Integrative action of axonal membrane explored by trains of subthreshold stimuli applied to the peripheral nerve.

OBJECTIVE: The objective of this study was to provide evidence on the integrative action of axonal membrane in humans and its ability to integrate multipulse subthreshold stimuli and generate action potential. METHODS: The median nerve was stimulated at the wrist in six healthy subjects and 17 patients who underwent low spine surgery by means of percutaneous electrodes, with trains of one to nine near-threshold constant-current stimuli of 500-µs duration. The interstimulus interval between stimuli was 2 or 4 ms. The compound muscle action potential (CMAP) was recorded from the abductor pollicis brevis muscle using subcutaneous needle electrodes in patients and surface electrodes in healthy subjects. Total intravenous anesthesia (TIVA) without a muscle relaxant was used in all patients, and measurements were performed at the end of surgery. RESULT: A single near-threshold stimulus did not generate CMAP either in the healthy subjects or in the patients. However, when the number of near-threshold stimuli was increased to two to nine stimuli, and packed into a short train with interstimulus intervals of 2 or 4 ms, a CMAP of varying amplitude from 100 to 200 µV was successfully elicited. CONCLUSION: We concluded that the described phenomenon might be explained by the integrative action of the axonal membrane, which is able to summate the trains of subthreshold stimuli, increasing the resting potential to the firing level, and consequently generating CMAP. This is because the subthreshold stimuli make the axonal membrane hyperexcitable. SIGNIFICANCE: This phenomenon is not very well explored in clinical neurophysiology, and it needs to be studied further. This can explain some neurophysiologic phenomena during intraoperative monitoring.

[Narcolepsy: update on etiology, clinical features and treatment]. / Narcolepsia: actualización en etiología, manifestaciones clínicas y tratamiento.

Narcolepsy is a disease that involves an alteration in the generation and organisation of sleep. The main symptoms are excessive daytime sleepiness and cataplexy, followed by hypnagogic hallucinations, sleep paralysis and disrupted nocturnal sleep. The prevalence of typical narcolepsy oscillates between 25-50: 100.000 in general. Recently there has been a peak incidence in patients born in the month of March. According to the new classification, the Multiple Sleep Latency Test (MSLT) is mandatory for diagnosing narcolepsy without cataplexy, and advisable for diagnosing narcolepsy with cataplexy. Until now, the attempt has been made to control each symptom by its own specific treatment. At present, new American and European treatment guidelines propose new drugs that act on all the symptoms. The application of new criteria of diagnosis and treatment has improved the diagnosis, giving better options of treatment.

Narcolepsia: actualización en etiología, manifestaciones clínicas y tratamiento / Narcolepsy: update on etiology, clinical features and treatment

La narcolepsia es una enfermedad que consisteen una alteración en la generación y organización delsueño. Los principales síntomas son la excesiva somnolenciadiurna y la cataplejía así como las alucinacioneshipnagógicas, parálisis del sueño y fragmentación delsueño nocturno. La prevalencia de la narcolepsia típicaoscila entre el 25 y 50 por cada 100.000 habitantes. Recientementese ha observado un pico de incidencia enpacientes nacidos en el mes de marzo.Según la nueva clasificación, el test de latenciasmúltiples de sueño (TLMS) es imprescindible para eldiagnóstico de narcolepsia sin cataplejía y aconsejablepara el diagnóstico de la narcolepsia típica.Hasta ahora se trataban de forma independiente lossíntomas, aunque actualmente las más recientes directricesde tratamiento proponen nuevos fármacos queactúan en todo el grupo de síntomas de forma global.La aplicación de nuevos criterios diagnósticos yterapéuticos permitirá un diagnóstico precoz y mejoresopciones de tratamiento en esta patología(AU)

Narcolepsy is a disease that involves an alterationin the generation and organisation of sleep. The mainsymptoms are excessive daytime sleepiness and cataplexy,followed by hypnagogic hallucinations, sleep paralysisand disrupted nocturnal sleep. The prevalenceof typical narcolepsy oscillates between 25-50: 100.000in general. Recently there has been a peak incidence inpatients born in the month of March.According to the new classification, the MultipleSleep Latency Test (MSLT) is mandatory for diagnosingnarcolepsy without cataplexy, and advisable for diagnosingnarcolepsy with cataplexy.Until now, the attempt has been made to controleach symptom by its own specific treatment. At present,new American and European treatment guidelinespropose new drugs that act on all the symptoms.The application of new criteria of diagnosis andtreatment has improved the diagnosis, giving betteroptions of treatment(AU)

Parálisis facial bilateral secundaria a infección por virus de Epstein-Barr / Bilateral facial palsy due to Epstein-Barr virus infection

Nuestro objetivo es describir dos pacientes jóvenescon parálisis facial periférica bilateral. Ambos presentaroninicialmente afectación en un lado de la cara,seguida pocos días después de afectación contralateraljunto con sintomatología compatible con infecciónaguda por el virus de Epstein-Barr, que se confirmó conla serología. Uno de los pacientes experimentó mejoríacompleta mientras que en el otro la recuperación fuelenta y quedaron secuelas permanentes. La lesión bilateraldel nervio facial es una complicación infrecuentede la infección por el virus de Epstein-Barr cuya evoluciónno siempre es favorable. Se discute su mecanismo patogénico (AU)

Two young patients with bilateral facial palsy are described. They initially presented unilateral facial palsy,followed by contralateral facial nerve involvement afew days later, together with clinical and serologic evidenceof acute Epstein-Barr virus infection. The outcomewas favourable in one patient but severe sequelspersisted in the second. These two cases show that thisinfrequent complication of Epstein-Barr virus infectionmay not always have a good outcome. The pathogenic mechanism of bilateral facial palsy is discussed (AU)

Monitorización neurofisiológica intraoperatoria: métodos en neurocirugía / Intraoperative neurophysiological monitoring: methods in neurosurgery

La monitorización neurofisiológica intraoperatoria (MIO) utiliza las distintas técnicas neurofisiológicas en el quirófano para monitorizar la función nerviosa durante la cirugía, evitando posibles lesiones neurológicas, con lo que disminuye la morbilidad y mejora el manejo quirúrgico, permitiendo cirugías más agresivas y mejorando las estrategias quirúrgicas. Existen dos tipos de técnicas en la monitorización neurofisiológica, las de mapeo -que identifican las estructuras en riesgo- y las de monitorización propiamente dichas -que proveen un feed-back continuo de la función- así como sus complicaciones, que aunque infrecuentes, existen. Se exponen las técnicas quirúrgicas que se pueden utilizar en la monitorización así como una posible guia orientativa sobre su uso según la zona quirúrgica y las estructuras en riesgo. La MIO constituye uno de los avances más importantes que ha tenido lugar en la neurocirugía moderna (AU)

IONM uses different neurophysiological techniques during surgery time, thus avoiding possible lesions to the neurological structures, making surgery safer and better. We describe two types of IONM: mapping techniques and monitoring techniques, as well as their advantages, disadvantages and complications. We look into the more useful techniques in this field, as well as providing orientation about its use according to the surgical areas and the neurological structures under risk. In conclusion, we affirm that IONM is one of the most important advances in modern neurosurgery (AU)

Monitorización neurofisiológica intraoperatoria en cirugía de columna / Intraoperative neurophysiological monitoring in spine surgery

La monitorización neurofisiológica intraoperatoria (MNIO) permite conocer el estado de las funciones neurológicas durante la cirugía, guiando al cirujano y minimizando los riesgos de lesión. En este trabajo se describen las diferentes técnicas neurofisiológicas disponibles para la MNIO en cirugía del raquis (potenciales evocados somatosensoriales, potenciales evocados motores, neurografía, electromiografía, reflejos y potenciales evocados dermatómicos), que se emplearán a criterio del neurofisiólogo según las estructuras nerviosas en riesgo. Para el éxito de la monitorización es indispensable la coordinación entre todos los profesionales del equipo. En el caso de que la MNIO muestre alteraciones, en primer lugar, el neurofisiólogo debe asegurar la integridad del sistema de registro. A continuación, el anestesista valorará la presión sanguínea, oxigenación, ventilación y hematocrito adecuados y revertirá los cambios recientes realizados en la anestesia. Por último, el cirujano, debería detener la intervención e intentar determinar la causa para revertirla en el caso de que fuera posible (AU)

Intraoperative neurophysiological monitoring (IONM) makes it possible to determine the status of neurological function during surgery. It guides the surgeon and minimises the risk of injury. This paper describes the different techniques available for IONM in spine surgery (somatosensory evoked potentials, motor evoked potentials, neurography, electromyography, reflexes and dermatomic evoked potentials), which neurophysiologists employ depending on the nerve structures at risk. In order for monitoring to be successful, coordination between all members of the surgical team is essential. In the event of IONM registering alterations, the neurophysiologist must first check the integrity of the recording system. The anaesthetist should then assess blood pressure, oxygen levels, ventilation and haematocrit values, and revert recent anaesthetic changes. Finally, the surgeon must stop the procedure and try to determine the cause of the event, and correct it if possible (AU)

[Pseudo-conduction block in nonsystemic vasculitic neuropathy]. / Pseudobloqueo de conducción en vasculitis aislada del sistema nervioso periférico.

SUMMARY: Introduction. Nonsystemic vasculitic neuropathy (NSVN) is an inflammatory disorder of the vasa nervorum which usually is expressed as a mononeuritis multiplex. We present a patient with NSVN with histological confirmination focused on the neurophysiological findings at the early stages. CASE REPORT: A 36 years-old woman presented with paresthesia and weakness in her right hand followed by left footdrop. The first neurophysiologic examination showed low amplitude of the right median nerve (RMN) CMAP with proximal stimulation. A second examination showed signs of axonal damage in several nerves, including the RMN. CONCLUSIONS: The acute ischemic damage of a nerve can give a pattern of conduction block in the electroneurographic study as in the RMN of the presented case. This phenomenon is referred as "pseudo-conduction block", since it is transient and evolves towards a definite pattern of axonal neuropathy. When a vasculitic neuropathy is suspected, repeated neurophysiologic studies are necessary in order to ensure a proper (appropriate) characterization of the lesional patterns.

Pseudobloqueo de conducción en vasculitis aislada del sistema nervioso periférico / Pseudo-conduction block in nonsystemic vasculitic neuropath

Fundamento. La vasculitis aislada del sistema nerviosoperiférico (VASNP) afecta selectivamente a los vasanervorum, expresándose generalmente como una mononeuropatíamúltiple. Presentamos un caso de VASNPconfirmado histológicamente, destacando los hallazgosneurofisiológicos en fase aguda.Observación clínica. Mujer de 36 años con parestesiasy debilidad en mano derecha seguidas de paresia parala dorsiflexión del pie izquierdo. El primer estudio neurofisiológicomostraba amplitud reducida del potencialmotor del mediano derecho con estímulos proximales.Un segundo estudio mostraba signos de lesión axonalen varios nervios, incluyendo el mediano derecho.Conclusiones. La lesión isquémica aguda de un nerviopuede dar lugar a un patrón electroneurográfico debloqueo de conducción, como en el mediano derechodel caso descrito. Este fenómeno es conocido como“pseudobloqueo”, dado su carácter transitorio, conevolución a un patrón de neuropatía axonal. La sospechade VASNP requiere estudios neurofisiológicosseriados para una correcta tipificación de los patrones lesionales(AU)

Summary. Introduction. Nonsystemic vasculitic neuropathy(NSVN) is an inflammatory disorder of the vasanervorum which usually is expressed as a mononeuritismultiplex. We present a patient with NSVN with histologicalconfirmination focused on the neurophysiologicalfindings at the early stages.Case report. A 36 years-old woman presented with paresthesiaand weakness in her right hand followed byleft footdrop. The first neurophysiologic examinationshowed low amplitude of the right median nerve (RMN)CMAP with proximal stimulation. A second examinationshowed signs of axonal damage in several nerves, includingthe RMN.Conclusions. The acute ischemic damage of a nerve cangive a pattern of conduction block in the electroneurographicstudy as in the RMN of the presented case. Thisphenomenon is referred as “pseudo-conduction block”,since it is transient and evolves towards a definite patternof axonal neuropathy. When a vasculitic neuropathyis suspected, repeated neurophysiologic studiesare necessary in order to ensure a proper (appropriate)characterization of the lesional patterns(AU)

[Intraoperative neurophysiological monitoring: methods in neurosurgery]. / Monitorización neurofisiológica intraoperatoria: métodos en neurocirugía.

IONM uses different neurophysiological techniques during surgery time, thus avoiding possible lesions to the neurological structures, making surgery safer and better. We describe two types of IONM: mapping techniques and monitoring techniques, as well as their advantages, disadvantages and complications. We look into the more useful techniques in this field, as well as providing orientation about its use according to the surgical areas and the neurological structures under risk. In conclusion, we affirm that IONM is one of the most important advances in modern neurosurgery.

[Intraoperative neurophysiological monitoring in spine surgery]. / Monitorización neurofisiológica intraoperatoria en cirugía de columna.

Intraoperative neurophysiological monitoring (IONM) makes it possible to determine the status of neurological function during surgery. It guides the surgeon and minimises the risk of injury. This paper describes the different techniques available for IONM in spine surgery (somatosensory evoked potentials, motor evoked potentials, neurography, electromyography, reflexes and dermatomic evoked potentials), which neurophysiologists employ depending on the nerve structures at risk. In order for monitoring to be successful, coordination between all members of the surgical team is essential. In the event of IONM registering alterations, the neurophysiologist must first check the integrity of the recording system. The anaesthetist should then assess blood pressure, oxygen levels, ventilation and haematocrit values, and revert recent anaesthetic changes. Finally, the surgeon must stop the procedure and try to determine the cause of the event, and correct it if possible.

[Neurocysticercosis. An emergent disease]. / Neurocisticercosis. Una enfermedad emergente.

Neurocysticerosis is an affection of the central nervous system by the larvae of the Taenia solium. Although its diagnosis in our country is exceptional, in recent years a notable increase in the number of cases diagnosed has been observed, due to the phenomenon of immigration from countries where the disease is endemic. The most frequent form of presentation of neurocysticercosis is seizures, followed by headache. To diagnose it we must evaluate the epidemiological data, the clinical record and confirm this through neuroimage and immunological studies. The treatment selected should be pharmacological, principally with albendazole, and surgery reserved for cases where the former fails. Hygienic measures and the treatment of patients with teniasis are of great importance. Neurocysticerosis has ceased to be an exceptional diagnosis and given the foreseeable increase of its incidence in our milieu, health professionals must understand this disease and include it at higher levels of the algorithms of differential diagnosis.

Neurocisticercosis. Una enfermedad emergente / Neurocysticercosis. An emergent disease

La neurocisticercosis es una afectación del sistema nervioso central por las larvas de la Taenia solium. Aunque en nuestro país su diagnóstico era excepcional, en los últimos años se ha observado un notable incremento en el número de casos diagnosticados, debido al fenómeno de la inmigración desde países donde la enfermedad es endémica. La forma de presentación más frecuente de la neurocisticercosis es la crisis epiléptica, seguida de la cefalea. Para el diagnóstico de sospecha debemos valorar los datos epidemiológicos y la clínica y confirmarlo mediante los estudios de neuroimagen e inmunológicos. El tratamiento de elección debe ser farmacológico, principalmente con albendazol, y reservar la cirugía para los casos en el que el primero falla. Las medidas higiénico-sanitarias y el tratamiento de los pacientes con teniasis son de suma importancia. La neurocisticercosis ha dejado de ser uno de esos diagnósticos excepcionales y dado el previsible aumento de su incidencia en nuestro medio, los profesionales sanitarios debemos conocer dicha enfermedad e incluirla en niveles más altos de los algoritmos de diagnóstico diferencial (AU)

[The pathophysiological basis of dystonia]. / Bases fisiopatológicas de la distonía.

OBJECTIVE: We review the mechanisms that may involved in the pathophysiology of dystonia. DEVELOPMENT: The role of basal ganglia, spinal and brainstem interneurons, and primary motor cortex in dystonia will be discussed. Abnormalities in the discharge pattern of internal pallidum or thalamus, secondary to basal ganglia disorders might be the cause of disbalance between excitatory and inhibitory mechanisms in motor cortex. Other factors such as excessive repetition of a movement or abnormal sensory afferent discharges may be participating in cortical reorganization. CONCLUSIONS: Overlapping of the cortical representation of dystonic muscles due to enlargement of cortical maps could explain overflow and co-contraction phenomena. The study of the exact role of these factors in each type of dystonia is a challenge for the future that opens the door for new therapeutic approaches.

Bases fisiopatológicas de la distonía / The pathophysiological basis of dystonia

Objetivo. Se revisan los mecanismos que participan en la fisiopatología de las distonías. Desarrollo. Se discute separadamente el papel de los ganglios basales, de las interneuronas espinales y troncoencefálicas, y de la corteza motora primaria, en la génesis de la distonía. Un mecanismo fundamental es la alteración en el patrón de descarga del pálido medial y tálamo, secundario a lesiones o disfunciones de los ganglios basales que sería la causa del desequilibrio entre excitación e inhibición presente en la corteza motora.Otros factores como la repetición excesiva de un movimiento o la descarga crónica anormal de aferencias sensitivas podrían ser agentes fisiopatológicos relacionados y que contribuyeran a la reorganización cortical. Esta se caracteriza por la ampliación de los campos receptivos sensoriales y las áreas de representación somatotópica de los músculos implicados en la distonía, causando solapamientos que explicarían fenómenos típicos de la distonía como el overflow y la co-contracción muscular. Conclusiones. Hipotéticamente, la aparición de alteración de los ganglios basales, la repetición exagerada de un movimiento de precisión, el cambio del esquema motor o un aumento crónico en la descarga de las aferencias sensoriales son causas que podrían sumarse y colaborar en distinta proporción en cada tipo de distonía. Determinar en qué medida interviene cada una es un reto para el futuro y abre una puerta a nuevas aproximaciones terapéuticas (AU)

[Clinical relevance of periodic limb movements during sleep in obstructive sleep apnea patients]. / Relevancia clínica de los movimientos periódicos de las piernas durante el sueño en pacientes con apneas obstructivas del sueño.

INTRODUCTION: The periodic limb movements disorder (PLMD) is frequently associated with the obstructive sleep apnea syndrome (OSAS), but the prevalence and clinical relevance of this association have not been studied in detail. OBJECTIVE: The objectives were to make a prospective study on the prevalence of PLMD in patients with OSAS, and correlate this association with clinical and respiratory parameters. PATIENTS AND METHODS: Forty-two patients diagnosed with OSAS, without clinical suspicion of PLMD, underwent a polysomnographic study. Clinical symptoms and signs were evaluated with an structured questionnaire, and respiratory parameters were obtained from the nocturnal study. RESULTS: Periodic limb movements were found in 10 patients (24%). There were no differences in clinical parameters between both groups (with and without periodical limb movements). However, respiratory parameters were significantly worse in patients without PLMD. CONCLUSIONS: PLMD is very frequent in patients with OSAS, and can contribute to worsen clinical signs and symptoms in these patients independently from respiratory parameters.

Relevancia clínica de los movimientos periódicos de las piernas durante el sueño en pacientes con apneas obstructivas del sueño / Clinical relevance of periodic limb movements during sleep in obstructive sleep apnea patients

Introducción. Los movimientos periódicos de las piernas durante el sueño (MPP) se relacionan con frecuencia al síndrome de apneas obstructivas del sueño (SAOS), aunque la prevalencia y relevancia clínica de esta asociación no ha sido suficientemente estudiada. Objetivo. El objetivo de este trabajo ha sido realizar un estudio prospectivo sobre la frecuencia de los MPP en pacientes con diagnóstico de SAOS, y valorar la relación de la asociación con parámetros clínicos y respiratorios. Pacientes y métodos. Se estudiaron 42 pacientes sin sospecha clínica de MPP, diagnosticados de SAOS mediante estudio polisomnográfico. Se evaluó la clínica de los enfermos mediante un cuestionario estructurado, así como los parámetros respiratorios obtenidos del estudio nocturno. Resultados. Diez pacientes fueron diagnosticados de MPP (24 por ciento). No hubo diferencias en la clínica al comparar ambos grupos (con o sin MPP). Sin embargo, la alteración de los parámetros respiratorios fue significativamente mayor en los pacientes sin MPP. Conclusiones. La presencia de MPP asociados es muy frecuente en pacientes con SAOS y puede contribuir a empeorar la clínica independientemente de los parámetros respiratorios (AU)

[Topographic distribution of visual evoked potentials in optic neuropathy]. / Distribución topográfica del potencial evocado visual en la neuropatía óptica.

INTRODUCTION: Digital treatment of electrical signals coming from the central nervous system on stimulation of the optic nerve path offers an objective method for evaluation of visual evoked potentials (VEP) shown graphically on a cerebral map. OBJECTIVE: To evaluate the topographical distribution of VEP in cases of optic neuropathy adding this parameter to the usual parameters of latency and amplitude. MATERIAL AND METHODS: We studied 35 patients with suspected optic neuropathy and normal findings on basic ophthalmological examination, in whom VEP and VEP mapping (VEPM) was done. RESULTS: In 26% of the cases there was no response for evaluation with the usual VEP recording techniques, whilst in those with VEPM this percentage was reduced to 11.5%. In the other cases there was a potential with characteristic distribution in the occipital areas and a maximally positive dipole posteriorly. CONCLUSION: VEPM is an objective method for evaluation of the visual pathway offering better discrimination than the usual VEP in more severe cases of neuropathy.