Vagus Nerve Stimulation in the Carotid Triangle: An Effective Method for Monitoring the Recurrent Laryngeal Nerve in Thyroid and Parathyroid Surgery.

OBJECTIVE: Our objective is the description of the technique of vagus nerve stimulation in carotid triangle in order to monitor the recurrent laryngeal nerve (RLN) during thyroid and parathyroid surgery. METHODS: We stimulated the vagus nerve in the carotid triangle during 150 thyroid or parathyroid surgeries using a monopolar electromyography electrode inserted under the mastoid process towards the jugular foramen as a cathode, and using another subdermal electrode in the mastoid as an anode. Another complementary method of vagus stimulation was achieved with a pair of subdermal electrodes, placing the cathode at the mandibular angle and the anode at the mastoid. RESULTS: In all patients, compound muscle action potential (CMAP) was recorded in the vocal cords with both stimulation techniques, allowing semi-continuous monitoring to be carried out. Intraoperative lesions were detected in 16 of the cases; 9 of them were transient with CMAP recovery achieved when modifying surgical maneuvers. CONCLUSIONS: Vagus nerve stimulation in the carotid triangle is a reliable technique for monitoring the RLN in thyroid surgery. Vagus nerve stimulation in the carotid triangle is effective and safe for RLN monitoring, and it is a clear alternative to direct continuous stimulation of the nerve that by contrast requires its dissection in the carotid sheath.

Pretarsal blepharospasm: Clinical and electromyographic characteristics.

OBJECTIVE: To describe the clinical and electromyographic characteristics of blepharospasm caused by selective involvement of the pars pretarsalis of the orbicularis oculi muscle. METHODS: Clinical assessment and simultaneous electromyographic recordings from levator palpebrae superioris and pars orbitaria and pretarsalis of orbicularis oculi muscles were performed in patients with blepharospasm and primary failure to botulinum toxin injections. Patients with selective abnormal electromyographic activity of the pars pretarsalis of the orbicularis oculi muscle were identified and treated with selective pretarsal injections of botulinum toxin. RESULTS: We found 24 patients with pretarsal blepharospasm confirmed by the electromyographic assessment. All of them were functionally blind. Three clinical-electromyographic patterns were identified: (a) Impairment of eyelid opening; (b) Increased blinking; (c) Spasms of eye closure combined with varying degrees of excessive blinking and impairment of eye-opening. Pretarsal injections of botulinum toxin induced a significant improvement in all patients and 50 % regained normal or near-normal vision. The clinical improvement was sustained after repeated pretarsal injections. CONCLUSIONS: Pretarsal blepharospasm can be suspected on clinical grounds and it can be confirmed by electromyographic recordings. SIGNIFICANCE: Recognition of this type of blepharospasm is important because of its excellent response to botulinum toxin injections applied into the pretarsal part of the orbicularis oculi muscle.

A new criterion for detection of radiculopathy based on motor evoked potentials and intraoperative nerve root monitoring.

OBJECTIVE: Our objective is to use the area of the motor evoked potential (MEP) as a diagnostic tool for intraoperative radicular injury. METHODS: We analyzed the intraoperative neurophysiological monitoring data and clinical outcomes of 203 patients treated for dorsolumbar spine deformity. The decrease in amplitude was compared with the reduction in the MEP area. RESULTS: In 11 cases, new intraoperative injuries occurred, nine of them were lumbar radiculopathies. Our new criteria, a decrease MEP area of 70%, yielded a sensitivity and specificity of 1, since it detected all the radicular injuries, with no false positive cases. Using a 70% amplitude decrease criteria, we obtained a sensitivity of 0,89 and a specificity of 0,99. A lower threshold (65% amplitude reduction) yielded a higher number of false positives, whereas a higher threshold (75 and 80%) gave rise to a higher number of false negatives. CONCLUSIONS: The measurement of the MEP area gave evidence to be more reliable and accurate than the measurement of the amplitude reduction in order to assess and detect intraoperative radicular injuries. SIGNIFICANCE: The criterion of decrease of the MEP area has a higher reliability and accuracy in the detection of intraoperative radicular lesions than the amplitude reduction.

[Critical illness myopathy. Neurophysiological and muscular biopsy assessment in 33 patients]. / Miopatia del enfermo crítico. Valoracion neurofisiológica y biopsia muscular en 33 pacientes.

INTRODUCTION: Critical illness patients may show marked weakness acquired in the Intensive Care Unit (ICU). There are some disagreements about the myopathic versus neuropathic damage in this condition, presumably due to the lack of reliable diagnostic criteria. AIMS: To report the neurophysiological findings in critical patients, to classify them in groups according to the electro-physiological data of myopathy, and to ascertain the rapport between the neurophysiological classification of myopathy and the muscle biopsy results. PATIENTS AND METHODS: A prospective assessment of 33 ICU patients with marked weakness by means of needle electro-myography, electroneurography, and percutaneous muscle biopsy was carried out. Direct muscle stimulation was performed in 9 patients and repetitive nerve stimulation in 14 cases. RESULTS. According to neurophysiological criteria, patients were classified in 3 groups: definite (33%), probable (46%), and uncertain (21%) myopathy. The most conspicuous myopathic pathological findings including fibrillar atrophy and necrosis, vacuoles, and myosin and mitochondrial anomalies, were observed in both, definite and probable groups (26 patients). In 17 of these cases, low amplitude of the compound motor action potentials and normal sensory nerve action potentials were found. Axonal sensory-motor neuropathy was present in 11 patients, concomitant with neurophysiological data of myopathy in 7 cases. CONCLUSIONS: Based on the neurophysiological criteria for the assessment and classification of acquired weakness in critically ill patients, myopathy is highly predominant over the neuropathic impairment. Histopathological findings are closely related to the electrophysiological diagnosis of myopathy. Neither neurophysiological nor pathological data support a hypothetic motor axonal neuropathy in this series.

Miopatía del enfermo crítico. Valoración neurofisiológica y biopsia muscular en 33 pacientes / Critical illness myopathy. Neurophysiological and muscular biopsy assessment in 33 patients

Introducción. Los enfermos críticos pueden desarrollar cuadros de debilidad importante en la Unidad de Cuidados Intensivos (UCI). Debido a la diversidad de criterios diagnósticos utilizados, existe desacuerdo sobre el origen miopático o neuropático de este cuadro. Objetivos. Describir las alteraciones neurofisiológicas de enfermos críticos, establecer grupos de pacientes según los datos electrofisiológicos de miopatía y determinar su correspondencia con los resultados de la biopsia muscular. Pacientes y métodos. Se estudiaron prospectivamente 33 pacientes en UCI con debilidad importante, mediante electromiografía, electroneurografía y biopsia muscular percutánea. En nueve casos se amplió el estudio con estimulación muscular directa y en 14 con estimulación repetitiva. Resultados. Aplicando criterios neurofisiológicos de miopatía, se describieron tres grupos de pacientes: miopatía definida (33%), miopatía probable (46%) y miopatía incierta (21%). En la biopsia muscular, las alteraciones miopáticas más intensas, con atrofia y necrosis fibrilar, vacuolas y alteraciones miosínicas y mitocondriales, se observaron en los grupos con miopatía definida y probable (26 casos). En 17 de ellos, los potenciales de acción muscular compuestos fueron de baja amplitud y los potenciales de acción del nervio sensitivo normales. Once pacientes mostraron polineuropatía axonal sensitivomotora, que en siete de ellos se asociaba con datos de miopatía. Conclusiones. En enfermos críticos con debilidad intensa, las alteraciones miopáticas en el estudio neurofisiológico son mucho más frecuentes que la afectación neuropática. En concordancia con estos hallazgos, las alteraciones miopáticas en la biopsia muscular son manifiestas y abundantes. Los datos histopatológicos y neurofisiológicos de esta serie no sustentan una hipotética neuropatía axonal motora pura (AU)

Introduction. Critical illness patients may show marked weakness acquired in the Intensive Care Unit (ICU). There are some disagreements about the myopathic versus neuropathic damage in this condition, presumably due to the lack of reliable diagnostic criteria. Aims. To report the neurophysiological findings in critical patients, to classify them in groups according to the electrophysiological data of myopathy, and to ascertain the rapport between the neurophysiological classification of myopathy and the muscle biopsy results. Patients and methods. A prospective assessment of 33 ICU patients with marked weakness by means of needle electromyography, electroneurography, and percutaneous muscle biopsy was carried out. Direct muscle stimulation was performed in 9 patients and repetitive nerve stimulation in 14 cases. Results. According to neurophysiological criteria, patients were classified in 3 groups: definite (33%), probable (46%), and uncertain (21%) myopathy. The most conspicuous myopathic pathological findings including fibrillar atrophy and necrosis,vacuoles, and myosin and mitochondrial anomalies, were observed in both, definite and probable groups (26 patients). In 17 of these cases, low amplitude of the compound motor action potentials and normal sensory nerve action potentials were found. Axonal sensory-motor neuropathy was present in 11 patients, concomitant with neurophysiological data of myopathy in 7 cases. Conclusions. Based on the neurophysiological criteria for the assessment and classification of acquired weakness in critically ill patients, myopathy is highly predominant over the neuropathic impairment. Histopathological findings are closely related to the electrophysiological diagnosis of myopathy. Neither neurophysiological nor pathological data support a hypothetic motor axonal neuropathy in this series (AU)

Neurological damage after radial artery harvesting in coronary surgery: a direct measure.

BACKGROUND: The incidence of neurological complications in the forearm after radial artery harvesting varies in the literature, ranging from 2% to more than 50%. Also, the areas affected and the type of neurological complications differ a lot. Peripheral nerve injuries may be divided into three types: neuroapraxia (conduction block that recovers within 3 months), axonotmesis (recovers 1 ml/day) and neurotmesis (needs surgery for recovering). We decided to perform a neuroelectrophysiological study, before and after surgery, in peripheral nerves of the forearm to find out the real incidence and the type of lesion after radial artery harvesting. METHODS: Fifteen consecutive patients whose RA was going to be harvested were selected. Emergency patients, patients with severe liver or renal dysfunction were excluded. A complete neuroelectrophysiological study was performed in the median, ulnar and radial nerve. The amplitude was measured to check mielina status, whereas with the latency and nerve velocity conduction (NVC) we checked the axonal integrity. An electromyogram was also performed in the forearm muscles. A neurological clinical exploration was also performed. All these tests were performed before surgery and two weeks and two months after surgery. RESULTS: Median nerve: A significant decrease in the amplitude that improved over time was registered. This decrease was observed in the motor and sensitive part of the nerve. No changes were observed regarding latency or NVC. Ulnar nerve: A decrease in the amplitude of the sensitive part of the nerve was observed (11.7-9.2-10.4 microV; P=0.006). No changes were observed regarding latency or NVC. Radial nerve: A statistical trend decrease observed regarding NVC of the sensitive part of the nerve branch was found (50.9 m/s vs. 47.1 m/s vs. 47.2 m/s; P=0.10). The electromyogram found no alterations. Clinically, three patients presented sensitive disorders in the median nerve territory and one of these also complained of sensitive disorders in the radial territory. Another patient referred dysesthesias in the ulnar nerve territory. All patients with the exception of one were asymptomatic two months after surgery. CONCLUSIONS: Although only a few patients refer symptoms, most patients suffer changes in the peripheral nerves of the forearm (especially in the sensitive part) after RA harvesting. In our study the median nerve and the sensitive part of the ulnar and radial nerve were affected. These changes were temporary, affecting mainly the axon. All these data suggest neuroapraxia as the main peripheral nerve type lesion. We think that physicians and patients must be aware of this.

Transient blepharospasm secondary to unilateral striatal infarction.

We report on a patient who presented a transient eyelid motor disorder characterized by bilateral reflex blepharospasm as the main clinical manifestation of a right-sided striatal infarction. This case emphasizes the role of the nondominant striatum in the pathophysiology of eyelid motor abnormalities.

Eyelid movements in health and disease. The supranuclear impairment of the palpebral motility.

The eyelid movements are mediated mainly by the orbicularis oculi (OO) and the levator palpebrae superioris (LPS) muscles. Dissociated upper lid functions exhibit different counterbalanced action of these muscles, and in blinking they show a strictly reciprocal innervation. The disturbance of this close LPS-OO relationship likely leads to many of the central lid movement disorders. Three groups of supranuclear motor impairment of lid movements are considered: the disorders of the lid-eye movements' coordination, the disturbances of blinking and lid "postural" maintenance, and the alteration of voluntary lid movements. Nuclei of the posterior commissure control the inhibitory modulation of LPS motor-neuronal activity and they are involved in the lid-eye coordination disorders such as lid retraction, which is observed in the Parinaud's syndrome and also in parkinsonism and progressive supranuclear palsy. Spontaneous (SB) and reflex blinking consist of two components: the inhibition of the basal tonic LPS activity, which keeps the eyes open, and the concurrent activation of the OO muscles. LPS inhibition precedes and outlasts the OO activation. This normal configuration is impaired in parkinsonism and blepharospasm (BSP). SB shows a highly interindividual rate variation (among 10-20 per minute in adults) and abnormal blink rates occur in neurological diseases related to dopaminergic transmission impairments. Lid postural abnormalities include involuntary eyelid closure, which is usually associated with inability to open the eyes. Two major disorders share these two aspects: BSP and blepharocolysis (BCO). BSP consists of an involuntary overactivity of the OO, with LPS co-contraction activity, and is expressed as frequent and prolonged blinks, clonic bursts, prolonged tonic contraction or a blend of all of them. BCO (commonly named "so-called lid opening apraxia") is an overinhibition of the LPS with no evidence of ongoing OO activity. BSP and BCO occur in many instances of idiopathic dystonias and basal ganglia diseases and, less frequently, in rostral brainstem lesions. Both may coincide in the same patient. Voluntary lid movement disorders comprise the impairment of Bell's phenomenon, the voluntary eyelid closure palsy and the so-called cerebral ptosis, all related to lesions of frontal cortical areas and/or the corticospinal system.