Beyond CDP
Static & Other Balance-Function Tests
Each section is layered for Foundation, Trainee, and Clinician readers — set your reading level in the sidebar.
Showing4of 4 sections·Trainee
In this module
- Static posturography and centre-of-pressure metricsFoundation · Trainee · Clinician
- The (modified) Clinical Test of Sensory Interaction on BalanceFoundation · Trainee · Clinician
- Functional balance and gait measuresTrainee · Clinician
- Choosing the right balance testTrainee · Clinician
Static posturography and centre-of-pressure metrics
Static posturography records postural sway while the patient simply stands quietly on a fixed force plate — no moving platform or visual surround. It is far cheaper than computerised dynamic posturography and is widely available, including on low-cost and research-grade force plates.
The core output is the centre-of-pressure (COP) trajectory and the metrics derived from it: sway path length, the 95% confidence ellipse area, root-mean-square displacement, and mean sway velocity in the anteroposterior and mediolateral directions. Eyes-open and eyes-closed conditions are compared.
The eyes-closed-to-eyes-open ratio — the Romberg quotient — estimates visual dependence: a large increase in sway with eyes closed implies heavy reliance on vision to compensate for somatosensory or vestibular deficit. Static posturography localises poorly but is a sensitive, quantitative screen for instability.
Optic flow and horizon cues. Lost: SOT 2 (eyes closed), 5; degraded SOT 3, 6.
Semicircular canal and otolith input. Lost: bilateral vestibulopathy. Critical for SOT 5 and 6.
Proprioception from feet, ankles and joints. Lost: peripheral neuropathy. Critical for SOT 4–6.
Mixed pattern. Sway broadly tracks total available sensory evidence.
Sway area small, CoP excursion within a narrow envelope.
The (modified) Clinical Test of Sensory Interaction on Balance
The Clinical Test of Sensory Interaction on Balance (CTSIB) is the bedside cousin of the SOT. The patient stands under four (or, in the modified mCTSIB, four) conditions crossing two surfaces (firm floor, foam pad) with two visual states (eyes open, eyes closed), and the examiner times how long balance is maintained.
Foam degrades somatosensory input the way the SOT's sway-referenced platform does; eyes closed removes vision. The eyes-closed-on-foam condition isolates vestibular-dependent balance — the bedside analogue of SOT conditions 5 and 6. Falling or stepping only in that condition points toward a vestibular contribution.
The mCTSIB requires only a foam pad and a stopwatch, costs almost nothing, and reproduces much of the SOT's sensory-conflict logic. It is the pragmatic first-line sensory-integration test where CDP is unavailable, and a reasonable triage to decide who needs formal CDP.
Functional balance and gait measures
Functional measures assess balance during whole-body tasks rather than quiet stance. The Berg Balance Scale, the Timed Up and Go, the Dynamic Gait Index, and the Functional Gait Assessment are validated, equipment-light tools that capture the real-world performance CDP cannot.
These scales predict falls, track rehabilitation, and translate directly into goals patients understand. Their weakness is that they do not separate the sensory contributions to imbalance — a low Berg score tells you the patient is unsteady, not why.
The complementary pairing is therefore CDP (or mCTSIB) to characterise the sensory mechanism, plus a functional scale to quantify the day-to-day impact and to anchor rehabilitation outcomes.
Choosing the right balance test
Match the test to the question. To document the functional impact of a known vestibular deficit and to separate sensory contributions, CDP or mCTSIB earns its place. To screen broadly and cheaply, static posturography and functional scales suffice.
Availability, cost, and the patient's tolerance all bear on the choice — frail or acutely vertiginous patients may manage a Timed Up and Go but not several minutes of sway-referenced stance. No single test is comprehensive; the balance battery is deliberately layered.
Critically, none of these tests localises a lesion. They quantify function, and are interpreted alongside the structural vestibular work-up — calorics, vHIT, VEMPs, and imaging — that answers the where question.