Development and evaluation of measurement properties of the Sensorimotor Dysfunction Questionnaire for Neuromodulation (SMDQ-n)

Technical Summary: Development and Evaluation of the Sensorimotor Dysfunction Questionnaire for Neuromodulation (SMDQ-n)

Problem Statement
Non-invasive brain stimulation (NIBS) techniques, such as transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS), are widely utilized to treat various sensorimotor disorders. However, existing clinical instruments are primarily designed to classify disease severity or predict prognosis within specific diagnostic categories. There is a notable absence of a validated tool capable of characterizing a patient's sensorimotor profile independently of their specific diagnosis. This gap hinders the emerging "symptom-driven" rationale for NIBS, which targets functional connectivity hubs shared across pathological conditions to attenuate symptoms regardless of underlying pathophysiology.

Methodology
The study employed a three-step design adhering to the Consensus-based Standards for the selection of health Measurement Instruments (COSMIN) framework to develop and validate the Sensorimotor Dysfunction Questionnaire for Neuromodulation (SMDQ-n).

• Step 1 (Item Generation): An initial item pool was generated through a systematic literature review (MEDLINE, LILACS, SciELO, Web of Science, CINAHL) and semi-structured interviews with experienced physiotherapists. Items were organized around three conceptual axes: sensory input, central processing, and motor output.
• Step 2 (Content and Face Validity):
  • Content Validity: A three-round Delphi study was conducted with five expert judges (physiotherapists with ≥5 years of clinical/research experience in NIBS). An 80% acceptance threshold was required for item retention.
  • Face Validity: A pilot study involving 20 patients with preserved cognitive function assessed item clarity and acceptability.
• Step 3 (Measurement Property Evaluation): A sample of 104 patients with sensorimotor dysfunction was recruited to evaluate:
  • Internal Consistency: Measured via Cronbach's alpha.
  • Structural Validity: Assessed using Exploratory Factor Analysis (EFA) with Varimax rotation.
  • Inter-rater Reliability: Evaluated using weighted kappa coefficients, comparing the SMDQ-n against expert clinician opinion (gold standard) and between two independent evaluators.
  • Construct Validity: Tested via the Mann-Whitney U test to discriminate between patients and healthy individuals (known-groups validity).
  • Criterion Validity: Determined through Receiver Operating Characteristic (ROC) curve analysis.

Key Results

• Instrument Structure: The final SMDQ-n comprises 26 items rated on a 5-point Likert scale, yielding a total score between 26 and 130 (higher scores indicate greater impairment).
• Reliability and Consistency:
  • Internal consistency was good (Cronbach's α = 0.863).
  • Inter-rater reliability ranged from fair to almost perfect (weighted κ: 0.319–1.0). Most items showed moderate-to-almost-perfect agreement, though three items (Q16, Q18, Q23) showed lower agreement, with Q23 not reaching statistical significance.
• Validity:
  • Structural Validity: EFA identified six clinically coherent domains explaining approximately 70% of the variance: upper limb movement dysfunction, lower limb movement/gait/balance dysfunction, motor coordination dysfunction, muscle tone dysfunction, somatosensory dysfunction, and praxis dysfunction.
  • Construct Validity: The instrument successfully discriminated between patients with sensorimotor dysfunction and healthy individuals (p < 0.001).
  • Criterion Validity: The SMDQ-n demonstrated outstanding discriminative accuracy (Area Under the Curve [AUC] = 0.984; 95% CI: 0.962–1.000). A cutoff point of 33.5 points yielded a sensitivity of 93.8% and specificity of 96.4%.

Significance and Claims
The authors claim that the SMDQ-n is the first instrument specifically designed to characterize the sensorimotor profile of patients eligible for NIBS treatment, independent of diagnosis. The study positions the SMDQ-n as a clinically viable, diagnosis-independent screening tool.

The paper asserts that the instrument offers high clinical utility, estimating a near-maximum score (9/10) based on administration time (<10 minutes), zero cost, lack of need for specialized equipment, and portability. The authors conclude that the SMDQ-n supports the selection of brain targets for neuromodulation practice by providing a standardized method to profile sensorimotor dysfunction.

Limitations Acknowledged
The authors note several limitations:

• The expert panel for the Delphi study consisted of only five judges from two Brazilian regions, potentially limiting the generalizability of content validity.
• The sample size for the Exploratory Factor Analysis (n=104) meets the minimum standard (4 participants per item) but falls below recommendations for stable factor solutions.
• The instrument was developed in Brazilian Portuguese, requiring cross-cultural adaptation for other languages.
• Future studies are needed to evaluate test-retest reliability, measurement error, minimal clinically important difference, and responsiveness to therapeutic change.