Thyroid gland neurofibroma in a NF1 patient

Neurofibromas are a hallmark of neurofibromatosis type 1 (NF1). They are usually benign and rarely present in the thyroid gland region. There is a suspected association between NF1 and intramedullary thyroid carcinoma and there is a well-known association between NF1 and pheochromocytoma. Here, we present a 55-year-old man with typical symptoms of NF1, whose course was complicated by a neurofibroma of the thyroid gland. His clinical spectrum of symptoms included bilateral cataract established before the age of 35 years, quadriparesis and an intrathoracic mass. The patient died because of abdominal carcinomatosis of unknown origin. The rarity of thyroid gland neurofibroma is discussed here, emphasizing the importance of early detection of these and other NF1 complications, also including the risk of malignant transformation with lethal outcome.

Frontal lobe dysfunction in amyotrophic lateral sclerosis

The aim of the present study was to investigate the involvement of frontal lobe dysfunction in amyotrophic lateral sclerosis (ALS) using ocular motor paradigms and neuropsychological testing. Fifty-one patients with ALS participated in the following ocular motor tasks: (1) a three-choice task and (2) a remembered saccade task. The patients underwent a clinical and neuropsychological evaluation. One-third of ALS patients presented with signs of frontal dysfunction, as determined by their high distractibility factors (DF) in the three-choice task and their performances in both the Wisconsin and Stroop tests. ALS patients exhibited longer latencies to eye movement than controls in the performance of the remembered saccade task, specifically in performance of both remembered and delayed saccades, but saccade accuracy was not impaired. Finally, performance indices of the ocular motor tasks, in particular the DF, was correlated only with the degree of dysarthria.

Frontal-parietal activation differences observed before the execution of remembered saccades: an event-related potentials study

Healthy subjects performed saccadic eye movements in one memory (MEM) and two delay tasks (delay, DEL and modified delay, M-DEL) while we recorded scalp event-related potentials (ERPs) from 25 electrode sites. In the MEM task the subjects were instructed to retain in memory the location of a visual target for a delay of 1-6 s and then perform a remembered saccade at the go signal. In the DEL task the target remained on until movement completion and in the M-DEL task the target, that was visible during the delay period, disappeared synchronously with the go signal. A reduction in response latency and an increase in the percentage of dysmetric movements were observed for the MEM task compared to the two delay tasks. An increased ERP activity at the central-frontal electrode sites compared to the parietal sites was significant only for the MEM task early on during the delay period (500-1000 ms). During the period preceding the onset of the saccade, a parietal increase of activity was observed for all tasks. Furthermore the activity was smaller for the frontal compared to the parietal areas only for the memory task thus indicating a near reversal of the previous pattern of activity observed during the early delay period. This specific activation pattern of frontal and parietal areas, observed for the MEM task only, requires further investigation focusing on the temporal pattern of activation of large brain areas involved in working memory processing.

Systematic errors of planar arm movements provide evidence for space categorization effects and interaction of multiple frames of reference

Healthy humans performed arm movements in a horizontal plane, from an initial position toward remembered targets, while the movement and the targets were projected on a vertical computer monitor. We analyzed the mean error of movement endpoints and we observed two distinct systematic error patterns. The first pattern resulted in the clustering of movement endpoints toward the diagonals of the four quadrants of an imaginary circular area encompassing all target locations (oblique effect). The second pattern resulted in a tendency of movement endpoints to be closer to the body or equivalently lower than the actual target positions on the computer monitor (y-effect). Both these patterns of systematic error increased in magnitude when a time delay was imposed between target presentation and initiation of movement. In addition, the presence of a stable visual cue in the vicinity of some targets imposed a novel pattern of systematic errors, including minimal errors near the cue and a tendency for other movement endpoints within the cue quadrant to err away from the cue location. A pattern of systematic errors similar to the oblique effect has already been reported in the literature and is attributed to the subject's conceptual categorization of space. Given the properties of the errors in the present work, we discuss the possibility that such conceptual effects could be reflected in a broad variety of visuomotor tasks. Our results also provide insight into the problem of reference frames used in the execution of these aiming movements. Thus, the oblique effect could reflect a hand-centered reference frame while the y-effect could reflect a body or eye-centered reference frame. The presence of the stable visual cue may impose an additional cue-centered (allocentric) reference frame.

A systematic directional error in 2-D arm movements increases with increasing delay between visual target presentation and movement execution

Forty-seven normal subjects performed two-dimensional arm movements on a digitizer board using a mouse device. The movements were projected on a computer monitor. Subjects were instructed to move the mouse using the whole arm from a center position to a peripheral target so that the projected movement would pass over the target without stopping on the target. A large number of targets (360) were used to cover the entire directional continuum. The direction of the arm movement was the parameter of interest, which was measured at an initial position, at one third of the distance towards the target, and at the vicinity of the target. Four conditions of delay between target presentation and movement execution were used (0, 2, 4, 6 s). A systematic directional error was observed at the initial portion of the trajectory. This error resulted from a clustering of movement directions on an axis that was perpendicular to the axis of the resting forearm before movement onset. This pattern of errors can be explained by the initial inertial anisotropy of the arm. As the trajectory evolved, a different directional error emerged, resulting from a clustering of movement directions in two orthogonal axes. This pattern of directional error increased in amplitude as the delay increased, in contrast to the error at the initial portion of the trajectory which remained invariant with increasing delay. Finally, the information transmitted by the movement direction was shown to increase with the evolution of the trajectory. The increase in delay resulted in a decrease in directional-information transmission. It is proposed that the directional bias towards the end of the movement trajectory might reflect the action of "movement primitives", that is patterns of muscle activation resulting from spinal interneuronal activation. It is further proposed that the directional bias observed at the vicinity of the target might reflect a loss of cortical directional information with increasing delay between target presentation and movement onset.

Changes of presaccadic cortical activity when performing horizontal, visually guided saccades

When a visually guided saccade task is running, the presaccadic potential obtained in the initial period of the task differs from those obtained later, while the subject's oculomotor performance remains unaffected. These time-related changes of cortical activity consist both of an overall decreasing electrical activity as well as a selective one over certain cortical areas. The generalised reduced activity already described in earlier studies is considered as an unspecified effect such as fatigue or decreased motivation. On the contrary, the pronounced selective changes of cortical activity obtained over cortical areas such as the centro-parietal and frontal cortices, should be related with more specific, that is, visuomotor function. We assume that at the beginning of the task of the performance of the saccade needs the activation of several cortical areas but later on the same oculomotor plan runs sufficiently under subcortical control.