DIAGNOSTIC TESTING IN MOVEMENT DISORDERS

PARKINSON'S DISEASE

The diagnosis of Parkinson's disease (PD) remains clinical, although tests sometimes are needed to rule out conditions that mimic idiopathic parkinsonism. Calcium, phosphorus, parathyroid hormone levels, and liver function tests help evaluate for hypo- or pseudohypoparathyroidism and hepatic disease, which have been associated with parkinsonism.

CT and MRI of the head especially early in PD, do not show any gross neuropathologic changes.38, 45, 58 In some patients, however, MRI shows a midbrain

MULTIPLE SYSTEM ATROPHY

Multiple system atrophy (MSA) is a general term advocated by Graham and Oppenheimer in 1969 that includes striatonigral degeneration (SND), olivopontocerebellar atrophy (OPCA), and Shy-Drager syndrome (SDS). SND can be difficult to distinguish from PD. On CT scan, the striatum is normal.1, 38 On MRI, there is narrowing of the pars compacta, as is seen in PD. T1 images show putaminal atrophy and high-field-strength T2 images reveal abnormal signal attenuation in the posterolateral putamen.1, 13,

PROGRESSIVE SUPRANUCLEAR PALSY

Progressive supranuclear palsy (PSP) may present with parkinsonism and could be difficult to differentiate from PD prior to the onset of supranuclear gaze abnormalities. Parkinsonism from secondary causes can be evaluated using the tests previously described in the section on PD. PSP patients have normal biochemistry screen, hematology, and urine analysis. CSF findings are nonspecific.¹⁴

Early in PSP, MRI and CT results are normal.21, 38 Later they can distinguish PSP from other parkinsonian

CORTICOBASAL GANGLIONIC DEGENERATION

In early stages, corticobasal ganglionic degeneration (CBGD) can be difficult to distinguish from PD, PSP, and MSA. Conventional laboratory blood tests are normal.⁴⁹ The only helpful abnormality on imaging studies is asymmetric cerebral atrophy.47, 48 The asymmetry sometimes is detected on repeated scan. Functional imaging reveals oxygen hypometabolism in the superior and posterior temporal, inferior parietal, and occipital association areas contralateral to the deficit.¹⁵ There also is

DYSTONIA

Dystonia is a physical sign characterized by sustained muscle contraction, causing twisting, abnormal postures, and repetitive movements. It can be idiopathic (sporadic or inherited) or symptomatic. Marsden³⁴ estimates that one fourth of patients have a secondary dystonia. Most types of dystonia require a minimal workup. Additional investigation depends on several conditions, including body part involved, age at onset, and presence of systemic or central nervous system findings. Testing for

MYOCLONUS

The purpose of investigation is first to study the myoclonus itself and differentiate it from other types of movements such as tics and dystonia. The second purpose of investigation is to find a cause. As in dystonia, the classification of myoclonus is of utmost importance. Investigation depends upon whether the myoclonus is focal, segmental, generalized, unilateral, bilateral, synchronous, or asynchronus, and whether it is stimulus-sensitive or triggered by action.¹⁷ Segmental, rhythmic

HEMIFACIAL SPASM

Hemifacial spasm is characterized by involuntary episodic tonic and clonic movements of facial muscles innervated by the facial nerve. Blood vessels in the posterior circulation compress the seventh nerve root at the entry zone (dolichoectatic vessels). Less frequently, arteriovenous malformations, aneurysms, and tumors cause hemifacial spasm.¹¹ Brain MRI, preferably with MR angiography, should be done on all patients to evaluate for seventh nerve root compression. If MRI is not available, head

CHOREA

Chorea consists of asynchronous involuntary movements that flow from one body part to another in a semipurposive way. Chorea often is generalized, although it can affect the face or lips only. Chorea is a clinical sign that can be a manifestation of underlying metabolic, hereditary, infectious, immunologic, or cerebrovascular disease or toxic exposure.31, 57 It can occur transiently as part of neuronal maturation, or as a drug side effect.31, 57 Family history, drug exposure, and systemic and

HUNTINGTON'S DISEASE

An adult patient with dementia, chorea, and positive family history is easy to diagnose and does not need any further investigation. An adult with chorea or dementia with no family history of Huntington's disease (HD), however, poses a difficulty in diagnosis. The same is true for a young patient with behavioral disturbance, parkinsonism, or chorea and negative family history. In this case, additional testing is necessary. A recent breakthrough was the discovery of expanded unstable CAG

TREMOR DISORDERS

Tremor is a rhythmical involuntary oscillatory movement of a body part. It can occur at rest (resting tremor), with movement (kinetic tremor), or when the body part is voluntarily maintained against gravity (postural tremor). Investigation of a tremor helps find a cause and define the tremor itself—specifically, frequency, amplitude, and muscles involved. Objective tremor recording is based on surface EMG, and recording of movement using accelerometers, potentiometers, movement analysis

WILSON'S DISEASE

WD is characterized by tremendous diversity of neurologic features at onset. It can present with any type of movement abnormality. It is important to have a high index of suspicion for the disease if it is to be diagnosed. WD should be explored in anyone with unexplained neurologic abnormalities involving the basal ganglia or cerebellum, especially before age 40. The gold standard for diagnosis of WD is hepatic copper content on liver biopsy.8, 46 More than 250 µg of copper per gram of dry

TIC DISORDERS

Tics are sudden, transient, repetitive, stereotypic movements. They can be simple or complex, vocal or motor, brief (clonic), or prolonged (dystonic).27, 30 Most tics are primary (idiopathic) and the best known is Gilles de la Tourette's syndrome. The majority of tics occur in childhood and do not need a workup. When a secondary cause is present, other neurologic, cognitive, and behavioral abnormalities are found that direct testing. When a cause is suspected, a blood smear should be checked

CONCLUSION

The diagnosis of movement disorders is mainly clinical. When the history and clinical evaluation is typical of a certain condition, further investigation is unnecessary. Such conditions include essential and physiologic tremor, physiologic myoclonus, tics, adult onset focal dystonia and PD. Neuroimaging is necessary to exclude hydrocephalus or focal lesions presenting with atypical parkinsonism. Few other tests might be helpful in parkinsonism (look for neuroacanthocytosis and