A distinct subset of patients with an idiopathic dystonia (Segawa disease, described also by Nygaard et al and discussed in Chap. 38) responds to extremely small doses of L-dopa. This disorder is familial, usually autosomal dominant, and the dystonia-athetosis may be combined with elements of parkinsonism. Marked diurnal fluctuation of symptoms is characteristic, with the movement disorder worsening as the day wears on and improving with sleep. Another rare hereditary dystonia, termed rapid-onset dystonia-parkinsonism, has its onset in adolescence or early adulthood and is of interest because of the rapid evolution, at times within an hour but more often over days, of severe dystonic spasms, dysarthria, dysphagia, and postural instability with bradykinesia (Dobyns et al). Dystonia is a component of a number of obscure multisystem degenerations that may include diverse features such as optic neuropathy and striatal necrosis.
A frequent cause of acute generalized dystonic reactions, more so in the past, had been from exposure to the class of neuroleptic drugs—phenothiazines, butyrophenones, or metoclopramide—and even with the newer agents such as olanzapine, which have the advantage of producing these side effects less frequently. A characteristic, almost diagnostic, example of the acute drug-induced dystonias consists of retrocollis (forced extension of the neck), arching of the back, internal rotation of the arms, and extension of the elbows and wrists—together simulating opisthotonos. These reactions respond relatively predictably to diphenhydramine or benztropine. L-Dopa, calcium channel blockers, and a number of antiepileptic drugs and anxiolytics are among a long list of other medications may on occasion induce dystonia, as listed in Table 4-5. The acute dystonic drug reactions are idiosyncratic and probably now as common as the tardive dyskinesias that had in the past followed long-standing use of a medication.
In the literature, there have been reported numerous cases of limb injury and subsequent reflex sympathetic dystrophy (see Chap. 10) that were accompanied by a variety of movement disorders, particularly dystonia. The nature and mechanism of this association are uncertain. Finally, a peculiar and dramatic spasm of a limb or the entire body may be seen in patients with multiple sclerosis. The movements have aspects of dystonia and may be provoked by hyperventilation but they may not be, strictly speaking, dystonic. They are most likely to occur in patients with large demyelinative lesions of the cervical spinal cord.
Restricted or fragmentary forms of dystonia are the types most commonly encountered in clinical practice. Characteristically the spasms involve only the orbicularis oculi and face or mandibular muscles (blepharospasm-oromandibular dystonia), tongue, cervical muscles (torticollis), hand (writer’s cramp), or foot. There may be an associated tremor, or tremor may be the only manifestation of an early dystonia. These are described further on and in Chap. 38.
Hemidystonia represents an unusual form of acquired movement that, in our experience, is rarely pure. In an analysis of 33 of their own cases and 157 previously published ones, Chuang and colleagues found stroke, mainly in the contralateral putamen, to be most often responsible. Traumatic and perinatal damage accounted for several cases and a large proportion had no lesions found by imaging tests. In traumatic cases, there was a delay of several years between the injury and the start of the movements; these authors also commented on the resistance of this syndrome to drug treatment.