High-frequency transcutaneous peripheral nerve stimulation induces a higher increase of heat pain threshold in the cutaneous area of the stimulated nerve when confronted to the neighbouring areas.

BACKGROUND: TENS (transcutaneous electrical nerve stimulation) is probably the most diffused physical therapy used for antalgic purposes. Although it continues to be used by trial and error, correct targeting of paresthesias evoked by the electrical stimulation on the painful area is diffusely considered very important for pain relief. AIM: To investigate if TENS antalgic effect is higher in the cutaneous area of the stimulated nerve when confronted to neighbouring areas. METHODS: 10 volunteers (4 males, 6 females) underwent three different sessions: in two, heat pain thresholds (HPTs) were measured on the dorsal hand skin before, during and after electrical stimulation (100 Hz, 0.1 msec) of superficial radial nerve; in the third session HPTs, were measured without any stimulation. RESULTS: Radial nerve stimulation induced an increase of HPT significantly higher in its cutaneous territory when confronted to the neighbouring ulnar nerve territory, and antalgic effect persisted beyond the stimulation time. CONCLUSIONS: The location of TENS electrodes is crucial for obtaining the strongest pain relief, and peripheral nerve trunk stimulation is advised whenever possible. Moreover, the present study indicates that continuous stimulation could be unnecessary, suggesting a strategy for avoiding the well-known tolerance-like effect of prolonged TENS application.

Capsaicina al 8 por ciento para controlar el dolor neuropático periférico: una estrategia basada en casos clínicos / No disponible

La reunión multidisciplinar organizada por Astellas tuvo lugar en Milán el 28 de agosto de 2012. Alrededor de 150 médicos invitados, especializados en el dolor, procedentes de toda Europa y con conocimientos o experiencia en el uso de los parches de capsaicina al 8 % para tratar el dolor neuropático (DN) periférico, asistieron a la reunión para escuchar la presentación de distintos casos clínicos tratados con el parche de capsaicina al 8%, por parte de un grupo de ponentes europeos expertos en la clínica del dolor. El objetivo de la reunión era compartir experiencia clínica real sobre el uso del parche de capsaicina al 8% para controlar el DN siguiendo un formato interactivo y dando a los asistentes la oportunidad de intercambiar experiencia práctica directa con el uso de este medicamento. La reunión estuvo presidida por el Dr. Arun Bhaskar del Reino Unido. Este inauguró la reunión dando la bienvenida a los delegados, presentando a los ponentes, resumiendo los objetivos de la reunión y realizando una demostración del ThoughtSort, el software que por grupos a través de un iPad, hizo posible que todos los participantes de la sesión pudiesen interactuar. Los detalles de los casos clínicos que se presentaron en la reunión y que se resumen en este artículo responden a las opiniones personales de los ponentes (AU)

The Astellas peer-to-peer meeting took place in Milan on the evening of Tuesday 28 August, 18:00-20:00. Approximately 150 invited pain physicians from across Europe, all with some knowledge or experience of using the high-dose capsaicin patch to treat peripheral neuropathic pain (NP), attended the meeting to hear an expert European faculty of practising physicians present different case studies involving treatment with high-dose capsaicin. The objective of the meeting was to share real-world experience in the use of high-dose capsaicin for the management of NP in an interactive format to provide delegates with the opportunity to liaise with physicians who have direct, handson experience of high-dose capsaicin. Interactivity was a key component of the meeting and iPad technology was utilised to encourage discussions between the faculty and the delegates. The ThoughtSort application enabled both the faculty to ask delegates questions related to their case studies and the delegates to ask the faculty questions throughout their presentations. The meeting was chaired by Dr Arun Bhaskar from the UK. He opened the meeting by welcoming the delegates, introducing the faculty, outlining the objectives of the meeting and performing a demonstration of ThoughtSort. The delegates had to work in groups to answer questions via ThoughtSort, using one iPad between four and five delegates. Details of the case studies that were presented at the meeting and summarised within this report are the personal opinions of the faculty members (AU)

Inhibition of somatosensory evoked potentials during spinal cord stimulation and its possible role in the comprehension of antalgic mechanisms of neurostimulation for neuropathic pain.

BACKGROUND: Spinal cord stimulation (SCS) has been widely used for pain relief of patients with neuropathic chronic pain, frequently with only partial efficacy. Further advancements probably need a better understanding of SCS mechanisms, yet largely unknown. Aims of this paper were to answer the question if the lumbar SCS inhibits the tibial nerve somatosensory evoked potentials (SEPs) and to discuss the role of lemniscal afferents modulation in the antalgic mechanism of SCS. METHODS: Ten consecutive patients successfully treated with implanted SCS devices for chronic pain in the lower limbs (four males, six females, age range 42-72 years) were enrolled. All the patients had an implanted system with an epidural lead connected to a pulse generator. The vertebral level ranged from T9 to T12. The cortical SEPs complex P39-N50-P60 was recorded at the basal (T0) evaluation, during the stimulation (T1) and immediately after the stimulation (T2). RESULTS: In two of ten patients (20%) the complex P39-N50-P60 became unrelievable at the T1 control (stimulator on). In the remaining eight patients statistical analysis showed a significant reduction of the P39/N50 amplitude at T1 recording. In all patients considered, T0 and T2 recordings were not significantly different, suggesting a fast recovery of the SCS effect on SEPs. CONCLUSION: The results obtained in the present study show an inhibitory effect of SCS on SEPs and support the hypothesis that in some forms of neuropathic pain the antalgic effect of SCS could be attributed to the collision of action potentials travelling in opposite direction on peripheral large diameter fibres.

Increase of the heat pain threshold during and after high-frequency transcutaneous peripheral nerve stimulation in a group of normal subjects.

AIM: Transcutaneous electrical nerve stimulation (TENS) is used worldwide for pain relief, but its mechanisms of action are not completely understood. High frequency transcutaneous peripheral nerve stimulation (HF-TPNS) is a term describing a type of TENS where a peripheral nerve is stimulated transcutaneously. The aim of the investigation was to verify the hypothesis that HF-TPNS increases the heat pain threshold in the skin territory of the stimulated nerve, during and after stimulation. METHODS: Eighteen volunteers (8 men, 10 women) participated in 2 sessions conducted on different days. In each session their heat pain thresholds were measured in basal conditions and after 5, 10, 15, 25, 40, 70 min. In one session, HF-TPNS was delivered for 10 min immediately after basal evaluation (HF-TPNS session). In the other session the heat pain thresholds only were measured (control session). The superficial radial nerve was stimulated at the wrist (frequency of 100 Hz, pulse duration of 0.1 ms). The heat pain threshold was studied using a contact thermode (surface of 12.5 cm(2)) placed in the cutaneous area of the stimulated nerve at the site where the paresthesia evoked by electrical stimulation could be felt. RESULTS: HF-TPNS significantly increased the heat pain threshold both during and after stimulation. CONCLUSION: This study confirms that HF-TPNS induces an important hypoalgesic effect. The prolonged duration of poststimulation hypoalgesia (60 min) indicates that continuous stimulation is probably unnecessary. Further studies are needed to test the hypothesis that intermittent HF-TPNS is able to maintain its hypoalgesic effectiveness over time.

Remembering familiar people: the posterior cingulate cortex and autobiographical memory retrieval.

Most functional imaging studies of memory retrieval investigate memory for standardized laboratory stimuli. However, naturally acquired autobiographical memories differ from memories of standardized stimuli in important ways. Neuroimaging studies of natural memories may reveal distinctive patterns of brain activation and may have particular value in assessing clinical disorders of memory. This study used functional magnetic resonance imaging to investigate brain activation during successful retrieval of autobiographical memories elicited by name-cued recall of family members and friends. The caudal part of the left posterior cingulate cortex was the most strongly activated region and was significantly activated in all eight subjects studied. Most subjects also showed significant activation of the left anterior orbitomedial, anterior middle frontal, precuneus, cuneus, and posterior inferior parietal cortices, and the right posterior cingulate and motor cortices.Our findings are consistent with prior studies showing posterior cingulate cortex activation during autobiographical memory retrieval. This region is also consistently activated during retrieval of standardized memory stimuli when experimental designs emphasizing successful retrieval are employed. Our results support the hypothesis that the posterior cingulate cortex plays an important role in successful memory retrieval. The posterior cingulate cortex has strong reciprocal connections with entorhinal and parahippocampal cortices. Studies of early Alzheimer's disease, temporal lobectomy, and hypoxic amnesia show that hypometabolism of the posterior cingulate cortex is an early and prominent indicator of pathology in these patients. Our findings suggest that autobiographical memory retrieval tasks could be used to probe the functional status of the posterior cingulate cortex in patients with early Alzheimer's disease or at risk for that condition.

[The clinical evaluation of conservative treatment in patients with the thoracic outlet syndrome]. / Valutazione clinica di un trattamento conservativo in pazienti con sindrome dello stretto toracico.

Conservative treatment of thoracic outlet syndrome is frequently recommended but few studies reporting conservative management are present in literature. Thirteen out-patients with thoracic outlet syndrome (4 males, 9 females) were admitted to a conservative treatment (massage and kinesitherapy) involving the cervical spine and shoulder girdle. All the patients were satisfied with the outcome of the treatment. In particular rest symptoms completely disappeared after treatment in all patients. This study confirms the efficacy of physical therapy in the conservative treatment of patients with thoracic outlet syndrome. Further studies on long-term outcome are needed.

Cardiovascular effects of TENS: heart rate variability and plethysmographic wave evaluation in a group of normal subjects.

Transcutaneous electrical nerve stimulation (TENS) is generally used in controlling pain. Side effects are not frequent, but sometimes do happen. Among these, automatic disturbances have been described. The purpose of the investigation was to study high frequency TENS effects on heart rate variability and the plethysmographic wave. Results showed no change in heart rate variability parameters (Standard Deviation, Mean Square Successive Difference) despite an increase in R-R interval, while a decrease in the amplitude of the plethysmographic wave was observed. This study seems to point out that high frequency TENS does not modify the neural control to the heart while a sympathominetic effect is shown on the peripheral plethysmographic wave.

The effect of intravenous gadolinium on the magnetic resonance appearance of cerebrospinal fluid.

The authors determined whether a sufficient amount of intravenously administered gadolinium enters the cerebrospinal fluid (CSF) to visibly shorten the T1 relaxation time. Transfer of intravenously administered contrast media into the CSF has been previously documented for iodinated contrast materials; however, the change in computed tomography density is not sufficient to have a clinically useful myelographic effect. Visible shortening of the T1 of CSF on gadolinium-enhanced magnetic resonance imaging of the spine may have clinical use. Twelve dogs were given gadolinium, and CSF was sampled at intervals over a 6-hour period. The T1 values of the CSF samples were quantitated and plotted against time. The average decrease in T1 was 23% at 60 minutes, which is nearly the peak effect. The increased signal intensity was visible at clinical window settings at 60 minutes. It is possible that this may be clinically useful for certain types of examinations. Importantly, this should be recognized as a normal appearance, and not necessarily a sign of pathology.