Peripheral dystonia

Pseudodystonia: A new perspective on an old phenomenon

Pseudodystonia represents a wide range of conditions that mimic dystonia, including disorders of the peripheral nervous system, spinal cord, brainstem, thalamus, cortex and non-neurological conditions such as musculoskeletal diseases. Here, we propose a definition of pseudodystonia and suggest a classification based on underlying pathophysiological mechanisms. We describe phenomenology of different forms of pseudodystonia and point to distinctions between dystonia and pseudodystonia as well as challenging issues that may arise in clinical practice. The term pseudodystonia can be used to describe abnormal postures, repetitive movements or both, in which results of clinical, imaging, laboratory or electrophysiological investigations provide definite explanation of symptoms which is not compatible with dystonia. Pseudodystonia can be classified into non-neurological disorders of the musculoskeletal system, disorders of sensory pathways, disorders of motor pathways and compensatory postures in other neurological diseases. Presence of associated neurological findings in the affected body part is the key towards diagnosis of pseudodystonia. Additional supporting features are the presence of fixed postures, the absence of sensory trick, acute mode of onset and severe pain. Worsening on eye closure, traditionally considered typical for pseudodystonia, is not always present and can also appear in dystonia. It is challenging to separate dystonia and pseudodystonia in patients with thalamic lesions or corticobasal syndrome, where abnormal postures coexist with sensory loss. Many cases of pseudodystonia are treatable. Therefore, it is essential to consider pseudodystonia in a differential diagnosis of abnormal postures until a detailed neurological examination rules it out.

Posttraumatic functional movement disorders

Traumatic injury to the nervous system may account for a range of neurologic symptoms. Trauma location and severity are important determinants of the resulting symptoms. In severe head injury with structural brain abnormalities, the occurrence of trauma-induced movement disorders, most commonly hyperkinesias such as tremor and dystonia, is well recognized and its diagnosis straightforward. However, the association of minor traumatic events, which do not lead to significant persistent structural brain damage, with the onset of movement disorders is more contentious. The lack of clear clinical-neuroanatomic (or symptom lesion) correlations in these cases, the variable timing between traumatic event and symptom onset, but also the presence of unusual clinical features in a number of such patients, which overlap with signs encountered in patients with functional neurologic disorders, contribute to this controversy. The purpose of this chapter is to provide an overview of the movement disorders, most notably dystonia, that have been associated with peripheral trauma and focus on their unusual characteristics, as well as their overlap with functional neurologic disorders. We will then provide details on pathophysiologic views that relate minor peripheral injuries to the development of movement disorders and compare them to knowledge from primary organic and functional movement disorders. Finally, we will comment on the appropriate management of these disorders.

The Dystonias

Dystonia is a difficult problem for both the clinician and the scientist. It is sufficiently common to be seen by almost all physicians, yet uncommon enough to prevent any physician from gaining broad experience in its diagnosis and treatment. Each case represents a difficult challenge even to the specialist. The basic scientist is faced with investigating a disorder that is without relevant animal models and which is so rare that obtaining suitable tissue for study is a major obstacle. Dystonia may be idiopathic, or associated with lesions from many sources, including a variety of rare diseases. If idiopathic, it may be genetically transmitted or sporadic. If genetically transmitted, it may be generalized or focal, with symptoms varying in different members of the same family. It may be refractory to treatment, or it may respond to any one of a number of individual drugs that have very different mechanisms of action. For idiopathic dystonias, no clear method of genetic transmission has been established and no consistent pathology identified.

Nonprimary dystonias

Dystonias can be classified as primary or secondary, as dystonia-plus syndromes, and as heredodegenerative dystonias. Their prevalence is difficult to determine. In our experience 80-90% of all dystonias are primary. About 20-30% of those have a genetic background; 10-20% are secondary, with tardive dystonia and dystonia in cerebral palsy being the most common forms. If dystonia in spastic conditions is accepted as secondary dystonia, this is the most common form of all dystonia. In primary dystonias, the dystonic movements are the only symptoms. In secondary dystonias, dystonic movements result from exogenous processes directly or indirectly affecting brain parenchyma. They may be caused by focal and diffuse brain damage, drugs, chemical agents, physical interactions with the central nervous system, and indirect central nervous system effects. Dystonia-plus syndromes describe brain parenchyma processes producing predominantly dystonia together with other movement disorders. They include dopa-responsive dystonia and myoclonus-dystonia. Heredodegenerative dystonias are dystonic movements occurring in the context of other heredodegenerative disorders. They may be caused by impaired energy metabolism, impaired systemic metabolism, storage of noxious substances, oligonucleotid repeats and other processes. Pseudodystonias mimic dystonia and include psychogenic dystonia and various orthopedic, ophthalmologic, vestibular, and traumatic conditions. Unusual manifestations, unusual age of onset, suspect family history, suspect medical history, and additional signs may indicate nonprimary dystonia. If they are suspected, etiological clarification becomes necessary. Unfortunately, potential etiologies are legion. Diagnostic algorithms can be helpful. Treatment of nonprimary dystonias, with few exceptions, does not differ from treatment of primary dystonias. The most effective treatment for focal and segmental dystonias is local botulinum toxin injections. Deep brain stimulation of the globus pallidus internus is effective for generalized dystonia. Antidystonic drugs, including anticholinergics, tetrabenazine, clozapine, and gamma-aminobutyric acid receptor agonists, are less effective and often produce adverse effects. Dopamine is extremely effective in dopa-responsive dystonia. The Bertrand procedure can be effective in cervical dystonia. Other peripheral surgery, including myotomy, myectomy, neurotomy, rhizotomy, ramizectomy, and accessory nerve neurolysis, has largely been abandoned. Central surgery other than deep brain stimulation is obsolete. Adjuvant therapies, including orthoses, physiotherapy, ergotherapy, behavioral therapy, social support, and support groups, may be helpful. Analgesics should also be considered where appropriate.

Clinical consequences of reinnervation disorders after focal peripheral nerve lesions

Axonal regeneration and organ reinnervation are the necessary steps for functional recovery after a nerve lesion. However, these processes are frequently accompanied by collateral events that may not be beneficial, such as: (1) Uncontrolled branching of growing axons at the lesion site. (2) Misdirection of axons and target organ reinnervation errors, (3) Enhancement of excitability of the parent neuron, and (4) Compensatory activity in non-damaged nerves. Each one of those possible problems or a combination of them can be the underlying pathophysiological mechanism for some clinical conditions seen as a consequence of a nerve lesion. Reinnervation-related motor disorders are more likely to occur with lesions affecting nerves which innervate muscles with antagonistic functions, such as the facial, the laryngeal and the ulnar nerves. Motor disorders are better demonstrated than sensory disturbances, which might follow similar patterns. In some instances, the available examination methods give only scarce evidence for the positive diagnosis of reinnervation-related disorders in humans and the diagnosis of such condition can only be based on clinical observation. Whatever the lesion, though, the restitution of complex functions such as fine motor control and sensory discrimination would require not only a successful regeneration process but also a central nervous system reorganization in order to integrate the newly formed peripheral nerve structure into the prepared motor programs and sensory patterns.

Complete suppression of paroxysmal nonkinesigenic dyskinesia by globus pallidus internus pallidal stimulation

Stereotactic functional surgery is being explored as potential therapies for medically intractable paroxysmal dyskinesias (PxD). We report on a 59-year-old man in whom stimulation of globus pallidus internus produced immediate and sustained relief of paroxysmal non-kinesigenic dyskinesia secondary to a rotator cuff tears on the left shoulder. Our finding strongly suggests that altered function of neuronal circuits of the basal ganglia underlies the manifestation of PxD.

Trauma-induced spinal vascular event producing hemipseudoathetosis

We report on a patient with spinal pseudoathetosis secondary to posterior column vascular incident and physical injury. This unusual case highlights sensory system abnormalities as a cause of movement disorders.

Treatment of tremors in complex regional pain syndrome

A 14-year-old girl presented with Complex Regional Pain Syndrome, Type I (CRPS-1) of the left ankle after a remote history of sprain. Allodynia, pain, temperature and color changes, and swelling were successfully treated with physical therapy, transcutaneous electrical nerve stimulation (TENS), gabapentin, amitriptyline, and tramadol. Five weeks later, she presented with a continuous, involuntary, intermittent coarse tremor of the left foot causing increased pain. The electromyogram showed rhythmic discharges of 3 Hz frequency lasting 20-80 milliseconds in the left tibialis, peroneus and gastrocnemius, suggestive of either basal ganglia or spinal origin. Tremor and pain were controlled with epidural bupivacaine, but the tremor reappeared after discontinuing epidural blockade. Carbidopa/levodopa 25/100 (Sinemet) was started and the tremor disappeared after two days. With continued physical therapy, pain and swelling resolved within two months and carbidopa/levodopa was discontinued after five weeks with no recurrence of the tremor. Our success in the treatment of CRPS-associated tremor in this young girl with carbidopa/levodopa suggests that this patient may have had underlying movement disorder which was unmasked by the peripheral injury.

Operative management of foot and ankle equinovarus associated with focal dystonia

Six surgical procedures, consisting of tendon transfers and releases, were performed in five patients with idiopathic focal dystonia involving the lower extremity. All patients were female. Surgical management was performed to correct clinically significant foot abnormalities. The goal of each procedure was functional improvement and obtaining a plantigrade foot. The SPLATT (split anterior tibial tendon transfer) procedure was performed in each foot with a flexible equinovarus foot abnormality. Follow up at a mean of 27.2 months (range, 8-40 months) yielded satisfactory clinical results without significant complications. Clinical equinovarus has not recurred after this procedure. All patients remain brace-free ambulators.

Delayed segmental axial dystonia of the trunk on standing after lumbar disk operation

We report four patients with various degrees of chronic, tonic, mildly painful, or non-painful, kyphoscolioses in orthostatism, which developed weeks, or months, after one or several laminectomies for lumbar disk hernia, in the absence of recurring radicular pain or acute lumbar pain. No family history or personal antecedent, of focal or generalized dystonia was found and the dystonia was not seen in any of the four patients pre-operatively, or during the immediate post-operative period. Only ill-defined lumbar 'discomfort', unlike their pre-operative lumbago, was reported by the patients, before and during the occurrence of the pathologic trunk posture on standing. Asymmetric lumbar muscle tonic contraction and hypertrophy was found on physical examination. In all patients, the kyphoscoliosis was maximal when standing, partially disappeared when seated, and completely when lying down. One patient responded well to clonazepam, but the other three showed no improvement with either clonazepam or local injections of botulinum toxin; L-dopa was ineffective in all cases, and trihexiphenidyle in three.

Foot dystonia and lumbar canal stenosis

We describe a patient who developed involuntary, painless, dystonic contraction of the toes of the right foot on standing or walking. The development of this abnormal movement had been preceded by sensory disturbance on the soles of both feet, triggered by dorsiflexion of the feet. Examination showed that weight bearing on the right foot and walking brought on clawing of the toes of the right foot, which was relieved within seconds of taking pressure off the right foot. There was sensory and reflex evidence of bilateral S1 root disturbance confirmed by electrophysiology. Magnetic resonance imaging of the lumbar spine showed marked stenosis of the lumbar canal with compression of the L5 and S1 nerve roots bilaterally. The patient underwent a lumbar laminectomy with nerve root exit foramina decompression, which abolished the foot dystonia and has considerably improved the sensory disturbance. This case demonstrates that lumbar canal stenosis and/or nerve root compression, may be responsible for foot dystonia. Amelioration of the abnormal movement by surgical decompression argues strongly in favour of this hypothesis.

Ulnar neuropathy and dystonic flexion of the fourth and fifth digits: clinical correlation in musicians

Peripheral nerve lesions are sometimes associated with focal dystonia. We diagnosed ulnar neuropathy in 28 of 73 (40%) cases of occupational cramp in musicians. Focal slowing of ulnar conduction across the elbow was identified in 15 of 19 (79%) patients using the near nerve technique and in 5 of 17 (29%) patients using surface recording. Ulnar neuropathy was present in 24 of 31 (77%) cases with flexion dystonia of the fourth and fifth digits and only 4 of the remaining 42 (10%) cases with other patterns of focal dystonia. Focal dystonia improved in 13 of 14 patients whose ulnar neuropathy improved and appeared or worsened in 2 patients following ulnar nerve injury. These data, together with our recent observation of a dystonic pattern of antagonist bursting in patients with isolated ulnar neuropathy (Muscle Nerve 1995, 18:606-611), suggest that ulnar neuropathy may initiate or sustain a specific dystonia, flexion of the fourth and fifth digits, by inducing a central disorder of motor control.

Does ulnar neuropathy predispose to focal dystonia?

We have observed a high incidence of ulnar neuropathy in musicians with dystonic flexion of the ipsilateral little and ring fingers. To investigate the relationship between ulnar neuropathy and focal dystonia, we compared the patterns of surface EMG activity in extensor digitorum communis (EDC4) and flexor digitorum superficialis (FDS4) during tapping of the ring finger in normal controls and patients with ulnar neuropathy or focal dystonia. Ten of 10 normal subjects exhibited well-formed alternating EMG bursts in EDC4 and FDS4 separated by clear silent periods. Seven of 7 patients with dystonic flexion of the little and ring fingers showed loss of silent periods between poorly formed bursts in FDS or EDC. Surprisingly, 9 of 10 patients with ulnar neuropathy showed burst pattern abnormalities qualitatively similar to those observed in the dystonic patients. These data suggest that ulnar neuropathy alters the execution of a motor task involving multiple peripheral nerves.

Laterality of onset in idiopathic torsion dystonia

Idiopathic torsion dystonia (ITD) is a dominantly inherited disorder with incomplete penetrance. It is important to identify factors that may cause dystonia or prevent its occurrence in a genetically predisposed individual. Because dystonia may be precipitated by peripheral triggers, we have investigated whether the preferential use of a limb affects the development of dystonia. Analysis of the correlation between the side of motor dominance and the limbs in which dystonic symptoms first appeared was performed in 49 patients with ITD ascertained in a country-wide survey in Israel. The dominant motor side was determined in 45 cases (92%). Among 29 patients with lateralized limb onset, 24 showed right-side motor dominance, of whom 21 had dystonia onset in a right limb. The first sign was in a left limb for all five cases with left-side motor dominance (90% coincidence). The pattern of limb involvement was studied. Detection bias could be ruled out. The highly significant relationship between the motor dominance and the laterality of limb onset in ITD patients suggests that the preferred use of a limb may trigger the onset of dystonia.

CT-scanning and magnetic resonance imaging in idiopathic spasmodic torticollis

Twenty-five consecutive patients with idiopathic spasmodic torticollis (IST) were investigated with computerized tomography (CT) or magnetic resonance imaging (MRI) of the brain. In only six patients (24%) did CT or MRI reveal brain pathology (focal cortical atrophy and lacunary infarcts). No consistent pathological pattern was detected. Consequently, CT and MRI of the brain provides little diagnostic information in this disorder.

Spasms of amputation stumps

Two patients are presented with muscle spasms in an amputation stump. Neither patient experienced neuropathic pain nor phantom sensations, though phantom sensory phenomena, severe pain, and lack of response to treatment is characteristic of reported cases. One patient, a 75 year old man, has had myoclonic activity of the stump for more than two years, and the other, a 79 year old woman, recovered spontaneously after three months and is symptom free after a one year follow up. We emphasise the lack of association with pain and the need to consider spontaneous improvement when therapy is evaluated.

Carpal tunnel syndrome: a complication of idiopathic torsion dystonia

Carpal tunnel syndrome (CTS) is usually an idiopathic disorder. Certain occupations that require frequent flexion movements of the hand at the wrist are recognized as precipitating the development of CTS. Dystonia can cause similar excessive movements at the wrists. We report the clinical and electromyographic findings of two patients with idiopathic torsion dystonia (ITD), with frequent flexion postures of the wrists, in both of whom typical CTS developed in the more involved hand. It is concluded that nerve entrapment such as CTS has to be considered a possible complication in patients with ITD and other motor control disorders.

Dystonia and tremor induced by peripheral trauma: predisposing factors

Movement disorders are usually of central origin, but sometimes involuntary movements occur after peripheral trauma. Twenty eight patients, 13 women and 15 men, mean age 37 years (range 15-78), were studied with dystonia or tremor in whom the onset of abnormal movements was related, in time and in distribution, to injury of a body part. Among 23 patients with latency of less than one year after injury, focal dystonia of the involved body part was found in 18, nine of whom had associated reflex sympathetic dystrophy (RSD). One of five patients with peripherally induced tremor had RSD. Abnormal electromyography or nerve conduction velocities were found in the affected limb in four patients, but other electrophysiologic techniques provided evidence for disturbed central function. In 15 patients (65%) possible predisposing factors may have contributed to the pathogenesis of the trauma induced abnormal involuntary movements.

Painful muscle spasms complicating algodystrophy: central or peripheral disease?

A 21 year old female patient developed Südeck's atrophy of the right foot secondary to a chronic Achilles tendinitis. The condition was complicated by the occurrence of painful muscle spasms in the right leg and incontinence of urine. The spasms had characteristics of both a tonic ambulatory foot response and a spinal flexor reflex. The movements disappeared during sleep. Regional anaesthesia of the right leg made the spasms disappear both in and outside the region of anaesthesia. Backaveraging of the EEG showed the involuntary spasms to be preceded by a cortical potential similar to a readiness potential, indicating a cortical potential similar to a readiness potential, indicating a cortical component in the pathophysiology of the muscle spasms complicating Südeck's atrophy.

Crural and axial myoclonic dystonia following meralgia paraesthetica

A 49-year-old man developed a syndrome of crural-axial dystonia combined with segmental myoclonus 3 months after the onset of meralgia paraesthetica of the left leg. The association of this remarkable movement disorder with the pain syndrome is discussed.