PubMed Health⌕ Search

Biomedical subjects

M Campero

Publications and source records attributed to M Campero.

At least 19 recordsLinked to original sources
PubMed2005

Temperature-dependent double spikes in C-nociceptors of neuropathic pain patients.

Five patients with small-fibre neuropathy characterized by temperature-dependent spontaneous pain, hyperalgesia/allodynia and signs of neurogenic inflammation were studied clinically and thermographically, and by microneurography. Thermography revealed hyperthermia confined to painful and hyperalgesic skin of distal extremities, in absence of sympathetic vasomotor denervation. Quantitative sensory testing documented either reduced thresholds or increased suprathreshold magnitude for heat pain. Microneurography identified 13 primary cutaneous C-nociceptors generating abnormal impulses in response to electrical stimuli and, in one patient, nociceptors firing spontaneously. All five patients showed examples of double spikes, in which a single brief electrical stimulus occasionally or regularly evoked two impulses. In one case, a second impulse occurred at one of three different delays. In all five patients, warming of the skin increased the probability of a second impulse occurring. Impulse doubling has previously been reported as occurring rarely in normal subjects and is attributable to unfiltering of multiple orthodromic impulses due to unidirectional conduction failure at branch points. A higher incidence of double firing in neuropathic pain patients is probably due to a reduced safety factor for conduction in the terminal arborizations of their C-nociceptors. These observations show that unidirectional conduction block provides a peripheral mechanism of temperature-dependent nociceptor hyperactivity in small-fibre neuropathy that may contribute to hyperalgesia.

Adolescent↗
PubMed2005

Peripheral projections of sensory fascicles in the human superficial radial nerve.

The sensory territories of different cutaneous fascicles of the superficial radial nerve were delineated by microneurography at the level of the distal forearm in humans. Three fascicular patterns were found at this level: one supplying the dorsum of the radial aspect of the dorsum of the hand over the first dorsal interosseous space; another supplying the lateral aspect of the first metacarpal extending to the lateral aspect of the thumb; and a third innervating the second interosseous space and the proximal phalanx of the index and middle fingers. The compound fascicular territory is comparable to the classical territory described for the superficial radial nerve. Intraneural microstimulation of individual fascicles did not evoke paraesthesiae or pain beyond their fascicular territory, regardless of the stimulus intensity. We conclude that the superficial radial nerve at the forearm in man is composed of only three fascicles, as shown by the present study and from previous anatomical work. Referred pain seems related to nerve activity in afferent fibres from fascicles supplying deep tissues and muscles, not from cutaneous afferents.

Electric Stimulation↗
PubMed2004

Partial reversal of conduction slowing during repetitive stimulation of single sympathetic efferents in human skin.

AIMS: To describe and identify the function of a class of human C fibre with an unusual response to repetitive electrical stimulation. Other C fibres slow progressively at 2 Hz (type 1), reach a latency plateau (type 2) or hardly slow at all (type 3). METHODS: C fibres innervating hairy skin were recorded by microneurography in the superficial peroneal nerves of 19 healthy volunteers. Baseline electrical stimulation of the skin was at 0.25 Hz, and activity-dependent slowing recorded during stimulation at 2 Hz for 3 min and after a 3-min pause in stimulation. RESULTS: In 41 units, there was a partial recovery of latency during repetitive stimulation. These were classified as 'type-4' units, and identified as sympathetic efferents, since they exhibited spontaneously activity, which was enhanced by manoeuvres that increase sympathetic outflow (15 of 16 cases) and/or suppressed by a proximal anaesthetic block (eight of eight cases). The peak slowing during 2 Hz trains averaged 6.47 +/- 2.06% (mean +/- SD, n=41), but after 3 min the slowing had reduced to 4.90 +/- 2.20%, which was less than in all type 1 (nociceptor) fibres but similar to that in type 2 (cold) fibres. Compared with cold fibres, type-4 sympathetic fibres slowed more after the first 10 impulses at 2 Hz (2.57 +/- 0.45%) and also after a pause in stimulation (1.66 +/- 0.51%). CONCLUSIONS: The distinctive activity-dependent slowing profiles of these type-4 sympathetic C units may help identification in vitro, and suggest that hyperpolarization-activated channels have a particularly prominent role in the axonal membrane.

Adolescent↗
PubMed2004

Spectrum of cutaneous hyperalgesias/allodynias in neuropathic pain patients.

OBJECTIVES: The aim of this study was to discern the pathophysio-logical bases for neuropathic hyperalgesias. METHODS: In this study, neurological and neurophysiological evaluation of 132 consecutive hyperalgesia patients using rigorous clinical and laboratory protocols were carried out. RESULTS: Two discrete semeiologic entities emerged: classic neurological vs atypical, fulfilling taxonomically complex regional pain syndrome (CRPS) II and I, respectively. The classic group (34.9%) exhibited sensorimotor patterns restricted to nerve distribution and documented nerve fiber dysfunction. Among them four (3.03%) had sensitization of C-nociceptors, seven (5.3%) had central release of nociceptive input, and 35 (26.52%) probable ectopic nerve impulse generation. The atypical group (65.1%) displayed weakness with interrupted effort; non-anatomical hypoesthesia and hyperalgesia; hypoesthesia or paresis reversed by placebo, or atypical abnormal movements, and physiological normality of motor and sensory pathways. CONCLUSIONS: Spatiotemporal features of neuropathic hyperalgesia constitute key criteria for differential diagnosis between CRPS II and I and, together with other behavioral sensorimotor features, signal psychogenic pseudoneurological dysfunction vs structural neuropathology. 'Neuropathic' hyperalgesias may reflect neuropathological or psychopathological disorders.

Adolescent↗
PubMed2001

Slowly conducting afferents activated by innocuous low temperature in human skin.

1. Microneurography was used to search for primary afferents responsive to innocuous low temperature in human nerves supplying the hairy skin of the hand or foot. Eighteen units were identified as cold-specific units: they displayed a steady-state discharge at skin temperatures in the range 28-30 degrees C, they were sensitive to small changes in temperature, and they responded vigorously when a cool metal probe touched their receptive fields (RFs). They were insensitive to mechanical stimuli and sympathetic activation. Their RFs comprised one, or at most two, spots less than 5 mm in diameter. 2. Nine units were characterised in detail by a series of 10 s cooling and warming pulses from a holding temperature of 35 degrees C. The threshold temperature for activation by cooling was 29.4 +/- 2.0 degrees C (mean +/- S.D.). Adaptation of the responses to supra-threshold cooling pulses was partial: mean peak and plateau firing rates were maximal on steps to 15 degrees C (35.9 and 19.9 impulses x s(-1), respectively). Three of these units also displayed a paradoxical response to warming, with a mean threshold of 42.3 degrees C. 3. Sixteen of the eighteen cold-specific units were also studied by electrical stimulation of their RFs. They conducted in the velocity range 0.8-3.0 m x s(-1). When stimulated at 2 Hz, their latency increased according to a characteristic time course, reaching a plateau within 3 min (mean slowing (+/- S.D.) 5.2 +/- 1.1 %) and recovering quickly (50 % recovery in 17.8 +/- 4.5 s). 4. To reconcile these findings with previous studies of reaction times and the effects of nerve compression on sensation, it is concluded that either human cold-specific afferent fibres are incompletely myelinated 'BC' fibres, or else there are C as well as A(delta) cold fibres, with the C fibre group contributing little to sensation.

Cold Temperature↗
PubMed1999

Activity-dependent slowing of conduction differentiates functional subtypes of C fibres innervating human skin.

1. The effects of impulse activity on conduction in cutaneous C fibres have been examined in 46 microneurographic recordings from 11 normal subjects and 11 diabetic patients with normal nerve conduction. A tungsten microelectrode was inserted into a cutaneous nerve, usually the superficial peroneal close to the ankle, and intraneural microstimulation was used to identify an area of skin innervated. Three minute trains of 0.25 ms stimuli at 1, 2 and 4 Hz were then delivered to the surface of the skin, separated by intervals of 6 min with stimulation at 0.25 Hz. Slowing and block of conduction were measured from the nerve responses for up to seven C units per stimulation sequence. 2. Three types of C unit were distinguished by their responses to repetitive stimulation: type 1 units slowed progressively during the 3 min trains; slowing of type 2 units reached a plateau within 1 min; while type 3 units hardly slowed at all. Data from normal and diabetic subjects did not differ and were pooled. After 3 min at 2 Hz, the percentage increases in latency were for type 1, 28.3 +/- 9.7 (n = 63 units, mean +/- s.d.); for type 2, 5.2 +/- 1.6 (n = 14); and for type 3, 0.8 +/- 0.5 (n = 5), with no overlap. After 3 min at 4 Hz, 58 % of type 1 units (but no type 2 or 3 units) blocked intermittently. Recovery of latency after stimulation was faster for type 2 than for type 1 units, but conduction velocities of the three types were similar. 3. Type 1 units were identified as nociceptors and 7 type 2 units were identified as 'cold' fibres, activated by non-noxious cold, with no overlap in modality. None of the units tested was activated by weak mechanical stimuli or reflex sympathetic activation. 4. Spike waveforms were averaged for 18 type 1, 10 type 2 and 6 type 3 units. All units had predominantly triphasic action potentials with a major negative peak, but those of type 3 units were on average both smaller and briefer than those of type 1 and type 2 units. 5. It is concluded that repetitive electrical stimulation reliably differentiates nociceptive from cold-specific C fibres innervating human hairy skin, as has previously been shown for the rat. Cold fibres can propagate impulses continuously at much higher rates than nociceptive fibres. The nature of the type 3 units is unclear.

Adult↗
PubMed1998

Ectopic impulse generation and autoexcitation in single myelinated afferent fibers in patients with peripheral neuropathy and positive sensory symptoms.

Microneurographic studies were performed using cutaneous nerves of 8 patients with documented peripheral neuropathy who expressed positive sensory symptoms. Intraneural recordings in single myelinated fibers revealed: (i) ectopic generation of bursts of spontaneous action potentials; (ii) ectopic generation of ongoing repetitive discharges transiently interrupted by natural stimulation of the receptive field; and (iii) repetitive discharges triggered by a preceding action potential. These results provide direct evidence of a peripheral pathophysiological basis for spontaneous and stimulus-induced paresthesias and dysesthesias in patients with peripheral neuropathy.

Action Potentials↗
PubMed1998

Flare and hyperalgesia after intradermal capsaicin injection in human skin.

Flare and hyperalgesia after intradermal capsaicin injection in human skin. J. Neurophysiol. 80: 2801-2810, 1998. We investigated the neurovascular mechanisms that determine the flare response to intradermal capsaicin injection in humans and delineated the associated areas of mechanical and heat hyperalgesia. The flare response was monitored both visually and with infrared telethermography. The areas of mechanical and heat hyperalgesia were determined psychophysically. Thermography detected very large areas of flare. As an early event underlying the flare and before onset of the area of rubor of the skin, thermography detected the appearance of multifocal spots of increased temperature caused by dilatation of cutaneous arterioles. Repetition of capsaicin injection days apart into the same forearm induced multifocal spots of temperature elevation identical to the ones obtained in the first session, indicating dilatation of the same arterioles. Reactive hyperemia also consisted in the appearance of multifocal spots of increased temperature, which were identical to the ones reacting during the flare response, suggesting participation of the same arterioles in both events. Strips of local anesthetic placed to block cutaneous nerves prevented the spread of both the thermographic flare and associated hyperalgesia. It is inferred that the cutaneous nerve fibers responsible for the thermographic flare branch, or have coupled axons, over a long distance. The large area of flare coincided with the area of mechanical and heat hyperalgesia. Equivalence of the areas of flare and mechanical and heat hyperalgesia induced by intradermal capsaicin injection suggests that all three phenomena are the consequence of neural factors that operate peripherally.

Adult↗
PubMed1998

[Optic neuromyelitis: a necrotizing disease of the central nervous system].

Optic neuromyelitis is characterized by simultaneous or successive necrotizing lesions involving the optic nerves and the spinal cord. We report two females with the disease, aged 30 and 34 years old. In the latter, a neuropathological study was done. Both patients had clinical, neuroradiological and pathological features that differed from those of primary demyelinating syndromes such as multiple sclerosis. These patients illustrate the selectivity of optic nerve and spinal cord lesions. The latter involve mainly pyramidal and Goll tracts while, within the necrotizing lesions of the optic chiasma, the fibers of the unaffected optic nerve are spared. This pattern suggests a selective injury to some population of axons. Blood vessels were not affected in the necrotizing areas and the lesions did not follow a vascular territory, therefore a vascular mechanism causing the disease is unlikely. The clinical and neuropathological features of neuromyelitis optic suggest a selective involvement of some axons.

Adult↗
PubMed1996

C-polymodal nociceptors activated by noxious low temperature in human skin.

1. Fifty-five C-polymodal nociceptors innervating hairy skin in human volunteers were tested for discrete stimulus-response properties through microneurography. 2. All fifty-five units were responsive to mechanical and heat stimuli. Twenty-two (40%) of these exhibited an additional response to noxious low temperature. The twenty-two mechano-heat-cold nociceptors displayed similar receptor responses to heat and mechanical stimuli, and conduction velocity, as those of the pure mechano-heat C-polymodal nociceptors. 3. Low temperature stimuli between 19 and 0 degree C evoked responses at low discharge frequency (0.4 +/- 0.22 impulses s-1, mean +/- S.E.M.) in the twenty-two units sensitive to such energy. These units displayed a tendency to decrease their discharge after a few seconds of steady stimulation. 4. Three units tested with a freezing stimulus responded with relatively vigorous discharge, which never exceeded the maximal discharge frequency elicited by either mechanical or heat stimuli. One of these units became sensitized to heat after the freezing challenge. 5. It is concluded that a subpopulation of C-polymodal nociceptors is sensitive to noxious low temperature and may thus contribute to the determination of cold pain. The same type of primary afferent is probably one mediator of the symptom cold hyperalgesia in peripheral nerve disease.

Action Potentials↗
PubMed1995

[Sympathetic denervation of an extremity as a presentation form of apical lung cancer].

We report a 56 years old male patient presenting with a sympathetic denervation of the right upper limb due to an apical lung cancer. Vasomotor paralysis of the limb was objectively documented with a contact termography. The clinical presentation of this patient was unusual, considering that the alteration occurred without sensory or motor changes of the limb or autonomic disturbances of the face. The absence of clinical and neurophysiological involvement of large and small caliber fibres of the brachial plexus and the lack of autonomic dysfunction of the face was explained by a predominant tumoral infiltration of T2 and T4 ventral roots, which supply autonomic innervation to the upper limbs.

Adenocarcinoma↗
PubMed1994

Phentolamine sympathetic block in painful polyneuropathies. II. Further questioning of the concept of 'sympathetically maintained pain'.

To test for the presence of "sympathetically maintained pain" (SMP), we administered placebo-controlled phentolamine sympathetic blocks to 14 patients with painful polyneuropathies. Six received i.v. infusion of saline for 30 minutes, followed by phentolamine (35 mg). In eight patients, the saline phase was followed by double-blind infusion of phentolamine or phenylephrine (500 micrograms), a second saline phase, and then the other active drug. We measured magnitudes of spontaneous pain and mechanical hyperalgesias on a 0-to-10 pain scale every 5 minutes and monitored sensory and sympathetic effects clinically and through quantitative thermotest and thermography. Five patients reported significant diminution of pain (> 50%), all in response to placebo. Neither phentolamine nor phenylephrine provided relief, although all patients had signs of physiologic abnormalities reputed to be determinants or predictors of SMP. These results complement previous studies demonstrating the nonexistence of SMP among "reflex sympathetic dystrophy" patients and further question the concept of SMP.

Adult↗
PubMed1993

Vasomotor innervation of the skin of the hand: a contribution to the study of human anatomy.

The sympathetic vasomotor innervation of the skin of the human hand was studied in 47 subjects who underwent local anaesthetic block of ulnar, median or radial nerves at elbow or wrist levels. Areas of cutaneous anaesthesia were compared with cutaneous territories of paralytic vasodilatation delineated by infrared telethermography. It was found that: (1) during ulnar nerve block the area of vasodilatation matched the area of anaesthesia in all 15 cases; (2) median nerve block induced paralytic vasodilatation which, in 14 of 15 cases, matched the area of cutaneous anaesthesia in median territory, but also extended to the unanaesthetised lateral part of the dorsum of the hand; (3) no vasodilatation developed during radial nerve block in 17 of 18 cases, whereas areas of sympathetic sudomotor paralysis matched the area of radial sensory loss in all 5 subjects in whom sweating function was studied. It is concluded that: (1) the ulnar nerve supplies vasomotor fibres to its cutaneous sensory territory, no less and no more; (2) the median nerve normally provides supplementary vasomotor innervation to the skin of the radial aspect of the dorsum of the hand; (3) the radial nerve supplies sudomotor innervation for the lateral aspect of the dorsum of the hand, but (4) does not normally contribute vasomotor sympathetic fibres to the skin of the hand.

Adult↗
PubMed1993

[Neuroacanthocytosis: report of 3 cases].

Neuroacanthocytosis is a syndrome characterized by extrapyramidal neurologic manifestations such as chorea, dystonia, parkinsonism or tics and acanthocytosis in the blood smear. It is often associated with self aggression (lips and tongue bites) and arreflectic amyotrophy of the extremities. Three adult patients with the characteristic neurologic manifestations of the syndrome, acanthocytosis in the blood smear and normal plasma lipoproteins are presented. Kell antigen was negative in all the patients. Two patients presented as a Gilles de la Tourette syndrome and one as a familiar Chorea. The diagnosis must be suspected in adult patients with extrapyramidal manifestations and in whom the blood smear shows the presence of acanthocytosis. This is the first report of neuroacathocytosis in Chile and the second in a group of patients of hispanic origin.

Adult↗
PubMed1992

A descriptive study of epilepsy in the district of El Salvador, Chile, 1984-1988.

To describe the epidemiological characteristics of epilepsy in a northern area of Chile, an investigation was conducted in four localities in the province of Copiapó (population of 17,694). Based on 314 cases of active epilepsy, the prevalence per 1000 at June 30, 1988 was 17.7. The average annual incidence for the period 1984-1988 was 113 per 100,000. Partial seizures were the most frequent type of seizure diagnosed (54.1%). Antecedents considered as possible etiological factors were found in 29.9% of cases. According to age of onset, 64.6% had their first attack before 15 years. Middle and low socioeconomic classes had higher prevalence rates of epilepsy. We compare our results with previous Latin-American studies.

Adolescent↗