollment events inthat the woke study, him given from that sleep this in wasan autonomically the patient’s mosthyper-aroused distressing state. PTSD For symptom, years he he the patient’s most distressing PTSD symptom, he was given a recording sheet on which he recorded was wouldgiven geta recording out of bed aftersheet these on whichnightmares he recorded and stand the in anumber cold shower and for subjective an hour or(0 more, none, trying 10 most thesevere) numberto “wash intensity and off” subjective theof residuethese (0 nightmares. none,of charred 10 most flesh As severe)heshown had experienced intensityin Figure of 4,enveloping these these nightmares. experiences him during Ashave the shown nightmare. decreased in Figure in 4, thesefrequency experiencesUpon enrollment and severity have in decreased the with study, DBS, ingiven frequencyand that have this not andwas recu the severity rredpatient’s as with of most the DBS, distressingtime and of have this PTSD writing not symptom, recurred (18 months he as of the timeafter ofwas initiation this given writing aof recording DBS). (18 months sheet after on which initiation he recorded of DBS). the number and subjective (0 none, 10 most severe) intensity of these nightmares. As shown in Figure 4, these experiences have decreased in frequency and severity with DBS, and have not recurred as of the time of this writing (18 months after initiation of DBS).

Figure 3. EEG at baseline and one year post-operatively. At baseline, the EEG shows robust PDR and Figure 3. EEG at baseline and one year post-operatively. At baseline, the EEG shows robust PDR and muscle artifacts in the frontal channels, possibly related to anxiety. At one year post-operatively, the muscleFigure artifacts 3. EEG in theat baseline frontal and channels, one year possiblypost-operatively related. At to baseline, anxiety. the At EEG one shows year post-operatively,robust PDR and the EEG shows a reduction in PDR and the presence of SWS, which may reflect a reduction in anxiety. EEG showsmuscle a artifacts reduction in the in frontal PDR channels, and the presencepossibly rela ofted SWS, to anxiety. which At may one reﬂectyear post-operatively, a reduction in the anxiety. Double Banana montage and a bandwidth of 1–70 Hz were used for displaying EEG tracings. DoubleEEG Banana shows montage a reduction and in a PDR bandwidth and the presence of 1–70 Hzof SWS, were which used may for displaying reflect a reduction EEG tracings. in anxiety. Tracings Tracings from the right hemisphere were color-coded as red, and left hemisphere as blue, and from theDouble right Banana hemisphere montage were and color-coded a bandwidth asof red,1–70 and Hz leftwere hemisphere used for displaying as blue, andEEG sagittaltracings. line as sagittalTracings line asfrom black. the Theright tracings hemisphere from weretop to color-co bottomded in sequenceas red, and were: left Fhemispherep2-F8, F8-T4, as T4-T6,blue, and T6-O2, black. The tracings from top to bottom in sequence were: Fp2-F8, F8-T4, T4-T6, T6-O2, Fp1-F7, F7-T3, Fp1-F7,sagittal F7-T3, line T3-T5, as black. T5-O1, The tracings Fp2-F4, frF4-C4,om top C4-P4, to bottom P4-O2, in sequence Fp1-F3, were:F3-C3, F pC3-P3,2-F8, F8-T4, P3-O1, T4-T6, Fz-Cz, T6-O2, Cz-Oz. T3-T5, T5-O1, Fp2-F4, F4-C4, C4-P4, P4-O2, Fp1-F3, F3-C3, C3-P3, P3-O1, Fz-Cz, Cz-Oz. One channel OneF channelp1-F7, F7-T3, EKG T3-T5, tracing, T5-O1, which Fp2-F4, was F4-C4, in red C4-P4, color, P4-O2,was shown Fp1-F3, at F3-C3, the bottom. C3-P3, P3-O1, Fz-Cz, Cz-Oz. EKG tracing,One channel which EKG was tracing, in red which color, was was in shownred color, at was the shown bottom. at the bottom.

Figure 4. Graph showing the self-reported frequency and intensity of nightmares over time after BLn FigureFigure 4. 4.Graph Graph showing showing the the self-reported self-reported frequencyfrequency and intensity intensity of of nightmares nightmares over over time time after after BLn BLn DBS. After month 10, the patient reported the occurrence of occasional bad dreams that were DBS.DBS. Afterdifferent After month monthfrom 10, his the10, typical patientthe nightmpatient reportedares reported in quality the occurrencethe and oc intensity.currence of occasional of occasional bad dreams bad dreams that were that different were fromdifferent his typical from nightmareshis typical nightm in qualityares in and quality intensity. and intensity. Brain Sci. 2016, 6, 28 7 of 9

4. Discussion BLn DBS may prove beneficial for psychiatric conditions characterized by the failure to extinguish the link between an emotion (fear, pleasure) and a stimulus. Thus far, our patient has shown a substantial clinical improvement [16]. This is the second reported case of BLn DBS [11]. In both cases, a transfrontal trajectory was safely employed. This approach allows for a DBS lead placement that spans the CeA, the BLn, and the head of the hippocampus. These structures are interconnected and have been implicated in PTSD. The transfrontal approach therefore allows us to modulate more than one target nucleus depending on the clinical response. In addition, this trajectory avoids the ventricle and the body of the hippocampus, both of which would be entered during a transoccipital approach. Finally, the transfrontal approach is comfortable for the patient and it permits a safe and tolerable subdermal implantation of the leads. A transtemporal approach would require dividing the temporalis muscle, thus causing pain and possibly interfering with subcutaneous tunneling. The neurostimulation in this acute setting triggered memories of childhood; this experience has been reported with mesiotemporal electrical stimulation in epilepsy patients [15] and may prove predictive of proper electrode placement. The MER findings were concordant with the anatomy as predicted by a stereotactic atlas. There is a relative paucity of neuronal spikes at the dorsal and the ventral extent of the BLn corresponding to white matter tracts at the margins of the nucleus. MER may predict the trajectory and span of the lead within the BLn. Our MER data also suggested more neuronal spikes in the right subcortical structures compared to the left. Several factors could account for this discrepancy. For instance, differences in anesthesia may account for this finding, although efforts were made to maintain the level of consciousness and the medication administered as constant during the right and the left MERs. Nevertheless, a benzodiazepine and a narcotic agent had to be administered to help the patient with pain and anxiety which became significant as the anesthesia was lifted. Other factors could also explain some of the differences between the right and left MER recordings. The trajectories may have been slightly different and the left electrode may have passed through a region with relative paucity in neurons compared to the right side. Alternatively, our MER findings may represent an overall increase in neuronal activity in the right hemisphere and the right amygdala in the context of PTSD. Other authors have reported hemispheric laterality findings in PTSD. Using resting-state magnetoenceopahlography (MEG), Engdahl et al. [17] showed that PTSD patients have more synchronous neuronal interactions in the right hemisphere compared to normal controls or PTSD patients in remission. Using a SPECT scan, Pagani et al. [18] showed an increase in right hemisphere cerebral blood flow when PTSD patients were exposed to a traumatic reminder compared to normal controls. Our ability to draw any conclusions in regard to this right and left discrepancy in MERs is limited by the fact that we have data for only one subject thus far. The EEG findings of reduced PDR frequency and increased presence of sleep may reflect an effect of BLn DBS on anxiety. The PDR frequency has been reported to be higher in anxious patients compared to normal controls [19]. This effect on the PDR can serve as a proxy for anxiety whether it is directly related to anxiety or related to the patient’s inability to achieve a relaxed state [20]. Clinically, DBS of the amygdala reduced hyper-arousal symptoms and the underlying anxiety associated with PTSD. This effect may translate into an overall reduction in PDR and the appearance of slow-wave sleep SWS on the EEG since the patient is less anxious and is able to fall asleep easily. During the same interval, the patient reported a subjective improvement in duration and quality of sleep. By reducing anxiety, DBS may permit the activation of amygdala circuits critical to sleep. Anxiety can be understood as the psychological percept associated with the inability to activate those sleep circuits due to amygdala-mediated hypervigilance.

5. Conclusions We describe our targeting technique and intraoperative findings for the placement of BLn DBS electrodes. BLn DBS may prove beneficial in conditions where emotional regulation mechanisms are dysfunctional, leading to a pervasive state of emotional inflexibility. In severe PTSD, failure of fear Brain Sci. 2016, 6, 28 8 of 9 extinction causes a generalized association of fear to benign stimuli. In substance abuse, dysfunction in pleasure control leads to a preoccupation with drug-seeking behavior due to a failure of reward extinction. We describe MER findings for a patient with severe PTSD. The MER data may predict the span of the DBS lead within the BLn. Furthermore, the increase in spike frequency can be explained by the increase in metabolism and cerebral blood flow seen in PTSD patients. On EEG, chronic BLn DBS was associated with an overall reduction in the PDR frequency and the presence of SWS. These findings may highlight a reduction in anxiety. Nevertheless, our study is limited to a single subject. In addition, MER in the clinical setting does not clearly distinguish the type and the exact number of neurons being recorded, limiting our analytic capability.

Acknowledgments: All sources of funding of the study should be disclosed. Please clearly indicate grants that you have received in support of your research work. Clearly state if you received funds for covering the costs to publish in open access. Author Contributions: Jean-Philippe Langevin conceptualized the use of BLn DBS for PTSD, performed the experiments and wrote the manuscript. W.Y. Chen designed the EEG surveillance portion of the protocol and he analyzed the EEG data. Ralph J. Koek designed the protocol, performed the experiments, gathered and analyzed the data. David L. Sultzer participated in the design of the protocol and the analysis of the data. Mark A. Mandelkern participated in the design of the protocol and the analysis of the data. Holly N. Schwartz performed the experiments, participated in gathering the data. Scott E. Krahl participated in the design of the protocol, he performed the experiments and participated in the analysis of the data. Conﬂicts of Interest: The authors declare no conﬂict of interest.

References

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