Effect of adjuncts on sensory properties and consumer liking of Scamorza cheese.

The present study aimed to evaluate the effect of a peptidolytic adjunct (Lactococcus lactis, Lactobacillus helveticus, and Lactobacillus paracasei), as a tool to accelerate ripening, on sensory properties and acceptability of Scamorza cheese obtained using 2 types of milk (Friesian and Friesian+Jersey) and Streptococcus thermophilus as primary starter. A 10-member panel was trained using a specific frame of references and used a specific vocabulary to assess cheese sensory properties through quantitative descriptive analysis (QDA), whereas 87 consumers were used to evaluate product acceptability. Analysis of variance showed that milk type did not markedly alter cheese sensory properties. Conversely, panelists perceived higher intensities of butter, saltiness, and sweetness flavors in cheese without adjunct culture (ST), whereas the addition of the adjunct culture (ST+A) induced higher and sourness flavors, oiliness and grainy textures, and lower adhesiveness, moisture, springiness, and tenderness. Principal component analysis showed positive relationships between pH and tenderness, sweetness and saltiness and a negative correlation between pH and grainy, oiliness, color and structure uniformity, sourness, and milk. Most of the differences observed in QDA and most of the relationships observed in the principal component analysis were linked to the higher microbial activity induced by the adjunct culture. Independently of milk and starter types, consumers perceived Scamorza cheese as characterized by a good eating quality (mean liking scores were all above the neutral point of the hedonic scale). Although ST cheeses showed higher values for overall liking, 2 homogeneous groups of consumers were identified using partial least squares regression analysis. One group preferred ST cheeses with higher levels of tenderness, adhesiveness, springiness, and moisture in terms of texture, butter in terms of flavor, and sweetness in terms of taste, whereas a second group preferred ST+A products characterized by specific attributes of texture (cohesiveness and oiliness), flavor (milk), taste (sourness), and appearance (structure and color uniformity). We conclude that further studies for the development of short-ripened products based on the use of adjunct cultures should be conducted to promote product differentiation and meet the sensory requirements of particular segments of consumers.

Exercise tolerance in systemic sclerosis patients without pulmonary impairment: correlation with clinical variables.

OBJECTIVES: In systemic sclerosis (SSc) patients pulmonary vasculopathy (PV) is present in the early stage of disease and impairs dilation of affected pulmonary blood vessels, impeding pulmonary blood flow during exercise. Abnormal gas exchange findings were early investigated by cardiopulmonary exercise test (CPET). METHODS: A total of 34 female and 6 male [median age 49 (20-63) years] SSc patients with normal chest imaging and pulmonary function tests were enrolled. Twenty healthy controls age and sex matched [16 female and 4 male; median age 51 (35-73) years] were also recruited. All subjects underwent a full clinical examination, including a nailfold video capillaros copy (NVC). An incremental symptom-limited CPET was performed with estimation of minute ventilation (VE), workload (WR), peak oxygen uptake (pVO22), and ventilatory efficiency (VE/VCO2 slope). RESULTS: A reduced exercise tolerance (pVO2<80% of predicted) was documented in 18 out of 40 subjects (45%). Six out of 18 patients with a reduced exercise tolerance showed indirect signs of ventilation perfusion mismatch (VE/ VCO2 slope >34). Patients with digital ulcers (DUs) history showed VE/VCO2slope values significantly higher [31.4 (18-39.6)] than in patients without DUs history [26.9 (22-29.4)] (p<0.0001). VE/VCO2slope values also significantly differed between the three capillaroscopic groups: early [26.3 (18-29.4)], active [28 (26.8-39.6)], and late [32.9 (22.4-39)] (p<0.0001). A positive correlation was found between the VE/ VCO2slope and both Disease Activity Index (p<0.0001, r=0.59) and Disease Severity Scale (p<0.0001, r=0.73). CONCLUSIONS: In SSc patients without evidence of pulmonary and cardiac involvement, CPET might be useful in disclosing an early PV.

[Diffusion of clinical governance among the Italian Local Health Units (LHUs). Analysis of the Health Surveys, the Firm Acts and the Health Plans]. / Come sono diffusi gli strumenti della Clinical Governance nelle ASL Italiane? I risultati dell'analisi delle Relazioni Sanitarie, degli Atti Aziendali e dei Piani Sanitari.

The objective of our research is to report on the diffusion of Clinical Governance, as introduced with the National Health Plan 2006-2008, by analysing the planning instruments set up by each Region (Regional Health Plans and Emergency Plans in regions with budget deficit), the organizational frameworks (Atti Aziendali, firm acts), and the surveys on performance and quality of healthcare among the Italian Local Health Units (Health Surveys). Our research was realized on September-December 2007 and consisted of the collection of all retrieved documents available on the web and on the online public access catalog (OPAC SBN) of the National Library Service. Futhermore, each document has been classified and analysed according to Chambers' Clinical Governance definition. A descriptive statistical and inferential analysis by applying the Chi-2 Test was performed to test the correlation between the diffusion of such a classified documents and the geographical partition of each LHU. Our results show a scarce diffusion of Firm acts (43%) and Health Surveys (24.9% of the total). Any remind to Clinical Governance instruments and methods inside each document resulted even poorer among both the organizational and performance surveys and the regional health planning frameworks, respectively.

Effect of pinching-evoked pain on jaw-stretch reflexes and exteroceptive suppression periods in healthy subjects.

OBJECTIVE: To investigate the influence of conditioning cutaneous nociceptive inputs by a new "pinch" model on the jaw-stretch reflex and the exteroceptive suppression periods (ES1 and ES2) in jaw muscles. METHODS: The jaw-stretch reflex was evoked with the use of a custom-made muscle stretcher and electrical stimuli were used to evoke an early and late exteroceptive suppression period (ES1 and ES2) in the jaw-closing muscles. Electromyographic (EMG) activity was recorded bilaterally from the masseter and temporalis muscles. These brainstem reflexes were recorded in 19 healthy men (28.8+/-1.1 years) during three different conditions: one painful clip applied to the earlobe; one painful clip applied to the nostril, and four painful clips applied simultaneously to the earlobe, nostril, eyebrow, and lower lip. Pain intensity induced by the application of the clips was scored continuously by the subjects on a 100mm visual analogue scale (VAS). RESULTS: The highest VAS pain scores were evoked by placement of four clips (79+/-0.5mm). There was no significant modulation of the jaw-stretch reflex (ANOVAs: P=0.929), the ES1 (P=0.298) or ES2 (P=0.082) in any of the three painful conditions. CONCLUSIONS: Intense and tonic cutaneous pain could be elicited by this new "pinch" pain model; however, there was no significant modulation on either excitatory or inhibitory brainstem reflex responses. SIGNIFICANCE: The novel observation that high-intensity pinch stimuli applied to the craniofacial region fail to modulate two different brainstem reflexes is in contrast to other experimental pain studies documented facilitation of the jaw-stretch reflexes or inhibition of exteroceptive suppression periods. The clinical implication of the present findings is that only some craniofacial pain conditions could be expected to show perturbation of the brainstem reflex responses.

Brainstem reflex circuits revisited.

Our current understanding of brainstem reflex physiology comes chiefly from the classic anatomical-functional correlation studies that traced the central circuits underlying brainstem reflexes and establishing reflex abnormalities as markers for specific areas of lesion. These studies nevertheless had the disadvantage of deriving from post-mortem findings in only a few patients. We developed a voxel-based model of the human brainstem designed to import and normalize MRIs, select groups of patients with or without a given dysfunction, compare their MRIs statistically, and construct three-plane maps showing the statistical probability of lesion. Using this method, we studied 180 patients with focal brainstem infarction. All subjects underwent a dedicated MRI study of the brainstem and the whole series of brainstem tests currently used in clinical neurophysiology: early (R1) and late (R2) blink reflex, early (SP1) and late (SP2) masseter inhibitory reflex, and the jaw jerk to chin tapping. Significance levels were highest for R1, SP1 and R2 afferent abnormalities. Patients with abnormalities in all three reflexes had lesions involving the primary sensory neurons in the ventral pons, before the afferents directed to the respective reflex circuits diverge. Patients with an isolated abnormality of R1 and SP1 responses had lesions that involved the ipsilateral dorsal pons, near the fourth ventricle floor, and lay close to each other. The area with the highest probabilities of lesion for the R2-afferent abnormality was in the ipsilateral dorsal-lateral medulla at the inferior olive level. SP2 abnormalities reached a low level of significance, in the same region as R2. Only few patients had a crossed-type abnormality of SP1, SP2 or R2; that of SP1 reached significance in the median pontine tegmentum rostral to the main trigeminal nucleus. Although abnormal in 38 patients, the jaw jerk appeared to have no cluster location. Because our voxel-based model quantitatively compares lesions in patients with or without a given reflex abnormality, it minimizes the risk that the significant areas depict vascular territories rather than common spots within the territory housing the reflex circuit. By analysing statistical data for a large cohort of patients, it also identifies the most frequent lesion location for each response. The finding of multireflex abnormalities reflects damage of the primary afferent neurons; hence it provides no evidence of an intra-axial lesion. The jaw jerk, perhaps the brainstem reflex most widely used in clinical neurophysiology, had no apparent topodiagnostic value, probably because it depends strongly on peripheral variables, including dental occlusion.

Laser-evoked potentials: normative values.

OBJECTIVE: Laser-evoked potentials (LEPs) currently represent the most reliable and widely agreed method of investigating the A delta-fibre pathways. Many studies dealt with the usefulness of LEPs in peripheral and central nervous system diseases. We aimed at gaining normative values for LEP data. METHODS: Using a CO2 laser stimulator we recorded LEPs after face, hand, and foot stimulation in 100 normal subjects. We measured the perceptive threshold, latency and amplitude of the main vertex components, and their side-to-side differences. We also studied the correlations between LEP data and age and body height, as well as gender differences. RESULTS: Laser perceptive threshold increased and LEP amplitude decreased from face to foot (P<0.0001). The latency of hand and foot-LEPs correlated significantly with body height (P<0.0001). The amplitude, though not the latency, correlated with age (P<0.0001). LEP data did not significantly differ between genders (P>0.1). CONCLUSIONS: This study provides normative values for the main LEP data and their absolute and side-to-side limits, highlighting the physiological differences related to, body height, age, gender and stimulation site. SIGNIFICANCE: Our data may help to improve the clinical reliability of LEPs as a diagnostic tool.

Laser evoked potentials and carbamazepine in epileptic patients.

AIMS OF THE STUDY: Nerve conduction studies have demonstrated that carbamazepine (CBZ), as well as other antiepileptic drugs (AEDs), can affect peripheral nerve conduction; reports on conventional somatosensory evoked potentials and CBZ are controversial. In a previous study, assessing laser-evoked potentials (LEPs) in CBZ-treated patients with idiopathic trigeminal neuralgia, we found that LEPs were dampened even after stimulation of the non-painful side, with a strong correlation between LEP latency and daily CBZ dose. No other study investigated the influence of AEDs on LEPs. In order to clarify the effect of CBZ on LEPs we sought possible LEP changes in epileptic patients taking CBZ. MATERIALS AND METHODS: We studied LEPs after trigeminal and hand CO(2)-laser stimulation in 20 patients with epilepsy taking CBZ and 20 age-matched controls. RESULTS: Although the trigeminal LEP mean latency was slightly longer in epileptic patients (P=0.11), we did not find significant differences between epileptic patients and controls for any LEP data. LEP data did not correlate with the daily CBZ dose, CBZ blood concentration, or duration of therapy (P>0.3). CONCLUSION: The lack of a CBZ-induced dampening of LEPs suggests that small-fibre pathways, compared to large-fibre, might be less susceptible to AED's toxic effect. Although the TN patients in our previous study were older than the epileptic patients in the present study, a possible combined effect induced by drug and age in patients with TN is unlikely because LEP latency is reportedly unaffected by age. The CBZ-induced effect in patients with trigeminal neuralgia is possibly related to pathophysiological changes specific to this disease.

Shortened cortical silent period in facial muscles of patients with cranial dystonia.

OBJECTIVE: To study the cortical silent period (SP) in the orbicularis oculi and perioral muscles in 23 patients with cranial dystonia and 10 age-matched control subjects. METHODS: High-intensity magnetic stimuli were delivered with a round coil centered at the vertex during a maximal muscle contraction. Electromyographic (EMG) responses were recorded from surface electrodes placed over the orbicularis oculi and perioral muscles. RESULTS: SPs elicited in upper and lower facial muscles had a similar duration. Facial muscle SPs were significantly shorter in patients than in control subjects. Patients with blepharospasm plus oromandibular dystonia had shorter SPs than patients with blepharospasm alone. Although patients' recordings showed reduced voluntary and evoked EMG activity, neither activities correlated with the duration of the SP. CONCLUSIONS: Silent period (SP) shortening depends neither on the level of electromyographic activity nor on segmentary mechanisms. The shortened SP in facial muscles reflects hypoexcitability of cortical inhibitory neurons in cranial dystonia.

Small-fiber dysfunction in trigeminal neuralgia: carbamazepine effect on laser-evoked potentials.

BACKGROUND: In patients with trigeminal neuralgia, results of clinical examination of sensory function are normal. Reflex and evoked potential studies have already provided information on large-afferent (non-nociceptive) function. Using laser-evoked potentials (LEP), the authors sought information on small-afferent (nociceptive) function. METHODS: The brain potentials evoked by CO(2)-laser pulses directed to the perioral and supraorbital regions were studied in 67 patients with idiopathic or symptomatic trigeminal neuralgia and 30 normal subjects. Of the 67 patients, 49 were receiving carbamazepine. RESULTS: All patients with symptomatic and 51% of those with idiopathic trigeminal neuralgia had frankly abnormal LEP on the painful side. The mean latency was significantly higher and mean amplitude lower on the painful than the nonpainful side. However, even on the nonpainful side, the mean latency was significantly longer than that of the age-matched controls. The nonpainful-side latency correlated significantly with the carbamazepine dose. CONCLUSIONS: LEP detect severe impairment of the nociceptive afferent system on the painful side of patients with idiopathic as well as symptomatic trigeminal neuralgia. A dysfunction of small-myelinated afferents may play an important role in the pathophysiology of neuralgic pain. Carbamazepine markedly dampens these brain potentials. The authors propose that this effect may result from inhibition of nociceptive transmission in the cingulate gyrus.

Assessment of nociceptive trigeminal pathways by laser-evoked potentials and laser silent periods in patients with painful temporomandibular disorders.

We assessed the trigeminal nociceptive pathways in patients with painful temporomandibular disorders (TMD) and control subjects using a CO(2)-laser stimulator which provides a predominant activation of the nociceptive system. Fifteen patients with unilateral pain were examined in accordance with the Research Diagnostic Criteria for TMD and 30 gender- and age-matched individuals were included as a control group. Laser-evoked potentials (LEPs) and laser silent periods (LSPs) after stimulation of the perioral region (V2/V3) on the painful and non-painful sides were recorded in all subjects. LEPs were evoked by low-intensity pulses (1.5 x perception threshold (PTh)) and recorded from scalp electrodes at the vertex. LSPs were evoked by high-intensity pulses (4 x PTh) and recorded bilaterally from masseter muscles with surface electromyogram (EMG) electrodes. Subjects also assessed the stimulus intensity on a 0-10 rating scale. LEPs had normal latency but smaller amplitude in TMD patients compared to the control group (P<0.001). Side-to-side comparison within patients showed that LEP amplitude was even more reduced after stimulation on the painful than the non-painful side (P<0.001). TMD patients showed a significant side-asymmetry of the pre-stimulus EMG activity, with a smaller value in the muscle on the painful side (P<0.001). LSPs were completely absent bilaterally in 12 TMD patients and unilaterally in two patients; only one patient had normal and bilateral LSPs. TMD patients perceived the laser stimulus less intense on the painful than the non-painful side (P<0.05). We found suppression of cortical responses and brainstem reflexes elicited by a predominantly nociceptive input in TMD patients. These findings are consistent with recent experimental pain studies and suggest that chronic craniofacial pain in TMD patients may be associated with a dysfunction of the trigeminal nociceptive system.

Excitability of the central masticatory pathways in patients with painful temporomandibular disorders.

Much is unclear about the pathophysiological mechanisms underlying painful temporomandibular disorders. In addition to various other theories, masticatory muscle dysfunction and pain have also been attributed to primary central nervous system hyperactivity. We assessed this possibility in a study using recent neurophysiological techniques. From among outpatients whose diagnosis of temporomandibular disorders had been obtained in stomatognathic facilities, we studied 10 patients with bilateral pain and 15 patients with unilateral pain, in whom electromyographic examination of the trigeminal reflexes disclosed normal findings except for absence or amplitude asymmetry of the jaw jerk. Transcranial magnetic stimulation yielded masseter motor evoked potentials of normal latency and amplitude, but five patients had to exert a near-maximum contraction to obtain their responses. The masseter silent periods elicited by the double-shock technique recovered normally. Because these tests measure the excitability of the masticatory system (including motor cortex, corticobulbar and corticoreticular connections, reticular interneurones and lower motoneurones), the lack of facilitation in these patients' responses excluded central hyperactivity as the primary cause of their masticatory dysfunction and pain.

Conduction velocity of the human spinothalamic tract as assessed by laser evoked potentials.

To study the conduction velocity of the spinothalamic tract (STT) we delivered CO2 laser pulses, evoking pinprick sensations, to the skin overlying the vertebral spinous processes at different spinal levels from C5 to T10 and recorded evoked potentials (LEPs) in 15 healthy human subjects. These stimuli yielded large-amplitude vertex potentials consisting of a negative wave at a peak latency of about 200 ms followed by a positive wave at a peak latency of about 300 ms. The mean conduction velocity of the STT was 21 m/s, i.e. higher than the reported velocity of the corresponding primary sensory neurons (type II AMH). Because dorsal stimulation readily yields reproducible brain LEPs, we expect this technique to be useful as a diagnostic tool for assessing the level of spinal cord lesions.

Effect of experimental pain from trigeminal muscle and skin on motor cortex excitability in humans.

The pathophysiology of many orofacial pain syndromes is still unclear. We investigated the effect of tonic muscle and skin pain on the excitability of the trigeminal motor pathways using transcranial magnetic stimulation (TMS). Motor evoked potentials (MEPs) were recorded in the masseter surface electromyogram (EMG). Magnetic pulses were delivered with a large coil at intensities 1.1 and 1.5 times the motor threshold, and for each intensity, MEPs were recorded at three different clenching levels: 15, 30 and 45% of maximum voluntary contraction (MVC). Baseline, pain and post-baseline recordings were compared in two sessions. Firstly, muscle pain was induced by infusion of hypertonic saline (5.8%) into the left masseter. Secondly, skin pain was induced by topical application of capsaicin (5%) on the left cheek. Muscle and skin pain did not induce significant effects on the amplitude or latency of the MEPs (ANOVAs: P>0.50). In both sessions, the amplitude of the MEPs increased with the increase of the clenching level and stimulus intensity (P<0.0001; P<0.005) whereas the latency was not significantly changed (P>0.05; P=0.11). Muscle pain was associated with an increase in the pre-stimulus EMG activity on the non-painful side compared with baseline (P<0.01), which could be due to compensatory changes in the activation of the painful muscle. The need for voluntary contraction to evoke MEPs in the masseter muscles and compensatory mechanisms both at the brainstem and cortical level might explain the lack of detectable modulation of MEPs. Nonetheless, the present findings did not support the so-called 'vicious cycle' between pain - central hyperexcitability - muscle hyperactivity.

Laser-evoked potentials in post-herpetic neuralgia.

OBJECTIVE: We evaluated the reliability of laser-evoked potentials (LEPs) as a diagnostic tool in patients with post-herpetic neuralgia (PHN), i.e. a chronic painful condition that causes small-diameter fibre dysfunction. Furthermore, we sought information on pathophysiology of PHN pain. METHODS: We recorded 'late' LEPs after stimulation of the supraorbital, upper cervical, lower cervical, upper thoracic, mid thoracic, and lower thoracic territories in 12 control subjects and 40 patients with PHN. We also determined the correlation of LEP data with age, duration of disease, and severity and quality of pain. RESULTS: At all stimulation sites, laser pulses invariably evoked high-amplitude brain potentials related to small-myelinated (A-delta) fibre activation. The laser perceptive threshold and LEP latency correlated with the distance of the dermatome from the brain (P<0.001). In patients, the perceptive threshold was higher and the LEP amplitude was lower in the affected dermatome than on the contralateral side (P<0.001). We found no significant LEP-clinical correlation except for a correlation between LEP abnormality and age. CONCLUSIONS: Being sensitive and reliable in assessing sensory function also in proximal dermatomes, LEPs are a promising diagnostic tool in radiculopathies. Although PHN severely impairs small myelinated fibres, the lack of a significant correlation between LEP abnormalities and pain suggests that pain in PHN does not chiefly arise from a dysfunction of small-myelinated afferents.

Dysfunction of small myelinated afferents in diabetic polyneuropathy, as assessed by laser evoked potentials.

OBJECTIVE: To verify whether laser evoked potentials are useful in assessing the function of small afferent fibers and to compare dysfunction of large and small afferent fibers in patients with diabetic polyneuropathy. METHODS: The brain potentials evoked by CO2 laser stimulation of the hand and foot were studied in diabetic patients (n = 45) with various degrees of peripheral nerve damage. Laser evoked potentials (which assess the function of small myelinated afferents) were also compared with ulnar and sural nerve sensory action potentials (which assess the function of large myelinated afferents) by scoring the abnormalities of the two neurophysiological tests with similar criteria. RESULTS: Laser evoked potentials were often absent; the mean latency was normal and mean amplitude decreased, as expected in axonopathies. Although clinical examination showed more frequent impairment of vibratory than pinprick sensation, laser evoked potentials and sensory action potentials yielded similar abnormality scores and showed a strong intra-individual correlation. CONCLUSIONS: Laser evoked potentials, possibly better than standard clinical examination for assessing the abnormalities of small-diameter afferents, indicate that diabetic polyneuropathy induces large- and small-afferent dysfunction in parallel.

Trigeminal small-fibre dysfunction in patients with diabetes mellitus: a study with laser evoked potentials and corneal reflex.

OBJECTIVE: To investigate trigeminal small-fibre function in patients with diabetes mellitus. METHODS: In 52 diabetic patients we studied the trigeminal laser evoked potentials after stimulation of the skin bordering the lower lip. In the 21 patients with the severest peripheral nerve damage we also studied the electrically evoked corneal reflex. Both responses are mediated by small myelinated afferents. RESULTS: Laser evoked potentials had a longer mean latency and lower amplitude in diabetic patients than in normal subjects (P<0.005). The abnormality frequency of the laser evoked potentials correlated with the severity of polyneuropathy (P<0.005). In contrast, the corneal reflex was normal. CONCLUSION: Dysfunction of small afferents of the mandibular nerve is frequent in patients with diabetic polyneuropathy. We speculate that the primary cause could be segmental demyelination.

Prepulse inhibition of the blink reflex by laser stimuli in normal humans.

The subcortical integrative effects of laser-induced activation of pain ascending tracts were examined in 11 healthy volunteers, aged 22-52 years. Subjects underwent either CO2 laser stimulation at the dorsum of the hand, electrical stimulation of digital nerves at the 3rd finger, or mechanical taps to the first dorsal interosseous space, preceding a blink reflex elicited by a supraorbital nerve electrical stimulus. The percentage inhibition induced in the R2 response of the blink reflex was similar for the three different stimulus modalities, but occurred at a different time interval. Compared to control trials, the R2 response of the test trials was a mean of 23.1% at the interval of 250 ms with laser stimuli, 17.4% at the interval of 100 ms with electrical stimuli to the 3rd finger, and 20.6% at the interval of 90 ms with a mechanical tap to the 1st interosseous space. Activation of pain receptors induces prepulse inhibition of the blink reflex at a delay corresponding to a slowly conducting pathway. The percentage inhibition is similar to that observed with other somatosensory inputs.

Laser evoked potentials for assessing sensory neuropathy in human patients.

Sensory neuropathy usually impairs tactile sensations related to large myelinated afferents (Abeta) as well as thermal-pain sense related to small myelinated (Adelta) and unmyelinated (C) afferents. By selectively affecting large or small fibres, some sensory neuropathies may also provoke a dissociated sensory loss. Standard nerve conduction studies and somatosensory evoked potentials assess Abeta-fibre function only. Laser pulses selectively excite free nerve endings in the superficial skin layers and evoke Adelta-related brain potentials (LEPs). From earlier studies and new cases we collected data on 270 patients with sensory neuropathy. LEPs often disclosed subclinical dysfunction of Adelta fibres and proved a sensitive and reliable diagnostic tool for assessing small-fibre function in sensory neuropathy.

Topographical distribution of pinprick and warmth thresholds to CO2 laser stimulation on the human skin.

We studied the topographical distribution of laser sensory thresholds on the human hairy skin, using a small laser beam for pinprick and a large beam for warmth sensations. The threshold for pinprick sensation correlated positively with the distance from the brain, suggesting that Adelta nociceptors, the fibers which convey pinprick sensation, are more dense at proximal than at distal body sites. This finding adds information to skin biopsy studies of epidermal free nerve endings which showed a similar gradient, but could not differentiate small myelinated from unmyelinated fiber afferents. Possibly because of a diffuse low density of warmth receptors, laser warmth thresholds showed no trend.

Trigeminal responses to laser stimuli.

The majority of the studies on laser evoked potentials (LEPs) have been focused on hand and foot stimulations and only lately on the trigeminal system. Because of a high receptor density in the facial skin and the very short conduction distance, LEP recordings after trigeminal stimulation are easier and quicker than those after stimulation of the limb extremities. Laser pulses with a stimulus intensity close to perception threshold can evoke well-defined LEPs. Few trials are sufficient to yield stable and reproducible averages. Even ultralate LEPs related to the C-fibre input are comparatively easily obtained from the trigeminal territory. The brain generators of the main LEP waves are probably very close for the trigeminal and limb stimulations. Trigeminal LEPs have been found absent or delayed in patients with trigeminal neuralgia, trigeminal neuropathies, posterior fossa tumors, and brainstem infarctions or demyelinating plaques. Conversely, trigeminal LEPs appear to be enhanced in patients with migraine. High-intensity pulses directed to any trigeminal division also elicit reflex responses: a blink-like reflex in the orbicularis oculi and a single silent period in the contracting masseter muscle. The availability of a neurophysiological method of assessing function of the trigeminal nociceptive pathways reaching both the cerebral cortex and the brainstem reflex circuits, has provided new opportunities for investigating the pathophysiology of orofacial pain syndromes.