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Browsing by Author "Vial Undurraga, Felipe"

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A novel exaggerated "Spino-bulbo-spinal like" reflex of lower brainstem origin
(2019) Merchant, Shabbir Hussain; Vial Undurraga, Felipe; Leodori, Giorgio; Fahn, Stanley; Pullman, Seth; Hallett, Mark
Background: Many different oligosynaptic reflexes are known to originate in the lower brainstem which share phenomenological and neurophysiological similarities. Objective: To evaluate and discuss the differences and aberrancies among these reflexes, which are hard to discern clinically using neurophysiological investigations with the help of a case report. Methods: We describe the clinical and neurophysiological assessment of a young man who had a childhood history of opsoclonus-myoclonus syndrome with residual mild ataxia and myoclonic jerks in the distal extremities presenting with subacute onset total body jerks sensitive to sound and touch (in a limited dermatomal distribution), refractory to medications. Results: Based on clinical characteristics and insights gained from neurophysiological testing we could identify a novel reflex of caudal brainstem origin. Conclusions: The reflex described is likely an exaggerated normal reflex, likely triggered by a dolichoectatic vertebral arterial compression and shares characteristics of different reflexes known to originate in caudal brainstem, which subserve distinctive roles in human postural control
BacAv, a new free online platform for clinical back-averaging
(2020) Vial Undurraga, Felipe; Attaripour, Sanaz; McGurrin, Patrick; Hallett, Mark
Objective. The back-average technique is very useful to study the relation between the activity in the cortex and the muscles. It has two main clinical applications, Bereitschaftspotential (BP) recording and myoclonus studies. The BP is a slow wave negativity originating in the supplementary motor cortex and premotor cortex that precedes voluntary movements. This wave also precedes involuntary movements in functional movement disorders (FMD), and it can be used as a helpful diagnostic tool. For the myoclonus studies, the back-average technique is very important to help localizing the source of the myoclonus. The hardware needed to do BP or myoclonus studies is standard and available in any electrophysiology lab, but there are not many software solutions to do the analysis. In this article together with describing the methodology that we use for recording clinical BPs and myoclonus, we present BacAv, an online free application that we developed for the purpose of doing back-average analysis. Methods: BacAv was developed in “R” language using Rstudio, a free integrated development environment. The recommended parameters for the data acquisition for BP recording and myoclonus studies are given in this section. Results: The platform was successfully developed, is able to read txt files, look for muscle bursts, segment the data, and plot the average. The parameters of the algorithm that look for the muscle bursts can be adapted according to the characteristics of the dataset. Conclusion: We have developed software for clinicians who do not have sophisticated equipment to do back-averaging. Significance: This tool will make this useful analysis method more available in a clinical environment.
Características clínicas de 63 pacientes con ataxia
(2018) Saffie Awad, Paula; Vial Undurraga, Felipe; Chaná-Cuevas, Pedro
Background: Ataxia can be classified as genetic, sporadic or acquired. Aim: To report the clinical features of a group of patients with ataxia. Material and Methods: Review of medical records of patients consulting in a specialized center in movement disorders. Those records in which the diagnosis of “ataxia” or “ataxic syndrome” appeared, were selected for the review. Results: Of 4,282 records surveyed, the diagnosis of ataxia appeared in 95. After eliminating re- peated or incomplete records, 63 were reviewed. Results: Ataxia was sporadic, genetic and acquired in 27, 22 and 14 patients, respectively. The mean age at presentation for genetic, acquired and sporadic ataxia was 24, 46 and 53 years respectively. All autosomal dominant ataxias were type 3 spinocerebellar ataxia (SCA). Friedrich’s ataxia was the most common recessive form. Most sporadic forms of ataxia were multiple system atrophy with predominant cerebellar ataxia (MSA-C) subtype. Conclusions: Considering the heterogeneity of patients with ataxia, we propose a method to approach them.
Caso clínico de una meningitis por reactivación del virus varicela zóster en un paciente inmunocompetente
(2013) Vial Undurraga, Felipe; González T-K., Sofía; López G., Mirta Javiera
En este reporte presentamos el caso de un niño de 15 años sin antecedentes mórbidos, que consulta por un cuadro de cefalea febril, erupción cutánea de características herpéticas en tórax, en quien finalmente se confirma el diagnóstico de meningitis por varicela zóster. La literatura nos muestra que la reactivación del virus varicela zóster en forma de meningitis es rara y en general afecta a la población inmunocomprometida, sin embargo, existen algunos reportes de casos similares al que se presenta, por lo que se debiese considerar como germen causal de meningitis, en la población inmunocompetente.
Electrophysiological Characterization of a MYH7 Variant with Tremor Phenotype
(2023) Vial Undurraga, Felipe; Gurrin, Patrick M.; Osterholt, Thomas; Ehrlich, Debra J.; Iannacone, Susan T.; Donkervoort, Sandra; Neuhaus, Sarah B.; Chao, Katherine C.; Bönnemann, Carsten G.; Haubenberger, Dietrich; Hallet, Mark
Background: The concept of a myopathy with associated tremor ("myogenic tremor") in humans has been previously described for specific MYBPC1 (Myosin-Binding Protein C) variants. Here we report for the first time an individual with tremor who was found to have a de-novo likely pathogenic variant in Myosin Heavy Chain 7 (MYH7). We provide a detailed electrophysiological characterization of the tremor syndrome in a human individual with a myopathy and this pathogenic MYH7 variant to provide further insight in the phenotypic spectrum and pathomechanism of myogenic tremors in skeletal sarcomeric myopathies. Methods: Electromyographic recordings were obtained from facial muscles, as well as bilateral upper and lower extremities. Results: 10 to 11 Hz activity was observed in the face and extremities during recordings with muscle activation. There were intermittent episodes of significant left-right coherence that would modulate across muscle groups throughout the recording, but no coherence between muscles at different levels of the neuraxis. Conclusions: A possible explanation for this phenomenon is that the tremor originates at the sarcomere level within muscles, which is then picked up by muscle spindles and leads to activating input to the neuraxis segment. At the same time, the stability of the tremor frequency does suggest the presence of central oscillators at the segmental level. Thus, further studies will be needed to determine the origin of myogenic tremor and to better understand the pathomechanism.
Electrophysiological Evidence for Functional (Psychogenic) Essential Palatal Tremor
(2020) Vial Undurraga, Felipe; Akano, Emmanuel; Attaripour, Sanaz; McGurrin, Patrick; Hallett, Mark
Background: There is little published work describing the electrophysiological characteristics of essential palatal tremor, a condition now believed by many to be a functional (psychogenic) movement disorder. Case Report: Here we combine electroencephalography and electromyography with time-locked video recordings to document two cases of essential palatal tremor in which a definitive diagnosis is achieved using these electrophysiological tools. Discussion: We believe that sharing how these objective tools can be used to diagnose a functional movement disorder, as well as providing more published evidence to support the functional origin of essential palatal myoclonus, will help to diagnose this condition in the future.
Expandiendo el espectro mutacional en pacientes chilenos con fibrosis quística
(2012) Vásquez, Marcos; Lay-son, Guillermo; Vial Undurraga, Felipe; Boza, María Lina; Contreras, Ilse; Lozano, Jaime; Zenteno, Daniel; Repetto, Gabriela
Introducción: La fibrosis quística (FQ) es una enfermedad con herencia autosómica recesiva, que presenta una incidencia de 1 en 8.000 a 9.000 recién nacidos en Chile. A la fecha se han descrito más de 1.800 mutaciones diferentes en el gen CFTR. El diagnóstico molecular disponible consiste en el análisis de las 36 mutaciones presentes con mayor frecuencia en población caucásica, donde se describe una tasa de detección de un 85%. Sin embargo, en Chile el rendimiento corresponde a un 42%. Por esta razón, hemos iniciado un análisis sistemático en la región codificante del gen CFTR con elfin de identificar los restantes alelos en pacientes chilenos con FQ. Métodos: Análisis por secuenciación de los exones 6,7,14,19y 20, en 48pacientes chilenos del Programa Nacional de FQ. Se incluyeron pacientes con criterios clínicos y de laboratorio de FQ, y con sólo una mutación identificada en el panel de 36 mutaciones. Resultados: Se identificaron 3 mutaciones diferentes que no se analizan en el panel de diagnóstico molecular y que no habían sido reportadas en pacientes chilenos, totalizando 14 casos. Cuatro casos corresponden a una nueva mutación en el exón 14, que produce un corrimiento en el marco de lectura y un codón de término prematuro (c.2462_2463delGT/p.Ser821ArgfsX4). Ocho casos presentan la mutación c.3196C>T en el exón 20, mientras que en 2 casos se encontró la mutación c.3039delC en el exón 19. Ambas mutaciones han sido descritas previamente en otras poblaciones.
Identifying transcranial magnetic stimulation induced EEG signatures of different neuronal elements in primary motor cortex
(2022) Ni, Zhen; Pajevic, Sinisa; Chen, Li; Leodori, Giorgio; Vial Undurraga, Felipe; Avram, Alexandru V.; Zhang, Yong; Mc Gurrin, Patrick; Cohen, Leonardo G.; Basser, Peter J.; Hallett, Mark
Objective: To investigate the neuronal elements involved in the activation of corticospinal neurons in the primary motor cortex (M1). Methods: We studied 10 healthy subjects. Cortical evoked potentials with different components induced by monophasic transcranial magnetic stimulation (TMS) in anterior-posterior and posterior-anterior currents recorded with electroencephalography (EEG) were analyzed. Results: EEG signatures with P25 and N45 components recorded at the C3 electrode with posterior-anterior current were larger than those with anterior-posterior current, while the signatures with P180 and N280 components recorded at the FC1 electrode with anterior-posterior current were larger than those with posterior-anterior current. The source localization analysis revealed that the cortical evoked potential with anterior-posterior current distributed both in the M1 and premotor cortex while that with posterior-anterior current only located in the M1. Conclusions: We conclude that the activation of corticospinal pyramidal neurons in the M1 is affected by various neuronal elements including the local intracortical circuits in the M1 and inputs from premotor cortex with different sensitivities to TMS in opposite current directions. Significance: Our finding helped answer a longstanding question about how the corticospinal pathway from the M1 is functionally organized and activated.
Intraventricular Bleeding and Hematoma Size as Predictors of Infection Development in Intracerebral Hemorrhage: A Prospective Cohort Study
(Elsevier, 2016) Vial Undurraga, Felipe; Brunser, Alejandro; Lavados, Pablo; Illanes, Sergio
BACKGROUND: Acute intracerebral hemorrhage (ICH) is associated with increased susceptibility to bacterial infection. The physiopathology of this phenomenon is not very clear. We conducted a prospective observational study investigating the correlation and independent predictors of infections in patients with ICH. PATIENTS AND METHODS: Patients admitted between April 1997 and June 2013 with ICH diagnosis were evaluated for inclusion and exclusion criteria. RESULTS: Two hundred twenty-two patients were included in this study. Ninety four patients (42.6%) presented with an infection during hospitalization being more common than pneumonia (30%) and urinary tract infections (14%). Intraventricular hemorrhage (IVH) (95% confidence interval [CI], 62.7% versus 39.3%; P < .001) and higher ICH score (95% CI, 2.31% versus 1.67%; P = .0014) were more common in patients who had infections. We found the following risk factors for having an infection in patients with ICH: IVH (odds ratio [OR] 2.3; 95% IC, 1.3-4.1), each point of ICH score (OR 1.3; 95% CI, 1.1-1.6), and having a hematoma volume larger than 30 cc (OR 2.0; 95% CI, 1.1-3.5). The localization of the hematoma was not found to be relevant. CONCLUSIONS: ICH score, size of the hematoma, and presence of IVH are independent risk factors for having an infection after ICH.
KCNN2 Mutation in Pediatric Tremor Myoclonus Dystonia Syndrome with Electrophysiological Evaluation
(2022) Lavenstein, Bennett; McGurrin, Patrick; Attaripour, Sanaz; Vial Undurraga, Felipe; Hallett, Mark
Background: Here we combine clinical, electrophysiological, and genetic findings to phenotype an unusual childhood movement disorder in a patient with a rare form of KCNN2 mutation. Case report: A 10-year-old male presented with a clinical syndrome of tremor and myoclonus. Electrophysiology demonstrated muscle activity indicative of myoclonus dystonia, an observation that was not appreciated clinically. Genetic testing revealed an abnormality in the KCNN 2 gene, not present in the parents, known to cause dystonia, as the etiology. Discussion: The value of utilizing noninvasive, electrophysiological recording in pediatric movement disorders expands the precision of diagnosis, potentially informing treatment when correlated with clinical and genetic findings.
Measuring conduction velocity distributions in peripheral nerves using neurophysiological techniques
(2020) Ni, Zhen; Vial Undurraga, Felipe; V. Avram, Alexandru; Leodori, Giorgio; Pajevic, Sinisa; J. Basser, Peter; Hallett, Mark
Objective: To determine how long it takes for neural impulses to travel along peripheral nerve fibers in living humans. Methods: A collision test was performed to measure the conduction velocity distribution of the ulnar nerve. Two stimuli at the distal and proximal sites were used to produce the collision. Compound muscle or nerve action potentials were recorded to perform the measurements on the motor or mixed nerve, respectively. Interstimulus interval was set at 1–5 ms. A quadri-pulse technique was used to measure the refractory period and calibrate the conduction time. Results: Compound muscle action potential produced by the proximal stimulation started to emerge at the interstimulus interval of about 1.5 ms and increased with the increment in interstimulus interval. Two groups of motor nerve fibers with different conduction velocities were identified. The mixed nerve showed a wider conduction velocity distribution with identification of more subgroups of nerve fibers than the motor nerve. Conclusions: The conduction velocity distributions in high resolution on a peripheral motor and mixed nerve are different and this can be measured with the collision test. Significance: We provided ground truth data to verify the neuroimaging pipelines for the measurements of latency connectome in the peripheral nervous system.
Measuring latency distribution of transcallosal fibers using transcranial magnetic stimulation
(2020) Ni, Zhen; Leodori, Giorgio; Vial Undurraga, Felipe; Zhang, Yong; V. Avram, Alexandru; Pajevic, Sinisa; J. Basser, Peter; Hallett, Mark
Background: Neuroimaging technology is being developed to enable non-invasive mapping of the latency distribution of cortical projection pathways in white matter, and correlative clinical neurophysiological techniques would be valuable for mutual verification. Interhemispheric interaction through the corpus callosum can be measured with interhemispheric facilitation and inhibition using transcranial magnetic stimulation. Objective: To develop a method for determining the latency distribution of the transcallosal fibers with transcranial magnetic stimulation. Methods: We measured the precise time courses of interhemispheric facilitation and inhibition with a conditioning-test paired-pulse magnetic stimulation paradigm. The conditioning stimulus was applied to the right primary motor cortex and the test stimulus was applied to the left primary motor cortex. The interstimulus interval was set at 0.1 ms resolution. The proportions of transcallosal fibers with different conduction velocities were calculated by measuring the changes in magnitudes of interhemispheric facilitation and inhibition with interstimulus interval. Results: Both interhemispheric facilitation and inhibition increased with increment in interstimulus interval. The magnitude of interhemispheric facilitation was correlated with that of interhemispheric inhibition. The latency distribution of transcallosal fibers measured with interhemispheric facilitation was also correlated with that measured with interhemispheric inhibition. Conclusions: The data can be interpreted as latency distribution of transcallosal fibers. Interhemispheric interaction measured with transcranial magnetic stimulation is a promising technique to determine the latency distribution of the transcallosal fibers. Similar techniques could be developed for other cortical pathways.
Myoclonus: An Electrophysiological Diagnosis
(2020) Merchant, Shabbir Hussain I.; Vial Undurraga, Felipe; Leodori, Giorgio; Gerpen, Jay A. van; Hallett, Mark
Background: Background Many different movement disorders have similar “jerk-like” phenomenology and can be misconstrued as myoclonus. Different types of myoclonus also share similar phenomenological characteristics that can be difficult to distinguish solely based on clinical exam. However, they have distinctive physiologic characteristics that can help refine categorization of jerk-like movements. Objectives: Objectives In this review, we briefly summarize the clinical, physiologic, and pathophysiologic characteristics of different types of myoclonus. The methodology and technical considerations for the electrophysiologic assessment of jerk-like movements are reviewed. A simplistic pragmatic approach for the classification of myoclonus and other jerk-like movements based on objective electrophysiologic characteristics is proposed. Conclusions: Conclusions Clinical neurophysiology is an underutilized tool in the diagnosis and treatment of movement disorders. Various jerk-like movements have distinguishing physiologic characteristics, differentiated in the milliseconds range, which is beyond human capacity. We argue that the categorization of movement disorders as myoclonus can be refined based on objective physiology that can have important prognostic and therapeutic implications.
Physiology of Tremor Reduction by Putting the Hands Together in Essential Tremor
(2022) McGurrin, Patrick; Vial Undurraga, Felipe; Osterholt, Thomas; Norato, Gina; Khan, Imran; Haubenberger, Dietrich; Ehrlich, Debra; Hallett, Mark
Background: Background Essential tremor is a common movement disorder, characterized by 4–12 Hz tremor of the hands and arms that can affect many activities of daily living. It has been reported by patients that when performing tasks bimanually their tremor is reduced, but why this happens is unknown. Objectives: Objectives We measured patients’ tremors in different conditions when performed with 1 hand and 2 hands to observe if bimanual task performance changes the characteristics of the tremor. Methods: Methods A total of 10 patients with essential tremor participated in the study. Electromyographic electrodes were attached bilaterally to the wrist flexor and extensor muscles, and accelerometers were attached to the dorsum of the hands. For each condition, holding a cup, wingbeat, and extending both arms up, data were collected with a single hand and bimanually with the hands touching. Results: Results When the hands were touching, there was a significant decrease in both accelerometric and electromyographic power at the tremor frequency. In addition, there was a decrease in coherence between accelerometer and electromyography on the same side. There was no change in the tremor frequency. Conclusions: Conclusions Tremor amplitude does decrease when the hands are together. Together, the characteristics underlying the decrease in tremor amplitude may indicate a decrease in power of the central oscillator driving the tremor, which we speculate is attributed to the differences in unimanual and bimanual motor control. However, given the small sample size, we note that future hypothesis-driven studies with an a priori power analysis will be required to further explore this phenomenon.
Purposely Induced Tics: Electrophysiology
(2020) McGurrin, Patrick; Attaripour, Sanaz; Vial Undurraga, Felipe; Hallett, Mark
Tics are non-rhythmic movements that can be simple or complex. Clinically, they may appear as quick voluntary movements (50–200 ms), but can also be longer and more sustained (>300 ms). These movements are often described as being predictable. An inner tension builds which is relieved by the movement in most cases, and the movement can be suppressed for some time. Most patients report a feeling of relief once they release the movement, and therefore do not prolong the suppression. Thus, to some extent, the movement is under voluntary control. Tics have been called “unvoluntary”; a movement between voluntary and involuntary behavior.4 Here we present a person who can purposely induce tics. Simultaneous electroencephalography (EEG) and electromyographic (EMG) activity were recorded to capture the Bereitschaftspotential (BP) to explore the physiology of this phenomenon.
Re-emergent Tremor in Parkinson’s Disease: The Role of the Motor Cortex
(2020) Leodori, Giorgio; Belvisi, Daniele; De Bartolo, Maria I.; Fabbrini, Andrea; Costanzo, Matteo; Vial Undurraga, Felipe; Conte, Antonella; Hallett, Mark; Berardelli, Alfredo
Background: Parkinson’s disease patients may show a tremor that appears after a variable delay while the arms are kept outstretched (re-emergent tremor). The objectives of this study were to investigate re-emergent tremor pathophysiology by studying the role of the primary motor cortex in this tremor and making a comparison with rest tremor. Methods: We enrolled 10 Parkinson’s disease patients with both re-emergent and rest tremor. Tremor was assessed by spectral analysis, corticomuscular coherence and tremor-resetting produced by transcranial magnetic stimulation over the primary motor cortex. We also recorded transcranial magnetic stimulation-evoked potentials generated by motor cortex stimulation during rest tremor, tremor suppression during wrist extension, and re-emergent tremor. Spectral analysis, corticomuscular coherence, and tremor resetting were compared between re-emergent tremor and rest tremor. Results: Re-emergent tremor showed significant corticomuscular coherence, causal relation between motor cortex activity and tremor muscle and tremor resetting. The P60 component of transcranial magnetic stimulation-evoked potentials reduced in amplitude during tremor suppression, recovered before re-emergent tremor, was facilitated at re-emergent tremor onset, and returned to values similar to those of rest tremor during re-emergent tremor. Compared with rest tremor, re-emergent tremor showed similar corticomuscular coherence and tremor resetting, but slightly higher frequency. Conclusions: Re-emergent tremor is causally related with the activity of the primary motor cortex, which is likely a convergence node in the network that generates re-emergent tremor. Re-emergent tremor and rest tremor share common pathophysiological mechanisms in which the motor cortex plays a crucial role.
Tremoroton, a new free online platform for tremor analysis
(2020) Vial Undurraga, Felipe; McGurrin, Patrick; Osterholt, Thomas; Ehrlich, Debra; Haubenberger, Dietrich; Hallett, Mark
Objective: The electrophysiological classification of tremors can be a key element in the diagnosis and can facilitate treatment of a patient with tremor; however, the ability to conduct electrophysiological studies of tremor is not widely available. The purpose of this study was to develop and validate a free online platform for tremor analysis. Methods: An online platform for tremor analysis was developed using "R" language; called Tremoroton". For validation, we compared the frequency estimation of the tremor obtained with Tremoroton compared with a commercially available software in a cohort of 20 patients (10 with essential tremor and 10 with Parkinson diagnosis), comparing the activity recorded on the accelerometer, extensor carpi radialis and flexor carpi radialis EMG. An intraclass correlation coefficient was used for the comparison. Results: The final version of tremoroton is now online. It allows reading up to 6 channels, and will do time, frequency, time-frequency analysis and calculate coherence. We demonstrated a high correlation in frequency measurements (0.97 (0.945-0.984, 95% IC) for the accelerometers, 0.98 (0.977-0.994, 95% IC) for the extensor carpi radialis EMG, and 0.99 (0.987-0.997, 95% IC) for the flexor carpi radialis EMG) when compared to a commercial software. Conclusion: We were able to develop and validate a free online platform for tremor analysis. Significance: Making this tool available should help expanding tremor analysis techniques from research to the clinical setting.

Browsing by Author "Vial Undurraga, Felipe"

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