In patients with distal symmetric polyneuropathy we assessed non-nociceptive Aβ- and nociceptive Aδ-afferents to investigate their role in the development of neuropathic pain. We screened 2240 consecutive patients with sensory disturbances and collected 150 patients with distal symmetric polyneuropathy (68 with pain and 82 without). All patients underwent the Neuropathic Pain Symptom Inventory to rate ongoing, paroxysmal and provoked pains, a standard nerve conduction study (NCS) to assess Aβ-fibre function, and laser-evoked potentials (LEPs) to assess Aδ-fibre function. Patients with pain had the same age (P > 0.50), but a longer delay since symptom onset than those without (P < 0.01). Whereas the LEP amplitude was significantly lower in patients with pain than in those without (P < 0.0001), NCS data did not differ between groups (P > 0.50). LEPs were more severely affected in patients with ongoing pain than in those with provoked pain (P < 0.0001). Our findings indicate that the impairment of Aβ-fibres has no role in the development of ongoing or provoked pain. In patients with ongoing pain the severe LEP suppression and the correlation between pain intensity and LEP attenuation may indicate that this type of pain reflects damage to nociceptive axons. The partially preserved LEPs in patients with provoked pain suggest that this type of pain is related to the abnormal activity arising from partially spared and sensitised nociceptive terminals. Because clinical and neurophysiological abnormalities followed similar patterns regardless of aetiology, pain should be classified and treated on mechanism-based grounds.
The Xe-133 inhalation method was used to study rCBF in 12 patients with partial epilepsy during the interictal phase. SPECT images evidenced a focal CBF defect in 10 out of 12 patients, while quantitative analysis showed CBF abnormalities in all the patients. The focal CBF defect corresponded to the site of EEG abnormalities in nine patients. Additional low-flow areas beyond the EEG focus were found. Five patients presented a significant CBF decrease in the cerebellar hemisphere contralateral to the EEG focus. In five patients with unilateral EEG abnormalities, a CBF reduction was found in the contralateral cerebral hemisphere, mirror to the EEG focus. Finally, a widespread CBF decrease involving one or both cerebral hemispheres was observed in seven patients. Global and rCBF values were not correlated with age, duration of disease, frequency of seizures, secondary generalization, or specific therapy. SPECT may be useful in evaluating EEG epileptic foci, and quantitative SPECT allows the detection of functional effects of the epileptic focus on anatomically connected remote areas, probably due to the decrease of afferent inputs (diaschisis phenomenon).
We studied the properties of motoneurones and Ia-motoneuronal connections in the human trigeminal system, and their functional interactions with other brainstem reflex pathways mediated by non-muscular (Abeta) afferents. With surface EMG recordings we tested the recovery cycles of the heteronymous H-reflex in the temporalis muscle and the homonymous silent period in the masseter muscle both elicited by stimulation of the masseteric nerve at the infratemporal fossa in nine healthy subjects. In four subjects single motor-unit responses were recorded from the temporalis muscle. In six subjects we also tested the effect of the stimulus to the mental nerve on the temporalis H-reflex and, conversely, the effect of Ia input (stimulus to the masseteric nerve) on the R1 component of the blink reflex in the orbicularis oculi muscle. The recovery cycle of the H-reflex showed a suppression peaking at the 5-20 ms interval; conversely the time course of the masseteric silent period was facilitated at comparable intervals. The inhibition of the test H-reflex was inversely related to the level of background voluntary contraction. Single motor units were unable to fire consistently in response to the test stimulus at intervals shorter than 50 ms. Mental nerve stimulation strongly depressed the H-reflex. The time course of this inhibition coincided with the EMG inhibition elicited by mental nerve stimulation during voluntary contraction. The trigeminal Ia input facilitated the R1 component of the blink reflex when the supraorbital test stimulation preceded the masseteric conditioning stimulation by 2 ms. We conclude that the time course of the recovery cycle of the heteronymous H-reflex in the temporalis muscle reflects the after-hyperpolarization potential (AHP) of trigeminal motoneurones, and that the Ia trigeminal input is integrated with other brainstem reflexes.
Background: Despite being widely prescribed, relatively few controlled trials have been conducted on the class of neurotrophic/antinociceptive nutraceuticals. While performing a search in the literature, we came across an old registration study on micronized palmitoylethanolamide in patients with low back pain – sciatica by Guida and colleagues. Methods: We contacted the authors of the article and obtained all the original material, which allowed us to reanalyze the study. We assessed its clinical relevance by calculating the numbers needed to treat for pain (visual analog scale) and function (Roland-Morris Questionnaire). After excluding patients for whom the information available was insufficient, we assigned each patient to one of the five categories of increasing probability of neuropathic pain: pure lumbago, lumbago with projecting pain to surrounding regions (e.g. gluteus or groin), lumbago with projecting pain to the thigh or leg, pure sciatica and radiculopathy, and investigated any correlations (Spearman) between the improvement in pain and function with these five classes. Results: Compared with placebo, palmitoylethanolamide 600 mg/die yielded a number needed to treat of 1.7 (95% confidence interval: 1.4-2) for pain, and 1.5 (95% confidence interval: 1.4-1.7) for function. The correlation between the five categories was highly significant for pain relief (P <0.0001), though not significant for reduced dysfunction. Conclusion: Palmitoylethanolamide was extremely effective on pain and function in a large cohort of patients with low back pain – sciatica. Although, the multiple mechanisms of action of palmitoylethanolamide are ideal for mixed pain conditions such as low back pain – sciatica, the correlation between pain relief and the likelihood of neuropathic pain suggests that this drug exerts a predominant action on the neuropathic pain component.
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)
