Síndrome de la persona rígida: manifestación de afectación inmunológica específica del sistema nervioso central / Stiff man syndrome: a specific immunological condition affecting the central nervous system

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[When should a brain scan with HMPAO be performed to diagnose brain death?]. / ¿Cuando realizar una gammagrafía cerebral con HMPAO en el diagnóstico de muerte encefálica?

INTRODUCTION: Current Spanish law defines the criteria to be met in the case of brain death (BD) and the complementary tests to confirm it, although they do not always need to be carried out. In Spain one of the most frequently used methods is the electroencephalogram (EEG), which has its shortcomings in patients who are under sedation with barbiturates. Transcranial Doppler (TCD) offers a number of advantages in the diagnosis of BD, but it also has certain limitations. In these cases, a cerebral perfusion scan (CPS) with HMPAO can be very useful. CASE REPORTS: We describe the case of two patients who were admitted to the Intensive Care Unit with serious traumatic brain injuries. Progress was unfavourable and the findings of the clinical exploration were compatible with BD. Since we were dealing with patients under barbiturate therapy, the EEGs were complex and difficult to interpret. TCD was difficult to perform in both cases because of loss of brain matter and displacement of intracranial structures, respectively. CPS, however, allowed us to confirm the diagnosis of BD. CONCLUSION: Although it has obvious advantages, TCD cannot always be performed to confirm BD diagnosis. In these cases, CPS can be an extremely valuable tool

¿Cuándo realizar una gammagrafía cerebral con HMPAO en el diagnóstico de muerte encefálica? / When should a brain scan with HMPAO be performed to diagnose brain death?

Introducción. La legislación española vigente establece los criterios de muerte encefálica (ME) y las pruebas complementarias de confirmación -que no siempre es necesario realizar-.Entre ellas, la más utilizada en nuestro país es el electroencefalograma (EEG), que tiene limitaciones en pacientes con sedación barbitúrica. El Doppler transcraneal (DTC) presenta numerosas ventajas para el diagnóstico de ME, pero también algunas limitaciones. En esos casos, la gammagrafía de perfusión cerebral (GPC) con HMPAO puede ser de gran utilidad. Casos clínicos. Se presentan dos pacientes jóvenes que ingresan en la Unidad de Cuidados Intensivos tras traumatismo craneoencefálico grave. Evolucionan desfavorablemente y presentan exploración clínica compatible con ME. Los EEG, al tratarse ambos pacientes con barbitúricos, son de interpretación compleja. El DTC es difícil de realizar en ambos casos, por presentar pérdida de masa encefálica y desplazamiento de estructuras intracraneales, respectivamente. La GPC, sin embargo, permitió confirmar el diagnóstico de ME. Conclusión. El DTC, aunque presenta evidentes ventajas, no siempre puede realizarse para confirmar el diagnóstico de ME. En esos casos, la GPC puede ser muy útil (AU)

Dissociation between intentional and incidental sequence learning in Huntington's disease.

The ability to acquire and act upon serial order information is fundamental to almost all forms of adaptive behaviour. There is growing evidence that such knowledge may be acquired through a number of different means, each perhaps with its own neuronal substrate. One major distinction is between serial order information acquired intentionally and leading to explicit conscious knowledge of the sequence structure, and information acquired incidentally through experience. While this latter form of knowledge influences behaviour, it may do so without the participant being aware of the sequential information, i.e. it is acquired implicitly. Evidence from physiological and lesion studies in animals and imaging studies in humans suggests that these two forms of learning may have dissociable neuronal substrates. Specifically, the striato-thalamo-cortical circuit centred on the caudate nucleus is proposed to be involved in intentional sequence learning and that based on the putamen on incidental learning. The present study tested one part of this proposed dissociation by assessing patients with Huntington's disease on tasks of the two forms of learning. On the test of trial-and-error intentional learning there were marked deficits, which were closely related to disease progression and to measures of executive cognitive dysfunction. This finding was in contrast to the finding from the incidental learning task. Performance of the Huntington's disease group was essentially normal and unrelated to measures of disease progression and cognitive status. The results, although supportive of the proposed dual-system hypothesis, offer only partial confirmation. Further direct study is required using similar tasks in patients with putamenal disorder or lesions within the skeletomotor striato-thalamo-cortical circuit.

[Executive dysfunction in Huntington's disease]. / Disfunción ejecutiva en la enfermedad de Huntington.

INTRODUCTION: In the early stages of Huntington s disease (HD), there is selective vulnerability of the medium-sized spinous cells of the striate nucleus. These cells are connected with the dorsolateral prefrontal cortex, which is an area involved in cognitive processes concerning attention and executive function, forming part of one of the cortico-striatal circuits. OBJECTIVE: To analyze and interpret the executive dysfunction of a group of patients with HD at a moderately advanced stage. PATIENTS AND METHODS: We evaluated 16 patients and controls. Three clinical scales were used: the motor section of the UHDRS, the independence scale and the total functional capacity scale. For cognitive evaluation we used the study protocol of the Core Assessment Program for Intracerebral Transplantation for HD (CAPIT-HD). RESULTS: The patients with EH showed significant deterioration on the tests to evaluate cognitive function, attention and working memory. There were only two exceptions, the WEST and the direct order digit span. CONCLUSIONS: Patients with HD have executive dysfunction, probably due to dysfunction of the cortico-striatal circuits. We therefore agree with the proposal that fronto-striatal cognitive dysfunction is the most suitable name for the cognitive deterioration seen in this condition.

Disfunción ejecutiva en la enfermedad de Huntington / Executive sysfunction in Huntington´s disease

Introducción. En los estadios precoces de la enfermedad de Huntington (EH) existe una selectiva vulnerabilidad de las células espinosas de tamaño medio del estriado. Estas células se hallan conectadas con el córtex prefrontal dorsolateral, área estrechamente relacionada con los procesos cognitivos que median la atención y la función ejecutiva, formando parte de uno de los circuitos corticostriatales. Objetivo. Analizar e interpretar la disfunción ejecutiva presente en un grupo de pacientes con EH en estadio moderadamente evolucionado. Pacientes y métodos. Se evaluaron 16 casos y controles. Se utilizaron tres escalas clínicas: la sección motora de la UHDRS, la escala de independencia y la de capacidad funcional total. Para la evaluación cognitiva se empleó el protocolo de estudio del Core Assessment Program for Intracerebral Transplantation para la EH (CAPIT-HD). Resultados. Los pacientes con EH mostraron un significativo deterioro en los tests que evalúan la función ejecutiva, la atención y la memoria de trabajo. Sólo hubo dos excepciones, el WCST y el span de dígitos en orden directo. Conclusiones. Los pacientes con EH presentan una disfunción ejecutiva, probablemente como consecuencia de la disfunción de los circuitos corticoestriatales. Por lo tanto, coincidimos con la propuesta de denominar disfunción cognitiva frontoestriatal como el término más apropiado para asignar el deterioro cognitivo que aparece en esta enfermedad (AU)

[Cognitive deterioration in Huntington disease]. / Deterioro cognitivo en la enfermedad de Huntington.

OBJECTIVES: To review, summarize and update data on the pattern of cognitive deterioration in Huntington's disease (HD). DEVELOPMENT: HD represents a paradigm of frontostriatal dementia in which cognitive deterioration affects three large domains: memory, executive and visual-spatial functions. Episodic explicit memory deficit mainly affects the processes of information recovery, whilst changes in implicit memory are impaired in learning procedures but not in priming. Executive dysfunction constitutes an essential characteristic, affecting the working memory, attention, sequencing and planning. Complex visual-spatial functions are severely affected and this may affect recognition of complex figures and facial gestures. Some of these mental changes may be detected during preclinical stages. At the present time, since it is possible to make a definite genetic diagnosis and there is neuropathological data on HD, this condition is considered to be an excellent clinical model for the study of the cognitive functions carried out by the cortico-striatal circuits. CONCLUSIONS: Using a multidisciplinary approach a cognitive model has been established in which the corpus striatum is considered to be the basic structure for selection of information which will generate the appropriate response, both motor and behavioral, for the context involved. Loss of this capacity leads to mental rigidity and perseveration in conduct, which are typical of the cognitive disorders of HD.

Deterioro cognitivo en la enfermedad de Huntington / Cognitive deterioration in Huntington's disease

Objetivos. Revisar, resumir y actualizar el patrón de deterioro cognitivo presente en la enfermedad de Huntington (EH).Desarrollo. La EH representa un paradigma de la demencia frontoestriatal cuyo deterioro cognitivo afecta a tres grandes dominios: la memoria, la función ejecutiva y las funciones visuoespaciales. El déficit de la memoria explícita episódica afecta principalmente a los procesos de recuperación de la información, en cambio la memoria implícita se halla deteriorada en el aprendizaje procedimental pero no en el priming. La disfunción ejecutiva constituye un rasgo esencial que afecta a la memoria de trabajo, la atención, la secuenciación y la planificación. Las funciones visuoespaciales complejas se alteran de manera importante y pueden afectar al reconocimiento visual de figuras complejas y de los gestos faciales. Algunos de estos cambios mentales referidos pueden ser objetivados ya desde estadios preclínicos. Actualmente, dada la posibilidad de establecer un diagnóstico genético de certeza y el conocimiento neuropatológico de la EH, se considera a esta patología un excelente modelo clínico para el estudio de la funciones cognitivas desempeñadas por los circuitos corticoestriatales. Conclusiones. Desde un enfoque multidisciplinario se ha establecido un modelo cognitivo en el que el estriado se considera como una estructura fundamental en la selección de la información que generará la respuesta apropiada, tanto motora como conductual, para el contexto en la que se halla inserta. La pérdida de esta capacidad origina la inflexibilidad mental y la perseveración en la conducta, rasgos típicos del trastorno cognitivo que caracterizan a la EH (AU)