Movement Disorders: Comprehensive Diagnosis and Management
Overview and Classification
Movement disorders encompass both hypokinetic disorders (Parkinsonian syndromes) and hyperkinetic disorders (including dystonia, chorea, tremor, tics, and myoclonus), with diagnosis requiring systematic identification of specific clinical patterns and exclusion of secondary causes 1.
Diagnostic Approach
Initial Clinical Assessment
Identify the specific movement disorder phenotype by observing:
- Dystonia: Sustained or intermittent muscle contractions causing twisting, repetitive movements, and abnormal postures that are typically spasmodic and follow a stereotyped pattern 2, 3
- Tremor: Rhythmic oscillatory movements that can be resting, postural, or action-related 3
- Chorea: Irregular, flowing, dance-like involuntary movements 3
- Myoclonus: Brief, shock-like jerks 3
- Tics: Stereotyped, suppressible movements or vocalizations 3
- Parkinsonism: Bradykinesia, rigidity, resting tremor, and postural instability 1
Key Diagnostic Pitfalls
Dystonia is frequently misdiagnosed as:
- Tremor (particularly when dystonic tremor is present) 3
- Parkinson's disease 3
- Psychogenic/functional neurological disorder 4
- Myoclonus, chorea, or tics 3
Red flags for functional (psychogenic) movement disorders include:
- Distractibility and variability between episodes 4
- Suggestibility 4
- Adult onset with altered responsiveness during attacks 4
- Atypical medication response 4
Imaging and Laboratory Evaluation
Structural Imaging
MRI brain without contrast is the initial imaging modality of choice for all movement disorders 1:
- Evaluate for patterns of atrophy, parenchymal abnormality, or abnormal substance deposition 1
- Exclude structural lesions, vascular disease, autoimmune/infectious processes, medication toxicity, or hydrocephalus 1
- Look for specific patterns: "eye-of-the-tiger sign" in neurodegeneration with brain iron accumulation (NBIA), showing T2 hyperintensity within the anteromedial globus pallidus 1
CT head has limited utility except to distinguish calcium from iron deposition or when MRI is contraindicated 1.
Advanced Imaging
Consider advanced MRI techniques when diagnosis remains uncertain:
- Diffusion tensor imaging to assess white matter tract integrity 1
- Magnetization transfer ratio imaging for microstructural analysis 1
- Quantitative volumetric analysis 1
Nuclear medicine studies (FDG-PET, dopamine transporter imaging) can evaluate:
- Abnormal glucose metabolism patterns 1
- Neuronal dysfunction or loss 1
- Differentiation of drug-induced from neurodegenerative parkinsonism 1
Laboratory Testing
Essential screening tests to exclude secondary causes:
- Serum ceruloplasmin and 24-hour urinary copper for Wilson's disease 4
- Calcium, parathyroid hormone, and magnesium for hypoparathyroidism-related dystonia 1, 4
- Thyroid function tests 1
- Glucose metabolism assessment 4
- Genetic testing for PRRT2 mutations in paroxysmal kinesigenic dyskinesia 4
Specific Movement Disorders
Cervical Dystonia (CD)
Clinical Features:
- Involuntary neck muscle contractions causing abnormal head postures: torticollis (turning), laterocollis (lateral flexion), retrocollis (extension), or anterocollis (flexion) 2
- Movements are typically spasmodic, repeated in stereotyped patterns, initially mild and intermittent but becoming constant with progression 2
- Associated head tremor (dystonic head tremor) occurs in 57.6% of patients 5
- Pain is common 2
- Reduced voluntary neck movement range 2
Diagnosis:
- Based on identification of typical symptoms and clinical signs 2
- Most often primary (unknown cause), but exclude secondary causes including Wilson's disease, multiple sclerosis, basal ganglia calcification, cerebrovascular disease, traumatic brain injury, and medication-induced dystonia 4
Management:
Botulinum toxin injection into affected neck muscles is the treatment of choice 1, 2:
- Proven efficient and safe with good long-term efficacy and quality of life in the majority of patients 2
- For patients with dystonic head tremor, bilateral injections are more commonly required in splenius capitis, sternocleidomastoid, trapezius, and obliquus capitis inferior muscles 5
- Patients with head tremor may demonstrate better treatment response with longer follow-up 6
Adjunctive treatments:
- Nerve-stabilizing agents (pregabalin, gabapentin, duloxetine) for pain management and spasm control 1
- Referral to rehabilitation specialist for comprehensive neuromusculoskeletal management 1
- Physical therapy to improve range of motion 1
For refractory cases with unsatisfactory response to botulinum toxin:
- Bilateral deep brain stimulation (DBS) of the globus pallidus internus (GPi) should be considered 7, 2
- DBS can achieve 56% improvement in severity, 52% in disability, and 38.5% in pain scores at 12 months 7
- Combination targeting (Vim thalamus plus bilateral GPi) may be used for severe dystonic tremor 7
Acute Dystonia
Clinical Presentation:
- Sudden spastic contraction of distinct muscle groups, most commonly neck, eyes, or torso, which can be life-threatening when laryngospasm occurs 8
Risk Factors:
- Young age (children and adolescents at highest risk) 8
- Male gender 8
- High-potency dopamine D2 receptor antagonists 8
- Initial treatment phases or dose increases of antipsychotic medications 8
Management:
Immediate treatment with anticholinergic or antihistaminic medications is required 8:
- Benztropine 1-2 mg IV/IM provides rapid relief within minutes 8
Prophylaxis:
- Consider prophylactic antiparkinsonian agents in high-risk patients: young males on high-potency agents or those with prior dystonic reactions 8
- Particularly important in patients with compliance concerns 8
- Reevaluate need after acute treatment phase or if antipsychotic doses are lowered 8
- Dystonic reactions are highly distressing and represent a common reason for medication noncompliance, increasing relapse risk and morbidity 8
Paroxysmal Kinesigenic Dyskinesia (PKD)
Diagnostic Criteria:
Core symptoms:
- Kinesigenic triggers (sudden voluntary movement) with attacks presenting as dystonia, chorea, ballism, or combinations 1
- No impairment of awareness during attacks 1
Supportive evidence:
- Presence of aura 1
- Attack duration <1 minute 1
- Positive high-knee exercise test 1
- Good response to low-dose voltage-gated sodium channel blockers, especially carbamazepine/oxcarbazepine 1
Differential Diagnosis - Exclude:
- Epileptic seizures (focal seizures with impaired awareness can mimic PKD) 1
- Psychogenic disorders (look for distractibility, variability, suggestibility) 1
- Tics (much briefer duration than PKD attacks) 1
- Hyperekplexia (triggered by sudden noise/touch, present from birth) 1
Genetic Testing:
- PRRT2 gene mutations (chromosome 16p11.2) are the major cause, with c.649dupC being a hotspot mutation 4
- Other genes: PNKD, SLC2A1, SCN8A, KCNMA1, KCNA19, DEPDC5 4
Parkinson's Disease and Atypical Parkinsonism
Clinical Features:
- Bradykinesia, rigidity, resting tremor, postural instability 1
- Adults with 22q11.2 deletion syndrome have increased risk of early-onset Parkinson's disease 1
Imaging:
- MRI shows decreased magnetization transfer ratio and functional anisotropy within substantia nigra 1
- Dopaminergic imaging assists in differentiating drug-induced from neurodegenerative parkinsonism 1
Management:
- Standard dopaminergic therapy 1
- For 22q11.2DS patients, use "start low, go slow" approach to medication dosing 1
Neurodegeneration with Brain Iron Accumulation (NBIA)
Clinical Presentation:
- Progressive gait disturbances, dystonia, dysarthria, spasticity, pyramidal tract signs 1
- Typically presents in first decade 1
Imaging:
- MRI demonstrates the pathognomonic "eye-of-the-tiger sign": T2 hyperintensity within the anteromedial globus pallidus surrounded by T2 hypointensity 1
- This finding reflects focal gliosis and vacuolization within a background of iron deposition 1
- May not be present in all cases and can change or disappear over time 1
- Increased fractional anisotropy in globus pallidus and substantia nigra on diffusion tensor imaging 1
Motor Neuron Disease (Amyotrophic Lateral Sclerosis)
Clinical Features:
- Hypertonicity and hyperreflexia (upper motor neuron) 1
- Muscle fasciculations, weakness, and atrophy (lower motor neuron) 1
Diagnosis:
- Electromyography and nerve conduction velocity are key diagnostic tests 1
- Imaging primarily used to exclude other conditions rather than confirm ALS 1
Rapidly Progressive Dementia/Creutzfeldt-Jakob Disease
Differential Diagnosis:
- 62% prion disease, 15% other neurodegenerative diseases, 8% autoimmune, 4% infectious, with 17% potentially treatable etiologies 1
Imaging:
- MRI is essential to evaluate for characteristic patterns and exclude reversible causes 1
Special Populations and Considerations
22q11.2 Deletion Syndrome
Neurologic manifestations include:
- 4-fold increased risk of epilepsy (various seizure types) 1
- Increased risk of early-onset Parkinson's disease 1
- Parkinsonism, dystonia, functional neurologic disorders more common 1
- Myoclonus, motor tics, restless legs, tremors, drug-induced movement disorders 1
Management considerations:
- Hypocalcemia may induce or worsen movement disorders and seizures 1
- Regular monitoring of calcium, parathyroid hormone, magnesium, thyroid function 1
- Increased risk during biological stress (surgery, infection, childbirth) 1
- Psychiatric medications may require "start low, go slow" dosing approach 1
Laryngeal Dystonia and Movement Disorders
Laryngeal electromyography (LEMG) has established utility for:
- Diagnosis of vocal fold movement disorders 1
- Guiding botulinum toxin injections into laryngeal muscles 1
LEMG has unknown diagnostic validity for:
- Upper motor neuron disorders involving the larynx 1
- Laryngeal dystonia and vocal tremor 1
- Muscle tension dysphonia 1
- Psychogenic dysphonia and malingering 1
Treatment Principles Across Movement Disorders
Pharmacologic Management
Dystonia:
- Botulinum toxin is first-line for focal dystonias 1, 2
- Nerve-stabilizing agents (pregabalin, gabapentin, duloxetine) for pain and spasm control 1
- Anticholinergics for acute dystonic reactions 8
Tremor:
- Treatment depends on tremor type and underlying etiology 3
- Dystonic tremor often responds to botulinum toxin targeting dystonic muscles 5
Surgical Management
Deep brain stimulation indications:
- Refractory cervical dystonia with inadequate response to botulinum toxin 7, 2
- Bilateral GPi targeting is standard 7, 2
- Can achieve substantial improvements in severity, disability, and pain 7
Rehabilitation
Physical and occupational therapy:
- Essential for spinal accessory nerve palsy post-neck dissection 1
- Improves range of motion and functional abilities 1
- Prevents and treats trismus 1
Speech-language pathology:
Monitoring and Follow-up
Regular neurologic assessments should include:
- Screening for seizures and seizure-like episodes 1
- Evaluation for cardinal motor features of Parkinson's disease 1
- Assessment for other movement disorders using standardized rating scales 1
- Monitoring for medication-induced movement disorders 1
Laboratory monitoring: