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OBJECTIVE: Children with cleft palate are at increased risk for Eustachian tube dysfunction (ETD) and conductive hearing loss from chronic otitis media. While it has been proposed that the severity of ETD is related to the severity of cleft palate, data are lacking to support this hypothesis. An improved understanding of the relevance of cleft width may have prognostic value that could inform decisions on the timing of tympanostomy tube placement and choice of tympanostomy tube design. The objective of this study was to assess severity of ETD in children with narrow, moderate, and wide cleft palate, with examination of hearing outcomes, number of tympanostomy procedures, and incidence of otologic complications. METHODS: Retrospective chart review was conducted on 58 patients with primary palatoplasty performed at a single academic medical center from January 1, 2016-December 31, 2019. The primary outcome was the number of otologic procedures performed after the initial palatoplasty. Secondary outcomes included audiometric findings, number of tympanostomy tube placements, presence of effusion at the time of myringotomy, and occurrence of any postoperative otologic complication. Outcomes were compared for patients with narrow (<10 mm), moderate (10-15 mm), and wide (>15 mm) cleft palate. Analysis included consideration of cleft palatal morphology (Veau I - IV), presence of Robin sequence or syndromes, and risk factors for otitis media. RESULTS: Patients with moderate and wide cleft palate underwent higher mean numbers of otologic procedures [narrow: 1.3 (95% confidence interval [CI] 0.9, 1.7); moderate: 1.6 (95% CI 1.1, 2.1); wide: 1.8 (95% CI 1.2, 2.4)]. Moderate and wide cleft palate were less likely to have normal hearing after their first tympanostomy (narrow: 50%, 10/20; moderate: 25%, 6/24; wide: 36%, 5/14). Patients with a wide cleft palate had a shorter median time between first and second tympanostomy procedures (median, IQR; narrow: 27.0, 20.8-35.7; moderate 20.4, 16.3-25.9; wide 17.3, 11.5-23.4). CONCLUSION: Our findings suggest that patients with wider cleft palate may be more susceptible to severe ETD. Further large-scale study may help to allow for more informed and personalized clinical decision making for management of cleft palate, incorporating cleft width for prognosis of risks for persistent middle ear dysfunction.
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Fisura del Paladar , Enfermedades del Oído , Otitis Media con Derrame , Otitis Media , Niño , Humanos , Lactante , Fisura del Paladar/complicaciones , Estudios Retrospectivos , Oído Medio , Enfermedades del Oído/etiología , Otitis Media/complicaciones , Ventilación del Oído Medio/efectos adversos , Otitis Media con Derrame/cirugíaRESUMEN
OBJECTIVE: To determine if long-term topiramate therapy is safe and slows disease progression in patients with ALS. METHODS: A double-blind, placebo-controlled, multicenter randomized clinical trial was conducted. Participants with ALS (n = 296) were randomized (2:1) to receive topiramate (maximum tolerated dose up to 800 mg/day) or placebo for 12 months. The primary outcome measure was the rate of change in upper extremity motor function as measured by the maximum voluntary isometric contraction (MVIC) strength of eight arm muscle groups. Secondary endpoints included safety and the rate of decline of forced vital capacity (FVC), grip strength, ALS functional rating scale (ALSFRS), and survival. RESULTS: Patients treated with topiramate showed a faster decrease in arm strength (33.3%) during 12 months (0.0997 vs 0.0748 unit decline/month, p = 0.012). Topiramate did not significantly alter the decline in FVC and ALSFRS or affect survival. Topiramate was associated with an increased frequency of anorexia, depression, diarrhea, ecchymosis, nausea, kidney calculus, paresthesia, taste perversion, thinking abnormalities, weight loss, and abnormal blood clotting (pulmonary embolism and deep venous thrombosis). CONCLUSIONS: At the dose studied, topiramate did not have a beneficial effect for patients with ALS. High-dose topiramate treatment was associated with a faster rate of decline in muscle strength as measured by MVIC and with an increased risk for several adverse events in patients with ALS. Given the lack of efficacy and large number of adverse effects, further studies of topiramate at a dose of 800 mg or maximum tolerated dose up to 800 mg/day are not warranted.
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Esclerosis Amiotrófica Lateral/tratamiento farmacológico , Fructosa/análogos & derivados , Fructosa/uso terapéutico , Adulto , Anciano , Esclerosis Amiotrófica Lateral/mortalidad , Progresión de la Enfermedad , Método Doble Ciego , Femenino , Fructosa/efectos adversos , Fructosa/farmacología , Fuerza de la Mano , Humanos , Tablas de Vida , Masculino , Persona de Mediana Edad , Contracción Muscular/efectos de los fármacos , Modelos de Riesgos Proporcionales , Seguridad , Análisis de Supervivencia , Tromboembolia/inducido químicamente , Topiramato , Insuficiencia del Tratamiento , Capacidad Vital/efectos de los fármacosRESUMEN
BACKGROUND: Inclusion body myositis (IBM) remains without effective therapy. As anabolic steroids have myotrophic properties, the authors studied whether a synthetic androgen, oxandrolone, would have efficacy in IBM. METHODS: A double-blind, placebo-controlled, crossover design was used. Patients received oxandrolone or placebo for 12 weeks followed by a minimum 2-month washout period, followed by 12 weeks of the alternative treatment. Maximal voluntary isometric contraction testing (MVICT), manual muscle testing (MMT), and functional performance testing were obtained before and after each treatment period, with the whole-body MVICT score as the primary outcome measure. RESULTS: Of 19 patients enrolled, 16 (14 men, 2 women; median age 68.5 years) had complete data for at least the first treatment period, with 13 completing the entire study. Whole-body MVICT improved by a median of 15.5 kg with drug and 4.1 kg with placebo (p = 0.06), whereas MMT demonstrated a median increase of 2.0 Medical Research Council points with drug and 0.9 point with placebo (p = 0.33). Upper-extremity MVICT demonstrated a significant treatment effect, with strength increasing a median 6.3 kg with drug vs 2.5 kg with placebo (p = 0.006). Stair climbing also increased a median of 1 step on average with drug versus no change with placebo (p < 0.001). Minimal adverse effects occurred. CONCLUSIONS: Oxandrolone had a borderline significant effect in improving whole-body strength and a significant effect in improving upper-extremity strength as measured by MVICT. Given these findings, further study of this drug, possibly in combination with an immunomodulating agent, is warranted.
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Anabolizantes/uso terapéutico , Miositis por Cuerpos de Inclusión/tratamiento farmacológico , Oxandrolona/uso terapéutico , Anciano , Anabolizantes/efectos adversos , Estudios Cruzados , Método Doble Ciego , Femenino , Humanos , Contracción Isométrica/efectos de los fármacos , Masculino , Oxandrolona/efectos adversos , Proyectos Piloto , Estadísticas no ParamétricasRESUMEN
OBJECTIVE: To determine the benefit of nasally inhaled dornase alfa in cystic fibrosis (CF) sinusitis. DESIGN: Retrospective chart review comparing postsurgical course, radiographic studies, and pulmonary function test results in patients who were treated with nasally inhaled dornase alfa with those in patients who were not treated with dornase alfa. PATIENTS: Twenty consecutive patients with CF who underwent functional endoscopic sinus surgery from 1993 to 1997 were included in the study. Treatment with nasally inhaled dornase alfa was initiated in 5 of the 20 patients after they underwent functional endoscopic sinus surgery. SETTING: Tertiary care academic center. RESULTS: The dornase alfa-treated patients had less mucosal edema and no polyps at serial endoscopy over 3 years compared with the non-dornase alfa-treated patients. The patients who received nasally inhaled dornase alfa also underwent fewer revision functional endoscopic sinus surgical procedures (1.6 vs 3.2), even though there was essentially no change in pulmonary function test results in these patients. CONCLUSIONS: Sinusitis continues to be a major cause of morbidity in patients with CF. Symptomatic patients frequently require multiple drug regimens, including long-term systemic antibiotic therapy, topical and systemic steroid therapy, and antibiotic nasal irrigations. This preliminary study indicates the potential impact of nasally inhaled dornase alfa in controlling postoperative symptoms in CF sinusitis.
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Fibrosis Quística/tratamiento farmacológico , Desoxirribonucleasa I/administración & dosificación , Expectorantes/administración & dosificación , Pólipos Nasales/cirugía , Complicaciones Posoperatorias/tratamiento farmacológico , Sinusitis/tratamiento farmacológico , Administración por Inhalación , Adolescente , Adulto , Niño , Enfermedad Crónica , Endoscopía , Femenino , Humanos , Masculino , Proteínas Recombinantes/administración & dosificación , Estudios RetrospectivosRESUMEN
A 30-year-old woman developed severe bilateral radial neuropathies during vaginal delivery of twins, likely secondary to positioning and muscular effort. Subsequent evaluation led to the diagnosis of hereditary neuropathy with predisposition to pressure palsies. Avoidance of prolonged muscular effort in the arms in conjunction with medial intervention to shorten the second stage of labor may help prevent debilitating radial nerve injury in women with this disorder.
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OBJECTIVE: To determine the relative importance of lumbosacral polyradiculopathy (PR) as a cause of distal lower extremity sensory loss, weakness, and hyporeflexia usually attributed to polyneuropathy (PN). METHODS.: We performed a chart review of all patients referred to our electromyography (EMG) laboratory for evaluation of polyneuropathy over a 23-month period. Requisitions, clinical histories, physical examinations, electromyography results, and subsequent evaluations were reviewed for each case. RESULTS: : Of 162 cases, 79 (49%) patients had evidence of PN, either alone or in combination with another abnormality. Twenty-two (14%) had findings consistent with PR alone, and an additional 14 patients (8.6%) were found to have simultaneous PR and PN. Of the 11 patients who underwent subsequent magnetic resonance imaging, nine (82%) had prominent lumbar stenosis. An asymmetric sensory examination was more common (p <0.002) in patients with PR than in patients with PN. CONCLUSION: : Lumbosacral PR should be considered in the differential diagnosis of all patients presenting with distal sensory loss, weakness, and hyporeflexia.
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Percutaneous endoscopic gastrostomy (PEG) is an effective method for providing alimentation in patients with upper aerodigestive tract carcinoma. Multiple complications of this procedure have been reported, ranging from leakage around the tube to tumor seeding of the abdominal cavity. This study was undertaken to determine whether the timing of PEG tube placement with respect to primary tumor extirpation led to a difference in the number and severity of observed complications. The medical records of 43 patients with head and neck carcinoma who had PEG tubes placed from 1995 to 1996 were retrospectively reviewed. Comparisons of timing of PEG tube placement, complication, location, and stage of the primary tumor were performed. In addition, the use of adjuvant therapy with respect to the time of PEG tube placement and complications was evaluated. Of these, 23% were done before and 30% during surgery at the time of primary tumor resection (9 of 13 were after primary removal). One patient had an intraabdominal abscess. Minor complications occurred in 15 of 43 patients (35%) and included granulation tissue at the PEG site, leakage, and tube displacement. Eight of the 9 patients who underwent intraoperative PEG after tumor resection had no complications. Patients who underwent PEG during or after surgery had significantly fewer complications than those who underwent preoperative PEG or had unresectable tumors (P = 0.038). The largest number of complications occurred in patients who underwent preoperative PEG (57%) followed by patients whose tumors were unresectable (31%). There was no statistical difference with regard to tumor location or postoperative x-ray therapy in PEG complications. This study demonstrates that PEG tube placement after tumor resection has the lowest incidence of postoperative complications. Performing PEGs intraoperatively after tumor resection can prevent the need for additional anesthesia to provide alimentation in patients with upper aerodigestive tract carcinoma.
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Endoscopía Gastrointestinal , Nutrición Enteral/métodos , Gastrostomía , Neoplasias de Cabeza y Cuello/cirugía , Intubación Gastrointestinal , Cuidados Paliativos , Femenino , Gastrostomía/efectos adversos , Gastrostomía/métodos , Humanos , Periodo Intraoperatorio , Intubación Gastrointestinal/efectos adversos , Intubación Gastrointestinal/métodos , Masculino , Persona de Mediana Edad , Complicaciones Posoperatorias , Estudios Retrospectivos , Factores de TiempoRESUMEN
Electromyography (EMG) and magnetic resonance imaging (MRI) are commonly used in the diagnosis of cervical and lumbosacral radiculopathy, but the agreement between the two studies is unknown. We retrospectively studied 47 patients with a clinical history compatible with either cervical or lumbosacral radiculopathy who were evaluated with both an EMG and a spine MRI within 2 months of each other. Among these patients, 55% had an EMG abnormality and 57% had an MRI abnormality that correlated with the clinically estimated level of radiculopathy. The two studies agreed in a majority (60%) of patients, with both normal in 11 and both abnormal in 17; however, only one study was abnormal in a significant minority (40%), suggesting that the two studies remain complementary diagnostic modalities. The agreement was higher in patients with abnormal findings on neurologic examination, underscoring the difficulty of confirming the diagnosis in mild radiculopathy.
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Electromiografía , Imagen por Resonancia Magnética , Radiculopatía/diagnóstico , Raíces Nerviosas Espinales/patología , Adulto , Anciano , Femenino , Humanos , Región Lumbosacra/patología , Masculino , Persona de Mediana Edad , Cuello/patología , Valor Predictivo de las Pruebas , Estudios RetrospectivosRESUMEN
Chronic immune and inflammatory motor neuropathies may resemble motor neuron disease, and the distinction may be particularly difficult if conduction block or GM1 antibodies are absent. The pathology of this axonal type of chronic motor neuropathy has not been characterized except in a few cases associated with paraproteinemia. We describe the clinical, electrophysiological, and pathological findings in a patient with a chronic motor axonal neuropathy, normal immunoelectrophoresis, and no GM1 antibodies. At autopsy the spinal cord was normal with the exception of chromatolytic motor neurons. All the ventral roots were greatly thinned. Of 10 mixed nerves and numerous spinal roots sampled, five showed areas of perineurial, perivascular lymphocytic infiltration. There was severe axonal loss in the motor roots that was not as evident in mixed nerves, and the sensory nerves and roots were virtually unaffected. Our findings suggest that a chronic motor axonal neuropathy without paraproteinemia or GM1 antibodies may, in some cases, result from an inflammatory process.
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Inflamación/patología , Enfermedad de la Neurona Motora/patología , Polirradiculoneuropatía/patología , Anciano , Anciano de 80 o más Años , Enfermedad Crónica , Diagnóstico Diferencial , Electrodiagnóstico , Resultado Fatal , Humanos , Plexo Lumbosacro/patología , Masculino , Enfermedad de la Neurona Motora/fisiopatología , Conducción Nerviosa , Polirradiculoneuropatía/fisiopatologíaRESUMEN
Elevations in temperature may produce conduction block in demyelinated neurons. A well-described phenomenon in multiple sclerosis, it has also been reported in some patients with inflammatory demyelinating polyneuropathies. We used carpal tunnel syndrome (CTS) as a model to study the effect of heat on nerves with focal demyelination secondary to chronic compression. Compound motor and sensory responses were measured in 12 CTS patients and 12 normal subjects at 32 degrees C and with heating to 42 degrees C. Changes in relative motor response amplitude and area were similar for both normal subjects and CTS patients. In CTS patients, however, sensory response amplitude and area decreased 34.3% and 48.9%, significantly more than the 25.2% and 39.1% reductions in normal subjects (P=0.021 and P=0.018 respectively). We hypothesize that these reductions in response amplitude are secondary to the occurrence of heat-induced conduction block in demyelinated sensory neurons.
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Síndrome del Túnel Carpiano/fisiopatología , Calor , Neuronas Aferentes/fisiología , Adulto , Factores de Edad , Anciano , Femenino , Humanos , Modelos Lineales , Masculino , Persona de Mediana Edad , Conducción Nerviosa/fisiologíaRESUMEN
High temperature enhances the decrement on repetitive nerve stimulation (RNS) in patients with myasthenia gravis (MG). However, the limit of this phenomenon at high temperature is unknown. Three-hertz ulnar RNS was performed in 7 patients with MG at a skin temperature of 32 degrees C and then with the hand in a 44 degrees C water bath. At 32 degrees C, the mean decrement preactivation was 5% (range, 0-24%); after 1 min of exercise, the mean decrement reached a maximum of 11% (range, 1-34%) 2 min postactivation. At a hand temperature of 42 degrees C, the mean decrement preactivation was 17% (range, 0-65%); after exercise, the mean decrement reached a maximum of 29% (range, 5-74%) 1 min postactivation. In 3 subjects, RNS was normal at 32 degrees C, but a definite decrement developed with heating. These findings demonstrate that very high temperature can improve the sensitivity of ulnar RNS for postsynaptic neuromuscular transmission defects.
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Calor , Músculo Esquelético/inervación , Miastenia Gravis/diagnóstico , Conducción Nerviosa , Potenciales de Acción/fisiología , Adulto , Anciano , Estimulación Eléctrica , Electrofisiología , Femenino , Mano/inervación , Mano/fisiología , Humanos , Masculino , Persona de Mediana Edad , Músculo Esquelético/fisiología , Tiempo de Reacción/fisiologíaRESUMEN
Although paraspinal muscle fibrillations and positive sharp waves (PSWs) are used to help identify neuromuscular disorders, the frequency of these abnormalities in normal subjects is uncertain. We performed lumbosacral paraspinal electromyography in 65 normal subjects. Twenty-seven (42%) had fibrillations and/or PSWs, with the prevalence of these findings increasing with age (r = 0.830, P = 0.040). These data suggest isolated fibrillations and PSWs in lumbosacral paraspinal muscles, especially of older subjects, are nonspecific findings.
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Músculo Esquelético/fisiología , Adulto , Anciano , Anciano de 80 o más Años , Envejecimiento/fisiología , Electromiografía , Humanos , Región Lumbosacra , Persona de Mediana Edad , Valores de Referencia , Columna VertebralRESUMEN
Nerve root stimulation may be employed in patients with motor neuron disease (MND) to rule out motor neuropathy with conduction block. The diagnostic utility of these studies is unknown, in part because the range of amplitude changes across nerve root segments in patients with active neuronal degeneration has not been well studied. We reviewed root stimulation studies in 32 patients (59 nerves) with MND and found segmental amplitude reduction from 0 to 45%, a range similar to values reported for normal subjects; there was no suggestion of conduction block based on our usual criteria.
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Enfermedad de la Neurona Motora/fisiopatología , Raíces Nerviosas Espinales/fisiopatología , Adulto , Anciano , Esclerosis Amiotrófica Lateral/diagnóstico , Esclerosis Amiotrófica Lateral/fisiopatología , Estimulación Eléctrica , Electrodiagnóstico , Femenino , Humanos , Masculino , Persona de Mediana Edad , Enfermedad de la Neurona Motora/diagnóstico , Conducción Nerviosa/fisiologíaRESUMEN
OBJECTIVE: To correlate the frequency of superimposed processes (SPs) such as radiculopathies, polyneuropathies, and plexopathies with median motor forearm conduction velocity (MMFCV) in patients with carpal tunnel syndrome (CTS). DESIGN: All cases of diagnosed CTS were retrospectively analyzed for evidence of SPs. SETTING: Electrophysiology laboratory of a tertiary care center. PARTICIPANTS: One hundred fifty-five patients (44 men, 111 women), ages 19 to 94, who were referred for and met electrophysiologic criteria for CTS, both with and without MMFCV slowing. MAIN OUTCOME MEASURE: The frequency of SPs in patients with no, mild, moderate, and severe MMFCV slowing. RESULTS: A total of 192 arms from 155 patients were studied. Of 14 arms with mild slowing (MMFCV of 47.0 to 49.9 m/sec), 2 (14%) had an SP. Of 15 arms with moderate slowing (MMFCV of 43.0 to 46.9 m/sec), 7 [corrected] (46%) had an SP. Of 9 arms with severe slowing (MMFCV of < 43.0 m/sec), 4 (44%) had an SP. The frequency of SPs for both the moderate and severe groups was significantly higher than that in patients with a normal MMFCV (p < .01); of 154 arms with a normal MMFCV, only 9 (6%) had an SP. CONCLUSION: In cases of CTS, the finding of moderate to severe slowing of MMFCV (< 47.0 m/sec) should prompt a careful electrophysiologic investigation to exclude an SP.
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Síndrome del Túnel Carpiano/fisiopatología , Antebrazo/fisiología , Conducción Nerviosa , Potenciales de Acción , Adulto , Anciano , Anciano de 80 o más Años , Síndrome del Túnel Carpiano/complicaciones , Electrofisiología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estudios RetrospectivosRESUMEN
As proximal nerves are relatively spared in length-dependent, axonal polyneuropathy, we theorized that a sural/radial amplitude ratio (SRAR) might be a sensitive indicator of mild polyneuropathy. In this study, sural amplitudes and SRARs in patients with signs of mild axonal polyneuropathy were compared to those of normal, age-matched control subjects. Sural and radial sensory responses were measured in a standard fashion in all subjects. Thirty polyneuropathy patients had an average SRAR of 0.29 as compared to 0.71 for the 30 normal subjects. An SRAR of less than 0.40 was a strong predictor of axonal polyneuropathy, with 90% sensitivity and 90% specificity, as compared to an absolute sural amplitude of less than 6.0 microV, which had sensitivity of only 66%. Additionally, unlike the sural amplitude, the ratio did not vary significantly with age. We conclude that the SRAR is a sensitive, specific, age-independent electrodiagnostic test for mild axonal polyneuropathy.
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Axones/fisiología , Enfermedades del Sistema Nervioso Periférico/diagnóstico , Enfermedades del Sistema Nervioso Periférico/fisiopatología , Nervio Radial/fisiopatología , Nervio Sural/fisiopatología , Adulto , Anciano , Electrodiagnóstico , Femenino , Humanos , Masculino , Persona de Mediana Edad , Conducción Nerviosa/fisiología , Valores de Referencia , Factores de TiempoRESUMEN
Sensorineural hearing loss has been identified in several types of muscular dystrophy, but few studies have investigated any relationship between Duchenne muscular dystrophy and hearing. An animal model of Duchenne muscular dystrophy, the mdx mouse, exhibits the same genetic defect as humans. We performed brainstem auditory evoked responses on mdx and control mice in order to assess sensorineural hearing loss. The amplitude and latency of wave I for each animal were measured at increasing sound pressure levels. A significant increase in threshold and a decrease in wave I amplitude were found in the mdx mice. These results indicate that significant sensorineural hearing loss is associated with muscular dystrophy in the mdx mouse. Possible cellular mechanisms contributing to the hearing deficit are presented.
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Modelos Animales de Enfermedad , Pérdida Auditiva Sensorineural/complicaciones , Ratones Endogámicos mdx , Distrofias Musculares , Distrofia Muscular Animal/complicaciones , Animales , Potenciales Evocados Auditivos del Tronco Encefálico , Pérdida Auditiva Sensorineural/diagnóstico , RatonesAsunto(s)
Esclerosis Amiotrófica Lateral/diagnóstico , Electrodiagnóstico , Músculos Faciales/fisiopatología , Músculos Masticadores/fisiopatología , Lengua/fisiopatología , Anciano , Anciano de 80 o más Años , Esclerosis Amiotrófica Lateral/fisiopatología , Electromiografía , Estudios de Evaluación como Asunto , Músculos Faciales/inervación , Humanos , Músculos Masticadores/inervación , Persona de Mediana Edad , Degeneración Nerviosa , Regeneración Nerviosa , Estudios Prospectivos , Lengua/inervaciónRESUMEN
Colchicine may induce a myoneuropathy in patients with renal insufficiency. To date, myotonia has not been described in this disorder. We recently studied 4 patients treated with routine doses of colchicine who, in the setting of renal insufficiency, developed a severe myoneuropathy characterized by prominent myotonic discharges on electromyography. In addition, 1 of the 4 patients had profound clinical myotonia. In the 3 patients in whom biopsies were performed, marked myopathic change with intracytoplasmic vacuolization was identified. All 4 patients improved rapidly with discontinuation of the medication. The patient in whom electrophysiologic studies were repeated had a complete resolution of the myotonic discharges. Colchicine myoneuropathy can present with prominent clinical and electrophysiologic myotonia that resolves completely with discontinuation of the medication.
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Colchicina/efectos adversos , Miotonía/inducido químicamente , Enfermedades Neuromusculares/inducido químicamente , Adulto , Anciano , Anciano de 80 o más Años , Colchicina/uso terapéutico , Electromiografía , Femenino , Humanos , Fallo Renal Crónico/tratamiento farmacológico , Masculino , Persona de Mediana Edad , Músculos/patología , Miotonía/patología , Miotonía/fisiopatología , Enfermedades Neuromusculares/patología , Enfermedades Neuromusculares/fisiopatologíaRESUMEN
The presence of significant slowing of motor nerve conduction velocity is considered one of the electrodiagnostic hallmarks of demyelinating neuropathies; however, slowing of conduction velocity may also accompany severe axonal loss. When compound muscle action potential (CMAP) amplitudes are markedly reduced, it is frequently difficult to determine if conduction velocity slowing is due to axonal loss with dropout of the fastest conducting fibers or demyelination. To evaluate the relationship between conduction velocity and axonal dropout, we compared conduction velocities through the same segment of nerve recording from distal and proximal peroneal muscles in patients with chronic neuropathies, in patients with motor neuron disease, and in control subjects. In controls and patients with motor neuron disease, conduction velocities were normal with no significant difference between proximal and distal sites. In patients with axonal neuropathies, conduction velocities were preferentially slowed when recording from distal muscles and relatively normal when recording from proximal sites. Patients with demyelinating neuropathies showed marked slowing of conduction at both sites. We conclude that comparing conduction velocity obtained from proximal versus distal muscle recordings provides a simple, reliable aid for differentiating between chronic axonal and demyelinating polyneuropathies, especially in cases with conduction velocity slowing and low CMAP amplitudes.