Unusual tremor syndromes: know in order to recognise

Tremor is a common neurological condition in clinical practice; yet, few syndromes are widely recognised and discussed in the literature. As a result, there is an overdiagnosis of well-known causes, such as essential tremor. Many important unusual syndromes should be considered in the differential diagnosis of patients with tremor. The objective of this review is to provide broad clinical information to aid in the recognition and treatment of various unusual tremor syndromes in the adult and paediatric populations. The review comprised of a comprehensive online search using PubMed, Ovid database and Google Scholar to identify the available literature for each unusual tremor syndrome. The review includes fragile X-associated tremor/ataxia syndrome, spinocerebellar ataxia type 12, tremors caused by autosomal recessive cerebellar ataxias, myorhythmia, isolated tongue tremor, Wilson's disease, slow orthostatic tremor, peripheral trauma-induced tremor, tardive tremor and rabbit syndrome, paroxysmal tremors (hereditary chin tremor, bilateral high-frequency synchronous discharges, head tremor, limb-shaking transient ischaemic attack), bobble-head doll syndrome, spasmus nutans and shuddering attacks. Rare tremors generally present with an action tremor and a variable combination of postural and kinetic components with resting tremors less frequently seen. The phenomenology of myorhythmia is still vague and a clinical definition is proposed. The recognition of these entities should facilitate the correct diagnosis and guide the physician to a prompt intervention.