The abstract below explains why I am so adamant that rosacea
sufferers not sitting down and get blasted by Candela's Pulsed Dye
Lasers – if the energy is not focused right on the blood vessel,
nerve irritation and physical damage can result. For the record, as
a medical scientist, I am against the studies performed below due to
the pain evoked to the animals. This study would have never passed
the Animal Care and Use Committee at our Medical University and for
good reasons. But, it does detail why I caution against treatment
at purpuric levels.

Regards,

Geoffrey
______________________________

Dr. Geoffrey Nase
Ph.D. Neurovascular Physiologist
http://www.drnase.com
______________________________





Neurobiol Dis. 2005 Feb;18(1):40-53. Related Articles, Links


Skin denervation, neuropathology, and neuropathic pain in a laser-
induced focal neuropathy.

Chiang HY, Chen CT, Chien HF, Hsieh ST.

Department of Anatomy and Cell Biology, National Taiwan University
College of Medicine, Taipei 10018, Taiwan.

Small-diameter sensory nerves innervating the skin are responsive to
noxious stimuli, and an injury to these nerves is presumably related
to neuropathic pain. Injury-induced neuropathic pain in animals can
be produced by laser irradiation, which usually requires concomitant
use of photosensitive dyes, known as the photochemical approach. It
is not clear whether laser irradiation alone can induce neuropathic
pain. In addition, two issues are important to apply these
approaches: the relationship between the extent of laser irradiation
and the occurrence of neuropathic pain, and the susceptibility of
small-diameter sensory nerves in the skin to laser-induced
neuropathic pain. To address these issues, we designed a new model
of focal neuropathy by applying a diode laser of 532 nm (100 mW) to
the sciatic nerve and evaluated small-diameter nerves by quantifying
skin innervation and large-diameter nerves by measuring amplitudes
of the compound muscle action potential (CMAP). Immediately after
laser irradiation, epineurial vessels were occluded due to the
formation of thrombi, and the blood flow through these vessels was
markedly reduced. On postoperative day (POD) 2, animals developed
characteristic manifestations of neuropathic pain, including
spontaneous pain behaviors, thermal hyperalgesia, and mechanical
allodynia. These phenomena peaked during PODs 7-21, and lasted for 3-
6 weeks. The neuropathology at the irradiated site of the sciatic
nerve included a focal area of axonal degeneration surrounded by
demyelination and endoneurial edema. The extent of damage to large-
diameter motor and sensory nerves after laser irradiation was
evaluated by nerve conduction studies. On the irradiated sides,
amplitudes of the compound muscle action potentials and sensory
nerve action potentials (SNAPs) were reduced to 65.0% (P < 0.0001)
and 42.5% (P < 0.01) of those on the control sides, respectively.
Motor innervation of the neuromuscular junctions (NMJs) on plantar
muscles was examined by combined cholinesterase histochemistry and
immunohistochemistry. The ratio of innervated NMJs on the operated
sides decreased to 76.3% of that on the control side. Skin
innervation in the territory of the irradiated sciatic nerves was
evaluated by immunohistochemistry with neuronal markers. Among these
markers, epidermal nerve densities for protein gene product (PGP)
9.5, calcitonin gene-related peptide (CGRP), and substance P (SP)
were significantly lower on the irradiated sides than the control
sides with a different degree of loss for each marker (42.1-53.1%, P
< 0.05). Results suggest that laser-induced focal neuropathy
provides a new system for studying neuropathic pain. With this
approach, the extent of nerve injury can be quantified. Both small-
diameter epidermal nerves and large-diameter sensory and motor
nerves are susceptible to laser-induced injury of different degrees.