Electrophysiological characteristics of asymptomatic relations of patients with type 2 spinocerebellar ataxia
Introduction. Electrophysiological studies have been shown to be useful in hereditary ataxia, but only a small number of patients have been studied, and the duration of the illness, serial studies and molecular definition have not been taken into account. Objective. We proposed, by means of electrophysiological techniques, to characterize the functional evolutionary state of the afferent and efferent systems in asymptomatic relations of patients with type 2 spinocerebellar ataxia (SCA2). Patients and methods. A 10 year longitudinal, prospective study was made of 59 children of patients with SCA2. The sequence included four studies: 1986, 1991, 1994 and 1996, all with informed consent for the investigation. The control group consisted of 108 volunteers. The electrophysiological studies recorded were: conduction studies in peripheral nerves and multimodal evoked potentials. For statistical analysis multivariate methods were used with a confidence interval of 95% (α= 0.05). Results. Electrophysiological alterations were observed even in the absence of clinical signs, such as reduced amplitude of sensory potentials, morphological changes and prolonged latency of the central components of somatosensory evoked potentials, and of brain stem auditory evoked potentials, whilst the visual evoked potentials remained normal. Of 79 relations studied during the 10 year investigation, 17 had clinical signs and were considered to be patients with SCA2. Conclusions. Four stages of the illness were defined: ‘healthy’, presymptomatic, and patients with and without nerve conduction block. These characterized the degenerative mechanisms of the afferent and efferent systems of the relations of patients with SCA2 who became ill themselves
Objetivo Caracterizar con técnicas electrofisiológicas el estado funcional evolutivo de los sistemas aferentes y eferentes en familiares asintomáticos de enfermos con ataxia espinocerebelosa tipo 2 (AEC2).
Pacientes y métodos Se realizó un estudio longitudinal prospectivo durante 10 años a 59 hijos de pacientes con AEC2. La secuencia incluyó cuatro estudios: 1986, 1991, 1994 y 1996 con el consentimiento informado. El grupo control contó con 108 sujetos voluntarios. Registros electrofisiológicos realizados: estudios de conducción en nervios periféricos y potenciales evocados multimodales. En el análisis estadístico se aplicaron métodos multivariados con una confiabilidad del 95% (a= 0,05).
Resultados Se observó la existencia de alteraciones electrofisiológicas aun en ausencia de manifestaciones clínicas tales como disminución de las amplitudes de los potenciales sensitivos, alteraciones en la morfología y prolongación de las latencias de los componentes centrales de los potenciales evocados somatosensoriales y cambios en la replicabilidad y morfología de los potenciales evocados auditivos de tallo cerebral, mientras los visuales permanecieron normales. De los 59 familiares estudiados en los 10 años de investigación, 17 presentaron manifestaciones clínicas y se les consideró enfermos de AEC2.
Conclusiones Se definieron cuatro etapas evolutivas: ‘sanos’, presintomáticos, enfermos con y sin bloqueo en la conducción nerviosa. Éstas caracterizaron los mecanismos degenerativos de sistemas aferentes y eferentes en los familiares de pacientes con AEC2 que enfermaron
