Decreased cutaneous sensory axon-reflex vasodilatation below the lesion in patients with complete spinal cord injury

Changes in sympathetic neurovascular function following spinal cord injury

The effects of spinal cord injury (SCI) on sympathetic neurovascular transmission have generally been ignored. This review describes changes in sympathetic nerve-mediated activation of arterial vessels to which ongoing sympathetic activity has been reduced or silenced following spinal cord transection in rats. In all vessels studied in rats, SCI markedly enhanced their contractile responses to nerve activity. However, the mechanisms that augment neurovascular transmission differ between the rat tail artery and mesenteric artery. In tail artery, the enhancement of neurovascular transmission cannot be attributed to changes in sensitivity of the vascular muscle to α₁- or α₂-adrenoceptor agonists. Instead the contribution of L-type Ca²⁺ channels to activation of the smooth muscle by nerve-released noradrenaline is greatly increased following SCI. By contrast, mesenteric arteries from SCI rats had increased sensitivity to phenylephrine but not to methoxamine. While both phenylephrine and methoxamine are α₁-adrenoceptor agonists, only phenylephrine is a substrate for the neuronal noradrenaline transporter. Therefore the selective increase in sensitivity to phenylephrine suggests that the activity of the neuronal noradrenaline transporter is reduced. While present evidence suggests that sympathetic vasoconstrictor neurons do not contribute to the normal regulation of peripheral resistance below a complete SCI in humans, the available evidence does indicate that these experimental findings in animals are likely to apply after SCI in humans and contribute to autonomic dysreflexia.

Some Problems of the Lower Extremity in Patients with Spinal Cord Injuries

Spinal cord injury (SCI) is devastating, leaving patients wholly or partly paralyzed. Health care providers who care for SCI patients during the acute or chronic phases are faced with different phenomena in the lower extremities of these subjects. In this article, the authors review the relevant changes associated with SCI. Preventive measures of these medical complications are directed according to the specific cause. Early comprehensive rehabilitation carried out by a specialized team prevents complications while enhancing functional gains.

Effect of Therapeutic Sequence of Hot Pack and Ultrasound on Physiological Response Over Trigger Point of Upper Trapezius

Background:

Musculoskeletal pain is a common problem among athletes. Apart from sport injuries, the myofascial pain syndrome is another important problem that affects performance of the athlete.

Objectives:

The aim of this study was to evaluate the effects of therapeutic sequences of the hot pack in combination with ultrasound on the physiological responses over the latent myofascial trigger point (LMTrP) of upper trapezius muscle.

Materials and Methods:

Thirty subjects with a latent myofascial trigger point (LMTrP) in both sides of the upper trapezius muscle participated in the study (age 27.33 ± 4.34 years, weight 58.11 ± 7.47 kg, height 161.50 ± 5.82 cm, pressure pain threshold 2.28 ± 0.24 kg/cm², pain intensity 7.17 ± 2.25 VAS). All subjects received both treatments (hot pack followed by ultrasound: HP + US; and ultrasound followed by hot pack: US + HP) by randomization with a 24 to 48-hour interval between sessions. Outcome measures, including the tissue blood flow (TBF), pressure pain threshold (PPT), supra-thermal threshold (STT) and visual analog scale (VAS) were evaluated at baseline, immediately, after 30 minutes and after 60 minutes.

Results:

The TBF and PPT significantly increased from baseline in both treatment conditions (i.e. HP + US and US + HP), while the HP + US condition showed a trend toward significant difference in VAS and STT in 45°C.

Conclusions:

The application of HP and US treatment induces physiological responses (especially, TBF and PPT) on the LMTrP. This finding provides the direction toward the management of MTrPs condition.

Spinal cord injury increases the reactivity of rat tail artery to angiotensin II

Studies in individuals with spinal cord injury (SCI) suggest the vasculature is hyperreactive to angiotensin II (Ang II). In the present study, the effects of SCI on the reactivity of the rat tail and mesenteric arteries to Ang II have been investigated. In addition, the effects of SCI on the facilitatory action of Ang II on nerve-evoked contractions of these vessels were determined. Isometric contractions of artery segments from T11 (tail artery) or T4 (mesenteric arteries) spinal cord-transected rats and sham-operated rats were compared 6–7 weeks postoperatively. In both tail and mesenteric arteries, SCI increased nerve-evoked contractions. In tail arteries, SCI also greatly increased Ang II-evoked contractions and the facilitatory effect of Ang II on nerve-evoked contractions. By contrast, SCI did not detectably change the responses of mesenteric arteries to Ang II. These findings provide the first direct evidence that SCI increases the reactivity of arterial vessels to Ang II. In addition, in tail artery, the findings indicate that Ang II may contribute to modifying their responses following SCI.

Prominent contribution of L-type Ca2+ channels to cutaneous neurovascular transmission that is revealed after spinal cord injury augments vasoconstriction

In patients with spinal cord injury (SCI), somatosympathetic reflexes produce exaggerated decreases in skin blood flow below the lesion. This hypoperfusion appears to result from an increased responsiveness of cutaneous arterial vessels to neural activation. Here we investigated the mechanisms that underlie SCI-induced enhancement of neurovascular transmission in a cutaneous vessel, the rat tail artery. Isometric contractions of arterial segments from T11 spinal cord transected and sham-operated rats were compared 6 wk postoperatively. SCI more than doubled the amplitudes of contractions of arteries in response to moderate frequencies of nerve stimulation (0.1 to 1 Hz). In arteries from SCI rats, but not those from sham-operated rats, the L-type Ca(2+) channel blocker nifedipine (1 μM) reduced the amplitudes of nerve-evoked contractions. Furthermore, while the sensitivity to the agonists phenylephrine (α(1)-adrenoceptor selective) and clonidine (α(2)-adrenoceptor selective) did not differ significantly between arteries from SCI and sham-operated rats, nifedipine had a greater inhibitory effect on contractions to both agents in arteries from SCI rats. Although sensitivity to clonidine was unchanged, SCI selectively reduced the contribution of postjunctional α(2)-adenceptors to nerve-evoked contractions. In arteries from unoperated rats, the L-type channel agonist BAY K 8644 (0.1 μM) produced a similar enhancement of nerve-evoked contraction to that produced by SCI and also selectively reduced the contribution of α(2)-adrenceptors to these responses. Together the findings demonstrate that the SCI-induced enhancement of neurovascular transmission in the rat tail artery can largely be accounted for by an increased contribution of L-type Ca(2+) channels to activation of the vascular smooth muscle.

Effect of functional electrostimulation on impaired skin vasodilator responses to local heating in spinal cord injury

Spinal cord injury (SCI) induces vascular adaptations below the level of the lesion, such as impaired cutaneous vasodilation. However, the mechanisms underlying these differences are unclear. The aim of this study is to examine arm and leg cutaneous vascular conductance (CVC) responses to local heating in 17 able-bodied controls (39 +/- 13 yr) and 18 SCI subjects (42 +/- 8 yr). SCI subjects were counterbalanced for functional electrostimulation (FES) cycling exercise (SCI-EX, n = 9) or control (SCI-C, n = 9) and reanalyzed after 8 wk. Arm and leg skin blood flow were measured by laser-Doppler flowmetry during local heating (42 degrees C), resulting in an axon-reflex mediated first peak, nadir, and a primarily nitric oxide-dependent plateau phase. Data were expressed as a percentage of maximal CVC (44 degrees C). CVC responses to local heating in the paralyzed leg, but also in the forearm of SCI subjects, were lower than in able-bodied controls (P < 0.05 and 0.01, respectively). The 8-wk intervention did not change forearm and leg CVC responses to local heating in SCI-C and SCI-EX, but increased femoral artery diameter in SCI-EX (P < 0.05). Interestingly, findings in skin microvessels contrast with conduit arteries, where physical (in)activity contributes to adaptations in SCI. The lower CVC responses in the paralyzed legs might suggest a role for inactivity in SCI, but the presence of impaired CVC responses in the normally active forearm suggests other mechanisms. This is supported by a lack of adaptation in skin microcirculation after FES cycle training. This might relate to the less frequent and smaller magnitude of skin blood flow responses to heat stimuli, compared with controls, than physical inactivity per se.

Diminished skin vasodilator response to local heating in patients with long-standingsubacute myelo-optico-neuropathy

BACKGROUND

Local heating of non-glabrous skin increases skin blood flow (SkBF) in two phases: the initial peak (P1) is mediated by sensory axon reflex, and the plateau phase (P2) is thought to be mediated by local production of substances including nitric oxide. We evaluated P1 and P2 responses in subacute myelo-optico-neuropathy (SMON).

METHODS

SkBF response to local heating from 32 degrees C (5 min of baseline) to 42 degrees C (at least for 30 min) of the dorsal surface of the hand skin were measured in 7 SMON patients (67.6+/-10.0 years) and 7 normal control volunteers (65.0+/-7.4 years) participated.

RESULTS

Mean values of SkBF at P1 (SkBFP1) and SkBF during P2 (SkBFP2) were significantly lower in SMON patients than in controls (p<0.05, p<0.05). Mean SkBFP1/SkBF at baseline (SkBFbase) and SkBFP2/SkBFbase ratios were significantly lower in SMON patients than in controls (p<0.01 and p<0.05, respectively).

CONCLUSIONS

The SkBF response to local heating was diminished in SMON patients. This may reflect the involvement of the spinal cord, peripheral sensory nerves, and sympathetic post-ganglionic nerves in SMON.

Heat-provoked skin vasodilatation in innervated and denervated trunk dermatomes in human spinal cord injury

STUDY DESIGN

Cross-sectional, observational, controlled study.

OBJECTIVE

High spinal cord injury (SCI) results in disruption of sympathetic vasomotor control. Vasodilatation as a response to local heating is a biphasic mechanism: the first phase (neurogenic) is mediated by the axon-reflex and is modulated by activity of sympathetic nerves. Our objective was to determine whether the response to heat provocation in trunk dermatomes may provide a measure of vasomotor sympathetic function in SCI.

SETTING

National Spinal Injuries Centre, Stoke Mandeville Hospital, Buckinghamshire, UK; Autonomic Unit, The National Hospital for Neurology and Neurosurgery, Queen Square, London, UK; Neurovascular Medicine Unit, Imperial College London at St Mary's Hospital, UK.

SUBJECTS

A total of 30 subjects were studied; 18 had chronic complete SCI (level C6-T11) and 12 were healthy controls.

METHODS

Recordings of skin blood flow (SkBF) were obtained with thermostatic laser Doppler probes placed in the upper trunk (at C4) and lower trunk (T10 or T12) dermatomes.

RESULTS

SkBF at baseline (SkBF(bas)) and SkBF at the first peak of vasodilatation (SkBF(max)) showed no significant differences between SCI and controls either in upper or lower trunk dermatomes. However, the ratio of SkBF(max)/SkBF(bas) was significantly different in lower trunk dermatomes in SCI at C6-T5 level (7.5+/-3.5 PU) compared to SCI at T6-T11 level (3.5+/-1.5 PU) (P < 0.01).

CONCLUSION

Measurement of SkBF in response to local heating may provide a safe, noninvasive method to assess integrity of sympathetic spinal pathways to the local vasculature. This may aid the classification of the SCI lesions, as the autonomic component currently is not included in the accepted American Spinal Injury Association scoring.

Skin reactivity to aeroallergens is reduced in human T-lymphotropic virus type I-infected healthy blood-donors (asymptomatic carriers)

BACKGROUND

A type 2 immune response, characterized by high levels of interleukin-4 and immunoglobulin E synthesis is a hallmark of respiratory allergic diseases. Individuals infected with human T-lymphotropic virus type I (HTLV-I) virus have spontaneous T-cell proliferation and increased interferon gamma production, which are immunological functions associated with a type 1 immune response.

OBJECTIVE

To determine the frequency of asthma and rhinitis symptoms and immediate skin reactivity to aeroallergens in HTLV-I infected individuals, compared with noninfected subjects.

METHODS

Cross sectional study of 101 HTLV-I infected and 101 control uninfected blood donors, assessed by enzyme-linked immunosorbent assay and Western blot assays. The subjects were age and sex-matched, identified as presenting allergy history by questionnaire, which was complemented by a complete clinical examination and skin prick tests for aeroallergens.

RESULTS

The frequency of atopy was lower in infected than uninfected subjects, 14.9 and 29.7% (P = 0.017), respectively. Skin reactivity to Dermatophagoides pteronissynus, Dermatophagoides farinae and Blomia tropicalis were the most frequently observed among all the tested antigens in both groups. Skin reactivity to histamine was also reduced in the infected individuals compared with uninfected subjects (medians 4.0 vs 5.0, respectively; P < 0.0001). Infection by HTLV-I was found to be a factor of protection to atopy (RP 0.44; P = 0.005).

CONCLUSIONS

The HTLV-I infection reduces the frequency of respiratory allergy and skin reactivity to aeroallergens.

Skin vasodilator response to local heating in human chronic spinal cord injury

Local heating evokes an increase in skin blood flow (SkBF), which consists of an initial peak (axon-reflex mediated) followed by a brief nadir and a secondary rise to a plateau. The aim of this study was to investigate whether heat provoked vasodilatation detects sympathetic vasomotor dysfunction and completeness of injury in patients with spinal cord injury (SCI). Twelve (seven complete, and five incomplete; level C4-L4) SCI patients, and nine healthy subjects as controls were studied. Thermostatic laser Doppler probes, which heat the skin locally, were placed on the dorsum of the hand and foot. SkBF was measured by laser Doppler flowmetry at baseline and at the first peak of vasodilatation (SkBF(max)). On the hand, SkBF at baseline and SkBF(max) were similar between the three groups. On the foot, SkBF at baseline was similar between the three groups but SkBF(max) was significantly diminished in complete SCI patients compared with controls (P < 0.01). In conclusion, heat provoked axon-reflex vasodilatation was diminished in the foot, below the level of lesion, in complete SCI. This test, that evaluates localized sympathetic vasomotor dysfunction, may be a useful non-invasive technique to detect completeness of autonomic disruption after SCI.

Towards improved clinical and physiological assessments of recovery in spinal cord injury: a clinical initiative

Clinical practice and scientific research may soon lead to treatments designed to repair spinal cord injury. Repair is likely to be partial in the first trials, extending only one or two segments below the original injury. Furthermore, treatments that are becoming available are likely to be applied to the thoracic spinal cord to minimise loss of function resulting from damage to surviving connections. These provisos have prompted research into the improvement of clinical and physiological tests designed (1) to determine the level and density of a spinal cord injury, (2) to provide reliable monitoring of recovery over one or two spinal cord segments, and (3) to provide indices of function provided by thoracic spinal root innervation, presently largely ignored in assessment of spinal cord injury. This article reviews progress of the Clinical Initiative, sponsored by the International Spinal Research Trust, to advance the clinical and physiological tests of sensory, motor and autonomic function needed to achieve these aims.