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Background: The existence of transsynaptic retrograde degeneration (TRD) in the human visual system has been established, however the dependence of TRD on different factors such as lesion location, size and manner of lesion acquisition has yet to be quantified., Methods: We obtained T1-weighted structural and diffusion-weighted images for 26 patients with adult-acquired or congenital hemianopia and 12 age-matched controls. The optic tract (OT) was defined and measured in the structural and diffusion-weighted images, and degeneration assessed by comparing the integrity of tracts in the lesioned and in the undamaged hemisphere., Results: OT degeneration was found in all patients with established lesions, regardless of lesion location. In patients with acquired lesions, the larger the initial lesion, the greater is the resulting TRD. However, this was not the case for congenital patients, who generally showed greater degeneration than would be predicted by lesion size. A better predictor of TRD was the size of the visual field deficit, which was correlated with degeneration across all patients. Interestingly, although diffusion-weighted imaging (DWI) is more frequently used to examine white matter tracts, in this study the T1-weighted scans gave a better indication of the extent of tract degeneration., Conclusions: We conclude that TRD of the OT occurs in acquired and congenital hemianopia, is correlated with visual field loss, and is most severe in congenital cases. Understanding the pattern of TRD may help to predict effects of any visual rehabilitation training.

Objective: The effects of 4-aminopyridine (4-AP) on downbeat nystagmus (DBN) were analysed in terms of slow-phase velocity (SPV), stance, locomotion, visual acuity (VA), patient satisfaction and side effects using standardised questionnaires., Methods: Twenty-seven patients with DBN received 5 mg 4-AP four times a day or placebo for 3 days and 10 mg 4-AP four times a day or placebo for 4 days. Recordings were done before the first, 60 min after the first and 60 min after the last drug administration., Results: SPV decreased from 2.42 deg/s at baseline to 1.38 deg/s with 5 mg 4-AP and to 2.03 deg/s with 10 mg 4-AP (p<0.05; post hoc: 5 mg 4-AP: p=0.04). The rate of responders was 57%. Increasing age correlated with a 4-AP-related decrease in SPV (p<0.05). Patients improved in the 'get-up-and-go test' with 4-AP (p<0.001; post hoc: 5 mg: p=0.025; 10 mg: p<0.001). Tandem-walk time (both p<0.01) and tandem-walk error (4-AP: p=0.054; placebo: p=0.059) improved under 4-AP and placebo. Posturography showed that some patients improved with the 5 mg 4-AP dose, particularly older patients. Near VA increased from 0.59 at baseline to 0.66 with 5 mg 4-AP (p<0.05). Patients with idiopathic DBN had the greatest benefit from 4-AP. There were no differences between 4-AP and placebo regarding patient satisfaction and side effects., Conclusions: 4-AP reduced SPV of DBN, improved near VA and some locomotor parameters. 4-AP is a useful medication for DBN syndrome, older patients in particular benefit from the effects of 5 mg 4-AP on nystagmus and postural stability.

Objectives: We describe a novel rehabilitation tool for patients with homonymous hemianopia based on a visual search (VS) paradigm that is portable, inexpensive, and easy to deploy. We hypothesised that by training patients to improve the efficiency of eye movements made in their blind field their disability would be alleviated., Methods: Twenty nine patients with homonymous visual field defects (HVFD) without neglect practised VS paradigms in 20 daily sessions over one month. Search fields comprising randomly positioned target and distracter elements, differing by a single feature, were displayed for three seconds on a dedicated television monitor in the patients' homes. Improvements were assessed by examining response time (RT), error rates in VS, perimetric visual fields (VFs) and visual search fields (VSFs), before and after treatment. Functional improvements were measured using objective visual tasks which represented activities of daily living (ADL) and a subjective questionnaire., Results: As a group the patients had significantly shorter mean RT in VS after training (p<0.001) and demonstrated a variety of mechanisms to account for this. Improvements were confined to the training period and maintained at follow up. Three patients had significantly longer RT after training. They had high initial error rates which improved with training. Patients performed ADL tasks significantly faster after training and reported significant subjective improvements. There was no concomitant enlargement of the VF, but there was a small but significant enlargement of the VSF., Conclusion: Patients can improve VS with practice. This usually involves shorter RTs, but occasionally a longer RT in a complex speed-accuracy trade-off. These changes translate to improved overall visual function, assessed objectively and subjectively, suggesting that they represent robust training effects. The underlying mechanism may involve the adoption of compensatory eye movement strategies.

Objectives: This study examined the scanpaths of patients with homonymous hemianopia while viewing naturalistic pictures in their original and also spatially filtered forms. Features of their scanpaths with respect to various saccade and fixation parameters were examined to determine whether they develop compensatory eye movement strategies. The effects of various lesion parameters including location, size, and age on the evolution of such strategies were considered., Methods: Eye movements of eight patients with homonymous hemianopia (four left, four right), but lacking neglect, were recorded while they viewed 22 images of real scenes, and they were compared with the eye movements of eight age matched controls. Subjects viewed each image for 3 seconds, initially in a spatially filtered form in which much of the semantic content had been removed, and then in their unfiltered, original form., Results: Patients differed significantly from controls in various fixation and saccade parameters. For fixation parameters patients with hemianopia fixated different spatial positions from controls, made more fixations which were more widely distributed and of shorter duration than controls, and spent a greater proportion of their total fixation time in the area corresponding to their blind hemifield. They did not make significantly more refixations than controls. For saccade parameters patients made more saccades into their blind hemifield, these saccades having shorter latencies and shorter amplitudes than those made into their seeing field, and had longer scanpaths than control subjects. The amplitude of their first saccade was longer than that of controls although its direction did not correlate simply with the side of the field defect. Their mean saccade amplitude was similar to that of controls. Filtering out high spatial frequencies within images seemed to accentuate the described differences between eye movement characteristics of hemianopes and controls. Scanpath differences correlated with increasing age but not location or size of lesions causing the hemianopia., Conclusion: Various features of scanpaths produced by hemianopes were different from normal subjects. These differences correlated with lesion age and may reflect the evolution of a compensatory eye movement strategy.

Two pairwise matched groups of patients with mild to moderate Parkinson's disease and a group of normal age matched controls were used to investigate the effects on simple and choice reaction time (RT) of brief withdrawal of levodopa therapy. Comparisons within and across these groups disclosed a selective effect of levodopa withdrawal. After about 12 hours of levodopa deprivation, patients exhibited an exaggeration of normal refractoriness, the well established tendency for RT to increase progressively as the delay between a response and the next imperative signal is reduced below 0.5 s. Increased refractoriness was at least as great for simple as choice RT. Choice RT on trials involving repetition (as opposed to alternation) of the previous response, however, showed no tendency towards greater impairment by brevity of the recovery period or by withdrawal of medication, eliminating an effector based account. With longer recovery periods, RT was unaffected by medication; indeed, unmedicated patients were as fast as normal subjects under these conditions. Even at the briefest delays, fully medicated patients did not differ from normal controls. The paper concludes with a critical review of chronometric studies of medication effects in Parkinson's disease.

This paper examines spatial and temporal processing in migraineurs (diagnosed according to International Headache Society criteria, 1988), using psychophysical tests that measure spatial and temporal responses. These tests are considered to specifically assess precortical mechanisms. Results suggest precortical dysfunction for processing of spatial and temporal visual stimuli in 11 migraineurs with visual aura and 13 migraineurs without aura; the two groups could not be distinguished. As precortical dysfunction seems to be common to both groups of patients, it is suggested that symptoms that are experienced by both groups, such as blurring of vision and photophobia, may have their basis at a precortical level.

Postural control was assessed on a tilting platform system in 20 patients with idiopathic Parkinson's disease and 20 age-matched controls. The amount of information provided by vision and lower limb proprioception was varied during the experiment to investigate the influence of changes in sensory cues on postural control. The patient group with clinical evidence of impaired postural control (Hoehn and Yahr III) had significantly higher sway scores over all sensory conditions than either the Hoehn and Yahr II group or controls. The pattern of sway scores indicated that no obvious deficit in the quality, or processing, of sensory information was responsible for the postural instability observed in this group. The patients in both Hoehn and Yahr groups were also able to respond appropriately to potentially destabilising sensory conflict situations and significantly improved their sway scores when provided with visual feedback of body sway. The results indicate that in Parkinson's disease, the main site of dysfunction in postural control is likely to be at a central motor level.

Study 1 examined the reliability of the ratings assigned to the performance of five sign-and-symptom items drawn from tests of motor impairment in Parkinson's disease. Patients with Parkinson's disease of varying severity performed gait, rising from chair, and hand function items. Video recordings of these performances were rated by a large sample of experienced and inexperienced neurologists and by psychology undergraduates, using a four point scale. Inter-rater reliability was moderately high, being higher for gait than hand function items. Clinical experience proved to have no systematic effect on ratings or their reliability. The idiosyncrasy of particular performances was a major source of unreliable ratings. Study 2 examined the intercorrelation of several standard rating scales, comprised of sign-and-symptom items as well as activities of daily living. The correlation between scales was high, ranging from 0.70 to 0.83, despite considerable differences in item composition. Inter-item correlations showed that the internal cohesion of the tests was high, especially for the self-care scale. Regression analysis showed that the relationship between the scales could be efficiently captured by a small selection of test items, allowing the construction of a much briefer test.

Antisaccades were studied in ten patients with mild to moderate Parkinson's disease and ten age-matched normal controls. Remembered saccades and reflex saccades were assessed for comparison. In the population of patients who showed the previously reported abnormalities of remembered saccades, antisaccades were indistinguishable from those of controls in latency, gain and peak velocity. This finding implies that antisaccades are mediated through pathways which are unaffected by Parkinson's disease, and which are therefore presumably distinct from pathways mediating other voluntary saccades.

Four patients with Friedreich's ataxia took part in an open trial, in which they consumed 50-100g/day lecithin granules (containing approximately 22% phosphatidycholine) for 16 weeks, but no improvement resulted. Several unwanted effects including diarrhoea, nausea, depression, "hot flushes" and weakness were experienced. Resting levels of free-choline in plasma were within the range found in 19 normal subjects. Sixteen other patients with Friedreich's ataxia also had normal free-choline levels. Treatment with lecithin significantly increased plasma free-choline levels, but there was a trend for these to fall towards baseline levels, despite continued ingestion of lecithin.

Twelve consecutive patients with Guillain-Barré syndrome were treated with plasma exchange. Examination two weeks after treatment was commenced showed that three had not improved. Five showed only a minimal improvement, which was considered to be compatible with the natural history of the disease. The remaining four patients showed a more substantial improvement which could have been related to the plasma exchange.

A quantitative analysis of unpredictable saccadic and smooth pursuit ocular motor and manual tracking was performed in 15 mildly affected, previously untreated subjects suffering from Parkinson's disease and in age-matched normal controls. The patients' ocular saccades were characterised by an increased variability of their latencies and reduced accuracy, with normal velocity profiles apart from saccadic duration. Their smooth pursuit had a decreased velocity gain. Similar abnormalities were found with manual tracking. Clinical improvement with dopaminergic drugs was associated with an improvement of saccadic accuracy and smooth pursuit gain. It is postulated that the ocular motor changes seen in Parkinson's disease are contingent upon functional dopamine levels in the basal ganglia.

In a coincidence timing task, Parkinsonian patients and a control group were instructed to synchronize a keypress with the onset of a visual signal which had been preceded by a regular train of warning signals. Although the Parkinsonian group had previously exhibited slower reactions in a conventional simple reaction-time task, they were able to generate predictive responses that fell as close to the target onset as the controls' but showed greater variability. In a second experiment, Parkinsonian patients and controls made saccadic eye movements to a visual target that stepped at regular intervals between two fixed locations. After a few trials all the subjects tended to make predictive saccades that were initiated before the target excursion. However, the Parkinsonian group were slower to develop this strategy and when they did their saccades became considerably more hypometric than those of the controls. Both groups were able to maintain predictive responding even when the visual target disappeared and responses were paced by a buzzer. We concluded that Parkinsonian patients are capable of initiating predictive responses of the eye and the hand, at least in some circumstances, but such responses tend to be inaccurate in execution. This, in turn, may dispose the Parkinsonian patient against predictive movement.

Sleep and respiration during sleep were studied in patients with idiopathic Parkinson's disease, patients with Parkinsonism with autonomic disturbance, and normal age and sex matched controls. Patients with idiopathic Parkinson's disease showed significantly reduced REM sleep, and more frequent and prolonged waking throughout the night. Hypoventilation and sleep apnoea did not occur in the idiopathic Parkinson's disease or normal groups, but respiration was disorganised with frequent central and obstructive apnoeas in the autonomic disturbance group. Respiratory rate during non rapid eye movement sleep was similar in the idiopathic Parkinson's disease and normal groups, but patients with idiopathic Parkinson's disease showed tachypnoea awake and during REM sleep.

A case of brainstem infection by Listeria monocytogenes is described. The patient was a 63 year old man previously in good health and his illness did not follow the usual bi-phasic pattern. There was no prodromal phase, and the progressive brainstem signs with a lymphocytosis and a normal sugar level in the CSF led to a tentative diagnosis of viral brainstem encephalitis. Ampicillin was begun only when signs of pulmonary infection developed. Clinical diagnosis is difficult but ampicillin should probably be used in any doubtful case in which a "viral" brainstem encephalitis is being considered.