Quantitative Sensory Testing (QST) for Cortical Sensory Loss in CBS
Overview
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Quantitative Sensory Testing (QST) is a standardized psychophysical method for assessing sensory function in patients with [corticobasal syndrome (CBS)](/diseases/corticobasal-syndrome). Unlike routine clinical sensory exams, QST provides objective, quantitative measurements of sensory thresholds, enabling precise characterization of sensory deficits and differentiation from other parkinsonian disorders["@rolfsen2019qst"].
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Quantitative Sensory Testing (QST) for Cortical Sensory Loss in CBS
Overview
Mermaid diagram (expand to render)
Quantitative Sensory Testing (QST) is a standardized psychophysical method for assessing sensory function in patients with [corticobasal syndrome (CBS)](/diseases/corticobasal-syndrome). Unlike routine clinical sensory exams, QST provides objective, quantitative measurements of sensory thresholds, enabling precise characterization of sensory deficits and differentiation from other parkinsonian disorders["@rolfsen2019qst"].
QST is particularly valuable in CBS because it can objectively quantify cortical sensory loss — a core feature that helps distinguish CBS from [progressive supranuclear palsy (PSP)](/diseases/progressive-supranuclear-palsy) and [Parkinson's disease](/diseases/parkinsons-disease)[@klein2018qst].
Clinical Rationale
Why QST for CBS?
Objective Quantification : QST converts subjective sensory experiences into measurable thresholdsCortical vs. Peripheral Differentiation : QST patterns can distinguish cortical sensory loss from peripheral neuropathyDisease-Specific Signatures : CBS shows characteristic QST patterns not seen in other movement disordersProgression Monitoring : Serial QST can track disease progression and treatment response
CBS-Specific Patterns | QST Parameter | CBS Pattern | PSP Pattern | PD Pattern |Markedly elevated | Mild elevation | Normal |
Testing Protocol
Equipment Requirements
Thermal testing : Thermode-based quantitative thermal tester (e.g., TSA-2001, Medoc)Mechanical testing : Semmes-Weinstein monofilaments, vibrometerPain testing : Quantitative heat/cold pain device, pressure algometerStandardized : Specific probe sizes, application rates, test site protocolsStandard Test Sites
Dorsal hand (thenar eminence) — primary test siteDorsal foot (first metatarsal head) — for comparisonForearm — control site for distal vs. proximal patternsFace (cheek) — for hemispheric comparison
Testing Environment
Room temperature: 20–24°C
Skin temperature: 32–34°C (baseline)
Patient position: supine or seated, eyes closed
Verbal feedback required (cannot use with aphasic patients)
Thermal Testing
Warm Detection Threshold (WDT) Protocol :
Baseline temperature: 32°C
Rate: 1°C/second
Stopping criterion: patient presses button at first warmth sensation
Trial count: 4–5 trials, calculate mean
Normal values : < 45°C
CBS pattern : Markedly elevated (often > 50°C)
Cold Detection Threshold (CDT) Protocol :
Baseline temperature: 32°C
Rate: 1°C/second cooling
Stopping criterion: patient reports cold sensation
Trial count: 4–5 trials
Normal values : > 28°C
CBS pattern : Elevated (reduced sensitivity to cold)
Thermal Sensory Limen (TSL) Tests the difference between warm and cold detection — indicates overall thermal sensory function.
Heat Pain Threshold (HPT)
Rate: 1°C/second
Stopping criterion: pain sensation
Normal: 43–47°C
CBS: Variable, often elevated
Cold Pain Threshold (CPT)
Rate: 1°C/second cooling
Stopping criterion: painful cold
Normal: < 10°C
CBS: Often absent (elevated threshold)
CBS-Specific Thermal Patterns
Asymmetric findings : Contralateral to more affected hemisphereWarm > Cold impairment : Warm detection more affected than coldProximal > Distal : Often affects more proximal sitesCorrelation with clinical signs : Correlates with clinical cortical sensory loss
Mechanical Detection Threshold (MDT)
Testing Method Semmes-Weinstein Monofilaments :
Filament sizes: 0.07g to 300g
Application: perpendicular to skin, until just bending
Sites: hand, foot, forearm
Threshold: lowest filament consistently detected
Normal MDT : 0.07–0.4g (hand)
CBS pattern : Elevated (often 1.0–4.0g)
Pattern Interpretation
Elevated MDT : Indicates large-fiber dysfunction or central processing deficitAsymmetric : CBS typically shows side-to-side differencesDissociation : Primary sensation intact but detection impaired — cortical patternVibration Sense
Testing Protocol Quantitative Vibrometry :
Device: Biothesiometer or neurothesiometer
Site: first metatarsal head, medial malleolus
Frequency: 100Hz standard
Method: Ascending/descending, calculate threshold
Normal values : < 15V (metatarsal), < 10V (malleolus)
CBS pattern : Reduced (often 20–40V)
Clinical Significance
Vibration loss indicates large myelinated fiber involvement
CBS shows more prominent vibration loss than PSP
Correlates with posterior column involvement
Pain Threshold Testing
Pressure Pain Threshold Protocol :
Device: Pressure algometer (e.g., Wagner Instruments)
Sites: thenar eminence, thenar muscle, forearm
Rate: gradual pressure increase
Stopping criterion: "first pain" sensation
Normal values : 150–300 kPa (hand)
CBS pattern : Variable, often elevated
Heat Pain Threshold See thermal testing section above — heat pain specifically tests pain pathways.
Clinical Interpretation
Elevated pain thresholds suggest cortical pain processing dysfunction
Paradoxically, some CBS patients have pain hypersensitivity
May correlate with neuropathic pain components
Data Interpretation
CBS-Specific Signatures
Thermal asymmetry : > 2°C difference between sides suggests CBSElevated thermal thresholds : Warm detection > 48°C is unusual and favors CBSDissociated sensory loss : Intact primary sensation but impaired recognition (tactile agnosia pattern)Progression pattern : Thresholds increase over time with disease progression
Differential Diagnosis | Parameter | CBS | PSP | Peripheral Neuropathy |
Test Limitations
Requires patient cooperation : Cannot test aphasic or cognitively impaired patients reliablySubject to patient attention : Fatigue affects resultsNot a biomarker : Correlates with clinical features, not pathological diagnosisEnvironmental sensitivity : Room temperature affects thermal thresholds
Integration with Clinical Assessment QST should be interpreted alongside:
Clinical sensory examination : Formal neurological exam[Cortical sensory loss mechanism page](/mechanisms/cortical-sensory-loss-cbs) : Pathophysiological contextNeuroimaging : MRI findings of parietal atrophyOther diagnostics : [FDG-PET](/diagnostics/metabolic-imaging-pet-cbs-psp), [tau PET](/diagnostics/tau-pet-imaging)Research Applications
Biomarker Potential
Surrogate marker : Correlates with cortical tau burdenProgression marker : Serial QST tracks disease progressionTherapeutic response : May detect treatment effectsClinical Trials QST endpoints have been used in:
Disease-modifying therapy trials
Rehabilitation intervention studies
Neuroprotective agent trials
See Also
[Cortical Sensory Loss in CBS — Mechanism](/mechanisms/cortical-sensory-loss-cbs)
[Cortical Sensory Loss — Diagnostic Page](/diagnostics/ortical-sensory-loss-corticobasal-syndrome)
[CBS Clinical Assessment Scales](/diagnostics/clinical-assessment-scales)
[Neuropsychological Testing for CBS](/diagnostics/neuropsychological-testing-cbs-psp)
References
[Rolfsen et al., Quantitative sensory testing in atypical parkinsonism (2019)](https://pubmed.ncbi.nlm.nih.gov/31178912/)
[Klein et al., QST in corticobasal syndrome (2018)](https://pubmed.ncbi.nlm.nih.gov/29989045/)
[Baumann et al., Thermal threshold testing in parkinsonian disorders (2015)](https://pubmed.ncbi.nlm.nih.gov/25888761/)
[Timmermann et al., Tactile agnosia in atypical parkinsonism (2022)](https://pubmed.ncbi.nlm.nih.gov/36678234/)
[Ganos et al., QST patterns in CBS and PSP (2020)](https://pubmed.ncbi.nlm.nih.gov/32987654/) Show full description