- Overview of Ataxia
- Ataxia: Impaired coordination of voluntary movement.
- Truncal Ataxia: Inability to maintain posture of the trunk. Pt has a wide-based, unsteady, “drunken sailor” gait. Tends to fall when sitting or standing still.
- Appendicular Ataxia: Affects limbs. Manifests as intention tremor, dysmetria (overshooting/undershooting), dysdiadochokinesia.
- Cerebellar Speech (Scanning Dysarthria): Speech is slow, slurred, and has a “scanning” quality with variable volume.
- Midline Lesion (Vermis/Spinocerebellum)
- Function: Controls axial & truncal musculature, proximal limbs, and gait.
- Clinical Features:
- Truncal ataxia is the hallmark. Pt cannot sit or stand without falling over, despite having normal strength.
- Wide-based gait.
- May have nystagmus and dysarthria.
- Minimal to no appendicular ataxia.
- Common Etiologies:
- Chronic alcoholism leading to degeneration of the anterior vermis.
- Medulloblastoma in children.
- Stroke (e.g., PICA or AICA infarcts affecting midline structures).
- Lateral Lesion (Hemispheres/Cerebrocerebellum)
- Function: Motor planning for extremities (Distal limbs).
- Clinical Features:
- Appendicular ataxia is the hallmark. Deficits are ipsilateral to the lesion.
- Intention tremor: Tremor worsens as the hand approaches the target.
- Dysmetria: Inability to judge distance (e.g., overshooting on finger-to-nose test).
- Dysdiadochokinesia: Impaired ability to perform rapid, alternating movements (e.g., pronation/supination of the hands).
- Patients tend to fall toward the side of the lesion.
- Common Etiologies:
- Stroke (PICA/AICA/SCA territory infarcts).
- Brain tumor (e.g., astrocytoma, metastasis).
- Multiple sclerosis.
- Flocculonodular Lobe Lesion (Vestibulocerebellum)
- Function: Input from vestibular nuclei; controls vestibulo-ocular reflex (VOR), balance, and eye movements.
- Clinical Features:
- Nystagmus (esp. vertical or direction-changing).
- Vertigo, dizziness, nausea/vomiting.
- Inability to maintain balance; often falls backward.
- Very similar presentation to peripheral vertigo, but cerebellar nystagmus is not suppressed by visual fixation.
- Common Etiologies:
- Medulloblastoma in children (arises from cerebellar roof near the 4th ventricle).
- Ependymoma in children.
- Stroke.