The most common disorder in a patient presenting to a movement disorder clinic will be parkinsonism. The challenge is to provide the patient with the most accurate diagnosis and prognosis possible. The assumption at the time of initial presentation of the clinical diagnosis of Parkinson's disease is often wrong (20-25%). Waiting to see the pattern of progression, and response to medication provides invaluable additional information. This manuscript summarizes the clinical manifestations of Parkinson's disease and the main akinetic-rigid syndromes (progressive supranuclear palsy, multiple system atrophy, cortical-basal ganglionic degeneration, and dementia with Lewy bodies) that make up the differential diagnosis.

There is growing recognition that Parkinson's disease (PD) is likely to arise from the combined effects of genetic predisposition as well as largely unidentified environmental factors. The relative contribution of each varies from one individual to another. Even in situations where more than one family member is affected, the predominant influence may be environmental. Although responsible for only a small minority of cases of PD, recently identified genetic mutations have provided tremendous insights into the basis for neurodegeneration and have led to growing recognition of the importance of abnormal protein handling in Parkinson's as well as other neurodegenerative disorders. Abnormal protein handling may increase susceptibility to oxidative stress; conversely, numerous other factors, including oxidative stress and impaired mitochondrial function can lead to impaired protein degradation. A limited number of environmental factors are known to be toxic to the substantia nigra; in contrast, some factors such as caffeine intake and cigarette smoking may protect against the development of PD, although the mechanisms are not established. We review the various genetic and environmental factors thought to be involved in PD, as well as the mechanisms that contribute to selective nigral cell death.

Although levodopa-related motor response complications remain challenging from a pathophysiological and therapeutic standpoint, major advances have been made in the last decade, supporting the development of several promising drugs. Eventually, these drugs may help us to prevent, alleviate, or even “deprime” these frequent and disabling complications. Knowledge of the basic mechanisms and hypotheses underlying this fascinating conversion in the parkinsonian brain allows neurologists to understand the rationale behind emerging treatment strategies.

Parkinson's disease is a progressive neurodegenerative disorder that demands a holistic approach to treatment. Both pharmacologic and nonpharmacologic interventions play an important role in the comprehensive management of this disorder. While levodopa remains the single most effective medication for symptomatic treatment, dopamine agonists are playing an increasingly important role. Motor complications of dopaminergic therapy are a significant issue, particularly in patients with more advanced disease who have been on levodopa for several years. All therapeutic interventions must be tailored to the individual and modified as the disease progresses, with the goal of minimizing significant functional disability as much as possible.

Dystonia is a syndrome of sustained muscular contractions with numerous underlying etiologies. This review examines the varied phenomenology of dystonias, its evolving classification including recent genetic data as well as its clinical investigation and treatment. Although age of onset, anatomical distribution and family history are key elements of the investigation of dystonia, classification increasingly relies on etiologic and genetic criteria. Physiological abnormalities in striatocortical circuits are common in dystonia but the pathophysiology is still unclear. In recent years, a great deal has been learned on the more common primary dystonias such as primary torsion dystonia and on dystonia-plus syndromes such as dopamine responsive dystonia. Treatment of dystonia has also evolved and there are now a number of therapeutic agents with clear beneficial effects including anticholinergics, benzodiazepines, and botulinum toxin and there is growing interest in neurofunctional surgery including deep brain stimulation.

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder characterized by abnormalities of movement and dementia. No curative treatment is available and HD results in gradually increasing disability. Characterization of the genetic abnormality has dramatically increased our understanding of the underlying mechanisms of the disease process, and has resulted in the development of a number of genetic models. These research tools are forming the basis of advanced work into the diagnosis, pathophysiology, and potential treatment of the disease. Clinically, the availability of genetic testing has eased confirmation of diagnosis in symptomatic individuals. Presymptomatic testing allows at-risk individuals to make informed choices but requires supportive care from physicians. Current clinical treatment is focused on symptom control. Advances in research have resulted in the development of potential neuroprotective strategies which are undergoing clinical testing.

Myoclonus refers to brief muscle jerks caused by neuronal discharges. Etiologies are numerous, ranging from physiological jerks to myoclonus secondary to severe neurodegenerative conditions. The source of myoclonus may be in the cerebral cortex, the brain stem or the spinal cord and multiple generators may be involved in a single patient. The clinical approach to myoclonus relies on both etiological and physiological classifications. Pharmacological therapy is largely based on the presumed site of origin of myoclonus. Polytherapy may be required, particularly in severe cases of cortical myoclonus.

Tremor is a common movement disorder yet many physicians struggle with its terminology as well as with its treatment. Attempts have been made to develop standard terminology and criteria for tremors but this process continues to evolve. In this review, a summary of the currently-proposed phenomenology and syndromic classification of all types of tremor is presented. The diagnosis and management of essential tremor is presented in more detail, as it is the most commonly encountered tremor.

Tourette's syndrome (TS) is a childhood onset neurological disorder characterized by motor and vocal tics. It may be associated with a number of co-morbidities including attention deficit hyperactivity disorder, obsessive compulsive symptomatology, and behaviour disorders. Prevalence of TS is higher than previously thought, and may be present in up to 2% of the population. Tourette's syndrome has a significant genetic component. Inheritance may involve several mechanisms including autosomal dominant, bilinear, or polygenic mechanisms. Pathophysiology is still unknown, although is thought to involve striatocortical circuits. Treatment begins with modification of the work and home environment. For more severe cases, medications such as tetrabenazine and neuroleptics may be helpful. Treatment of co-morbidities needs to be considered, as these may result in more disability than the tics themselves.

Stereotactic neurosurgery for the treatment of movement disorders focuses primarily on the treatment of Parkinson's disease (PD), essential tremor (ET), and dystonia. The surgical targets in use are the subthalamic nucleus (STN) and the globus pallidus internus (GPi) for PD, GPi for dystonia, and ventralis intermedius (Vim) nucleus of the thalamus for ET. Following target selection, procedures include the generation of lesions or the placement of deep brain stimulating electrodes in the selected target. Additionally, transplantation has been used in the treatment of PD. The indications, outcomes, and risks of the various procedures are reviewed.

The neuropsychologist plays a crucial role in three phases of the neurosurgical treatment of movement disorder patients, namely screening, outcome evaluation and research. In screening patients, the differential diagnosis of dementia, impact of depression or other psychiatric conditions, and the influence of disease and medication-induced symptoms on cognitive performance must be determined. Postoperatively, systematic evaluations elucidate the cognitive costs or benefits of the procedure. The neuropsychologist is then able to provide feedback and counselling to the professional staff, patient and family to inform management strategies. Neuropsychologists also study alteration of cognitive processing due to lesions or stimulation, which, in tandem with functional imaging, shed light on plasticity in cortical and subcortical processing.

Psychogenic movement disorders (PMD) are challenging to diagnose and to treat. Since the nineteenth century, PMDs were recognized and described in painstaking detail. In the modern neurology clinic, PMDs may comprise 2-25% of the patient population. Recognition of the various types of PMDs, differentiation from organic illness and an approach to PMDs are described in this article.

Very early in the process of diagnosing abnormal involuntary movement (AIM) disorders, one can be rewarded by keeping a high index of suspicion for possible drug-induced causes, not only through a complete list of current medications, but also identification of the drugs the patient used to take and other possible offending medications that might be available from family members and other sources. Among drug-induced movement disorders, antipsychotic drugs and other dopamine receptor blocking agents occupy a central place. Their various acute and tardive motor complications provide the template of this short review. Movement disorders caused by antidepressants, lithium, antiemetics, antiparkinsonian agents, anticonvulsants, calcium channel blockers, sympathomimetics and others are only briefly covered in table form.