Movement Disorders Movement disorders are a group of conditions characterized by alteration in normal motility, posture or tone, alone or in combination. Changes caused by motor paralysis, severe sensory loss, painful syndromes or skeletal deformities, etc. are not included in these disorders. Though movement abnormalities may be seen with lesions of the cerebral hemispheres, cerebellum, and brainstem or in metabolic disorders, the most common site is the extrapyramidal system (basal ganglia). This is a phylogenetically older motor system and is responsible for regulation of tone, automatic movements and posture. The basal ganglia cannot produce fine voluntary movement in man, which is a function of the pyramidal system. The extrapyramidal system “sets the background for efficient functioning of the pyramidal system”. The manifestation of an extrapyramidal lesion depends on the role of a given part within the overall organization of the system. Whereas lesions of the substantia nigra often produce typical parkinsonism (with tremor, bradykinesia and rigidity), akinetic-rigid parkinsonism may be produced by lesions of the globus pallidus. Focal lesions in the caudate can produce chorea, while lesions in the putamen may cause dystonia. The clinical findings will be contralateral to the side of the lesion. Movement disorder manifestations are characterized as either hyperkinetic (increased movement) or hypokinetic (decreased movement). Hyperkinetic movement disorders include tremor, chorea, ballismus, athetosis, myoclonus, tics, and dyskinesias. Parkinsonism is a hypokinetic movement disorder, with overall paucity of movement, with the exception of tremor (hyperkinesia). Dystonia is also a 1 combination of hypokinesis and hyperkinesis, with the dominant picture of increased tone caused by agonist and antagonist co-contraction with rare dystonic tremor. All movement disorders are worsened with stress, fatigue, anxiety or concomitant illness (e.g. pneumonia, UTI, etc.). As a rule, movement disorders show significant or complete relief during sleep. Tremor Tremor is the most common movement disorder. It is defined as “an involuntary rhythmical movement about an axis.” It can involve any body part but most commonly affects the limbs or head. Everyone has physiological tremor but it is not clinically evident. Tremor is classified as follows: (1) Resting – Parkinsonian tremor. The limbs are fully supported against gravity i.e. patient lying supine on the examining table. (2) Postural – the body part held out against gravity i.e. hands out in front. Examples include: (a) exaggerated physiological tremor as seen with anxiety, thyrotoxicosis, caffeine, fatigue, etc.; (b) essential tremor; (c) cerebellar tremor (slow, and patient is also ataxic); (d) other metabolic disorders (including drug-induced) (3) Kinetic (Action) – with activity i.e. asked to perform finger/nose/finger. This type of tremor is seen in essential tremor. Tremor seen near the end of movement is also called “terminal” or “intention” tremor. Lesions in the cerebellar outflow tract are associated with prominent terminal tremor (as well as ataxia). Tics These are stereotyped, repetitive, rapid coordinated movements. They can involve any body part but typically involve the head, neck, eyes or upper extremities. The pattern is the same in a given patient. These movements can 2 be voluntarily suppressed but this causes a build-up of tension. When the tension is “released” there are exaggerated movements and the patient feels more comfortable. Tics may be simple or complex. Tic disorder is not uncommon in children but typically resolves spontaneously. The diagnosis of Tourette’s syndrome requires the presence of multiple motor and one or more vocal tics (e.g. grunting, sniffing, other vocalizations, etc.) lasting more than 1 year, with onset before age 18. There is an association between obsessive- compulsive disorder (OCD), attention-deficit hyperactivity disorder (ADHD) and Tourette’s. Dystonia Dystonia is characterized by sustained muscle contractions resulting in abnormal movement or posture. The “dystonic movement” is brief, irregular, intermittent, twisting or turning in nature producing distortion of the involved part, hence the term “torsion dystonia”. Dystonia usually begins as a dystonic movement and further progression leads to sustained abnormal posture lasting for 30 seconds or longer – known as “dystonic posture”. Dystonia may involve any part of the body such as the neck (cervical dystonia, or torticollis), or the whole body as in dystonia musculorum deformans. In adults, dystonia is typically focal (most commonly cervical) while in childhood, dystonia is more often generalized. In most cases, the pathological basis of dystonic movement and dystonic posture is not known. Lesions that have been identified include the putamen or diffuse basal ganglia involvement. Dystonia may be classified as symptomatic, i.e. a component of another disease such as Wilson’s disease (disorder of copper metabolism) or idiopathic. Idiopathic dystonia may be sporadic or inherited as an autosomal dominant or recessive disorder. Acute or chronic dystonia may be caused by neuroleptics. 3 Blepharospasm is a form of cranial dystonia consisting of involuntary eye closure affecting the orbicularis oculi muscles. Initially there may be symptoms of increased blinking; in severe cases patients are rendered functionally blind from sustained eye closure. Writer’s cramp is the most common type of task-specific dystonia. The hand assumes a dystonic posture with writing, the handwriting becoming progressively more effortful and illegible the longer the person writes. Other activities such as typing are unaffected. Other task-specific dystonias include musician’s dystonia (such as playing the piano or violin), and golfing (the “yips” with putting). Task- specific dystonias are thought to be due to repeated movements resulting in abnormal sensorimotor integration. Botulinum toxin injections are useful for cranial and cervical dystonia, as well as focal dystonias. Botulinum toxin produces weakness by inhibiting presynaptic release of acetylcholine at the neuromuscular junction. Onset of benefit is typically within 1-2 weeks following the injection, and benefit lasts for approximately 3 months. Adverse effects may include weakness, dysphagia and dysarthria, however injections are generally well tolerated. Dopa-Responsive Dystonia (DRD) is an uncommon form of dystonia with onset in childhood or adolescence. It may be mistaken for cerebral palsy, with some patients wheelchair bound for years until correctly diagnosed and treated. There is a diurnal pattern, with dystonia typically worse in the afternoon or evening, and improvement after sleep. DRD is very sensitive to small amounts of levodopa – excellent response and long-term benefit is the rule. The rule is that any child with dystonia warrants a trial of levodopa. Chorea From the Greek word “dance”, chorea is characterized by involuntary, irregular, purposeless, asymmetrical, non-rhythmic movements. Sometimes patients 4 attempt to incorporate these movements into semi-voluntary movements (parakinesia) e.g. involuntary movement of the arm is incorporated in an attempt to scratch the head, etc. The anatomical substrate is varied – a lesion affecting the caudate, or diffuse cerebral hemisphere or subcortical dysfunction. The differential diagnosis of chorea includes: (1) Huntington’s Disease. This has autosomal dominant inheritance (chromosome 4p, trinucleotide CAG repeat expansion) and is the most common genetic cause of chorea. There is anticipation, with future generations developing earlier and more severe disease. In addition to chorea, personality change and progressive dementia are common features. (2) Sydenham’s Chorea. This is seen following streptococcal infection (usually in children) and is self-limited. It is also known as “St. Vitus’ dance”. (3) Metabolic/systemic conditions. These include Wilson’s disease, polycythemia, hypocalcemia, hypoglycemia, thyrotoxicosis. (4) Vascular/Autoimmune disease e.g. systemic lupus erythematosus. (5) Drugs/medications – includes cocaine, amphetamines, neuroleptics, calcium channel blockers, oral contraceptives. (There are many more entities associated with chorea, and it makes for an excellent Royal College Fellowship examination question.) Athetosis This means “without fixed position”. Athetosis is a relatively uncommon movement disorder. The movements are purposeless, bizarre, complex and writhing. There is lack of agonist and antagonist coordination. In comparison to chorea, the movements are slower, more sustained, writhing and “snakelike”. Abnormal posturing is often associated with voluntary movements i.e. outstretched hands may show extension of the thumb and fingers but flexion at the wrist and pronation of the forearm. The tone is often increased, but not as 5 pronounced as in dystonia. The most common site of lesion is the putamen and/or caudate. The most common causes of athetosis are: (1) birth trauma or neonatal asphyxia; (2) Wilson’s disease; (3) post-encephalitic; (4) kernicterus; and (5) carbon monoxide poisoning. (Note: this is more information than you will ever need about athetosis; in practice these movements are usually called “choreoathetoid”.) Dyskinesias These are abnormal movements, usually choreiform in nature, but sometimes with athetoid and dystonic movements as well. Dyskinesias are seen in some cases after prolonged use of neuroleptics and may become persistent (tardive