How should I assess truncal ataxia?

Assessment of Truncal Ataxia

Truncal ataxia should be assessed through observation of sitting and standing balance, gait analysis with and without visual input (Romberg test), and examination for associated cerebellar signs, with the key distinguishing feature being whether instability worsens with eye closure (indicating sensory ataxia) or remains unchanged (indicating cerebellar ataxia). 1

Clinical Examination Approach

Observation of Truncal Stability

• Observe the patient sitting unsupported to assess truncal ataxia, as this reveals midline cerebellar dysfunction—patients with truncal ataxia cannot maintain upright posture without support 1
• Look for titubation (rhythmic and spasmodic nodding or swaying of the head or body), which is especially characteristic of midline cerebellar disorders 1
• Truncal ataxia is typical of cerebellar vermian pathology specifically 1

Gait Assessment

• Assess for a wide-based, unsteady gait, which is a hallmark compensatory feature adopted to improve stability 1, 2, 3
• Observe gait pattern for stamping quality due to impaired proprioceptive feedback 2
• Test gait with simultaneous head rotations—a lurching gait triggered by head rotation suggests vestibular dysfunction 1
• Evaluate tandem gait (heel-to-toe walking), as this is particularly sensitive for detecting cerebellar dysfunction 4

Critical Distinguishing Test: Romberg Test

• Perform the Romberg test by having the patient stand with feet together, first with eyes open, then closed 1, 2
• Sensory ataxia shows dramatic worsening with eye closure (positive Romberg), as patients rely heavily on visual guidance for balance when proprioception is impaired 2, 3
• Cerebellar ataxia remains relatively unchanged with eye closure (negative Romberg), as the coordination centers themselves are damaged regardless of visual input 2, 3

Associated Signs to Examine

Cerebellar Signs

• Check for nystagmus, dysmetria, and intention tremor—their presence confirms cerebellar pathology 2
• Assess limb ataxia using finger-to-nose and heel-to-shin testing 1
• Evaluate for dysarthria and dysdiadochokinesis (inability to perform rapid alternating movements) 1, 5
• Examine oculomotor function, particularly saccades and vestibulo-ocular reflex, as these are helpful for differential diagnosis 5

Sensory and Motor Signs

• Test for sensory loss and hyporeflexia, which accompany sensory ataxia due to peripheral neuropathy or dorsal column dysfunction 1, 2, 3
• Assess for weakness, hyperreflexia, and spasticity, which suggest spinal cord involvement 1
• Check for pupillary abnormalities, which may suggest drug/toxin ingestion or cranial nerve compression 1

Vestibular Signs

• Look for nausea, vomiting, and vertigo, which suggest vestibulo-cerebellar system involvement 1
• Assess for torticollis or resistance to head/neck motion, which may indicate craniocervical junction pathology or posterior fossa tumor 1

Quantitative Assessment Methods

• Trunk sway measurements during stance and gait can quantify severity—patients with cerebellar ataxia show significantly larger trunk angle displacement and angular velocity in both pitch (anterior-posterior) and roll (lateral) directions 4
• Pitch plane instability typically dominates over roll instability in cerebellar ataxia, especially when standing on foam, with pronounced oscillations at 1.4 and 2.5 Hz 4
• Within-subject variability of trunk-thigh coordination correlates negatively with clinical severity scores 6

Common Pitfalls to Avoid

• Do not assume all truncal ataxia is cerebellar—always perform the Romberg test to distinguish sensory from cerebellar causes, as management differs significantly 2, 3
• Do not overlook associated signs—pure ataxia is rare in acquired disorders; associated symptoms almost always exist to suggest the underlying cause 7
• Do not miss acute presentations—truncal ataxia with headache and altered consciousness may indicate acute cerebellitis with risk of herniation, requiring urgent imaging 1
• In children, recognize that detailed neurological examination is often challenging, making clinical observation of gait and posture particularly important 1