Automated Electrical Sensory Test Maps the Body’s Touch Thresholds Across 56 Skin Points

For people living with spinal cord injury, one of the most consequential questions after trauma is deceptively simple: what can the body still feel? Clinicians answer it today with pinprick and light touch examinations performed at 56 standardized sensory key points on the skin, two on each side of the body for every sensory dermatome from the second cervical segment down to the sacral region. That examination, codified in the International Standards for Neurological Classification of Spinal Cord Injury, or ISNCSCI, remains the backbone of sensory assessment worldwide. Yet it is fundamentally subjective, dependent on the examiner’s technique and the patient’s verbal reports, and it yields coarse ordinal scores rather than continuous measurements. A new study published in BioMedical Engineering OnLine describes an automated system designed to change that, delivering precisely controlled electrical stimuli across the entire dermatomal map while logging every response electronically.

The technology, called the multi-dermatome computer-controlled electrical perceptual threshold test, or multi-dermatome CCEPT, was developed by a team led by Siti Nurfaezah Binti Zahari and Milos R. Popovic at the Institute of Biomedical Engineering at the University of Toronto and the KITE Research Institute at University Health Network. Electrical perceptual threshold testing itself is not new. The principle is straightforward: a small electrical current is gradually increased until the person being tested first reports feeling it, and that minimal current level becomes a quantitative proxy for sensory function. Because the stimulus is generated by an instrument rather than applied by hand, the measurement has the potential to be far more reproducible than manual sensory testing. What has held the approach back is workflow. Existing EPT procedures tend to be time-consuming and labour-intensive, often requiring the examiner to control stimulus delivery manually and to record participant responses by hand, and no standardized workflow existed for covering all 56 ISNCSCI sensory key points.

The multi-dermatome CCEPT system addresses those bottlenecks through integration. It combines standardized stimulus delivery with automated channel selection, meaning the hardware can switch between electrode locations without the examiner repositioning equipment for each dermatome. Participant responses are captured directly through the system rather than transcribed on paper, the examiner retains a verification step to confirm that reported sensations correspond to the intended stimulation site, and all data are logged in synchronization across bilateral test locations. The result is a testing pipeline that can, in principle, sweep the full sensory map of the body in a single structured session while preserving a complete digital record of every threshold measurement.

To find out whether the system could produce trustworthy numbers, the researchers put it through a formal reliability evaluation. Sixteen non-disabled participants underwent testing across 28 bilateral dermatomes in two separate sessions, with a median interval of 14 days between visits. Within each session, three repeated trials were performed to assess how consistent the measurements were from trial to trial, while the two-week gap between sessions allowed the team to evaluate test-retest reliability over a clinically meaningful timeframe. The statistical framework relied on intraclass correlation coefficients calculated under a two-way mixed effects model for single measures, supplemented by the standard error of measurement and the minimal detectable change at the 95 percent confidence level, statistics that together describe both the repeatability of the test and the smallest change that can be distinguished from measurement noise.

The first and most fundamental finding was that the procedure proved feasible and safe. No adverse events occurred, and no participant reported intolerable discomfort, an important validation for a technique that deliberately delivers perceptible electrical stimulation to conscious volunteers. Reliability, however, was not uniform across the body. Within-session reliability ranged from poor to excellent across the various dermatome-side combinations, although most combinations demonstrated moderate-to-good reliability. Notably, the strongest consistency appeared in several cervical and upper thoracic dermatomes, the segments of the neck and upper trunk, while measurements were more variable at selected lumbosacral sites in the lower back and legs. That anatomical pattern matters, because it tells future users of the technology where its readings can be trusted most and where additional refinement or repeated trials may be needed.

Between-session reliability told a more complicated story. When measurements taken on one day were compared with those taken two weeks later, the correlations were more heterogeneous, varying by dermatome and by side of the body. This indicates greater measurement variability over the two-week interval, which could reflect genuine physiological fluctuation in sensory thresholds, subtle differences in electrode placement between visits, or ordinary day-to-day variation in how participants perceive and report faint sensations. For any candidate clinical tool, this kind of heterogeneity is a caution flag: a threshold change measured between two visits in a single patient may fall within the range of normal variation at some dermatomes, so clinicians interpreting serial measurements will need dermatome-specific knowledge of the minimal detectable change rather than a single global number.

Despite that variability, the study produced one of its most striking results when the team examined how perception thresholds were distributed across the body in these healthy participants. The data revealed a clear rostro-caudal gradient: thresholds were lower in the cervical and upper thoracic dermatomes and rose progressively toward the lumbosacral dermatomes. In practical terms, people required less current to feel stimulation on the skin of the neck and upper trunk than on the skin of the lower back and legs. This is exactly the pattern that a healthy sensory system would be expected to produce, and its emergence in the data suggests the system is capturing real neuroanatomical structure rather than random noise. The team compiled these findings into a preliminary healthy dermatomal reference profile, a first normative baseline against which future measurements in patients can be compared.

The clinical motivation behind all of this engineering is spinal cord injury care. After an injury, the ISNCSCI sensory examination determines the neurological level and severity of injury, guides rehabilitation planning, and serves as a primary outcome measure in clinical trials. But its ordinal scoring system can miss subtle changes, and inter-rater variability is a persistent concern. A quantitative, automated threshold test could complement the clinical examination by providing continuous, instrument-based measurements of sensory function at every key point, potentially detecting recovery or deterioration earlier and with less dependence on examiner skill. The authors are explicit that their system is positioned as an adjunct to, not a replacement for, the standard clinical assessment, and that realizing that role will require larger studies in both non-disabled and spinal cord injury cohorts to refine the protocol and establish robust normative reference profiles.

The study also illustrates a broader trend in rehabilitation engineering: the migration of bedside assessment from subjective observation toward instrumented, digitally logged measurement. The multi-dermatome CCEPT workflow automates the most error-prone elements of sensory testing, stimulus control, response capture, and record keeping, while deliberately keeping a human examiner in the loop for verification. That hybrid design reflects a pragmatic understanding of clinical reality. Fully autonomous diagnostics face regulatory and trust barriers in medicine, but systems that standardize the measurement while preserving clinician oversight can be adopted incrementally. The synchronization of data logging across bilateral dermatomes also opens the door to computational analysis of whole-body sensory profiles, an approach that could eventually feed machine learning models trained to detect patterns of sensory change that individual threshold values might not reveal.

Much work remains before this technology reaches the clinic. The present study involved 16 participants, a sample adequate for a feasibility and reliability assessment but far too small to define definitive normative ranges, and the between-session variability at some lumbosacral sites will need to be understood and reduced. Testing in people with spinal cord injury, whose sensory systems deviate dramatically from the healthy gradient documented here, is the essential next step. Still, the study delivers what a first validation should: evidence that automated, standardized electrical perceptual threshold testing across all 56 sensory key points is safe, feasible, and capable of reproducing the expected architecture of human sensation. If subsequent larger studies confirm and extend these results, the humble pin and cotton wisp that have anchored sensory examination for decades may soon be joined by a computer that can map the body’s sense of touch in numbers.

Subject of Research: Reliability of automated multi-dermatome electrical perceptual threshold testing for quantitative sensory assessment in spinal cord injury

Article Title: A multi-dermatome computer-controlled electrical perceptual threshold (multi-dermatome CCEPT) test: reliability assessment and development of a preliminary healthy dermatomal reference profile

Article References: Zahari, S. N. B., Furlan, J. C., Iwasa, S. N., Eftekhar, P., Rashidi, A., Khan, S. S., & Popovic, M. R. (2026). A multi-dermatome computer-controlled electrical perceptual threshold (multi-dermatome CCEPT) test: reliability assessment and development of a preliminary healthy dermatomal reference profile. BioMedical Engineering OnLine. https://doi.org/10.1186/s12938-026-01634-2

Image Credits: AI Generated

DOI: 10.1186/s12938-026-01634-2

Keywords: electrical perceptual threshold, spinal cord injury, dermatomes, sensory assessment, ISNCSCI, reliability, normative data, biomedical engineering, quantitative sensory testing, automation, rehabilitation, neurological classification