Intention Tremor is Cerebellar
Intention tremor is a hallmark sign of cerebellar dysfunction, not basal ganglia pathology. This tremor characteristically increases in amplitude during goal-directed movements and is a classic cerebellar sign observed during finger-to-nose or heel-to-shin testing 1.
Anatomical Localization
Intention tremor specifically indicates cerebellar or cerebellar pathway dysfunction, distinguishing it from the resting tremor characteristic of basal ganglia disorders like Parkinson's disease 2, 1.
The cerebellum and its connections (cerebellar inflow/outflow pathways through the brainstem) are the primary anatomical substrates responsible for intention tremor 3.
In multiple sclerosis patients with intention tremor, lesion load correlates significantly with brainstem (particularly pontine) pathology affecting cerebellar pathways, not with basal ganglia involvement 3.
Clinical Distinction from Basal Ganglia Tremor
Basal ganglia pathology produces resting tremor (as seen in Parkinson's disease), characterized by tremor present at rest that diminishes with voluntary movement 2.
Parkinsonian syndromes demonstrate tremor, rigidity, postural instability, and bradykinesia due to degeneration of dopaminergic neurons in the substantia nigra/striatum (basal ganglia structures) 2.
The tremor pattern fundamentally differs: cerebellar intention tremor worsens during movement execution, while basal ganglia resting tremor improves with intentional action 2, 1.
Cerebellar Tremor Spectrum
While intention tremor is the most recognized cerebellar tremor type, cerebellar dysfunction can produce a heterogeneous spectrum including postural tremors, kinetic tremor, and even the characteristic "wing-beating" tremor described in Wilson's disease (though Wilson's also involves basal ganglia) 2, 4.
Essential tremor, increasingly recognized as a form of cerebellar degeneration, demonstrates intention tremor in 25% of patients with moderate-to-severe disease and mild intentional components in another 33% 5, 6.
Fragile X tremor/ataxia syndrome (FXTAS) presents with progressive intention tremor and ataxia in older premutation carriers, further confirming the cerebellar localization of intention tremor 2.
Diagnostic Approach
MRI is the preferred imaging modality to evaluate intention tremor, focusing on the cerebellum, brainstem, and cerebellar pathways 2, 1.
Morphologic changes (atrophy) and signal alterations primarily involve the cerebellum and brainstem in patients with intention tremor, not the basal ganglia 2.
Clinical examination should assess for other cerebellar signs including dysmetria (over/under-reaching targets), ataxia, and dysdiadochokinesia to confirm cerebellar localization 1.