Quantitative Sensory Testing for Cortical Sensory Loss in CBS

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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)

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 thresholds

Cortical vs. Peripheral Differentiation: QST patterns can distinguish cortical sensory loss from peripheral neuropathy

Disease-Specific Signatures: CBS shows characteristic QST patterns not seen in other movement disorders

Progression Monitoring: Serial QST can track disease progression and treatment response

CBS-Specific Patterns

| QST Parameter | CBS Pattern | PSP Pattern | PD Pattern |
|--------------|-------------|-------------|------------|
| Thermal thresholds | Markedly elevated | Mild elevation | Normal |
| Mechanical detection | Elevated | Normal-mild | Normal |
| Vibration sense | Reduced | Mild reduction | Normal |
| Pain thresholds | Variable | Normal | Normal |

Testing Protocol

Equipment Requirements

Thermal testing: Thermode-based quantitative thermal tester (e.g., TSA-2001, Medoc)
Mechanical testing: Semmes-Weinstein monofilaments, vibrometer
Pain testing: Quantitative heat/cold pain device, pressure algometer
Standardized: Specific probe sizes, application rates, test site protocols

Standard Test Sites

Dorsal hand (thenar eminence) — primary test site

Dorsal foot (first metatarsal head) — for comparison

Forearm — control site for distal vs. proximal patterns

Face (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 hemisphere

Warm > Cold impairment: Warm detection more affected than cold

Proximal > Distal: Often affects more proximal sites

Correlation 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 deficit
Asymmetric: CBS typically shows side-to-side differences
Dissociation: Primary sensation intact but detection impaired — cortical pattern

Vibration 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 CBS

Elevated thermal thresholds: Warm detection > 48°C is unusual and favors CBS

Dissociated 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 |
|-----------|-----|-----|----------------------|
| Thermal asymmetry | Marked | Mild | Symmetric |
| Primary sensation | Intact | Intact | Impaired |
| Object recognition | Impaired | Intact | Variable |
| Distribution | Asymmetric | Rare | Distal/symmetric |

Test Limitations

Requires patient cooperation: Cannot test aphasic or cognitively impaired patients reliably

Subject to patient attention: Fatigue affects results

Not a biomarker: Correlates with clinical features, not pathological diagnosis

Environmental 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 context
Neuroimaging: MRI findings of parietal atrophy
Other 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 burden
Progression marker: Serial QST tracks disease progression
Therapeutic response: May detect treatment effects

Clinical Trials

QST endpoints have been used in:

Disease-modifying therapy trials
Rehabilitation intervention studies
Neuroprotective agent trials

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/)

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Quantitative Sensory Testing for Cortical Sensory Loss in CBS

Quantitative Sensory Testing (QST) for Cortical Sensory Loss in CBS

Overview

Quantitative Sensory Testing (QST) for Cortical Sensory Loss in CBS

Overview

Clinical Rationale

Why QST for CBS?

CBS-Specific Patterns

Testing Protocol

Equipment Requirements

Standard Test Sites

Testing Environment

Thermal Testing

Warm Detection Threshold (WDT)

Cold Detection Threshold (CDT)

Thermal Sensory Limen (TSL)

Heat Pain Threshold (HPT)

Cold Pain Threshold (CPT)

CBS-Specific Thermal Patterns

Mechanical Detection Threshold (MDT)

Testing Method

Pattern Interpretation

Vibration Sense

Testing Protocol

Clinical Significance

Pain Threshold Testing

Pressure Pain Threshold

Heat Pain Threshold

Clinical Interpretation

Data Interpretation

CBS-Specific Signatures

Differential Diagnosis

Test Limitations

Integration with Clinical Assessment

Research Applications

Biomarker Potential

Clinical Trials

See Also

References