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Biomedical subjects

A E Lang

Publications and source records attributed to A E Lang.

At least 19 recordsLinked to original sources
PubMed1992

Stimulus-sensitive myoclonus in akinetic-rigid syndromes.

The cutaneous reflexes of upper limb muscles were studied in five patients with Parkinson's disease and 10 patients with stimulus-sensitive myoclonus associated with akinetic-rigid syndromes. The middle finger was stimulated with ring electrodes and rectified electromyographs were averaged from seven upper limb muscles and orbicularis oculi. Responses from subjects with Parkinson's disease without stimulus-sensitive myoclonus were similar to those of normal subjects. The responses from patients with stimulus-sensitive myoclonus associated with Parkinson's disease or multiple system atrophy had the normal pattern except that a long latency facilitation, which is present in normal subjects and known as E2, was greatly exaggerated. Patients with stimulus-sensitive myoclonus associated with cortical-basal ganglionic degeneration had a completely different pattern of responses. There was synchronous activation of all recorded upper limb muscles with latencies substantially shorter than those of the long latency facilitation (E2) in normal subjects. Cutaneous reflex testing may therefore be useful in the differentiation of akinetic-rigid syndromes.

Aged↗
PubMed1992

Tizanidine in cranial dystonia.

Recent electrophysiological studies in patients with cranial dystonia (CD) have demonstrated evidence for hyperactivity of brainstem interneurons. Tizanidine (Tz), a centrally acting skeletal muscle relaxant, is thought to act by antagonizing the activity of excitatory interneurons which mediate hypertonic processes (e.g. spasticity). Theoretically this agent may be effective in patients with CD. Ten patients were enrolled in an open-label study with a single-blind placebo wash-in. Eight patients tolerated doses of between 28-36 mg per day. For the most part tizanidine was ineffective for the symptoms of CD. This failure suggests that the reported brainstem interneuronal disturbances may not be altered by Tz. Further studies using concomitant electrophysiological assessment would be necessary to assess this possibility. Alternatively, these disturbances may not be a principle cause of the dystonic movements. The finding of similar changes in other basal ganglia diseases lacking CD (e.g. Parkinson's disease) favours this latter explanation.

Brain Stem↗
PubMed1992

Can the Lombard effect be used to improve low voice intensity in Parkinson's disease?

Low voice intensity is a common problem in Parkinson's disease. It is typically resistant to drug therapy and often persists despite extensive behavioural speech and language therapy. Based on previous findings that masking noise will produce a consistent increase in voice intensity in most normal individuals, the effects of white masking noise, presented at a sound pressure level of 90 dB, was examined in 10 parkinsonian patients with low voice intensity. Results indicated that all Parkinson's disease patients showed a marked increase in their voice intensity. Given this finding, it is proposed that masking noise may be an effective treatment for reduced voice intensity in parkinsonian speakers, particularly with the future adaptation of portable voice-activated maskers, such as the Edinburgh Masker.

Aged↗
PubMed1992

Stiff-person syndrome.

The stiff-person syndrome is a disorder of persistent, painful muscle contractions predominately affecting the axial musculature. We describe a patient with this disorder and review its pathophysiology. Molecular biologic and immunologic techniques have recently added to the understanding of the mechanism of this disorder. Association with diseases such as diabetes, vitiligo and hypothyroidism have strengthened the auto-immune nature of this syndrome. Auto-antibodies against glutamic acid decarboxylase (GAD), an intraneuronal enzyme, have been implicated in the etiology of this unique disease. Therapeutic intervention with agents such as benzodiazepines that modify central GABAergic activity have demonstrated significant benefit in patients with stiff-person syndrome.

Female↗
PubMed1991

National conference on Parkinson's disease.

A National Conference on Parkinson's disease was held on September 7th-8th, 1990 in Victoria, British Columbia. The scientific program included 11 formal presentations, 10 small group workshops and video presentations of interesting examples of movement disorders. The subjects discussed ranged from epidemiology and etiology to current and possible future modes of management of Parkinson's disease.

Humans↗
PubMed1991

Cognitive processes in idiopathic dystonia treated with high-dose anticholinergic therapy: implications for treatment strategies.

Studies utilizing single doses of scopolamine have suggested a role for the cholinergic system in memory. Results are consistent in identifying a selective effect on the early encoding stage of information processing. In terms of long-term administration of anticholinergics, patients with Parkinson's disease often display memory deficits. However, underlying pathology within the forebrain cholinergic system complicates the study of treatment effects in this disorder. We therefore assessed multiple memory routines in 20 cognitively intact patients with dystonia where no such pathology has been identified. Patients were tested before and after 2-4 months of 15-74 mg of trihexyphenidyl daily. Twelve tolerated this regime. Compared to control subjects, matched for age and I.Q., only tests with a single presentation of the material to be remembered were affected at follow-up. The speed of information processing was also significantly reduced. Age was strongly related to memory performance in the patient group alone and interacted with dose and duration of treatment. Results suggest that drug-induced slowing of mentation was responsible for impaired encoding, particularly in older patients. These findings affect treatment strategies, especially now that injections of botulinum toxin have proved to be highly effective for certain forms of focal dystonia.

Adult↗
PubMed1990

Parkinsonism in alcohol withdrawal: a follow-up study.

Transient parkinsonism associated with alcohol intake and withdrawal has previously been described. We followed-up three patients with acute alcohol withdrawal-induced parkinsonism 9-11 years after their initial presentation. None showed any evidence of parkinsonism at follow-up. This suggests that withdrawal-induced parkinsonism is caused by a completely reversible abnormality in nigrostriatal dopamine transmission, which is unaccompanied by underlying nigral degeneration, as we had previously hypothesized.

Acute Disease↗
PubMed1990

Hypoxic-ischemic damage of the basal ganglia. Case reports and a review of the literature.

Three cases of movement disorders secondary to hypoxic-ischemic encephalopathy are reported. Despite similarities among the clinical events, the neurological syndromes produced were dissimilar. Cerebral hypoxia-ischemia typically produces lesions of the globus pallidus that may result in an akinetic rigid syndrome. Due to its unique blood supply, vascular insufficiency is found to be a major factor. Lesions in the putamen also occur, and these tend to be associated with dystonia. Recent evidence supports a specific neuronal sensitivity in the striatum, possibly due to afferent excitatory amino acid connections. These two components and changes in the levels of neurotransmitters during hypoxia-ischemia may interact to produce varied clinical outcomes. These factors must also be considered when planning therapeutic interventions.

Adult↗
PubMed1990

Memory and learning in early Parkinson's disease: evidence for a "frontal lobe syndrome".

Fifteen untreated patients in the earliest stages of Parkinson's disease were compared to fifteen age- and intellectually matched control subjects on a number of memory tasks assessing short- and long-term recall of both meaningful and unrelated material, semantic relations in the organization of memory, priming, and source forgetting, and the ability to form new stimulus-response associations under conditions of maximal task interference. While patients demonstrated considerable evidence of preserved function, impaired performance on a subgroup of tasks was consistent with selective frontostriatal system involvement. These findings are discussed with reference to the underlying pathological processes in Parkinson's disease.

Corpus Striatum↗
PubMed1990

Clinical differences between metoclopramide- and antipsychotic-induced tardive dyskinesias.

A patient with tardive dyskinesia dominated by pelvic thrusting movements is described. A retrospective review of the clinical features documented in patients with metoclopramide- and antipsychotic-induced tardive dyskinesias seen over a six year period demonstrated that the occurrence of pronounced pelvic thrusting and respiratory dyskinesias were significantly more common in the metoclopramide treated group. The occurrence of bucco-linguomasticatory movements, limb stereotypies or chorea, and mild truncal or abdominal rocking were not significantly different between the two groups. None of the tardive dystonia patients had metoclopramide as the causative agent. These findings will require confirmation in larger, better matched patient populations. Whether the differences relate to different pharmacologic profiles of drug action, patient populations exposed, or other factors, remains to be elucidated.

Aged↗