The contribution of tremor studies to diagnosis of parkinsonian and essential tremor: a statistical evaluation.

This study statistically evaluated a set of commonly measured tremor parameters to determine their individual and combined ability to discriminate between essential tremor (ET) and Parkinsonian tremor (PT). Accelerometer and surface electromyographic (EMG) records of moderate to severe upper limb tremor in 20 patients with ET and 22 patients with PT were used to quantitatively compare tremor amplitude, frequency and pattern of muscle bursting in two resting and three non resting postures. The group statistics showed significant differences between ET and PT with respect to tremor frequency in all five postures, tremor amplitude at rest and muscle bursting patterns. Discriminant function analysis showed that no single parameter or combination of parameters was able to correctly classify all patients. Frequency was much more discriminating than amplitude or muscle bursting patterns in all limb postures. The best amplitude discrimination was obtained when the hand and forearm were both fully supported. Muscle bursting patterns were poorly discriminating and did not assist in correct classification of single patients. Group statistics confirmed a highly significant biological difference between the two tremor types. Optimal classification of single PT (86% correct) and ET (95% correct) patients was obtained using frequency and two selected amplitude parameters from the resting limb. Limb posture was an important variable in optimising the discriminative ability of tremor studies. The implications for routine tremor studies are summarised.

A video review of the diagnosis of psychogenic gait: appendix and commentary.

The gait and other clinical features of 22 patients presenting to our hospital over the last 10 years are shown on video. In 12 patients, a diagnosis of psychogenic gait was made; in the remainder, the gait abnormality was the result of a neurologic disease. Psychogenic gaits are compared and contrasted with "organic" gaits. In one patient, the psychogenic gait occurred in the setting of a neurologic disease. The "traditional" approach to psychogenic gait, attempting to exclude underlying neurologic and psychiatric disease and seeking evidence for primary and secondary gain, was found to be of limited value. More useful were the features of the gait itself, in particular, exaggerated effort, extreme slowness, variability throughout the day, unusual or uneconomic postures, collapses, convulsive tremors, and distractibility; certain aspects of the history were also helpful. A list of comments is provided. The diagnosis of psychogenic gait, particularly in the elderly, remains fraught with hazard, and a balance has to be sought between subjecting an anxious patient to needless investigations and yet not losing sight of the fact that the patient may be elaborating on symptoms of genuine disease. The bizarre gait of some neurologic disorders, particularly dystonia and chorea, may be a pitfall for the unwary.

X-linked Dystonia-Deafness syndrome.

We report a family with early-onset deafness and progressive dystonia exclusively involving males over two successive generations. There is also evidence of cognitive impairment and corticospinal tract involvement. The pedigree suggests an X-linked inheritance. A similar family was originally described by Scribanu and Kennedy. Tranebjaerg et al. have recently reported two other families with linkage to Xq22 and also proposed a novel X-linked candidate gene. These findings support the existence of a distinct neurodegenerative syndrome principally characterized by early-onset deafness and progressive dystonia. Neuropathology of one case showed a mosaic pattern of neuronal loss and gliosis in the caudate and putamen suggesting that this pattern is not restricted to XDP or Lubag.

Treatment of upper limb dystonia with botulinum toxin.

The use of botulinum toxin A (BTX A) in upper limb dystonia is gaining increasing acceptance and it has recently been suggested that it be considered as first line treatment.(1) We have reviewed our experience since 1991 of treating 20 cases of upper limb dystonia. 14 patients had task-specific dystonias (6 simple writer's cramp, 5 dystonic writer's cramp, 3 musician's cramp) and 6 had secondary focal or segmental dystonias (4 with early cortico-basal degeneration). All patients had electromyography to both determine and guide muscle selection. Pre- and post-treatment video as well as questionnaires formed the basis for outcome assessment. Botulinum toxin therapy was clearly beneficial in about two-thirds of those with primary upper limb dystonia, a condition affecting young adults (mean onset 32.9 years). In contrast, BTX A was far less effective in secondary upper limb dystonias which occurred in the elderly (mean onset 71.7 years). Optimal treatment strategies are discussed. In conclusion, botulinum toxin is an effective form of treatment for primary upper limb dystonia; its role in late onset secondary dystonia is mainly palliative.

Optimal training parameters in the two-bar fixed-ratio drug discrimination task.

In a two-lever compartment, thirsty rats were trained to press one bar when drugged with phenobarbital and the other bar when undrugged using water as a reinforcer. Several different training procedures were employed in order to compare their effects on speed of acquisition and/or asymptotic accuracy of discrimination. Results were as follows: (1) Some shaping procedures allowed more rapid acquisition of discriminative control than others. The "traditional" shaping procedure was significantly less efficient than any others tested. (2) Several indices of degree of discriminability based on the speed of acquisition of discriminations were compared and evaluated. Some varied linearly with 1n dosage. (3) Variations in session duration from 5 to 60 minutes did not alter asymptotic accuracy. (4) Fixed ratio sizes ranging from FR-3 to FR-30 resulted in similar asymptotic accuracies. Overall, the results define alterations in the fixed-ratio training procedure that will make it somewhat easier to use. However, no procedures were found that fundamentally improved the properties of the paradigm.