What is Ataxia
Ataxia is the inability to generate coordinated voluntary movement, manifesting clinically as clumsiness, nystagmus, dysmetria, abnormal or unsteady gait, dysdiadochokinesis, or dyssynergia 1.
Core Definition and Pathophysiology
Ataxia represents a neurological sign indicating loss of coordination of muscle movement due to dysfunction in one or more components of the nervous system 2. While cerebellar dysfunction is the dominant cause, particularly in children, disruptions in multiple neuronal circuits can produce ataxia 1:
- Cerebellum (most common) - affects neural information integration, coordination, and planning
- Basal ganglia
- Cerebral cortex (frontal lobe and thalamic lesions can cause gait and limb ataxia)
- Spinal cord and peripheral nerves - affects proprioception (sensory ataxia)
- Vestibular system - affects balance and equilibrium maintenance
Clinical Manifestations by Location
Truncal ataxia indicates cerebellar vermian pathology 1.
Sensory ataxia can be revealed by a positive Romberg test examining the dorsal columns, and worsens when movements are made with eyes closed 1, 3.
Vestibular dysfunction produces a lurching gait triggered by head rotation 1.
Ataxia with hemiparesis suggests cerebral infarct involving the thalamus, pons, corona radiata, or internal capsule 2.
Important Mimics and Pitfalls
Several conditions can mimic ataxia 1:
- Muscle weakness and hypotonia causing gait and postural abnormalities
- Postictal ataxia in children with epilepsy
- "Pseudoataxia" occurring with functional disorders
- Hydrocephalus
Temporal Classification
Acute ataxia develops within hours or days, typically presenting within 72 hours 1. Common causes include:
- Infectious/postinfectious (most common in children - approximately 50% of emergency presentations)
- Inflammatory
- Toxic
- Ischemic
- Traumatic etiologies
Chronic ataxia lasts longer than 2 months 1. Nonprogressive forms suggest congenital brain malformation or early prenatal/perinatal injury, while progressive forms indicate inherited causes or acquired posterior fossa lesions 1.
Intermittent/episodic ataxia may represent migraine, benign positional vertigo, or intermittent metabolic disorders 1.
Epidemiology
The estimated prevalence of childhood ataxia from genetic and acquired causes is approximately 26 per 100,000 children, with regional variations based on consanguinity rates and infectious disease prevalence 1.
Underlying Mechanism
The basic mechanism involves an inability to coordinate the relative activity of multiple muscles and adjust movements at a given joint for the effects of other moving joints (interaction torques) 3.