Part front matter for Section 5 Chorea

The term ‘chorea’ is derived from the Greek word ‘choreia’ which literally means to dance. It was used in the Middle Ages to describe a dancing mania that swept through Europe. This disorder which is now thought to have been a form of ‘hysteria’ caused the afflicted to dance wildly until they dropped with exhaustion. Paracelsus (1492–1541) suggested that this complaint was really a disease, which he called chorea. It became known as chorea santi viti or the dance of Saint Vitus after the patron saint of this mysterious disorder. A visit to the Chapel of Saint Vitus was believed to have curative powers. In Italy it was thought to be due to the bite of the tarantula spider and was named tarantarism. A rapid whirling Italian dance, the trantella was considered to be a cure for the venomous bite (Haas 1991).

In 1895 Thomas Sydenham described a different disorder which he called ‘Saint Vitus's dance’, but which subsequently became known as Sydenham's chorea (see Chapter 22 on ‘Sydenham's Chorea’). The term chorea has subsequently been used to describe this pattern of involuntary movements, whatever its cause.

Chorea is a disorder characterized by involuntary brief jerky movements, which appear at random in the affected body part or parts. The movements are sometimes described as being semi-purposeful because they may mimic a fragment of normal motor activity, commonly of the automatic but voluntary kind. Thus, individual choreic movements may resemble winking, smiling, grimacing, shrugging, gesturing, or the like. They are characterized by their rapidly and continually changing nature so that they occur at irregular intervals in a variety of sites within the affected part.

Movements with which chorea tends to be confused include dystonia, tics, and myoclonus. There is usually no difficulty in distinguishing it from the rhythmically sinusoidal displacements that occur in tremor. Dystonic movements are more prolonged than those of chorea, resulting in slower sinuous movements or sustained postures. Because of this, dystonia produces much more disability than chorea, and patients with even quite severe chorea may have little if any functional impairment. In addition, patterns of voluntary movements are relatively preserved in chorea so that disturbance in performing willed actions is largely the result of superimposed involuntary jerks. In dystonia, by contrast, the patterns of normal voluntary activity are severely disorganized, resulting in disability additional to that caused by the involuntary movements.

Chorea differs from tics in that the latter consist of stereotyped repetitive movements which are relatively constant, although they may change over months or years. Tics may be simple and just involve a single movement or they can be complex and consist of meaningful patterns of behaviour, requiring integration of the action of many different muscles. Tics are usually accompanied by an inner compulsion to perform the movement and this is absent in chorea. It is difficult to suppress significant chorea for more than a few seconds, but patients can often resist performing a tic for quite long periods if the need arises. The movements of myoclonus tend to be briefer, more shock-like, and repetitive than those of chorea.

Like most of the other above involuntary movements, chorea tends to be made worse by emotional stress and improved by relaxation and sleep. The pathophysiological mechanisms underlying chorea have been outlined in Section 1 in the ‘Function of the Basal Ganglia’.

Conditions presenting with chorea sometimes show a mixed clinical picture with elements of other movement disorders, especially dystonia.

This is particularly likely to occur in the presence of hypertonia, which may result in slowing of the involuntary movements, making them less jerky in appearance (see under ‘Huntington's Disease’ Chapter 20]). This has led to the common use of terms such as ‘choereoathetosis’ and ‘choreothetoid’. Frequently, however, these labels have been used to describe movements that are clearly and soley choreic. By and large, their use is to be discouraged. This is not to say that some patients do not show a mixture of chorea and dystonia. Nonetheless, in most situations chorea is quite distinct from dystonia and every effort should be made to clearly describe and directly categorize these involuntary movements rather than lazily use unsatisfactory combination terms.

We have divided the choreic syndromes into those that are idiopathic and usually inherited on the one hand, and those that are symptomatic of other recognized disorders on the other. Most of the latter are acquired, but in some cases they are due to inherited diseases in which the metabolic defect is known. This division and the way that the material is covered is shown in Table 1.

It would have been just as satisfactory to separate the choreic syndromes into two major categories, namely inherited and acquired. The first would include groups A I and A II from the idiopathic disorders in Table 1, along with group B I from the symptomatic disorders. The second category would include group A III from the idiopathic disorders and group B II from the symptomatic disorders. Unlike the dystonic syndromes, there is no choreic disorder analogous to the primary or idiopathic dystonias, such as dystonia musculorum deformans, cranial dystonia, spasmodic torticollis, and writer's cramp. With the exception of benign hereditary chorea and paroxysmal kinesiogenic dyskinesia, the other idiopathic choreic syndromes are caused by progressive disorders with major neurological features apart from the chorea. In this sense, virtually all choreas can be regarded as secondary, and thus they require investigation to establish a cause. Not infrequently, sporadic chorea turns out to be a rare manifestation of a relatively common medical condition.

The arguments about whether ballism is just a severe form of chorea or is a separate entity are covered in Chapter 25. For historical, aetiological, and clinical reasons we have chosen to deal with it separately, although we regard it as a form of chorea.