In an adult presenting with a movement disorder, how should I classify it as hyperkinetic or hypokinetic, define the specific phenotype, and initiate appropriate management?

Movement Disorders in Adults: Classification, Definition, and Management

Initial Classification: Hypokinetic vs. Hyperkinetic

Begin by categorizing the movement disorder as either hypokinetic (reduced movement) or hyperkinetic (excessive movement), as this fundamental distinction drives all subsequent diagnostic and therapeutic decisions. 1, 2

Hypokinetic Disorders (Parkinsonian Syndromes)

• Characterized by bradykinesia plus either rigidity or resting tremor 3
• Test for bradykinesia by observing finger tapping, hand opening/closing, and rapid alternating movements 3
• Check for rigidity by passively moving limbs while the patient relaxes, noting any cogwheel phenomenon 3
• Include idiopathic Parkinson's disease and atypical parkinsonian syndromes 1

Hyperkinetic Disorders

• Encompass chorea, ballism, tremor, dystonia, myoclonus, and tics 4, 5
• Most acute presentations are hyperkinetic, though some are mixed 2
• Caused by disturbances in circuitry connecting cerebral cortex, thalamus, basal ganglia, and cerebellum 4

Specific Hyperkinetic Phenotypes: Definitions and Key Features

Dystonia

• Sustained or intermittent muscle contractions causing abnormal postures 5
• May be focal, segmental, or generalized based on body distribution 6
• Deep brain stimulation has a well-defined role in medically refractory cases 6

Chorea

• Irregular, flowing, dance-like involuntary movements 4, 5
• Includes Huntington disease as prototypical example 1
• Symptomatic pharmacological treatment remains the mainstay 6

Tremor

• Rhythmic oscillatory movements 5
• Can be resting (Parkinson's), action (essential tremor), or postural 3
• Internal tremor sensations may precede visible tremor in Parkinson's disease 3

Myoclonus

• Sudden, brief, shock-like jerks 5
• Address prejerk cognitions including anxiety, frustration, and breath-holding 7
• Diaphragmatic breathing and progressive muscular relaxation can be beneficial 7

Tics

• Very brief jerks or dystonic postures, typically shorter than paroxysmal dyskinesia attacks 1
• Cardinal features of Tourette syndrome 6
• Pimozide is superior to haloperidol in efficacy and side effects for tic control 7

Ballism

• Large-amplitude, flinging movements typically affecting proximal limbs 4

Paroxysmal Movement Disorders: Critical Distinctions

Paroxysmal Kinesigenic Dyskinesia (PKD)

• Triggered by sudden voluntary actions (standing, starting to run, getting on/off a car) 1
• Attacks last seconds to minutes, consciousness preserved 1
• Carbamazepine 50-200 mg/day achieves complete remission in >85% of patients 7
• Start at 50 mg (or 1 mg/kg in children), titrate based on response 7
• Screen for HLA-B*15:02 in Han Chinese populations before initiating carbamazepine to reduce Stevens-Johnson syndrome risk 7
• Oxcarbazepine 75-300 mg/day is an alternative option 7

Paroxysmal Nonkinesigenic Dyskinesia (PNKD)

• Triggered by nonkinesigenic factors: tea, coffee, alcohol, psychological stress, fatigue 1
• Attacks last 10 minutes to 1 hour, longer than PKD 1
• Lower attack frequency than PKD 1

Paroxysmal Exercise-Induced Dyskinesia (PED)

• Induced by prolonged or continuous exercise (5-30 minutes) 1
• Not triggered by nonkinesigenic factors like cold, alcohol, or coffee 1
• Duration ranges 5-45 minutes, typically not exceeding 2 hours 1

Differential Diagnosis: Critical Distinctions

PKD vs. Frontal Lobe Epilepsy

• PKD has clear kinesigenic trigger and preserved consciousness during attacks 1
• Frontal lobe epilepsy may have slight consciousness disturbance and can occur during sleep 1
• PKD only occurs when patients are awake 1

Functional (Psychogenic) Movement Disorders

• Red flags: distractibility, variability between paroxysms, suggestibility 1
• Adult age of onset, altered responsiveness during attacks, medically unexplained somatic symptoms 1
• Atypical response to medications 1
• Video recording interventions demonstrates symptom changeability and highlights successes 7

Management Algorithm

Step 1: Identify and Address Reversible Causes

Always check serum calcium first, as hypocalcemia can induce or worsen any movement disorder 3

• Obtain parathyroid hormone if calcium is low 3
• Check magnesium levels, as hypomagnesemia frequently coexists with hypocalcemia 3
• Measure TSH to exclude thyroid dysfunction 3
• Check glucose in diabetic patients, as hypoglycemia produces tremor sensations 3

Step 2: Medication Review

Drugs are a common cause of movement disorders 4

• Primary intervention is discontinuation or dose reduction of the offending agent when clinically feasible 8
• Switch to lower-risk agents (quetiapine or clozapine for antipsychotics) when complete discontinuation is not possible 8
• Drug-induced tremor usually resolves after discontinuation 3
• Distinguish drug-induced effects from disease progression by decreasing dose or stopping medication 7

Step 3: Drug-Induced Parkinsonism Management

For drug-induced parkinsonism and acute dystonia, initiate benztropine 1-4 mg once or twice daily 8

• Most effective for tremor and rigidity components 8
• Avoid benztropine in elderly patients with Alzheimer's disease or dementia due to anticholinergic cognitive side effects 8
• Use anticholinergic medications with caution in elderly patients 8

Step 4: Specific Hyperkinetic Disorder Management

Dystonia

• Encourage optimal postural alignment with even weight distribution in sitting, standing, and walking 7
• Grade activities to increase affected limb use with normal movement techniques 7
• Avoid end-range joint positioning (full hip, knee, or ankle flexion while sitting) 7
• Support the affected limb at rest using pillows or furniture to reduce overactivity, pain, and fatigue 7
• Address pain and hypersensitivity as associated problems 7
• Do not discourage splinting, as it may prevent restoration of normal movement and potentially trigger complex regional pain syndrome 7

Functional Tremor

• Superimpose alternative voluntary rhythms on existing tremor, gradually slowing to complete rest 7
• Use the unaffected limb to dictate a new rhythm (tapping or opening/closing the hand) to entrain tremor to stillness 7
• Assist muscle relaxation to prevent cocontraction 7
• Use gross rather than fine movements (large marker on whiteboard versus normal handwriting) 7
• Discourage cocontraction or tensing as a tremor suppression method 7

Functional Jerks/Myoclonus

• Address prejerk cognitions: anxiety, frustration, and breath-holding 7
• Implement diaphragmatic breathing and progressive muscular relaxation 7
• Use sensory grounding techniques: noticing environmental details, feeling textured items, cognitive distractors 7
• Encourage slow movement activities (yoga or tai chi) to regain movement control and redirect attention 7

Tourette Syndrome/Tic Disorders

• Pimozide is superior to haloperidol in efficacy and side effects for tic control 7
• Both pimozide and haloperidol are FDA-approved 7
• Deep brain stimulation of CM-Pf thalamus, GPi, or NAc shows substantial improvement in approximately 97% of severe, treatment-refractory cases 7
• DBS should only be considered after failure of standard pharmacological and behavioral therapies in severe cases with significant impact on daily functioning 7

Step 5: Monitoring and Re-evaluation

• Regular monitoring using standardized scales like the Abnormal Involuntary Movement Scale (AIMS) every 3-6 months 8
• Periodically re-evaluate treatment necessity by assessing chorea effect versus adverse effects 7
• Correct metabolic abnormalities before attributing symptoms to disease progression or psychiatric causes 3

Critical Clinical Pitfalls

• If anticholinergic medication is added during initial antipsychotic treatment, maintain it well after antipsychotic discontinuation to prevent delayed emergence of symptoms 8
• In psychiatric patients requiring antipsychotics, carefully balance the risk of psychotic relapse against the severity of parkinsonian symptoms 8
• Propranolol is first-line for essential tremor but has no established role in managing drug-induced movement disorders 8
• Anxiety management and distraction techniques are helpful across all hyperkinetic symptom types 7
• Refer to movement disorders neurology if diagnostic uncertainty exists about whether symptoms represent early Parkinson's disease, atypical parkinsonism, or another condition 3

Imaging Considerations

MRI is preferred over CT for initial structural imaging assessment 1

• Look for patterns of atrophy, parenchymal abnormality, or abnormal substance deposition 1
• Exclude underlying structural or vascular lesions, autoimmune or infectious processes, drug toxicity, or hydrocephalus 1
• Nuclear medicine studies can evaluate abnormal glucose metabolism patterns, buildup of abnormal proteins, or neurochemical deficits 1