Unilateral pure thalamic asterixis: clinical, electromyographic, and topographic patterns

Bilateral asterixis in a patient with bilateral anterior cerebral artery infarction

A 83-year-old woman complained of muscular weakness in the left leg and trembling in all extremities. She was apathetic and had left leg paresis and asterixis in all extremities. Magnetic resonance imaging revealed acute cerebral infarctions in the bilateral frontal lobes perfused by the anterior cerebral artery (ACA). Anticoagulant treatments improved ischemia-induced damage of the frontal lobes, and then her neurological symptoms including asterixis gradually disappeared. A unique point of this case is that acute stroke in the bilateral ACA territory induced bilateral asterixis resembling metabolic encephalopathy. Occurrence of the bilateral ACA territory infarction is extremely rare, but it should be considered in patients presenting with bilateral asterixis.

Post-Thalamic Stroke Movement Disorders: A Systematic Review

BACKGROUND

After a stroke, movement disorders are rare manifestations mainly affecting the deep structures of the brain like the basal ganglia (44%) and thalamus (37%), although there have been case studies of movement disorders in strokes affecting the cerebral cortex also.

SUMMARY

This review aims to delineate the various movement disorders seen in association with thalamic strokes and tries to identify the location of the nuclei affected in each of the described movement disorders. Cases were identified through a search of PubMed database using different search terms related to post-thalamic stroke movement disorders and a secondary search of references of identified articles. We reviewed 2,520 research articles and only 86 papers met the inclusion criteria. Cases were included if they met criteria for post-thalamic stroke movement disorders. Case-cohort studies were also reviewed and will be discussed further. Key Messages: The most common post-stroke abnormal movement disorder reported in our review was dystonia followed by hemiataxia. There was a higher association between ischaemic stroke and movement disorder. Acute onset movement disorders were more common than delayed. The posterolateral thalamus was most commonly involved in post-thalamic stroke movement disorders.

Milestones in myoclonus

This review examines some of the advances in understanding myoclonus over the last 25 years. The classification of myoclonus into cortical, brainstem, and spinal forms has been consolidated, each with distinctive clinical characteristics and physiological mechanisms. New genetic causes of myoclonus have been identified, and the molecular basis of several of these conditions has been discovered. It is increasingly apparent that disease of the cerebellum is particularly important in the genesis of cortical reflex myoclonus. However, the precise mechanism and origin of myoclonus in many situations remain uncertain. Effective treatment of myoclonus remains limited, and the challenge lies ahead to develop more therapeutic options.

Cortical activities associated with voluntary movements and involuntary movements

Recent advance in non-invasive techniques including electrophysiology and functional neuroimaging has enabled investigation of control mechanism of voluntary movements and pathophysiology of involuntary movements in human. Epicortical recording with subdural electrodes in epilepsy patients complemented the findings obtained by the non-invasive techniques. Before self-initiated simple movement, activation occurs first in the pre-supplementary motor area (pre-SMA) and SMA proper bilaterally with some somatotopic organisation, and the lateral premotor area (PMA) and primary motor cortex (M1) mainly contralateral to the movement with precise somatotopic organisation. Functional connectivity among cortical areas has been disclosed by cortico-cortical coherence, cortico-cortical evoked potential, and functional MRI. Cortical activities associated with involuntary movements have been studied by jerk-locked back averaging and cortico-muscular coherence. Application of transcranial magnetic stimulation helped clarifying the state of excitability and inhibition in M1. The sensorimotor cortex (S1-M1) was shown to play an important role in generation of cortical myoclonus, essential tremor, Parkinson tremor and focal dystonia. Cortical myoclonus is actively driven by S1-M1 while essential tremor and Parkinson tremor are mediated by S1-M1. 'Negative motor areas' at PMA and pre-SMA and 'inhibitory motor areas' at peri-rolandic cortex might be involved in the control of voluntary movement and generation of negative involuntary movements, respectively.

Myoclonic disorders: a practical approach for diagnosis and treatment

Myoclonus is a sudden, brief, involuntary muscle jerk. It is caused by abrupt muscle contraction, in the case of positive myoclonus, or by sudden cessation of ongoing muscular activity, in the case of negative myoclonus (NM). Myoclonus may be classified in a number of ways, although classification based on the underlying physiology is the most useful from the therapeutic viewpoint. Given the large number of possible causes of myoclonus, it is essential to take a good history, to clinically characterize myoclonus and to look for additional findings on examination in order to limit the list of possible investigations. With regards to the history, the age of onset, the character of myoclonus, precipitating or alleviating factors, family history and associated symptoms and signs are important. On examination, it is important to see whether the myoclonus appears at rest, on keeping posture or during action, to note the distribution of jerks and to look for the stimulus sensitivity. Electrophysiological tests are very helpful in determining whether myoclonus is cortical, subcortical or spinal. A single pharmacological agent rarely control myoclonus and therefore polytherapy with a combination of drugs, often in large dosages, is usually needed. Generally, antiepileptic drugs such as valproate, levetiracetam and piracetam are effective in cortical myoclonus, but less effective in other forms of myoclonus. Clonazepam may be helpful with all types of myoclonus. Focal and segmental myoclonus, irrespective of its origin, may be treated with botulinum toxin injections, with variable success.

Symptomatic myoclonus

A huge number of neurological disorders are associated with myoclonus. This paper describes these disorders whose diagnosis partly relies on the presence of myoclonus. The diagnostic approach is related to certain clinical features of myoclonus, which, after their integration in the clinical context, help orientate towards diagnosis. Myoclonus is frequent during dementia. Although its presence is well-known to take part in the diagnosis of Creutzfeldt-Jakob disease (CJD), myoclonus can also be present to a significant degree in Alzheimer's disease and Lewy body dementia (LBD), which raises a diagnostic issue. Both its clinical and electrophysiological features may help differential diagnosis, given that myoclonus with fast-evolving dementia and focal neurological signs should favor the diagnosis of CJD. Myoclonus in a context of progressive ataxia suggests one clinical form of the Ramsay-Hunt syndrome (progressive myoclonic ataxia, PMA), whose most frequent causes are: coeliac disease, mitochondriopathies, some spino-cerebellar degenerations, and some late metabolic disorders. In addition to ataxia and myoclonus, the presence of opsoclonus directs diagnosis toward the opsoclonus-myoclonus syndrome (OMS), whose origin, in adult, is idiopathic or paraneoplastic. Palatal tremor (myoclonus) with ataxia may represent either a sporadic pattern, which often reflects the evolution of degenerative or lesional disorders, or a familial pattern in some degenerative affections or metabolic diseases. Of more recent knowledge is the association of progressive ataxia, myoclonus, and renal failure, which corresponds to a recessive autosomic disease. In a context of encephalopathy, myoclonus is frequent in metabolic or hydro-electrolytic disorders, and in brain anoxia. One should distinguish these various forms of myoclonus which may occur in the acute post-anoxic phase, from those occurring as sequels at a later stage, i.e. the Lance and Adams syndrome whose clinical aspects are also multiple. Myoclonus is less frequent during toxic or drug exposures. Irrespective of its acute or insidious onset, Hashimoto's encephalopathy is accompanied by myoclonus and tremor. Myoclonus may also be present during encephalic and/or spinal infectious disorders. Myoclonus with focal neurological signs may be observed in thalamic lesions, responsible for unilateral asterixis or unilateral myoclonus superimposed on dystonic posture. Segmental spinal myoclonus or propriospinal myoclonus may be associated with several spinal-cord disorders. Myoclonus associated with peripheral nerve lesions is exceptional or even questionable for some of these.

Movement disorder emergencies

Movement disorders may present acutely, and failure to recognize and exclude important differential diagnoses can result in significant morbidity or mortality. Unfortunately, much of the literature pertaining to this topic is scattered and not easily accessible. This review aims to address this deficit. Movement disorder emergencies are discussed according to their most likely mode of presentation. Diagnostic considerations and early management principles are reviewed, along with appropriate pathophysiology where relevant.