14.8. Differential Diagnosis of Hyperkinetic Movement Disorders
The hyperkinetic movement disorders are the choreas, myoclonic diseases, ballisms, dystonias, tics and those seen with sleep. The difficulty is not distinguishing the categories, but correctly diagnosing the entities within a specific category.
Huntington's disease is probably the most common of the choreas that will be encountered. The severity of the dementia, choreatic eye movements and lurching gait are dramatic. Family history is sometimes hard to get, but when obtained, it is clear that this is AD.
Sydenham's chorea is not hard to diagnose in childhood. As an adult, it may be associated with old rheumatic heart diseases, is often familial, and may not have an antibody response to streptococcus. Rarely, it is associated in an adult with Jaccoud's arthritis.
Benign familial chorea is not associated with cognitive decline and has a normal life span.
Medications, particularly D2 agonists, anticonvulsants, steroids and neuroleptics, cause chorea. "Crack dancing" is becoming a craze. Patients that have chorea on birth control pills often get it during pregnancy. As noted earlier, many systemic diseases, particularly SLE, hyperthyroidism as well as metabolic derangements such as renal failure are associated with chorea.
Recent post pump chorea and CHAP syndrome (choreoathetosis; orofacial dyskinesis, hypotonia and pseudobulbar palsy) declare themselves by the circumstances.
Hereditary diseases in which chorea may be a component of the symptom complex all have striking seminal features are: Niemann Pick type 2C (failure of vertical gaze), Pelizaeus, Merzbacher (nystagmus), Wilson's disease (Kayser–Fleischer ring) Lesch–Nyhan syndrome (mutilated lower lip), ataxia telangiectasia (ataxia and scleral telangiectasia) the mitochondrial encephalopathies (hearing loss, short stature, cardiomyopathy) and paroxysmal kinesogenic choreoathetosis (chorea and dystonia). Neuroacanthocytosis (Huntington disease like-2), familial abetalipoproteinemia, ferritinopathy and Bassen Kornzweig) all have a complex of akinetic rigid features, tic, seizures, and rarely vertical gaze deficits. DRPLA also has a gamut of other movement dysfunctions (seizures, dementia, and myoclonus) as well as acanthocytes on blood smear.
Hemichorea most often is seen with congenital disease of the striatum (severe hemiplegia) with atrophy of the affected side. Infarction of the thalamus (thalamoperforate artery), trauma, post ViM thalamotomy for tremor, hemorrhages and tumor are causative.
Hemiballismus is an instant diagnosis. The proximal flailing movements require the arm to be tied down. Usually, it is secondary to infarction of the interpeduncular artery from the top of the basilar artery or the thalamoperforate artery.
Tardive dyskinesias almost always have an oral lingual buccal component. The extremities, axial musculature and diaphragm may develop rhythmic movements over time. Akathisia, dystonic sustained movements (tardive dystonia) as well as facial dystonia, blepharospasm, mandibular dystonia and neck dystonia occur. Neuroleptic induced oculogyric crisis, myoclonus and tremors occur.
Abdominal dyskinesias usually occur after trauma and may be difficult to distinguish from propriospinal myoclonus. The clue is surgery in the former and progressive waves of spreading myoclonus in the latter.
Athetosis is immediately recognized by its slow, sinuous writhing quality that primarily affects distal musculature. Pseudoathetosis is an updrift of the extremities with sinuous finger piano playing movements. It is usually seen in the context of congential stroke, birth trauma, anoxia, kernicterus or Wilson's disease.
The dystonias are easily diagnosed because of the obvious abnormally held posture. The features that are peculiar to the diagnosis are sensory "tricks" dystonic spasms, and peculiar stereotyped maintained postures (dropped plantar flexed and inverted foot, retrocollis or torticollis). Dystonic spasms and tremors may be confusing. The dystonia of chronic regional pain syndrome (CRPS) is very common, often associated with severe allodynia. It may occur without pain. It is invariably misdiagnosed.
Movement specific, athletic and musicians' dystonia are easily diagnosed by the specific initiating movement and possibly due to a re -wiring of the motor cortex or incorrect programing by the SMA or PMC of the intended movement. Continued input to the brain changes functional glucose metabolism of the active area of the homunculus. Rarely, peripheral surgery such as discectomy in the neck causes axon rewiring or ephaptic conduction such that intended extension of the wrist results in hand flexion.
Spasmodic dysphonia is differentiated from lesions of components of the Xth nerve by its intermittent nature. These patients also demonstrate other neurologic abnormalities such as tremor.
The paroxysmal dyskinesias cannot be missed as a group due to their spectacular onset. Paroxysmal kinesigenic dyskinesias are composed of chorea athetosis, ballism and dystonic postures. Interruption of speech as well as frequent falls may be confusing. The attacks usually last for seconds to minutes.
Spontaneous paroxysmal non-kinesigenic dyskinesia are not initiated by movement and last from minutes to hours. They are similar to kinesigenic dyskinesia, but are triggered by stress, alcohol and caffeine. Specific paroxysmal dyskinesias are easily defined by initiating triggers such as sleep, or exercise, and whether they are short lasting (less than five minutes) or long lasting (greater than five minutes). Paroxysmal ataxia and tremor has been designated as a spinocerebellar degeneration (SCA 7). It is likely that these paroxysmal disorders will be defined as channelopathies.
The differential diagnosis of myoclonus is wide and the setting in which it occurs most often determines the diagnosis. Hospital settings suggest metabolic or toxic etiologies. Renal failure and post dialysis-states often are accompanied by intention myoclonus. Hyperosmolar states from non-ketotic hyperglycemia often are segmental. Myoclonus with hepatic insufficiency is accompanied by asterixis, lethargy and hyperreflexia. Mitochondrial diseases and myoclonus should always be expected in a short patient with deafness, fatigue with exercise and cardiomyopathy.
The Lance–Adams syndrome of post hypoxic myoclonus should be expected following resuscitation from cardiac arrest or any anoxic state. The intention and postural kinetic components of the syndrome are seminal. Most poisonings are accompanied by nausea, vomiting, and a large anion gap with a large and long fiber neuropathy.
The hereditary progressive myoclonic epilepsies are rare, dementia predominates. Neuronal ceroid lipofuscinosis and Lafora body disease are most often seen in adults. Visual hallucinations and occipital lobe symptomatology is seen in 50% of patients with Lafora body disease. Dementia and severe ataxia are the seminal features of Ramsay–Hunt syndrome.
Myoclonus is a feature of all of the basal ganglia degenerations. Most present with akinetic rigid features. Low blood pressure and cold hands suggest MSA. Severe dysarthria, wing-beating tremor and a Kayser–Fleisher ring are pathognomonic of Wilson's disease. The "eye of the tiger" sign cannot be missed in the globus pallidus by MRI in Hallervorden-Spatz disease (PANK-2).
Rapid dementia with myoclonus in an adult is Creutzfeldt-Jacob disease until proven otherwise. The 14-3-3 protein and neuron specific enolase as well as a characteristic EEG support the diagnosis. Late severe Alzheimer's disease may demonstrate myoclonus, but the loss of memory and cognitive impairment has made the diagnosis of Alzheimer's long before myoclonus is prominent. Both may have anterior cell involvement with fasciculations. Diffuse Lewy body disease may be associated with myoclonus, but visual hallucinations, transient loss of consciousness, falls and fluctuations in cognitive abilities are its most prominent characteristics. Palatal myoclonus cannot be missed if the palate is examined. Rhythmic contractions of the platysma muscle, clicking in the ears and ocular and diaphragmatic movements secure the diagnosis. Rhythmic palatal myoclonus has torsional and rotary nystagmus while in the midline form pendular nystagmus is noted.
The spinocerebellar ataxias, particularly SCA3/Machado–Joseph disease have myoclonus as a component of the movement disorder. Bulging eyes and amyotrophy often are present.
Propriospinal myoclonus is striking with axial and extremity arrhythmic jerks. The myoclonus of the abdomen is striking.
Myoclonus diagnosed in the office is primarily a hereditary form, part of an ataxic syndrome or rarely a fragment of seizure activity.
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