Can intention tremor be unilateral?

Intention Tremor: Definition and Unilateral Presentation

Intention tremor is a type of kinetic tremor that worsens as the affected limb approaches a target during voluntary movement, and it can indeed present unilaterally, particularly when associated with focal cerebellar lesions or certain neurological conditions.

Definition and Characteristics of Intention Tremor

• Intention tremor is characterized by an involuntary, rhythmic oscillatory movement that increases in amplitude as the affected body part approaches a target during purposeful movement 1
• Unlike postural tremor (which occurs when maintaining a position against gravity), intention tremor specifically worsens during the terminal phase of goal-directed movements 1, 2
• The frequency of intention tremor typically ranges from 1.9-5.8 Hz, which is generally slower than other tremor types 3

Unilateral Presentation of Intention Tremor

• Intention tremor can absolutely present unilaterally, particularly when caused by focal lesions affecting the cerebellum or its connections on one side 1, 2
• Unilateral intention tremor is often associated with ipsilateral cerebellar pathology, such as cerebellar strokes, tumors, or other focal lesions 1
• Neurophysiological studies have confirmed that unilateral intention tremor correlates with abnormal activity in the contralateral thalamic nuclei (particularly the ventral intermediate nucleus - Vim), which receive cerebellar projections 3, 4

Common Causes of Unilateral Intention Tremor

• Focal cerebellar lesions including:
  • Cerebellar strokes affecting one cerebellar hemisphere 1
  • Cerebellar tumors or space-occupying lesions 1
  • Demyelinating lesions (such as in multiple sclerosis) affecting cerebellar pathways 1
• Advanced essential tremor can develop an intentional component that may be asymmetric or unilateral 5, 4, 2
• Certain forms of spinocerebellar ataxias may present with asymmetric intention tremor 1

Diagnostic Considerations

• Neuroimaging (particularly MRI) is essential when evaluating unilateral intention tremor to identify potential structural lesions 1
• Electrophysiological studies can help differentiate intention tremor from other tremor types by analyzing frequency, amplitude, and phase relationships 3, 4
• Clinical examination should assess for other cerebellar signs that often accompany intention tremor, such as dysmetria, dysdiadochokinesia, and ataxic gait 2

Clinical Pearls and Pitfalls

• Don't confuse intention tremor with other forms of kinetic tremor; true intention tremor specifically worsens as the limb approaches the target 1
• Intention tremor can affect various body parts beyond the limbs, including the head and chin in some patients 5
• Patients with essential tremor who develop intention tremor (ET-IT) tend to be older and more likely to have head and trunk involvement compared to those with purely postural essential tremor 2
• The presence of unilateral intention tremor should prompt a thorough evaluation for underlying cerebellar pathology, as it may be the presenting sign of a serious neurological condition 1, 2