Table 5.
Sensor-based balance evaluation in neurological disorders.
| Disease and Number of Studies | Studies with a Control Group | Type and Main Locations of Sensors | Other Measurements | Main Experimental Setups | Main Postural Measures | Main Findings | Clinical-Behavioural Correlations |
|---|---|---|---|---|---|---|---|
| Alzheimer’s disease N = 3 [32,202,203] |
N = 3 [32,202,203] |
1 to 5 IMUs on trunk, waist, legs and thighs | Not performed | Upright stance with open or closed eyes, different BOS amplitudes and surfaces (e.g., firm and foam), as well as during virtual perturbations | Pitch and roll angles; COM displacement; sway velocity, area and path; RMS acceleration | Lower minimal roll angle, larger COM displacement, higher sway area and RMS acceleration in AD than HS | Not significant or not performed |
| Parkinson’s disease N = 17 [114,122,124,125,156,157,158,159,160,161,162,163,164,165,166,167,168] |
N = 16 [114,122,124,125,156,157,158,159,160,161,162,163,164,165,166,168] |
1 to 8 IMUs on trunk, waist, wrists, thighs, shanks and feet; 10 to 22 sEMG on lower limb muscles, lumbar erector spinae, thoracic erector spinae and rectus abdominis | Force plate (COP measures) and infrared optical system | Gait initiation; upright stance with open or closed eyes, different BOS amplitudes and surfaces (e.g., firm and foam), under and not under cognitive load; SOT; ISAW; self-triggered and external postural perturbations; OLS | IMUs: APAs; mean velocity; RMS acceleration; jerkiness; peak-to-peak sway; 95% ellipse area; strategy index. sEMG: amount of variance accounted for; synergy index; ASAs; modulation index |
Correlation between inertial, COP and optical measures; hypometric APAs, higher mean velocity, acceleration size and jerkiness, larger peak-to peak sway and 95% ellipse area, predominant ankle strategy; lower VAF and synergy index, reduced ASAs and muscle modulation in PD than HS | Acceleration changes correlated with PIGD and UPDRS-III scores, strategy index with ABC scores, muscle modulation with postural ability and disease severity in PD |
| Multiple sclerosis N = 11 [118,146,169,170,171,172,173,174,175,176,177] |
N = 10 [118,146,169,170,171,172,173,174,175,177] |
1 to 6 IMUs on trunk, waist, wrists, thighs, shanks and feet | Force plate (COP measures) and infrared optical system | Upright stance with open or closed eyes and different surfaces (e.g., firm and foam); walking tasks (e.g., TUG, timed 25-foot walk, 6-minute walk test); external perturbations (e.g., push and release test, backward perturbation) | RMS acceleration; mean velocity; sway jerk, path length, area; F95%; time to reach stability; coherence of acceleration between trunk and legs | Correlation between inertial and COP measures; larger sway acceleration amplitude, angular trunk range of motion in roll and yaw axes, sway path length and area, reduced ML sway jerk, higher F95%, longer time to reach stability and lower acceleration coherence between trunk and legs in MS than HS | Sway acceleration correlated with ABC and MSWS12 scores; RMS acceleration, displacement, mean frequency and time to reach stability correlated with EDSS scores |
| Huntington’s disease N = 2 [46,204] |
N = 2 [46,204] |
1 to 2 IMUs on trunk and waist | Not performed | Upright stance with open or closed eyes and different BOS amplitudes; sitting, standing and walking | RMS acceleration; total, peak and mean angular excursion | Higher RMS acceleration; larger peak and total excursions in HD than HS | Not significant or not performed |
| Cerebellar ataxia N = 7 [130,190,191,192,193,194,195] |
N = 7 [130,190,191,192,193,194,195] |
1 to 6 IMUs on trunk, waist, wrists, ankles and feet | Force plate (COP measures) | Upright stance with open or closed eyes and different surfaces (e.g., firm and foam); walking tasks and external perturbations (e.g., retropulsion test) | Trunk angular displacement and velocity, sway path length, area of the convex hull, convex polyhedron volume, entropy, 95% of the ellipse sway area | Correlation between inertial and COP measures; larger trunk angular displacement and velocity, sway path length, area of the convex hull, convex polyhedron volume, entropy and 95% of the ellipse sway area in CA than HS | Inertial measures (e.g., trunk angular displacement and velocity) correlated with ICARS scores, Tinetti’s Mobility Index and SARA scores |
| Stroke N = 8 [52,178,179,180,181,182,183,184] |
N = 5 [179,181,182,183,184] |
1 to 5 IMUs on head, trunk, waist and shins | Force plate (COP measures) | Upright stance with open or closed eyes and different BOS amplitudes; walking tasks; functional reach test; Fukuda stepping test; OLS | Body displacement (time, velocity, acceleration); RMS acceleration | Higher maximum and minimum acceleration, LL trunk acceleration, angular velocity in ST than HS | Gyroscope data negatively correlated with Berg balance scale scores |
| Traumatic brain injury N = 7 [123,126,185,186,187,188,189] |
N = 6 [123,126,185,186,188,189] |
1 IMU on waist | Force plate (COP measures) | Upright stance with open or closed eyes, different BOS amplitudes and surfaces (e.g., firm and foam); standard and modified balance error scoring system | RMS acceleration; sway amplitude, velocity, variability and frequency; ellipse and total sway area; 95% ellipsoid sway volume | Higher RMS, total power, mean distance, acceleration range, path length, ellipse and total sway area, 95% ellipsoid sway volume and area in TBI than HS | Self-reported symptoms (e.g., dizziness, headache) correlated with sway path length and postural sway area |
| Neuropathies N = 3 [199,200,201] |
N = 3 [199,200,201] |
1 to 2 IMUs on waist and shin | Force plate (COP measures) | Upright stance with open or closed eyes, different BOS amplitudes and surfaces (e.g., firm and foam) | RMS acceleration; range of acceleration; peak velocity; body sway area | Correlation between inertial and COP measures; higher RMS acceleration, acceleration range, and peak velocity; larger body sway area in NP than HS | Vibration perception threshold negatively correlated with postural control |
| Vestibular syndromes N = 4 [196,197,198,199] |
N = 4 [196,197,198,199] |
1 to 4 IMUs on head, trunk, waist and legs | Not performed | Upright stance with open or closed eyes, different BOS amplitudes and surfaces (e.g., firm and foam); walking tasks; shortened functional mobility test |
Range of acceleration; peak velocity; RMS acceleration; mean power frequency; quotient of Romberg for inertial measures | Higher range of acceleration, peak velocity, RMS acceleration and quotient of Romberg for some inertial measures; smaller mean power frequency in VS than HS | Not significant or not performed |
ABC: Activities-Specific Balance Confidence Scale; AD: patients with Alzheimer’s disease; ASA: Anticipatory Synergy Adjustment; APA: anticipatory postural adjustment; BOS: base of support; CA: patients with cerebellar ataxia; COM: centre of mass; COP: centre of pressure; EDSS: Expanded Disability Status Scale; F95%: frequency comprising 95% of the signal; HD: patients with Huntington’s disease; HS: healthy subjects; ICARS: International Cooperative Ataxia Rating Scale; IMU: Inertial Measurement Unit; ISAW: Instrumented Stand and Walk Test; LL: latero-lateral; ML: medio-lateral; MS: patients with multiple sclerosis; MSWS12: 12-Item Multiple Sclerosis Walking Scale; N: number; NP: patients with neuropathies; OLS: one-leg stance; PIGD: Postural Instability/Gait Difficulty score; PD: patients with Parkinson’s disease; RMS: root mean square; SARA: Scale for the Assessment and Rating of Ataxia; sEMG: surface electromyographic sensors; SOT: Sensory Organisation Test; ST: patients with previous stroke; TBI: patients with previous traumatic brain injury; TUG: Timed-Up and Go test; UPDRS-III: Unified Parkinson’s Disease Rating Scale—part III; VAF: variance accounted for; VS: patients with vestibular syndrome.