Common Etiologies of Postural Tremor
The most common causes of postural tremor are physiological tremor, essential tremor, and drug-induced tremor, with essential tremor being the most prevalent movement disorder globally affecting approximately 1% of the general population 1, 2.
Primary Etiologies
Essential Tremor (Most Common)
- Bilateral 4-8 Hz kinetic and postural tremor with regular, rhythmic EMG bursts 3
- Affects ~1% of general population, 5% of those over 65 years 2
- 50% report affected relatives; 7% report alcohol improvement 4
- Predominantly involves upper limbs, may include cephalic tremor 4
- Results from cerebello-thalamo-cortical pathway dysfunction 3, 2
Physiological Tremor (Enhanced)
- Normal tremor that becomes exaggerated by metabolic, toxic, or emotional factors 1, 5
- Typically 8-12 Hz, fine amplitude
- Reversible when precipitating factor removed
Drug-Induced Tremor
Psychiatric medications are major culprits 6:
- Lithium - most common psychiatric drug causing postural tremor
- Valproic acid - dose-dependent tremor
- Lamotrigine - postural tremor reported
- Antidepressants - SSRIs, SNRIs can induce tremor
- Neuroleptics - both typical and atypical agents
- Other medications: carbamazepine, phenytoin, antihypertensives, cardiovascular medications 7
Parkinsonian Postural Tremor
- 4-6 Hz "re-emergent" postural tremor that appears after latency when holding posture 3
- May coexist with classic 4-6 Hz rest tremor
- Driven by abnormal pallido-thalamo-cortical oscillations 3
- Accounts for ~10% of postural tremor referrals 4
Secondary/Less Common Etiologies
Metabolic Tremor
- Thyrotoxicosis - should be considered in any recent-onset postural tremor 1
- Hypoglycemia
- Hypocalcemia - particularly relevant in 22q11.2 deletion syndrome 8
Cerebellar Tremor
- Predominantly axial postural tremor, 3-10 Hz, often frequency-jumping 9
- Associated with cerebellar pathology (degeneration, tumors, multiple sclerosis)
- May have subclinical palatal involvement 9
Dystonic Tremor
- Frequently unilateral, irregular, position- or task-specific 3
- 3-5 Hz oscillations superimposed on dystonic co-contractions
- Arises from cerebello-thalamo-cortical disturbances 3
Tremor in Hepatic Encephalopathy
- Asterixis ("flapping tremor") - actually a negative myoclonus, not true tremor 10
- Loss of postural tone elicited by wrist hyperextension
- Can occur in feet, legs, arms, tongue, eyelids
- Not pathognomonic (also seen in uremia) 10
Parkinson-Plus Syndromes
- Multiple system atrophy, progressive supranuclear palsy, corticobasal degeneration 11
- Postural tremor with additional atypical parkinsonian features
Rare but Important Causes
- Wilson's disease - critical to identify, treatable 1
- Fragile X-associated tremor/ataxia syndrome - important genetic cause 1
- Hirayama disease - can mimic essential tremor in young men with asymmetric postural tremor and distal muscle wasting 12
Clinical Pitfalls
Red flags arguing against essential tremor:
- Onset before age 20 or very asymmetric presentation
- Absence of family history in young patients
- Muscle wasting or weakness
- Involvement of finger joints rather than wrists/elbows 12
- Irregular or jerky quality
- Task-specificity or position-dependence
- Associated neurological signs (dysarthria, ataxia, rigidity)
Key diagnostic discriminators 4:
- Affected relatives (77% sensitivity for ET)
- Synchronous EMG pattern (79% sensitivity for ET)
- Alcohol improvement (100% specificity but only 7% of ET patients)
- Cephalic tremor (80% sensitivity for ET)
The diagnostic approach relies primarily on clinical history and examination, as neuroimaging and laboratory tests are typically normal in essential tremor 5. Consider metabolic workup (thyroid function, calcium, glucose) and medication review in all cases of new-onset postural tremor.