Functional brain mapping using depth electrodes

OBJECTIVE

This study investigated the neurological symptoms and stimulus intensities in the stimulation of deep structures and subcortical fibers with the depth electrodes.

METHODS

Seventeen patients with drug-refractory epilepsy who underwent functional brain mapping with the depth electrodes were enrolled. The 50 Hz electrical stimulation was applied, and the diffusion tensor image was used to identify subcortical fibers. The responsible structures and stimulus intensities for the induced neurological symptoms were evaluated.

RESULTS

Neurological symptoms were induced in 11 of 17 patients. The opercular stimulation elicited the neurological symptoms in six patients at the median threshold of 4.0 mA (visceral/face/hand sensory, hand/throat motor, negative motor and auditory symptoms). The insular stimulation induced the neurological symptoms in four patients at the median threshold of 4.0 mA (auditory, negative motor, and sensory symptoms). The stimulation of subcortical fibers induced in five of nine patients at the median threshold of 4.5 mA. The thresholds of depth electrodes were significantly lower than those of subdural electrodes in eight patients who used both subdural and depth electrodes and induced symptoms with both electrodes.

CONCLUSION

The stimulation of depth electrodes can identify the function of deep structures and subcortical fibers with lower intensities than subdural electrodes.

Intraoperative nerve stimulation during vagal nerve stimulator placement

Background

Vagal nerve stimulation (VNS) is a palliative treatment for refractory epilepsy and intraoperative nerve stimulation is applied to the vagal and other nerves to prevent electrode misplacement. We evaluated these thresholds to establish intraoperative monitoring procedures for VNS surgery.

Methods

Forty-six patients who underwent intraoperative nerve stimulation during VNS placement were enrolled. The vagal nerve and other exposed nerves were electrically stimulated during surgery, and muscle contraction was confirmed by electromyography of the vocal cords and visual recognition of cervical muscle contraction. The nerve thresholds and the most sensitive parts of the vagal nerve were analyzed retrospectively.

Results

The stimulation of vagal nerves induced vocal cord responses in all 46 patients; the median thresholds of the most sensitive parts and all parts were 0.2 mA (range: 0.05-0.75 mA) and 0.25 mA (range: 0.15-1.5 mA), respectively. The medial middle region was identified as the most sensitive part of the vagal nerve in the majority of participants (82.5%). In 11 patients, other cervical nerves were stimulated and sternohyoid muscle contraction was induced with a median threshold of 0.35 mA (range: 0.1-0.7 mA) in eight patients, while sternocleidomastoid muscle contraction was induced with a median threshold of 0.2 mA (range: 0.1-0.2 mA) in three.

Conclusion

Intraoperative stimulation of vagal nerves induces vocal cord responses with locational variations, and the middle part stimulation could minimize the stimulus intensities. The nerves innervating the sternohyoid and sternocleidomastoid muscles may be exposed during the procedure. Knowledge of these characteristics will enhance the effectiveness of this technique in future applications.

Steady-State Cortico-Cortical Evoked Potential

PURPOSE

The present study evaluated the utility of the steady-state responses of cortico-cortical evoked potentials (SSCCEPs) and compared them with the responses of conventional CCEPs.

METHODS

Eleven patients with medically intractable focal epilepsy who underwent the implantation of subdural electrodes or stereoelectroencephalography were enrolled. Conventional CCEPs were obtained by averaging responses to alternating 1-Hz electrical stimuli, and 5-Hz stimuli were delivered for recording SSCCEPs. The distribution of SSCCEPs was assessed by a frequency analysis of fast Fourier transform and compared with conventional CCEPs.

RESULTS

Steady-state responses of cortico-cortical evoked potentials were successfully recorded in areas consistent with conventional CCEPs in all patients. However, SSCCEPs were more easily disturbed by the 5-Hz stimulation, and small responses had difficulty generating SSCCEPs.

CONCLUSIONS

Steady-state responses of cortico-cortical evoked potentials may be a useful alternative to conventional CCEPs.

Deep learning for the diagnosis of mesial temporal lobe epilepsy

OBJECTIVE

This study aimed to enable the automatic detection of the hippocampus and diagnose mesial temporal lobe epilepsy (MTLE) with the hippocampus as the epileptogenic area using artificial intelligence (AI). We compared the diagnostic accuracies of AI and neurosurgical physicians for MTLE with the hippocampus as the epileptogenic area.

METHOD

In this study, we used an AI program to diagnose MTLE. The image sets were processed using a code written in Python 3.7.4. and analyzed using Open Computer Vision 4.5.1. The deep learning model, which was a fine-tuned VGG16 model, consisted of several layers. The diagnostic accuracies of AI and board-certified neurosurgeons were compared.

RESULTS

AI detected the hippocampi automatically and diagnosed MTLE with the hippocampus as the epileptogenic area on both T2-weighted imaging (T2WI) and fluid-attenuated inversion recovery (FLAIR) images. The diagnostic accuracies of AI based on T2WI and FLAIR data were 99% and 89%, respectively, and those of neurosurgeons based on T2WI and FLAIR data were 94% and 95%, respectively. The diagnostic accuracy of AI was statistically higher than that of board-certified neurosurgeons based on T2WI data (p = 0.00129).

CONCLUSION

The deep learning-based AI program is highly accurate and can diagnose MTLE better than some board-certified neurosurgeons. AI can maintain a certain level of output accuracy and can be a reliable assistant to doctors.

Effect of Early Surgical Intervention for Brain Tumors Associated with Epilepsy on the Improvement in Memory Performance

We evaluated the effect of early surgical intervention on the change in memory performance of patients with low-grade brain tumors associated with epilepsy. Twenty-three adult patients with low-grade brain tumors and epilepsy who underwent surgery at our institution between 2010 and 2019 were included. The Wechsler Memory Scale-Revised (WMS-R) was used to assess cognitive memory performance. Memory performance before and after surgery was retrospectively evaluated. In addition, the relationships among preoperative memory function, postoperative seizure outcome, preoperative seizure control, temporal lobe lesion, and change in memory function were examined. There were statistically significant improvements from median preoperative to postoperative WMS-R subscale scores for verbal memory, general memory, and delayed recall (p<0.001, p<0.001, and p=0.0055, respectively) regardless of preoperative sores and tumor location. Good postsurgical seizure control was associated with significant improvements in postoperative WMS-R performance. Our results indicated that early surgical intervention might improve postoperative memory function in patients with low-grade brain tumors and epilepsy.

Motor Mapping with Functional Magnetic Resonance Imaging: Comparison with Electrical Cortical Stimulation

The aim of the present study was to evaluate motor area mapping using functional magnetic resonance imaging (fMRI) compared with electrical cortical stimulation (ECS). Motor mapping with fMRI and ECS were retrospectively compared in seven patients with refractory epilepsy in which the primary motor (M1) areas were identified by fMRI and ECS mapping between 2012 and 2019. A right finger tapping task was used for fMRI motor mapping. Blood oxygen level-dependent activation was detected in the left precentral gyrus (PreCG) /postcentral gyrus (PostCG) along the "hand knob" of the central sulcus in all seven patients. Bilateral supplementary motor areas (SMAs) were also activated (n = 6), and the cerebellar hemisphere showed activation on the right side (n = 3) and bilateral side (n = 4). Furthermore, the premotor area (PM) and posterior parietal cortex (PPC) were also activated on the left side (n = 1) and bilateral sides (n = 2). The M1 and sensory area (S1) detected by ECS included fMRI-activated PreCG/PostCG areas with broader extent. This study showed that fMRI motor mapping was locationally well correlated to the activation of M1/S1 by ECS, but the spatial extent was not concordant. In addition, the involvement of SMA, PM/PPC, and the cerebellum in simple voluntary movement was also suggested. Combination analysis of fMRI and ECS motor mapping contributes to precise localization of M1/S1.

Cortical regions and networks of hyperkinetic seizures: Electrocorticography and diffusion tensor imaging study

OBJECTIVE

The present study investigated the cortical areas and networks responsible for hyperkinetic seizures by analyzing invasive recordings and diffusion tensor imaging (DTI) tractography.

METHODS

Seven patients with intractable focal epilepsy in whom hyperkinetic seizures were recorded during an invasive evaluation at Sapporo Medical University between January 2012 and March 2020 were enrolled in the present study. Intracranial recordings were analyzed to localize seizure-onset zones (SOZs) and symptomatogenic zones (spread areas at clinical onset). DTI was used to identify the subcortical fibers originating from SOZs.

RESULTS

Ten SOZs were located in four areas: (1) the inferior parietal lobule (two SOZs in two patients), (2) temporo-occipital junction (three SOZs in two patients), (3) medial temporal area (three SOZs in three patients) and (4) medial/lateral frontal lobe (two SOZs in two patients). Symptomatogenic zones appeared to be the premotor area, basal temporal area, temporo-occipital junction, and the postcentral gyrus/supramarginal gyrus. The tractographic analysis revealed that the inferior fronto-occipital fasciculus (IFOF), inferior longitudinal fasciculus (ILF), middle longitudinal fasciculus (MLF), arcuate fasciculus (AF)/superior longitudinal fasciculus (SLF) II, III, and cingulum bundle may be associated with hyperkinetic seizures.

CONCLUSION

The present results suggest the cortical areas (the inferior parietal lobule, temporo-occipital junction, medial temporal area, and medial/lateral frontal lobe) and subcortical fibers (IFOF, ILF, MLF, AF/SLFII, III, and the cingulum bundle) responsible for generating hyperkinetic seizures.

Effects of polarity of bipolar sensorimotor direct cortical stimulation on intraoperative motor evoked potentials

OBJECTIVE

The present study investigated the effects of the stimulus polarity and location of motor evoked potential (MEP) to establish a stimulation protocol.

METHODS

Nineteen patients who intraoperatively underwent MEP in bipolar direct cortical stimulation were enrolled in the present study. Somatosensory evoked potentials (SEP) of the contralateral median nerve stimulation were recorded to determine stimulation sites. MEP was performed under two settings in all patients: 1. Anodal bipolar stimulation: an anode on the precentral gyrus and a cathode on the postcentral gyrus, 2. Cathodal bipolar stimulation: a cathode on the precentral gyrus and an anode on the postcentral gyrus. MEP amplitudes and the coefficient of variation (CV) at a stimulation intensity of 25 mA and the thresholds of induced MEP were compared between the two settings.

RESULTS

An electrical stimulation at 25 mA induced a significantly higher amplitude in cathodal bipolar stimulation than in anodal bipolar stimulation. Cathodal bipolar stimulation also showed significantly lower thresholds than anodal stimulation. CV did not significantly differ between the two groups.

CONCLUSIONS

These results indicate that cathodal bipolar stimulation is superior to anodal bipolar stimulation for intraoperative MEP monitoring.

SIGNIFICANCE

MEP in cathodal bipolar cortical stimulation may be used in a safe and useful evaluation method of motor fiber damage that combines sensitivity and specificity.

Eye Movement Network Originating from Frontal Eye Field: Electric Cortical Stimulation and Diffusion Tensor Imaging

This study investigated the networks originating from frontal eye fields (FEFs) using electric cortical stimulation and diffusion tensor imaging (DTI). Seven patients with intractable focal epilepsy, in which FEFs were identified by electrical cortical stimulation, were enrolled in this study. Electric stimulation at 50 Hz was applied to the electrodes for functional mapping. DTI was used to identify the subcortical fibers originating from the FEFs with two regions of interests (ROIs) in the FEF and contralateral paramedian pontine reticular formation (PPRF). FEFs were found in the superior precentral sulcus (pre-CS) in six patients and superior frontal gyrus (SFG) in three patients. DTI detected fibers connecting FEFs and contralateral PPRFs, passing within the internal capsule. The fibers were located close to the lateral antero-superior border of the subthalamic nucleus (STN) and medial posterior border of the globus pallidus internus (GPi). This study found the characteristic subcortical networks of the FEF. These tracts should be noted to prevent complications of deep brain stimulation (DBS) of the STN or GPi.

Forgetting to take antiseizure medications is associated with focal to bilateral tonic-clonic seizures, as revealed by a cross-sectional study

Objectives

To evaluate the effects of nonadherence to antiseizure medications (ASMs) and clinical characteristics on seizure control, we employed a prospective cohort cross-sectional study using self-reports and medical records of patients with epilepsy (PWEs).

Methods

Eight hundred and fifty-five PWEs taking ASMs were enrolled from fourteen collaborative outpatient clinics from January 2018 to March 2019. Questions from the Morisky Medication Adherence Scale were used as adherence self-reports. If a PWE’s questionnaire indicated that they had missed doses of their ASMs, outpatient physicians asked them directly about the details of their compliance, including the timing of intentionally or unintentionally missed doses. The association between lack of seizure control and utilization outcomes, such as missed doses, demographics, and clinical characteristics of the PWEs, were assessed by univariate and multivariate analyses.

Results

Multivariate analysis revealed that forgetting to take ASMs was associated with lack of seizure control and the existence of focal to bilateral tonic–clonic seizures. Dementia, younger age, use of three or more antiepileptic agents, and living in a one-person household were associated with the risk of forgetting to take ASMs.

Significance

For PWEs with poor drug management or a high incidence of missed doses of ASMs, efforts to improve adherence could facilitate better seizure control and decrease focal to bilateral tonic–clonic propagation.

Anatomical and functional distribution of functional MRI language mapping

OBJECTIVE

The aim of the present study was to compare localization of the language cortex using electrical cortical stimulation (ECS) and functional magnetic resonance imaging (fMRI) to establish the relevance of fMRI language mapping.

METHODS

Language mapping with fMRI and functional ECS mapping were retrospectively compared in ten patients with refractory epilepsy who underwent fMRI language mapping and functional ECS mapping between June 2012 and April 2019. A shiritori task, a popular Japanese word chain game, was used for fMRI language mapping.

RESULTS

BOLD signal activation was observed in the left inferior frontal gyrus (including the pars opecularis and the pars triangularis), and superior temporal gyrus, which is a language-related area, as well as in the left superior and middle frontal gyri, the intraparietal sulcus, and fusiform gyrus. These results were compared with ECS to elucidate the functional role of the activated areas during fMRI language tasks. These activated areas included language areas, negative motor areas, supplementary motor areas (SMAs), and non-functional areas.

CONCLUSION

The activated areas of fMRI language mapping include language-related areas, the negative motor area, and SMAs. These findings suggest the involvement of language and higher order motor networks in verbal expression.

The Immediate Effects of Vagus Nerve Stimulation in Intractable Epilepsy: An Intra-operative Electrocorticographic Analysis

The purpose of this study was to investigate whether and how vagus nerve stimulation (VNS) reduces the epileptogenic activity in the bilateral cerebral cortex in patients with intractable epilepsy. We analyzed the electrocorticograms (ECoGs) of five patients who underwent callosotomy due to intractable epilepsy even after VNS implantation. We recorded ECoGs and analyzed power spectrum in both VNS OFF and ON phases. We counted the number of spikes and electrodes with epileptic spikes, distinguishing unilaterally and bilaterally hemispherically spread spikes as synchronousness of the epileptic spikes in both VNS OFF and ON phases. There were 24.80 ± 35.55 and 7.20 ± 9.93 unilaterally spread spikes in the VNS OFF and ON phases, respectively (P = 0.157), and 35.8 ± 29.21 and 10.6 ± 13.50 bilaterally spread spikes in the VNS OFF and ON phases, respectively (P = 0.027). The number of electrodes with unilaterally and bilaterally spread spikes in the VNS OFF and ON phases was 3.84 ± 2.13 and 3.59 ± 1.82 (P = 0.415), and 8.20 ± 3.56 and 6.89 ± 2.89 (P = 0.026), respectively. The ECoG background power spectra recordings in the VNS OFF and ON phases were also analyzed. The spectral power tended to be greater in the high-frequency band at VNS ON phase than OFF phase. This study showed the reduction of epileptogenic spikes and spread areas of the spikes by VNS as immediate effects, electrophysiologically.

P599Native T1 mapping is useful for detection of myocardial fibrosis in cases with ischemic and non-ischemic myocardial diseases

Background

Evaluation of myocardial fibrosis (MF) as late gadolinium enhancement (LGE) on MRI is useful for differential diagnosis of various myocardial diseases and prediction of future adverse cardiac events in some specific myocardial diseases. Gadolinium contrast is contraindicated for cases with severe renal dysfunction, therefore non contrast MRI is necessary for detection of MF in cases with both myocardial disease and severe renal dysfunction.

Purpose

We aimed to evaluate diagnostic accuracy of native T1 mapping for detection of MF compared with LGE in cases with various myocardial diseases, including ischemic and non-ischemic myocardial diseases.

Methods

We selected consecutive 40 patients who were suspected of having various myocardial diseases and underwent cardiac MRI, using 1.5T MRI (Ingenia, Philips) in 10 cases (25%) or 3T MRI (Ingenia, Philips) in 30 cases (75%), including native T1 mapping (without contrast) and LGE using contrast media from Jan 2018 to Feb 2019 in our institution. We evaluated diagnostic accuracy for detection of MF in left ventricular myocardium (LVM) of native T1 mapping image compared with LGE as the gold standard, in a patient-based and segment-based analysis. In T1 mapping images, segmental high T1 lesions were defined as MF. In a segment-based analysis, MF was evaluated using 17 LVM segments model in American Heart Association.

Results

MF was detected in 139 LVM segments in 25 (63%) cases. Sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of native T1 mapping for detection of MF were 90%, 89%, 95%, 80% and 90% in a patient-based analysis, and 63%, 96%, 84%, 89% and 88% in a segment-based analysis (left figure). Native T1-values of LVM with MF were significantly higher than LVM without LGE (1351±79 vs 1093±124 in 1.5T and 1562±131 vs 1291±43 in 3T) (p<0.05 and p<0.01). Interobserver agreement of native T1 mapping and LGE were not significantly different (0.88 and 0.89, P=0.70). Overall diagnostic accuracy of native T1 mapping for detection of MF in a patient-based analysis, was not significantly different in between the cases with ischemic (n=18) and non-ischemic (n=22) myocardial disease (90% and 83.3%, P=0.10).

Conclusion

Native T1 mapping (without contrast) is useful for detection of MF in various myocardial diseases and high diagnostic accuracy is expected especially in a patient-based analysis.

P6182Combination of a new iterative reconstruction technique with low tube voltage and high tube current has important role of detection of late enhancement on 320 slice CT

Background

New iterative reconstruction tecniques, including Adaptive Iterative Dose Reduction 3D (AIDR 3D) and Forward Projected Model-based Iterative Reconstruction SoluTion (FIRST), have been recently available on new generation 320 slice CT, and they can provide high-quality CT images.

Purpose

The aim of this study was to evaluate the diagnostic performance of detection of abnormal late enhancement (LE) in left ventricular (LV) myocardium (LVM) using 320-slice CT with new iterative reconstruction techiniques, AIDR 3D (Figure A) and FIRST (Figure B).

Methods

A total of 100 patients who were suspected of having various myocardial diseases and underwent late phase acquisition both on cardiac CT and CMR within 3 months were analyzed. The first 50 consecutive patients (Group 1) underwent 320-slice CT with AIDR 3D, 120 Kv tube voltage, 519±71 mA tube current. The next 50 consecutive patients (Group 2) underwent 320-slice CT with FIRST, 80 or 100Kv tube voltage, 803±20 mA tube current. We compared diagnostic accuracy of CT for detection of LE in LVM against that of CMR (the gold standard) in between the 2 groups.

Results

On patient-by-patient analysis, sensitivity, specificity, positive (PPV) and negative predictive values (NPV), and overall accuracy for detection of LE on CT vs CMR were 87, 95, 96, 82, and 90% in Group 1, and 97, 83, 91, 88, and 90% in Group 2. There were no significant difference of diagnostic accuracy on patient-by-patient analysis in between the 2 groups (Figure C). However, on a segment-by-segment analysis (using 17 American Heart Association LV segment model), these values for detection of LE on CT vs CMR were 60, 95, 73, 91, and 88% in Group 1, and 85, 95, 86, 95, and 93% in Group 2. Sensitivity, PPV, NPV and overall accuracy were significantly higher in Group 2 than in Group 1 (all P<0.01) (Figure D).

Conclusions

Diagnostic accuracy of detection of LE in LVM on CT combining low tube voltage and high tube current acquisition on a new generation 320-slice CT with FIRST was superior to 320-slice CT with AIDR 3D.

Acknowledgement/Funding

TSUCHIYA MEMORIAL MEDICAL FOUNDATION

Intraoperative Monitoring for Vagus Nerve Stimulation

BACKGROUND

Vagus nerve stimulation is a palliative treatment for patients with refractory epilepsy; however, the misplacement of electrodes may cause complications and thus needs to be avoided.

METHODS

We herein report an intraoperative monitoring technique to prevent the misplacement of electrodes. Endotracheal tube electrodes were inserted to record electromyographic activity from the vocal cords and identify the vagus nerve. Electromyography electrodes were placed on the sternomastoid muscle, sternohyoid muscle, geniohyoid muscle, and trapezius muscle to record muscle activities innervated by the ansa cervicalis. The vagus nerve and ansa cervicalis were electrically stimulated during surgery, and electromyography of the vocal cords and muscles innervated by the ansa cervicalis was recorded. The threshold of vagus nerve activation ranged between 0.05 and 0.75 mA.

RESULTS

The vagus nerve was successfully identified and differentiated from the nerve root of the ansa cervicalis using this technique.

CONCLUSIONS

Intraoperative monitoring of the vagus nerve and ansa cervicalis is useful for safe and effective vagus nerve stimulation.

Psychogenic Pseudo-responses in an Electrical Cortical Stimulation

An electrical cortical stimulation provides important information for functional brain mapping. However, subjective responses (i.e. sensory, visual, and auditory symptoms) are purely detected by patients’ descriptions, and may be affected by patients’ awareness and intelligence levels. We experienced psychogenic responses in the electrical cortical stimulation of two patients with intractable epilepsy. A sham stimulation was useful for differentiating pseudo-responses from real responses in the electrical cortical stimulation. Inductive questions, long testing durations, and clear cues of stimulation onsets need to be avoided to prevent psychogenic pseudo-responses in the electrical cortical stimulation. Furthermore, a sham stimulation is applicable for detecting pseudo-responses the moment patients show atypical or inexplicable symptoms.

Interhemispheric Asymmetry of Network Connecting Between Frontal and Temporoparietal Cortices: A Corticocortical-Evoked Potential Study

BACKGROUND

The connection between the ventrolateral frontal and temporoparietal cortices has an important role in language function on the language-dominant side and spatial awareness on the nondominant side. However, the laterality of these pathways remains controversial. We investigated the laterality of this connection using corticocortical-evoked potentials (CCEPs).

METHODS

From April 2014 to March 2016, 27 patients who had undergone frontotemporal craniotomy were enrolled. With the patients under general anesthesia, subdural electrodes were placed on both frontal and temporoparietal areas intraoperatively. Alternating 1-Hz electrical stimuli were delivered to the pars opercularis and pars triangularis with a stimulus intensity of 10 mA. CCEPs were obtained from temporoparietal areas by averaging the electrocorticogram time-locked to the stimulus onset. The amplitudes and latencies of the CCEP N1 components were compared between the dominant and nondominant sides.

RESULTS

The median amplitudes of the CCEPs were 335.1 μV (range, 60.2-750) and 125.65 μV (range, 55.1-634) on the dominant and nondominant sides, respectively. The CCEP amplitudes were significantly larger on the dominant side than on the nondominant side (P = 0.013). In contrast, the median latency was 27.8 ms (range, 19.3-36.6) on the language-dominant side and 28.9 ms (range, 8.9-38.5) on the nondominant side. The latencies were not significantly different between the 2 sides (P = 0.604).

CONCLUSIONS

The CCEP amplitudes were significantly larger in the dominant hemisphere. These findings can lead to better hypotheses regarding the relationship between language functions and the development of the network connecting the frontal and temporoparietal cortices.

The auditory cortex network in the posterior superior temporal area

OBJECTIVE

This study investigated the function and networks of the auditory cortices in the posterior lateral superior temporal area (PLST) using a combination of electrical cortical stimulation and diffusion tensor imaging (DTI).

METHODS

Seven patients with intractable focal epilepsy in which the PLST auditory cortices were identified during the electrical cortical stimulation were enrolled in this study (left side: four patients, right side: three patients). Electrical stimulation at 50 Hz was applied to the chronically implanted subdural electrodes to identify the PLST auditory cortices. DTI was used to identify the subcortical fibers originating from the PLST auditory cortices found by electrical stimulation.

RESULTS

Electrical stimulation of the right PLST auditory cortices induced hearing impairment in three patients and left side stimulation elicited hearing illusory sounds in four patients. DTI detected the middle longitudinal fasciculus (MLF) in all patients, the superior longitudinal fasciculus (SLF) in six patients and the inferior fronto-occipital fasciculus (IFOF) in three patients, originating from the PLST auditory cortices.

CONCLUSION

This study suggests different functional roles between the right and left PLST auditory cortices, and the networks originating from these areas.

SIGNIFICANCE

MLF, SLF and IFOF might be associated with the auditory processing.

Location and Threshold of Electrical Cortical Stimulation for Functional Brain Mapping

BACKGROUND AND OBJECTIVE

Although many studies have investigated functional localization by electrical stimulation, the threshold to identify each area remains controversial. The present study aimed to elucidate the threshold of a cortical stimulation for functional mapping.

METHODS

We analyzed data from 17 patients with medically intractable epilepsy who underwent a 50-Hz electrical cortical stimulation for functional mapping between October 2013 and May 2017. The symptoms induced by the stimulation and the thresholds of the stimulation for these responses were evaluated.

RESULTS

Motor responses were observed after the stimulation of the primary motor cortex, supplementary motor area, and frontal eye field, and sensory responses after the stimulation of the primary and secondary sensory cortex. Regarding negative responses, language impairment was observed after the stimulation of the anterior, posterior, and basal temporal language areas, negative motor responses after the stimulation of the premotor cortex, posterior parietal cortex, and the pre- supplementary motor area, and an impairment in spatial recognition after the stimulation of the right posterior parietal cortex. Negative or positive auditory symptoms were observed with the stimulation of the posterior superior temporal gyrus. The thresholds for positive phenomena were significantly lower than those for negative phenomena (Mann-Whitney U test, P < 0.01), and sensory responses were induced at significantly lower intensities than motor responses (P < 0.01).

CONCLUSIONS

Positive and sensory effects are induced by lower intensities than negative and motor responses, respectively. The present results provide not only a practical guide for functional mapping, but also a hierarchal concept of processing in the brain.

Threshold and distribution of afterdischarges with electrical cortical stimulation

OBJECTIVE

The present study aimed to investigate the threshold and distribution of afterdischarges (ADs) with cortical electrical stimulation for functional brain mapping.

METHOD

We retrospectively analyzed data from 11 patients with medically intractable epilepsy who underwent 50-Hz cortical electrical stimulation for functional mapping followed by resection. These patients became seizure free for more than six months. The threshold and distribution of ADs induced by the stimulation were evaluated.

RESULTS

The median threshold was 6 mA (range: 2-15 mA) for the frontal lobe, 8 mA (3-15 mA) for the temporal lobe, 6 mA (2-15 mA) for the parietal lobe, and 6 mA (4-12 mA) for the occipital lobe. No significant interlobar differences were observed in AD thresholds. No significant differences were noted between within and outside epileptogenic zones. The distribution of ADs, remote spread was observed in all patients, reflecting fronto-parieto-temporal connections, as well as contiguous spread. The stimulation of premotor areas, the inferior parietal lobule, supplementary motor area, and basal temporal areas appeared to induce ADs in remote cortices.

CONCLUSION

While no locational differences were observed in AD thresholds, each brain region showed a characteristic pattern for AD spread. Remote AD spread needs to be considered for safe functional mapping.

The Involvement of Sensory-motor Networks in Reflex Seizure

Reflex seizures are epileptic events triggered by specific external stimuli, or less commonly, internal mental stimuli. Understanding the characteristics of reflex seizures is important to elucidate the mechanisms underlying network abnormalities in epileptic conditions. This report details a patient with medically intractable reflex seizures provoked by sensory stimuli to the patient's right foot. Single-photon emission computed tomography (SPECT) during the seizure induced by sensory stimulation showed hyperperfusion in broad sensory-motor networks (dorsal column-medial lemniscus pathway, left thalamus, bilateral postcentral gyri and posterior parietal cortices, left supplementary motor area (SMA), and left paracentral lobule) and left caudateputamen. The irritative zones and ictal onset zone were localized to the left medial frontoparietal (SMA, anterior and middle cingulate gyrus, and paracentral lobule) and lateral posterior parietal cortices, as evidenced by amelioration of reflex seizures following intracranial electroencephalography and surgical resection of these areas. The neuroradiological and electrophysiological findings in our case study illustrate that the mechanism of reflex seizures may be associated with hyperexcitability of the broad sensory-motor networks, including the basal ganglia. Disconnection of these networks is necessary to treat reflex seizures.

Etiology of Sudden Cardiac Arrest in Patients with Epilepsy: Experience of Tertiary Referral Hospital in Sapporo City, Japan

It has been reported that epilepsy patients had higher risk of sudden death than that of the general population. However, in Japan, there is very little literature on the observational research conducted on sudden fatal events in epilepsy. We performed a single-center, retrospective study on all the out-of-hospital cardiac arrest (OHCA) patients treated in our emergency department between 2007 and 2013. Among the OHCA patients, we extracted those with a history of epilepsy and then analyzed the characteristics of the fatal events and the background of epilepsy. From 1,823 OHCA patients, a total of 10 cases were enrolled in our study. The median age was 34 years at the time of the incident [9–52 years; interquartile range (IQR), 24–45]. We determined that half of our cases resulted from external causes of death such as drowning and suffocation and the other half were classified as sudden unexpected death in epilepsy (SUDEP). In addition, asphyxia was implicated as the cause in eight cases. Only the two near-drowning patients were immediately resuscitated, but the remaining eight patients died. The median age of first onset of epilepsy was 12 years (0.5–30; IQR, 3–21), and the median disease duration was 25 years (4–38; IQR, 6–32). Patients with active epilepsy accounted for half of our series and they were undergoing poly anti-epileptic drug therapy. The fatal events related to epilepsy tended to occur in the younger adult by external causes. An appropriate therapeutic intervention and a thorough observation were needed for its prevention.

Abstract P6-12-04: Delayed hospital visits in patients with breast cancer after the great East Japan earthquake and the subsequent Fukushima Daiichi nuclear power plant accident: A retrospective comparative analysis

Introduction

In breast cancer, delay in first presentation and self-interruption of continuous treatment are associated with lower survival. It has been suggested that risk factors for such behavioral patterns include poor social support.

Minamisoma City, located within a 30 kilometers radius from Fukushima Daiichi nuclear power plant, has experienced rapid change in social structures following the Great East Japan Earthquake and the subsequent power plant accident. There has been a mass evacuation among young and middle-aged generations for fear of potential irradiation, and this has resulted in the separation of families and friends. These changes may have resulted in a deterioration of social support for residents, which could consequently lead to changed patterns of behavior in diseases such as breast cancer.

Objectives

This study compared the behavioral patterns before and after the disasters in patients with breast cancer in Minamisoma City.

Methods

We retrospectively analyzed data from patients with breast cancer who were diagnosed from January 2008 through March 2015 in the two main cancer centers in Minamisoma City. Demographic and clinical information was extracted from medical records, including age, stage, pathological findings, treatment, and the reason for the first hospital visit. The main outcome was a change of interval from the appearance of initial symptoms to the first hospital visit before and after the disasters. We also assessed whether continuous follow-up was maintained after the disasters. We used an unpaired t-test for numerical variables and a chi-squared test for categorical variables.

Results

A total of 102 and 97 patients were diagnosed with breast cancer before and after the disasters, respectively. There were no statistically significant differences between the 2 groups concerning average age (61 years old vs. 61 years old, p=1), stage 3 or 4 cancer (18% vs. 17%, p=0.81), invasive cancer (92% vs. 93%, p=0.87) and symptomatic patients (75% vs. 74%, p=0.74), respectively. However, after the disasters, there were significant increases in the ratio of patients with more than a one-year delay from the appearance of the initial symptom to the first hospital visit (5.4% vs. 15%, p&lt;0.05). The patients with more than a one-year delay had a significantly higher ratio of advanced stage cancer compared with patients who visited a hospital earlier. Continuous follow-up was maintained in all patients diagnosed after the disasters.

Discussion

The characteristics of patients were not significantly different before and after the disasters, while the ratio of patients with more than a one-year delay of the first hospital visit significantly increased after the disasters. Although information on social capital and other sociodemographic factors was not available, we speculate that poor social support due to changed social structures after the disasters might contribute to delay in first presentation in symptomatic breast cancer patients. Further study is warranted to clarify the factors associated with delayed hospital visits, in order to establish effective health interventions in the aftermath of mass disasters.

Citation Format: Ozaki A, Tsubokura M, Nomura S, Morita T, Ochi S, Kato S, Saji S, Yokota T, Leppold C, Tanimoto T, Kami M, Tsukada M, Ohira H. Delayed hospital visits in patients with breast cancer after the great East Japan earthquake and the subsequent Fukushima Daiichi nuclear power plant accident: A retrospective comparative analysis. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-12-04.

Subcortical heterotopia appearing as huge midline mass in the newborn brain

INTRODUCTION

We report the case of a 2-year-old boy who showed a huge midline mass in the brain at prenatal assessment.

CASE REPORT

After birth, magnetic resonance imaging (MRI) revealed a conglomerate mass with an infolded microgyrus at the midline, which was suspected as a midline brain-in-brain malformation. MRI also showed incomplete cleavage of his frontal cortex and thalamus, consistent with lobar holoprosencephaly. The patient underwent an incisional biopsy of the mass on the second day of life. The mass consisted of normal central nervous tissue with gray and white matter, representing a heterotopic brain. The malformation was considered to be a subcortical heterotopia. With maturity, focal signal changes and decreased cerebral perfusion became clear on brain imaging, suggesting secondary glial degeneration. Coincident with these MRI abnormalities, the child developed psychomotor retardation and severe epilepsy focused on the side of the intracranial mass.

Predictive factors for epilepsy in moyamoya disease

BACKGROUND

Epilepsy cannot always be recognized in patients with moyamoya disease. In this report, the clinical features of patients with epilepsy were evaluated for assessing the predictive factors of epilepsy in moyamoya disease.

METHODS

A total of 64 consecutive patients with moyamoya disease were included in this study. During their follow-up periods, 7 patients were diagnosed with epilepsy. Then, the patients with epilepsy were compared with the patients without epilepsy regarding their clinical features.

RESULTS

Analysis of patient background characteristics revealed a significantly higher incidence of epilepsy in patients with high modified Rankin Scale (mRS) scores, high cerebrovascular attack scores, onset age of 3 years or less, early seizures, cortical involvement, stroke subtype, and diffuse brain atrophy. A logistic analysis of epilepsy data revealed significant differences between the 2 groups in mRS score, cerebrovascular attack score, onset age 3 years or less, early seizure, cortical involvement, stroke subtype, and diffuse brain atrophy. Of these, significant differences were noted in 3 items (mRS score, early seizure, and diffuse brain atrophy) on multivariate analysis. These 3 items were selected as the basis of our new moyamoya disease epilepsy risk scale (MDERS), which we then evaluated. The cutoff value estimated by the receiver operating characteristic curve was set at 1 (sensitivity, .857; specificity, .825) or 2 (sensitivity, .571; specificity, 1.000).

CONCLUSIONS

Epilepsy in moyamoya disease is associated with clinical factors and is not an independent category. For prediction of epilepsy in moyamoya disease, MDERS is a simple and convenient assessment scale.

Missense variants of the alanine: glyoxylate aminotransferase 2 gene correlated with carotid atherosclerosis in the Japanese population

Alanine:glyoxylate aminotransferase 2 (AGXT2; EC 2.6.1.44) degrades asymmetric dimethylarginine (ADMA), a competitive inhibitor of nitric oxide (NO) synthase. Increased ADMA, reduced NO, and hypertension are shown in Agxt2 knockout mice. There are four single nucleotide polymorphisms (rs37370, rs37369, rs180749, and rs16899974) with which AGXT2 activity changes in humans and may be related to vulnerability of vascular sclerosis. To examine the relationship between them, we studied the functional haplotypes of the AGXT2 gene and decided their relationship with arteriosclerotic changes via carotid intima-media thickness (carotid IMT) in Japanese subjects. Genotyping of those polymorphisms and the carotid IMT in 1,426 Japanese subjects were then evaluated. Subjects with C-A-A-A haplotype (rs37370, rs37369, rs180749, rs16899974) showed low AGXT2 activity (P<0.0001; Pearson’s correlation coefficients: 0.497). The C-A-A-A haplotype was significantly associated with mean carotid IMT (P=0.049) and max carotid IMT (P=0.004). Subjects with two C-A-A-A haplotypes exhibited thicker mean carotid IMT (P=0.022) and maximum carotid IMT (P=0.001). In multiple regression analysis, subjects with two C-A-A-A haplotypes were independently and positively associated with mean carotid IMT (P=0.02) and maximum IMT (P=0.005) after correction. There was a significant correlation between the functional variants in the AGXT2 gene and carotid IMT in Japanese. The AGXT2 genotype may be an important factor underlying atherosclerosis.

Absorption, distribution and excretion of radioactivity by male rats after a single intravenous or subcutaneous dose of 14C-azacitidine

The absorption, distribution and excretion of radioactivity were investigated in male Sprague-Dawley rats after a single intravenous or subcutaneous dose of 14C-azacitidine. After subcutaneous administration, 14C-azacitidine was rapidly absorbed and the radioactivity was distributed to the tissues. The absorption of radioactivity after subcutaneous administration was 76.6% of that observed after intravenous administration. There were no marked differences in the tissue distribution of the radioactivity between administration routes. The concentrations of radioactivity in most tissues, including the spleen and bone marrow, which are sites of action of azacitidine, were higher than those in the plasma. Particularly high concentrations of radioactivity were detected in the spleen, kidney and liver. The accumulation of radioactivity in blood cells increased from 0.5 to 48 h. The binding of azacitidine to serum protein was low at <9%, and the cumulative urinary and fecal excretion of radioactivity for 168 h after intravenous or subcutaneous administration was >95% of the administered dose, indicating that radioactivity did not accumulate in the tissues. The radioactivity was mainly excreted in the urine.

Extraction of nonylphenol and nonylphenol ethoxylates from sewage sludge using the pressurized fluid extraction method and the supercritical fluid extraction method

To establish endocrine disruptor (ED) monitoring and control methods for wastewater treatment plants, it is necessary to clarify the fate of EDs in each process of a sludge treatment system. However, the ED analysis method for sewage sludge containing large quantities of organic matters has not been established. So, a highly reliable analytical method that accurately measures EDs in sewage sludge must be developed. This paper reports on the results of applying the Pressurized Fluid Extraction (PFE) method and the Supercritical Fluid Extraction (SFE) method to the extraction of nonylphenol (NP) and nonylphenol ethoxylate (NPnEO) existence of which has often been confirmed in past surveys. To clarify the quantity of EDs in sludge specimens and the fate of EDs in the sludge treatment process, appropriate analytical methods should be developed. In this study, the PFE method and the SFE method were tested to extract NP and NPnEO from sewage sludge specimens. The findings indicate that the extraction from dried sludge by the PFE method can extract a larger quantity of NP and NPnEO in a shorter time than the widely used heating reflux method. Regarding the extraction by the SFE method, conditions for extraction of NP and NPnEO at a higher rate than the heating reflux method were not found.

Fate of nonylphenol and 17beta-estradiol contained in composted sewage sludge after land application

Many environmental problems caused by endocrine disrupters (EDs) have been reported. Because little is known about the fate of EDs accumulated in sewage sludge, we carried out a study to clarify the fate of EDs in composted sludge after its application to soil. Nonylphenol (NP) and 17beta-estradiol (E2) were measured for leachate and soil. High concentrations of NP and E2 were detected in the leachate at the early stage, but they decreased rapidly. Also, the high contents of NP and E2 in soil decreased significantly within 300 days. Because the decrease of NP and E2 in the soil was much larger than that of NP and E2 in the leachate, there must have been a physicochemical or biological decomposition mechanism in the soil layer. We also tried to clarify the transfer of NPs to plants from compost. In the experimental conditions of this study, the transfer of NPs to plants from compost was not observed.

Fate of nonylphenol polyethoxylates and nonylphenoxy acetic acids in an anaerobic digestion process for sewage sludge treatment

Many environmental problems caused by endocrine disruptors (EDs) have been reported. It is reported that EDs flow into sewage treatment plants, and it has been pointed out that these may be shifted from the wastewater treatment process to the sludge treatment process. Little is known about the fate of EDs accumulated in sewage sludge, so we carried out a study to clarify the fate of EDs in sewage sludge treatment processes, especially in an anaerobic digestion process. In this study, nonylphenol (NP) was selected as a target ED. Nonylphenol ethoxylates (NPnEO) or nonylphenoxy acetic acids (NPnEC), which were the precursor of NP, were added to an anaerobic digestion process, and mass balance was investigated. The following results were obtained from the anaerobic digestion experiments. (1) NP1EO was injected to an anaerobic digestion testing apparatus that was operated at a retention time of approximately 28 d and a temperature of 35 degrees C with thickened sludge sampled from an actual wastewater treatment plant. Approximately 40% of the injected NP1EO was converted to NP. (2) NP1EC was injected to an anaerobic digestion testing apparatus with thickened sludge. As a result, almost all injected NP1EC was converted to NP. When NP2EC was injected, NP2EC was not converted to NP until the 20th day.

[Fulminating midbrain irradiation injury of pediatric brain tumor]

We report two children with post radiation midbrain damage causing severe neurological symptoms. A twelve-year-old boy with a four year history of hydrocephalus was diagnosed with tectal glioma, which endoscopic biopsy revealed to be low grade. He underwent gamma knife radiation surgery (central 24 Gy/peripheral 12 Gy). Two months later bilateral ptosis followed by total oculomotor palsy and drowsiness developed. Despite pulsed-steroid therapy the tumor size increased up to 4.6 times in volume. The tumor was totally removed and was diagnosed as an early delayed radiation reaction pathologically. His symptoms disappeared except for a slight upper gaze palsy. The second patient was a six-year-old girl with a medulloblastoma. Following total resection and a VP shunt she received conventional radiation therapy along with chemotherapy. After the final irradiation she became comatose (JCS II-2) and MRI revealed diffuse midbrain damage with acute aqueduct obstruction, which recovered in two weeks. Reports of irradiation injuries of the midbrain in childhood are rare but it should be considered as a possible cause of fulminant symptoms requiring emergency treatment. Because of midbrain anatomical complexity, midbrain radiation therapy requires great care, especially in children.

Favorable outcomes with tacrolimus in two patients with refractory interstitial lung disease associated with polymyositis/dermatomyositis

Two cases of progressive interstitial lung disease associated with polymyositis/dermatomyositis are presented. Both patients were refractory to conventional therapy with high-dose corticosteroids, cyclosporine, and intermittent pulse cyclophosphamide, and thus a therapeutic trial of tacrolimus was instituted. Tacrolimus was markedly effective in achieving subjective, laboratory and radiographic improvement in both patients.

Clostridium perfringens epsilon-toxin increases permeability of single perfused microvessels of rat mesentery

Epsilon-toxin, the primary virulence factor of Clostridium perfringens type D, causes mortality in livestock, particularly sheep and goats, in which it induces an often-fatal enterotoxemia. It is believed to compromise the intestinal barrier and then enter the gut vasculature, from which it is carried systemically, causing widespread vascular endothelial damage and edema. Here we used single perfused venular microvessels in rat mesentery, which enabled direct observation of permeability properties of the in situ vascular wall during exposure to toxin. We determined the hydraulic conductivity (L(p)) of microvessels as a measure of the response to epsilon-toxin. We found that microvessels were highly sensitive to toxin. At 10 microg ml(-1) the L(p) increased irreversibly to more than 15 times the control value by 10 min. At 0.3 microg ml(-1) no increase in L(p) was observed for up to 90 min. The toxin-induced increase in L(p) was consistent with changes in ultrastructure of microvessels exposed to the toxin. Those microvessels exhibited gaps either between or through endothelial cells where perfusate had direct access to the basement membrane. Many endothelial cells appeared necrotic, highly attenuated, and with dense cytoplasm. We showed that epsilon-toxin, in a time- and dose-dependent manner, rapidly and irreversibly compromised the barrier function of venular microvessel endothelium. The results conformed to the hypothesis that epsilon-toxin interacts with vascular endothelial cells and increases the vessel wall permeability by direct damage of the endothelium.

Role of Women in Medicine: A Look at the History, the Present Condition and the Future Status of Women in the Surgical Field, Especially Neurosurgery

We have analyzed the historical background of women's progress in medicine in Japan and the role of female neurosurgeons as models for the next generation. Female neurosurgeons were asked to complete a questionnaire regarding their professional life in detail and the problems they are facing while managing their personal life after getting married and having a child. Some feel that there remain some constraints at work for being a female, due to their male colleagues who are not so understanding in nature. The younger generation is not so keen on joining the neurosurgical branch as their life career due to hard work and complete dedication demanded by neurosurgery. It is not easy for all to manage a neurosurgical career along together with a married life and children. Hence it is now time for those successful female neurosurgeons to become role models. Government can play an important role in these social reforms by coming up with programs to give social security to females and initiate programs for child care for married females pursuing such a demanding profession. Certain measures to encourage females to take up surgery are providing more time by arranging care for babies and families, flexibility in working hours, in addition to having a considerate husband and a considerate chief of department and senior staff. Departmental policies need to be completely impartial and should promote everyone based on their skills and knowledge. Women neurosurgeons need to get together and discuss all these issues so that the younger generation will not hesitate to take up this profession and become stalwarts of neurosurgery like their male counterparts.

A new implant designed to maximize contact with trabecular bone: survival to 18 months

PROBLEM

A roughened, commercially pure titanium (CP-Ti) implant design has been developed that features a different length and pitch for each screw thread to direct functional stresses away from cortical bone and to the more resilient trabecular bone. Abutment-implant connection is made using a conical taper to provide a seal against invasion by microorganisms.

PURPOSE

To assess short-term (18 months) clinical performance of this innovative implant design.

METHODS

A total of 1,419 implants were placed in 313 patients to support 419 prostheses in a multidisciplinary, multicentered, prospective clinical study conducted by the Ankylos Implant Clinical Research Group (AICRG). More than 100 dentists at 32 centers in the United States, 1 in Korea, and 1 in Taiwan are involved in the study. Failure was defined as implant removal for any reason. The influence of mobility at placement, implant length and diameter, incision type, augmentation, crestal bone reduction, bone density, and the use of the operating room or dental clinic on survival were evaluated over 18 months. Crestal bone loss between placement and uncovering was also determined.

RESULTS

Crestal bone loss ranged from 0.2 to 0.5 mm. The overall success rate from placement to 18 months was 96.6%. Implants mobile at placement failed more frequently (16.9%) compared with stable implants (3.1%). Wide-diameter implants and longer implants exhibited higher survival rates. Incision design and surgery location did not influence survival. Bone density was important to clinical survival.

A 48-month multicentric clinical investigation: implant design and survival

This report is based on a total of 2,955 implants of 6 different designs, randomized and placed in 829 patients and followed for 48 months. Implant failure was defined as nonintegration at uncovering or removal due to mobility, persistent pain, infection, and evidence of radiographic bone loss. Failures were reported for 3 phases of treatment: implant placement to uncovering (phase 1), uncovering to loading (phase 2), and postloading (phase 3). Differences in survival were compared with Kaplan-Meier survival curves. The maxillary single tooth application resulted in 95.2% survival for the hydroxyapatite-coated grooved implants. In the maxillary completely edentulous application, survival of hydroxyapatite grooved and screw implants were considerably better compared with the titanium screw implants. The hydroxyapatite-coated cylinder had better survival than the titanium basket and screw designs in the mandibular completely edentulous application. The hydroxyapatite-coated cylinder and grooved implants in the maxillary posterior partially edentulous application had similar survival rates. The survival of the hydroxyapatite-coated cylinder exceeded that of the titanium basket in mandibular posterior partially edentulous applications. Analyses by phase of treatment indicated a pattern of early failure for nonhydroxyapatite-coated implants compared with hydroxyapatite-coated implants. The implant with the highest survival at all phases of treatment was the hydroxyapatite-coated press-fit cylinder. Two hydroxyapatite-coated implant designs performed well in the challenging posterior maxillary region.

The ankylos endosseous dental implant: assessment of stability up to 18 months with the Periotest

Osseointegration is an ongoing histometric process that may vary during clinical function. The implant must be stable at uncovering, which reflects the status of bone-implant interface. The physiology of bone healing associated with endosseous implants suggests that this process occurs between 8 and 12 months, and Periotest values (PTVs) tend to reflect changes in the stability of the bone-implant interface. Stability generally increases gradually from the time of uncovering to an optimal PTV that occurs at a point close to 12 months. This stable interface must remain intact for long-term clinical survival. Rapid development of this optimal PTV is highly desirable in order to prevent premature overloading of the bone-implant interface. The Ankylos implant is a new screw-type implant design in which the thread pitch and length vary to maximize trabecular bone contact. The purpose of this report is to evaluate to 18 months the stability (PTVs) of this implant design. More than 457 implants were placed and followed for a period of 18 months by the multicentered, multidisciplinary Ankylos Implant Clinical Research Group (AICRG). Implant stability (PTVs) was assessed using the Periotest at abutment connection and at 3, 6, 9, 12, and 18 months after uncovering. The Periotest values for all implants rapidly reached an optimal status between uncovering (-3.1 PTVs) and 3 months (-3.4 PTVs). This rapid increase in stability has not previously been reported for other implant designs. The mandibular arch was more negative (-3.8 PTVs) at uncovering as compared with the PTVs for the maxillary arch (-1.7 PTVs). Negative PTVs were recorded (1) as length and diameter increased, (2) as bone density increased, (3) in certain jaw regions, (4) as the number of implants/case increased, and (5) for implants stabile at placement. The Ankylos screw implant design produced rapid stabilization 3 months after uncovering.