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S80. Utility of reduced montage EEG in detecting seizures or seizure-like activity
Abstracts / Clinical Neurophysiology 129 (2018) e142–e212
Parkinsonian syndrome. This new system may provide the personalized rehabilitation in patients with Parkinson related disorders. doi:10.1016/j.clinph.2018.04.437
S78. MRI assessment of neck muscles in patients with unilateral cervical radiculopathy patients—Joon Shik Yoon *, Seok Kang, Hanboram Choi, Kwang-Jae Lee, Jang-Yeol Kim, Seong-Ho Son (Republic of Korea) ⇑
Presenting author.
Introduction: Several recent studies have investigated the changes of multifidus muscles in patients with chronic neck pain. Also, the longus coli muscle, one of the deep cervical flexor muscles, showed smaller cross sectional area (CSA) in patients with chronic neck pain in comparison with healthy people. To our knowledge, there is no study investigating the association between morphological features of cervical paravertebral muscles in electrodiagnosed cervical radiculopathy patients. In this study, we investigate the change in CSA and composition of the cervical flexor and multifidus muscles using the digital data from MRIs of patients with electrodiagnosed cervical radiculopathy. Methods: Twenty-four patients with unilateral cervical radicular pain who had cervical MRI and EMG examinations between 1 January 2015 and 2016 were retrospectively analysed. The inclusion criteria were as follows: (1) patients with the symptoms of unilateral cervical pain or referral to one upper limb, (2) diagnosis of cervical radiculopathy in EMG. Exclusion criteria included: (1) a history of cervical surgery; (2) a history of spinal fracture or injuries; (3) primary or metastatic spinal tumor. Axial slice at the level of C4-5 mid disc level image was selected to calculate the muscle CSA, with their maximal CSAs. Total CSA and functional CSA measurements of the bilateral longus colli, sternocleidomastoid and multifidus muscles were measured by using Image J (version 1.43, National Institutes of Health, Bethesda, Maryland). All muscle measurements were acquired by one investigators. Functional CSA measurement was obtained by using threshold method (including only pixels within lean muscle tissue range). Statistical analysis was performed using SPSSÒ v. 15. Results: The baseline characteristics of the study participants are shown in Table 1. There was no significant difference in total CSA in longus colli, sternocleidomastoid and multifidus muscles between involved and uninvolved groups. Data analysis showed significant difference between the functional CSA of the lognus colli muscle the involved/uninvolved sides (Table 2). Also, there is significant difference in the ratio of longus colli musle (functional longus colli muscle CSA/total longus colli muscle CSA) between the involved and uninvolved sides (P < 0.001). Conclusion: This is the study to show via MRI assessment that patients with cervical radiculopathy have smaller ipsilateral functional CSA of the longus colli muscle LCM in comparison with uninvolved side. Consideration of these muscles in MRI could be helpful in the diagnosis and prognosis of cervical radiculopathy. doi:10.1016/j.clinph.2018.04.438
S79. The utility of tibial nerve SEPs in diagnosing lumbar spinal stenosis, comparison with NCS and F-Waves—Chizuko Oishi *, Yoshikazu Mizoi, Chiba Atsuro, Masahiro Sonoo (Japan) ⇑
Presenting author.
e171
Introduction: Lumbar spinal stenosis (LSS) is a popular cause of lower limb motor and sensory impairments and gait disturbance. SEPs can be a tool to evaluate LSS, and there have been considerable number of studies investigating the utility of dermatomal SEP in evaluating LSS or lumbar radiculopathy. However, few studies investigated the utility of tibial nerve SEPs. Tibial nerve SEPs have an advantage that they can evaluate plural points along the whole course of the peripheral nerve and can localize the lesion site. Three segments of ankle-knee, knee-pelvis, and pelvis-spinal entry can be evaluated by N8o latency, N8o-P15 interval, and P15-N21 interval. In this study, we compared the utility of tibial nerve SEPs with nerve conduction studies (NCS) and F-waves. Methods: We searched our EMG database from 2012 to 2017 with the keyword of ‘‘LSS” or ‘‘lumbar” and SEP examinations. For extracted cases, we retrospectively reviewed clinical and EMG records and MRI images. The entry criteria were as follows: (1) presence of sensory, motor, or gait (typically, intermittent claucication) complaints, (2) unequivocal LSS in lumbar MRI, (3) final diagnosis that the chief complaint was caused by the MRI-documented LSS, (4) Tibial nerve SEPs, motor conduction study (MCS) and F waves of the tibial nerve, and sensory conduction study (SCS) of the sural nerve were conducted for the same lower-limb that was the more affected, (5) no other causes that can explain his or her symptoms, especially neuropathies and diabetes, (6) no prior lumbar surgery. Results: Among 39 patients initially extracted, many have been excluded by the strict inclusion criteria. Finally enrolled were 8 patients (53–82 years, all men). The clinical features of these patients were as follows. Weakness was present in 7 (absent in 1). Sensory symptoms or signs were present in 4 (absent in 4). Intermittent claucication was present in 3 patients. Tibial nerve SEPs were abnormal in 7, and could localize the lesion at the lumbar segment (P15-N21) in 6. Notably, in 3 out of 4 patients without sensory symptoms or signs, tibial nerve SEPs localized the lesion at lumbar segment. The amplitude of the compound muscle action potential (CMAP) of the tibial MCS was reduced in 2 cases, and Fwave latency was prolonged in the same 2 cases. In no cases, Fwaves were abnormal despite normal SEPs. Sural SCS was normal for all cases. In two patients in which tibial nerve SEPs could not localize the lesion, needle EMG confirmed the diagnosis of LSS. Conclusion: Tibial nerve SEPs are useful in diagnosing LSS by localizing the lesion at the lumbar segments. Especially the fact that they documented lumbar lesions in patients lacking sensory symptoms or signs would contribute to the differentiation from amyotrophic lateral sclerosis. The sensitivity of F-waves was much lower than tibial nerve SEPs and added no value to the amplitude of the tibial CMAP. doi:10.1016/j.clinph.2018.04.439
S80. Utility of reduced montage EEG in detecting seizures or seizure-like activity—Kapil Gururangan *, Babak Razavi, Josef Parvizi (USA) ⇑
Presenting author.
Introduction: Standard scalp EEG is used to detect a wide range of cerebral pathologies. However, its utility in emergency and resourcelimited settings may be impeded by delays in setup and interpretation. Past studies have investigated reduced channel arrays as screening tools, but inferred a lower utility in detecting epileptiform abnormalities. The current study tested the utility of reduced (8channel) montage (rm-EEG) covering the lateral hemispheres compared to full (18-channel) montage (fm-EEG) for detection of generalized and hemispheric seizures and seizure-like patterns by
e172
Abstracts / Clinical Neurophysiology 129 (2018) e142–e212
neurologists with extensive EEG training, neurology residents with minimal EEG training, and medical students without EEG training. Methods: Forty neurologists (7 epileptologists, 13 epilepsy fellows, 20 neurology residents) from 7 institutions and 42 medical students from Stanford University were presented 44 samples of EEG recordings (15-s long) as both fm-EEG and rm-EEG formats in a random order. Samples represented seizures (n = 8), seizure-like activity (lateralized or generalized periodic discharges or burst suppression, n = 12) or non-rhythmic, non-periodic patterns (normal or slowing, n = 24) as determined by majority agreement among 3 senior epileptologists with >10 years of training (Fleiss’ kappa 0.79). Both physicians and students were asked to determine whether each sample represented seizure activity (yes/no), while epileptologists and residents were also asked to specify any and all pathological activity present in each sample. We calculated the overall accuracy of fm-EEG and rm-EEG, as well as their sensitivity and specificity for seizures and seizure-like activity; differences were assessed using paired t-tests. Results: EEG samples were evaluated with almost identical accuracy using fm-EEG (epileptologists: 88%; residents: 75%; students: 57%) and rm-EEG (epileptologists: 84%, p = 0.156; residents: 75%, p = 0.086; students: 57%, p = 0.461). While epileptologists identified hemispheric or generalized seizure activity with high sensitivity using fm-EEG (99%) and rm-EEG (94%, p = 0.172), individuals with minimal or no EEG experience demonstrated lower sensitivity using rm-EEG (residents: 79%; students: 45%) compared to fm-EEG (residents: 91%, p = 0.031; students: 62%, p = 0.048). However, specificity for seizures/seizure-like activity was greater using rm-EEG (epileptologists: 91%; residents: 84%; students: 73%) compared to fm-EEG (epileptologists: 85%, p = 0.015; residents: 77%, p = 0.018; students: 63%, p < 0.001). Conclusion: Our study demonstrates that a reduction from 18 to 8 channels does not degrade the sensitivity for generalized and hemispheric seizures, and yet provide more specific information for ruling in such epileptic activity even when read by individuals with minimal or no EEG experience. On the basis of these findings, we suggest that a restricted channel configuration can be used for faster diagnosis of generalized and hemispheric seizures that ought to be detected and treated expeditiously. doi:10.1016/j.clinph.2018.04.440
S81. The first hour sleep EEG recording predicts the occurrence of interictal epileptiform discharges during long-term video-EEG monitoring—Xi Liu 1,*, Sandra Rose 2, Naoum Issa 2, Shasha Wu 2, Leo Towle 2, Peter Warnke 2, James X. Tao 2 (1 China, 2 USA) ⇑
Presenting author.
Introduction: To determine the predictive value of the first hour sleep EEG recording in identifying patients with interictal epileptiform discharges (IEDs) during long-term video-EEG monitoring in an adult epilepsy monitoring unit. Methods: We retrospectively reviewed 255 consecutive patients who underwent continuous long-term video-EEG monitoring in the University of Chicago EMU. The complete video-EEG recording was reviewed, and the occurrence of IEDs was determined for each patient. We compared the occurrence of IEDs observed during the first hour sleep EEG recordings with the occurrence of IEDs observed during the complete long-term video-EEG recordings; inclusive of the first hour of sleep. Results: Overall, IEDs were observed in 134(53%) of 255 patients during the full long-term video-EEG recording with a duration of 4 ± 0.8 days. IEDs were identified in the first hour sleep EEG recording in 125 (sensitivity 93%) of the 134 patients. IEDs were found in
the first hour sleep EEG recording in 92 (94%) of 98 patients with temporal lobe epilepsy, 11 (92%) of 12 patients with frontal lobe epilepsy, 3 (100%) of 3 patients with parietal lobe epilepsy, 1 (50%) of the 2 patients with occipital lobe epilepsy, and 15 (88%) of the 17 patients with generalized epilepsy. The ictal onset in remaining 2 patients with multi-focal IEDs could not be localized due to muscle artifacts. The negative predictive value of the first hour EEG was 93%. Conclusion: The first hour of sleep EEG recording reliably predicts the occurrence of interictal epileptiform activity in a long-term video-EEG recording, and therefore can be used efficiently for identifying patients with IEDs during long-term video-EEG recording in the adult epilepsy monitoring unit. doi:10.1016/j.clinph.2018.04.441
S82. Paroxysmal sympathetic hyperactivity evident as cyclical pattern on quantitative EEG analysis—Jennifer Percy *, Ognen A. Petroff, Aline Herlopian (USA) ⇑
Presenting author.
Introduction: Episodic fluctuations in sympathetic activity following traumatic brain injury (TBI) have been described for decades, with paroxysmal sympathetic hyperactivity (PSH) being the currently accepted term for this entity. While early reports postulated an epileptic mechanism, our understanding of the pathophysiology of PSH has evolved. Current hypotheses center around deregulation of central descending inhibitory inputs from the insula and cingulate cortex, resulting in increased sympathetic output from the hypothalamus, diencephalon and brainstem. We present a case of PSH with evidence of disrupted sympathetic arousal networks. Methods: A 41-year-old woman suffered a TBI with multifocal supratentorial hemorrhages and intraparenchymal contusions. Eight days post-MVA she developed episodes of tachycardia, hypertension, diaphoresis, back-arching and extensor posturing of the upper extremities upon stimulus. These events were assumed to be epileptic and treated with lorazepam (up to 16 mg/24 h) and phenobarbital (up to 345 mg/24 h) to no avail. Episodes improved with dexmedetomidine and clonidine. Continuous video-EEG was ordered for event characterization. Results: EEG background was characterized by reactive generalized theta activity without interictal discharges. Multiple stimulusinduced stereotypical events were captured on the first EEG, prior to initiation of anti-epileptic drugs and dexmedetomidine. These were time-locked with static generalized rhythmic delta activity, often sharply contoured (GRDA + S). Quantitative EEG cycled between GRDA+S and polymorphic theta; transitions were often associated with stimulation or arousal. Thus, the events were shown to be stimulus/arousal-induced PSH time-locked with GRDA+S. The second EEG on lorazepam (2 mg q6h) and dexmedetomidine (26 mcg/kg/h) demonstrated less GRDA and no PSH. The third EEG on phenobarbital (130 mg qhs) and less dexmedetomidine (1.5 mcg/ kg/h) demonstrated polymorphic delta slowing during episodes of PSH. Therefore, PSH was seen prior to initiation of dexmedetomidine and while on a low dose, but not while on a higher dose. Phenobarbital did not improve PSH. Conclusion: Episodes of PSH were non-epileptic and concordant with cyclical stimulus or arousal-induced GRDA. This pattern is thought to represent cortical-subcortical dysfunction rather than hyperexcitability, as shown in a recent retrospective analysis of critical care continuous EEG in which no association was found between GRDA and seizures. The cyclical pattern on scalp and quantitative EEG reflected increased generalized rhythmicity with arousal and episodes of PSH; akin to stimulus/arousal-induced rhythmic or
Parkinsonian syndrome. This new system may provide the personalized rehabilitation in patients with Parkinson related disorders. doi:10.1016/j.clinph.2018.04.437
S78. MRI assessment of neck muscles in patients with unilateral cervical radiculopathy patients—Joon Shik Yoon *, Seok Kang, Hanboram Choi, Kwang-Jae Lee, Jang-Yeol Kim, Seong-Ho Son (Republic of Korea) ⇑
Presenting author.
Introduction: Several recent studies have investigated the changes of multifidus muscles in patients with chronic neck pain. Also, the longus coli muscle, one of the deep cervical flexor muscles, showed smaller cross sectional area (CSA) in patients with chronic neck pain in comparison with healthy people. To our knowledge, there is no study investigating the association between morphological features of cervical paravertebral muscles in electrodiagnosed cervical radiculopathy patients. In this study, we investigate the change in CSA and composition of the cervical flexor and multifidus muscles using the digital data from MRIs of patients with electrodiagnosed cervical radiculopathy. Methods: Twenty-four patients with unilateral cervical radicular pain who had cervical MRI and EMG examinations between 1 January 2015 and 2016 were retrospectively analysed. The inclusion criteria were as follows: (1) patients with the symptoms of unilateral cervical pain or referral to one upper limb, (2) diagnosis of cervical radiculopathy in EMG. Exclusion criteria included: (1) a history of cervical surgery; (2) a history of spinal fracture or injuries; (3) primary or metastatic spinal tumor. Axial slice at the level of C4-5 mid disc level image was selected to calculate the muscle CSA, with their maximal CSAs. Total CSA and functional CSA measurements of the bilateral longus colli, sternocleidomastoid and multifidus muscles were measured by using Image J (version 1.43, National Institutes of Health, Bethesda, Maryland). All muscle measurements were acquired by one investigators. Functional CSA measurement was obtained by using threshold method (including only pixels within lean muscle tissue range). Statistical analysis was performed using SPSSÒ v. 15. Results: The baseline characteristics of the study participants are shown in Table 1. There was no significant difference in total CSA in longus colli, sternocleidomastoid and multifidus muscles between involved and uninvolved groups. Data analysis showed significant difference between the functional CSA of the lognus colli muscle the involved/uninvolved sides (Table 2). Also, there is significant difference in the ratio of longus colli musle (functional longus colli muscle CSA/total longus colli muscle CSA) between the involved and uninvolved sides (P < 0.001). Conclusion: This is the study to show via MRI assessment that patients with cervical radiculopathy have smaller ipsilateral functional CSA of the longus colli muscle LCM in comparison with uninvolved side. Consideration of these muscles in MRI could be helpful in the diagnosis and prognosis of cervical radiculopathy. doi:10.1016/j.clinph.2018.04.438
S79. The utility of tibial nerve SEPs in diagnosing lumbar spinal stenosis, comparison with NCS and F-Waves—Chizuko Oishi *, Yoshikazu Mizoi, Chiba Atsuro, Masahiro Sonoo (Japan) ⇑
Presenting author.
e171
Introduction: Lumbar spinal stenosis (LSS) is a popular cause of lower limb motor and sensory impairments and gait disturbance. SEPs can be a tool to evaluate LSS, and there have been considerable number of studies investigating the utility of dermatomal SEP in evaluating LSS or lumbar radiculopathy. However, few studies investigated the utility of tibial nerve SEPs. Tibial nerve SEPs have an advantage that they can evaluate plural points along the whole course of the peripheral nerve and can localize the lesion site. Three segments of ankle-knee, knee-pelvis, and pelvis-spinal entry can be evaluated by N8o latency, N8o-P15 interval, and P15-N21 interval. In this study, we compared the utility of tibial nerve SEPs with nerve conduction studies (NCS) and F-waves. Methods: We searched our EMG database from 2012 to 2017 with the keyword of ‘‘LSS” or ‘‘lumbar” and SEP examinations. For extracted cases, we retrospectively reviewed clinical and EMG records and MRI images. The entry criteria were as follows: (1) presence of sensory, motor, or gait (typically, intermittent claucication) complaints, (2) unequivocal LSS in lumbar MRI, (3) final diagnosis that the chief complaint was caused by the MRI-documented LSS, (4) Tibial nerve SEPs, motor conduction study (MCS) and F waves of the tibial nerve, and sensory conduction study (SCS) of the sural nerve were conducted for the same lower-limb that was the more affected, (5) no other causes that can explain his or her symptoms, especially neuropathies and diabetes, (6) no prior lumbar surgery. Results: Among 39 patients initially extracted, many have been excluded by the strict inclusion criteria. Finally enrolled were 8 patients (53–82 years, all men). The clinical features of these patients were as follows. Weakness was present in 7 (absent in 1). Sensory symptoms or signs were present in 4 (absent in 4). Intermittent claucication was present in 3 patients. Tibial nerve SEPs were abnormal in 7, and could localize the lesion at the lumbar segment (P15-N21) in 6. Notably, in 3 out of 4 patients without sensory symptoms or signs, tibial nerve SEPs localized the lesion at lumbar segment. The amplitude of the compound muscle action potential (CMAP) of the tibial MCS was reduced in 2 cases, and Fwave latency was prolonged in the same 2 cases. In no cases, Fwaves were abnormal despite normal SEPs. Sural SCS was normal for all cases. In two patients in which tibial nerve SEPs could not localize the lesion, needle EMG confirmed the diagnosis of LSS. Conclusion: Tibial nerve SEPs are useful in diagnosing LSS by localizing the lesion at the lumbar segments. Especially the fact that they documented lumbar lesions in patients lacking sensory symptoms or signs would contribute to the differentiation from amyotrophic lateral sclerosis. The sensitivity of F-waves was much lower than tibial nerve SEPs and added no value to the amplitude of the tibial CMAP. doi:10.1016/j.clinph.2018.04.439
S80. Utility of reduced montage EEG in detecting seizures or seizure-like activity—Kapil Gururangan *, Babak Razavi, Josef Parvizi (USA) ⇑
Presenting author.
Introduction: Standard scalp EEG is used to detect a wide range of cerebral pathologies. However, its utility in emergency and resourcelimited settings may be impeded by delays in setup and interpretation. Past studies have investigated reduced channel arrays as screening tools, but inferred a lower utility in detecting epileptiform abnormalities. The current study tested the utility of reduced (8channel) montage (rm-EEG) covering the lateral hemispheres compared to full (18-channel) montage (fm-EEG) for detection of generalized and hemispheric seizures and seizure-like patterns by
e172
Abstracts / Clinical Neurophysiology 129 (2018) e142–e212
neurologists with extensive EEG training, neurology residents with minimal EEG training, and medical students without EEG training. Methods: Forty neurologists (7 epileptologists, 13 epilepsy fellows, 20 neurology residents) from 7 institutions and 42 medical students from Stanford University were presented 44 samples of EEG recordings (15-s long) as both fm-EEG and rm-EEG formats in a random order. Samples represented seizures (n = 8), seizure-like activity (lateralized or generalized periodic discharges or burst suppression, n = 12) or non-rhythmic, non-periodic patterns (normal or slowing, n = 24) as determined by majority agreement among 3 senior epileptologists with >10 years of training (Fleiss’ kappa 0.79). Both physicians and students were asked to determine whether each sample represented seizure activity (yes/no), while epileptologists and residents were also asked to specify any and all pathological activity present in each sample. We calculated the overall accuracy of fm-EEG and rm-EEG, as well as their sensitivity and specificity for seizures and seizure-like activity; differences were assessed using paired t-tests. Results: EEG samples were evaluated with almost identical accuracy using fm-EEG (epileptologists: 88%; residents: 75%; students: 57%) and rm-EEG (epileptologists: 84%, p = 0.156; residents: 75%, p = 0.086; students: 57%, p = 0.461). While epileptologists identified hemispheric or generalized seizure activity with high sensitivity using fm-EEG (99%) and rm-EEG (94%, p = 0.172), individuals with minimal or no EEG experience demonstrated lower sensitivity using rm-EEG (residents: 79%; students: 45%) compared to fm-EEG (residents: 91%, p = 0.031; students: 62%, p = 0.048). However, specificity for seizures/seizure-like activity was greater using rm-EEG (epileptologists: 91%; residents: 84%; students: 73%) compared to fm-EEG (epileptologists: 85%, p = 0.015; residents: 77%, p = 0.018; students: 63%, p < 0.001). Conclusion: Our study demonstrates that a reduction from 18 to 8 channels does not degrade the sensitivity for generalized and hemispheric seizures, and yet provide more specific information for ruling in such epileptic activity even when read by individuals with minimal or no EEG experience. On the basis of these findings, we suggest that a restricted channel configuration can be used for faster diagnosis of generalized and hemispheric seizures that ought to be detected and treated expeditiously. doi:10.1016/j.clinph.2018.04.440
S81. The first hour sleep EEG recording predicts the occurrence of interictal epileptiform discharges during long-term video-EEG monitoring—Xi Liu 1,*, Sandra Rose 2, Naoum Issa 2, Shasha Wu 2, Leo Towle 2, Peter Warnke 2, James X. Tao 2 (1 China, 2 USA) ⇑
Presenting author.
Introduction: To determine the predictive value of the first hour sleep EEG recording in identifying patients with interictal epileptiform discharges (IEDs) during long-term video-EEG monitoring in an adult epilepsy monitoring unit. Methods: We retrospectively reviewed 255 consecutive patients who underwent continuous long-term video-EEG monitoring in the University of Chicago EMU. The complete video-EEG recording was reviewed, and the occurrence of IEDs was determined for each patient. We compared the occurrence of IEDs observed during the first hour sleep EEG recordings with the occurrence of IEDs observed during the complete long-term video-EEG recordings; inclusive of the first hour of sleep. Results: Overall, IEDs were observed in 134(53%) of 255 patients during the full long-term video-EEG recording with a duration of 4 ± 0.8 days. IEDs were identified in the first hour sleep EEG recording in 125 (sensitivity 93%) of the 134 patients. IEDs were found in
the first hour sleep EEG recording in 92 (94%) of 98 patients with temporal lobe epilepsy, 11 (92%) of 12 patients with frontal lobe epilepsy, 3 (100%) of 3 patients with parietal lobe epilepsy, 1 (50%) of the 2 patients with occipital lobe epilepsy, and 15 (88%) of the 17 patients with generalized epilepsy. The ictal onset in remaining 2 patients with multi-focal IEDs could not be localized due to muscle artifacts. The negative predictive value of the first hour EEG was 93%. Conclusion: The first hour of sleep EEG recording reliably predicts the occurrence of interictal epileptiform activity in a long-term video-EEG recording, and therefore can be used efficiently for identifying patients with IEDs during long-term video-EEG recording in the adult epilepsy monitoring unit. doi:10.1016/j.clinph.2018.04.441
S82. Paroxysmal sympathetic hyperactivity evident as cyclical pattern on quantitative EEG analysis—Jennifer Percy *, Ognen A. Petroff, Aline Herlopian (USA) ⇑
Presenting author.
Introduction: Episodic fluctuations in sympathetic activity following traumatic brain injury (TBI) have been described for decades, with paroxysmal sympathetic hyperactivity (PSH) being the currently accepted term for this entity. While early reports postulated an epileptic mechanism, our understanding of the pathophysiology of PSH has evolved. Current hypotheses center around deregulation of central descending inhibitory inputs from the insula and cingulate cortex, resulting in increased sympathetic output from the hypothalamus, diencephalon and brainstem. We present a case of PSH with evidence of disrupted sympathetic arousal networks. Methods: A 41-year-old woman suffered a TBI with multifocal supratentorial hemorrhages and intraparenchymal contusions. Eight days post-MVA she developed episodes of tachycardia, hypertension, diaphoresis, back-arching and extensor posturing of the upper extremities upon stimulus. These events were assumed to be epileptic and treated with lorazepam (up to 16 mg/24 h) and phenobarbital (up to 345 mg/24 h) to no avail. Episodes improved with dexmedetomidine and clonidine. Continuous video-EEG was ordered for event characterization. Results: EEG background was characterized by reactive generalized theta activity without interictal discharges. Multiple stimulusinduced stereotypical events were captured on the first EEG, prior to initiation of anti-epileptic drugs and dexmedetomidine. These were time-locked with static generalized rhythmic delta activity, often sharply contoured (GRDA + S). Quantitative EEG cycled between GRDA+S and polymorphic theta; transitions were often associated with stimulation or arousal. Thus, the events were shown to be stimulus/arousal-induced PSH time-locked with GRDA+S. The second EEG on lorazepam (2 mg q6h) and dexmedetomidine (26 mcg/kg/h) demonstrated less GRDA and no PSH. The third EEG on phenobarbital (130 mg qhs) and less dexmedetomidine (1.5 mcg/ kg/h) demonstrated polymorphic delta slowing during episodes of PSH. Therefore, PSH was seen prior to initiation of dexmedetomidine and while on a low dose, but not while on a higher dose. Phenobarbital did not improve PSH. Conclusion: Episodes of PSH were non-epileptic and concordant with cyclical stimulus or arousal-induced GRDA. This pattern is thought to represent cortical-subcortical dysfunction rather than hyperexcitability, as shown in a recent retrospective analysis of critical care continuous EEG in which no association was found between GRDA and seizures. The cyclical pattern on scalp and quantitative EEG reflected increased generalized rhythmicity with arousal and episodes of PSH; akin to stimulus/arousal-induced rhythmic or