Effect of painful heterotopic stimulation on the cutaneous silent period in the upper limbs.
OBJECTIVE
To evaluate the effect of heterotopic painful stimulation (HPS) on the cutaneous silent period (CSP) and the withdrawal flexor reflex (WFR) in the upper limbs, in an attempt to better identify the nociceptive component of the CSP and its functional relationship with the flexor reflex.


METHODS
The CSP at different stimulus intensities, the WFR and the H/M ratio were studied in 12 healthy adults. Neurophysiological measurements were recorded in the following 4 conditions: (1) control session; (2) non-painful session (dipping hand in water at 25 degrees C); (3) painful (cold pressor test, CPT); and (4) after-effect (3-8 min after taking hand out of water at 5-6 degrees C).


RESULTS
During the CPT, the duration of the high-threshold CSP was approximately 23% shorter than the baseline value, the high-threshold CSP latency was approximately 10% longer than the baseline value, and the mean RIII reflex area was approximately 40% smaller than the baseline reflex area (all P<0.05). A significant correlation was found between the percentage decrease in the CSP duration and the WFR area (r=0.61, P<0.05).


CONCLUSIONS
Our findings indicate that the HPS specifically inhibits both the high-threshold CSP and the WFR, thereby providing further evidence that these cutaneous reflexes are functionally and anatomically related, and that they represent different aspects of a complex nocifensive response.
Rossi
Paolo
P
Dipartimento di Neurologia Clinica e Otorinolaringoiatria, Istituto di Clinica delle Malattie Nervose e Mentali, II Clinica Neurologica, Università di Roma 'La Sapienza', Viale dell'Università 30, 00185, Rome, Italy.
Pierelli
Francesco
F
Parisi
Leoluca
L
Perrotta
Armando
A
Bartolo
Michelangelo
M
Amabile
Giuseppe
G
Serrao
Mariano
M
D000328:Adult; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D008297:Male; D009119:Muscle Contraction; D009431:Neural Conduction / Q000502:physiology*; D017288:Pain Threshold; D011930:Reaction Time; D012018:Reflex / Q000502:physiology*; D012684:Sensory Thresholds; D012879:Skin Physiological Phenomena; D034941:Upper Extremity