Neural Noise- Cutaneous silent periods are an electrophysiological measure used in peripheral neuropathy.
- In Charcot-Marie-Tooth type 1A disease, cutaneous silent periods have been characterized (Clinical Neurophysiology, Vol 183, March 2026). 1
Weekly enrichment (2026-07-20)
- The cutaneous silent period (CSP) is an oligosynaptic nociceptive spinal reflex in which ongoing voluntary muscle contraction is briefly suppressed after strong electrical stimulation of a cutaneous nerve; its afferent arc is carried by small-diameter A-delta fibers and its efferent arc by alpha motoneurons, making it one of the few routine electrophysiological probes of small-fiber (rather than large-fiber) function.23
- Standard recording parameters are onset latency, 50%-reduction latency, end latency, and CSP duration; typical EMG-lab normative values are an onset latency <80 ms for the upper limbs and <120 ms for the lower limbs, with duration >30 ms.2
- Standard technique has the patient hold a near-maximal voluntary contraction while a painful stimulus of roughly 10–20x the sensory threshold (≈500 µs pulse) is delivered; about 4–5 trials at ~0.7 Hz are rectified and averaged, with latency and duration read where the trace crosses ~80% of pre-stimulus EMG activity.3
- An earlier CMT parameter study (Arq. Neuro-Psiquiatr., 2022) used a cohort of 10 CMT1, 10 CMT2, 24 diabetic, and 59 control subjects; control median-nerve onset latency averaged 79.2 ms and sural onset latency 99.4 ms, and all neuropathy groups showed significantly prolonged latencies versus controls (p<0.001).4
- In that study, end latency in the lower limbs was the parameter that best separated the demyelinating subtype (CMT1) from the axonal subtype (CMT2).4
- A 2024 Clinical Neurophysiology case report by Köfler and colleagues (Landeskrankenhaus Feldkirch) first documented that CSPs reveal A-delta fiber involvement in Charcot-Marie-Tooth type 1, providing the rationale for the larger CMT1A characterization in the source article.51
- Reported CSP sensitivity for diagnosing small-fiber neuropathy is only about 35%, but specificity exceeds 95%, so an abnormal CSP is informative when present while a normal result cannot exclude disease.2
- Limb temperature affects CSP onset and end latencies more than large-fiber conduction velocities; cooling delays the latencies without altering duration, so limb temperature and stimulus intensity must be controlled for reproducible measurements.2
- The source article (Clinical Neurophysiology, Vol. 183, March 2026) characterizes CSPs specifically in CMT1A, but its exact sample size and effect sizes were not retrievable from the primary source and are not reported here.1