Tremors: Essential Tremor and Beyond
Introduction
Tremor is a common symptom encountered by pediatric neurologists. Although not life threatening, chronic tremor can negatively impact the quality of life of a child. Tremor can interfere with a developing child′s fine motor skills such a hand-writing or even participation in some sports activities. It may represent an important source of distress for the child and the family.
As with most neurologic conditions, a thorough history and physical examination is essential to appropriately diagnose and treat tremor. It is important to characterize the type, duration, and time course of tremor symptoms, as this can help to include or exclude specific diagnoses. Other significant symptoms or physical examination findings such as focal weakness or ataxia should be considered to better localize potential lesion causing the tremor. Family history can also be critical when considering inherited causes of tremor in the child.
Etiologies vary widely and differ much between children and adults. While Parkinson disease (PD) is not an uncommon encounter in older patients, “benign” essential tremor (ET) and enhanced physiological tremor are by far the most common diagnoses in children who do not have other underlying neurologic conditions. Medication induced tremor is also frequently seen and a matter of concern for families.
In most patients, tremor has little clinical significance, needing no further diagnostic testing or medical treatment. However, in many cases, it may be a sign of a more ominous neurologic problem. Evaluation tools include brain imaging studies to investigate the possibility of a structural lesion (cerebral ischemia, brain tumor, or neurodegenerative process). Genetic testing, although expensive, can be diagnostic when no structural lesion is found, especially in the setting of a significant family history of tremor or a suspected neurodegenerative disorder. Laboratory testing for thyroid and parathyroid disease, hypoglycemia, vitamin deficiencies (vitamin B12), and heavy metal toxicity should be considered since these are potentially treatable causes of tremor.1, 2, 3, 4, 5, 6
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Pathophysiology
We have made progress in understanding the anatomical regions in the central nervous system (CNS) as well as specific pathways involved in the generation of tremor, however, the pathophysiology of tremogenesis is still incompletely defined. Two sets of neuronal networks appear to be particularly important (Fig. 1).7 One is the cortico-striato-thalamo-cortical loop, whose physiological task is to integrate different muscle groups for complex movement programs and to ensure that an ongoing
Classification
Tremor is defined as an involuntary, rhythmic, oscillatory movement of a body part. Using phenomenology, tremor can be classified according to is clinical features and activation conditions (Table 1).18 Tremor can also be classified along 2 axes, taking into consideration clinical features, diagnostic testing, and etiology (Fig. 2).19
Axis 1—clinical features, including historical data (age at onset, family history, and temporal evolution), tremor characteristics (body distribution, activation
Tremor Syndromes
A tremor syndrome can be isolated (consisting only of tremor) or combined (tremor associated with other systemic or neurologic signs). Both common and rare tremor syndromes are described below.
Conclusion
Tremor, although not life threatening, can negatively impact the quality of life of a child. A thorough history and physical examination is essential to appropriately characterize and treat. Secondary underlying neurologic conditions need to be excluded. Brain imaging studies and genetic testing may be indicated in select cases. Management is highly dependent on the degree of functional impairment. Treatment should include a multidisciplinary approach in which comprehensive rehabilitation
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