What is the difference between sensory and cerebellar ataxia?

Distinguishing Sensory from Cerebellar Ataxia

The fundamental difference is that sensory ataxia dramatically worsens with eye closure (positive Romberg test), while cerebellar ataxia remains unchanged regardless of visual input. 1, 2

Key Clinical Distinction: The Romberg Test

• Sensory ataxia shows a positive Romberg test – unsteadiness significantly worsens when the patient closes their eyes because they lose visual compensation for impaired proprioception 1, 3
• Cerebellar ataxia shows a negative Romberg test – unsteadiness persists equally with eyes open or closed, as the deficit is in motor coordination rather than sensory feedback 2, 4
• The Romberg test examines dorsal column function and is the single most important bedside tool for this differentiation 1

Anatomical Basis

Sensory Ataxia Origin

• Results from damage to dorsal root ganglia, dorsal columns of the spinal cord, or peripheral sensory nerves – not the cerebellum 3
• Impairs proprioceptive feedback necessary for coordinated movement 5, 6

Cerebellar Ataxia Origin

• Results from damage to the cerebellum and/or its connections (cerebellar peduncles, brainstem pathways) 1, 2
• Impairs motor coordination despite intact sensory feedback 2

Clinical Examination Findings

Cerebellar Ataxia Characteristics

• Wide-based gait that does not improve with visual input 2, 7
• Dysmetria (overshooting/undershooting) on finger-to-nose and heel-to-shin testing 2
• Dysdiadochokinesia (impaired rapid alternating movements) 2
• Truncal instability and titubation, especially with vermian lesions 1, 2
• Dysarthria with scanning or ataxic speech pattern 2
• Ocular dysmetria and gaze-evoked nystagmus 2
• Dyssynergia (loss of coordinated multi-joint movements) 2
• Symptoms persist regardless of lighting conditions 2, 6

Sensory Ataxia Characteristics

• Positive Romberg sign – the defining feature 1, 3, 4
• Gait unsteadiness that dramatically worsens in darkness or with eyes closed 3, 5
• Patients often watch their feet while walking to compensate 5
• Impaired vibratory sensation and proprioception on examination 8
• Absent or reduced deep tendon reflexes if peripheral nerve involvement 8
• May have "stomping gait" due to loss of position sense 5

Diagnostic Workup Differences

For Suspected Cerebellar Ataxia

• MRI of the head without IV contrast is the preferred initial imaging 2, 4
• Look for cerebellar atrophy, structural lesions, or signal abnormalities in cerebellum/brainstem 1, 2
• Add contrast if inflammatory, infectious, or neoplastic causes suspected 1

For Suspected Sensory Ataxia

• MRI of cervical and thoracic spine without IV contrast is the primary imaging 3
• Evaluate dorsal columns for compressive myelopathy, B12/copper deficiency changes, or tabes dorsalis 3
• Electrodiagnostic testing (nerve conduction studies and EMG) to document large fiber sensory neuropathy 3
• Laboratory workup for treatable causes: vitamin B12, copper, neurosyphilis serology 3

Common Causes by Type

Sensory Ataxia Etiologies

• Vitamin B12 deficiency (subacute combined degeneration) 3
• Copper deficiency 3
• Neurosyphilis (tabes dorsalis) 3
• Compressive cervical myelopathy 3
• Sensory neuropathies (diabetic, paraneoplastic, autoimmune) 5, 8
• Friedreich ataxia (combined sensory and cerebellar features) 1

Cerebellar Ataxia Etiologies

• Acute cerebellitis (postinfectious) 1
• Posterior fossa tumors 1
• Stroke (cerebellar infarction or hemorrhage) 1
• Multiple sclerosis and demyelinating diseases 1
• Toxic/metabolic (alcohol, metronidazole, mercury) 1
• Hereditary spinocerebellar ataxias 1
• Paraneoplastic cerebellar degeneration 1

Critical Pitfalls to Avoid

• Do not mistake sensory ataxia for cerebellar ataxia – this leads to incorrect diagnostic workup and delays treatment of potentially reversible causes 3, 5
• Always perform the Romberg test properly – have the patient stand with feet together and arms at sides, then close eyes for 30 seconds 1, 4
• Recognize that some conditions cause mixed ataxia – CANVAS syndrome (Cerebellar Ataxia, Neuropathy, Vestibular Areflexia Syndrome) combines both sensory neuropathy and cerebellar degeneration 8
• Do not overlook vestibular causes – a lurching gait triggered by head rotation suggests vestibular dysfunction rather than cerebellar or sensory ataxia 1
• Always investigate treatable causes first in sensory ataxia (B12, copper, neurosyphilis, compression) before concluding it is idiopathic 3

Rehabilitation Approach Differences

Sensory Ataxia Rehabilitation

• Emphasize visual compensation techniques since patients rely heavily on vision 3
• Ensure adequate lighting in home environment 3
• Prescribe assistive devices (canes, walkers) for additional sensory feedback 3
• Ankle-foot orthoses may improve proprioceptive input 3

Cerebellar Ataxia Rehabilitation

• Focus on repetitive motor training and task-specific practice 2
• Balance and postural training programs 2
• Visual input does not significantly help, so focus on motor strategies 2, 6
• Consider teaching slower, single-joint movements to reduce complexity 6