Sensory abnormalities in consecutive, unselected patients with central post-stroke pain

This study examined the sensory abnormalities in an unselected, consecutive group of patients with central post-stroke pain (CPSP) surviving more than 1 year after stroke. The sensory examination included clinical examination and quantitative measures with detection and pain thresholds to heat and cold stimuli, argon laser, bon Frey hair and determination of stimulus-response function in the 10–45°C range. Sensory examination was in 11 identified CPSP patients (5 female, 6 male; aged 43–80 years) carried out in the painful area using the contralateral homologue area as reference. Pain rating was performed using the McGill Pain Questionnaire and a VAS scale.

All patients had ischemic (MRI verified) infarction. Of the 11 patients with supratentorial lesions, 5 had thalamic lesions; in addition, 7 patients had lesions in the brain stem/cerebellum. Median present spontaneous pain intensity on the VAS scale was 3.3 (range: 0–7.7).

All patients had pain in the body part with sensory abnormalities, which in 8 patients extended the area with pain. Warm detection threshold was higher in the pain area in all patients, and all except 1 patient had increased cold detection threshold. Cold and heat pain thresholds were raised as well, but to a lesser degree. Sensibility to touch (bon Frey hairs) and pain (argon laser) were changed in only 4 and 3 patients, respectively. A stimulus-response curve in the 10–45°C range showed different patterns compared to the non-affected side. A cold allodynia in the 10–45°C range was present in the painful area in 6 (56%) Of the patients.

The results support the theory that damage to the spino-thalamo-cortical pathway is a necessary condition in CPSP. It is proposed that the spontaneous pain in CPSP is linked to hyperexitability or spontaneous discharges in thalamic or cortical neurons that have lost part of their normal input.