Clinical Manifestations of Cerebellar Hemispheric Syndrome
Cerebellar hemispheric syndrome presents with ipsilateral limb ataxia, dysmetria, dysdiadochokinesia, tremor, and hypotonia, which significantly impact coordination and motor function on the same side as the cerebellar lesion. 1, 2
Core Clinical Features
Motor Manifestations
- Ipsilateral limb ataxia: Incoordination affecting the arm and/or leg on the same side as the cerebellar hemisphere lesion 3
- Dysmetria:
- Hypermetria (overshooting targets)
- Hypometria (undershooting targets) 2
- Dysdiadochokinesia: Inability to perform rapid alternating movements smoothly 2
- Tremor:
- Action tremor
- Postural tremor
- Kinetic tremor (intention tremor) 2
- Hypotonia: Decreased muscle tone in affected limbs 2, 1
- Impaired check and rebound: Inability to properly control movements against resistance 2
Coordination Deficits
- Decomposition of movement: Multi-joint movements appear broken down into component parts 1
- Isometrataxia: Inability to maintain steady muscle contraction 2
- Impaired fine motor skills: Difficulty with tasks requiring precision 2
- Handwriting abnormalities: Irregular handwriting, sometimes with megalographia (abnormally large writing) 2
Associated Features
Speech and Language
- Ataxic dysarthria: When cerebellar hemispheric syndrome affects speech areas 4
Cognitive Manifestations
- Executive function impairments: When lesions extend to cognitive areas of cerebellum 1
- Visual-spatial processing deficits: Difficulty with spatial orientation tasks 1
- Linguistic function abnormalities: Including disruption of articulatory planning and verbal fluency 1
Distinguishing Features from Other Cerebellar Syndromes
Unlike midline cerebellar (vermis) lesions, hemispheric syndrome:
- Lacks prominent truncal ataxia: Vermis lesions primarily affect trunk stability and gait 3
- Shows minimal gait disturbance: Unless the lesion is extensive or affects the vermis 2
- Demonstrates unilateral symptoms: Affecting the ipsilateral side of the body 3
Clinical Evaluation
When assessing for cerebellar hemispheric syndrome, specific tests include:
- Finger-to-nose test: Reveals dysmetria and intention tremor 2
- Rapid alternating movements: Demonstrates dysdiadochokinesia 2
- Rebound testing: Shows impaired check and rebound phenomena 2
- Handwriting assessment: May reveal irregular letter formation and spacing 2
Diagnostic Imaging
MRI is the preferred imaging modality for evaluating cerebellar pathology 5, 3:
- Allows visualization of hemispheric lesions (stroke, tumors, demyelination)
- Can identify patterns of regional volume loss characteristic of neurodegenerative disorders
- Superior to CT for posterior fossa imaging (CT may miss up to 25% of early cerebellar lesions) 3
Common Pitfalls in Diagnosis
- Mistaking for weakness: Cerebellar ataxia is often misinterpreted as weakness rather than incoordination
- Overlooking cognitive symptoms: Non-motor manifestations may be subtle but significant 1
- Failing to test specific cerebellar functions: Targeted examination is required to identify hemispheric syndrome 2
- Attributing symptoms to peripheral causes: Particularly when tremor or coordination deficits are the primary complaint
Understanding the distinct pattern of ipsilateral motor deficits is crucial for correctly identifying cerebellar hemispheric syndrome and distinguishing it from other neurological disorders that may present with similar symptoms.