Institutionen för odontologi / Department of Odontology
Abstract
The aim of this investigation was to study chronic jaw muscle pain in
fibromyalgia, local myalgia and healthy individuals in relation to the
pain mediators PGE2, LTB4 and NPY and to study the effects of
glucocorticoid administration and repetitive isometric contraction.
A questionnaire showed presence of symptoms from the temporomandibular
region in almost all fibromyalgia patients and the local pain was
correlated to the general pain but on a lower level.
The clinical part comprised patients with fibromyalgia and local myalgia
in the orofacial region as well as healthy individuals. The subjects were
examined for local spontaneous pain, palpatory tenderness, pressure pain
threshold and tolerance levels of the superficial masseter muscle, bite
force, intramuscular temperature and mobility of the mandible. Both
patient groups showed low values of pain threshold as well as
intramuscular temperature and maximum voluntary mouth opening compared to
the healthy individuals. The number of tender mandibular muscles was
higher than the pressure pain threshold lower in fibromyalgia than in
local mylgia. This result and the high frequency of temporomandibular
disorders in the fibromyalgia patients indicates that involvment of the
temporomandibular system is common in fibromyalgia.
Microdialysis was used to sample PGE2 and LTB4 from the superficial
masseter muscle in patients with fibromyalgia and local myalgia as well
as in healthy individuals and venous blood was collected for analysis of
plasma levels of these substances. Intramuscular PGE2 and LTB4 were found
in all groups. LTB4 levels increased upon the trauma created by
microdialysis in patients with fibromyalgia and local myalgia, but not in
the healthy individuals. PGE2 levels were related to muscular pain in the
fibromyalgia patients and was negatively correlated to pressure pain
threshold in the healthy individuals. Masseter muscle pain therefore
seems to be partly of peripheral inflammatory origin.
To evaluate the effects of glucocorticoid administration into the painful
masseter muscle microdialysis and clinical examination was performed two
weeks before and after its local administration in fibromyalgia and local
myalgia. Both groups showed a similar response regarding clinical
parameters but only the patients with local myalgia reported a positive
subjective treatment result. In the patients with fibromyalgia a
reduction of masseter muscle level of PGE2 was associated with a decrease
of spontaneous pain, while the masseter muscle level of LTB4 increased in
both patient groups after the intramuscular glucocorticoid
administration.
In an experimental microdialysis study the intramuscular levels of NPY
and its relation to development of pain was determined during rest and
during repetitive isometric contraction of the superficial masseter and
trapezius muscles in healthy females. The NPY level in the masseter
muscle at rest was higher than the corresponding levels of the trapezius
muscle and plasma. In the trapezius muscle NPY increased during isometric
contraction, while development of pain was associated with a high
precontraction plasma level of NPY. High precontraction level of NPY in
the masseter muscle was associated with development of pain after
isometric contraction of this muscle
