Main Findings :
The existence of PUS by central sensitization, as defined above, which
in particular causes severe dysmenorrhoea, appears increasingly
plausible, regardless of whether endometriosis is present or not. Recent
studies by Evans (43), Stratton (44), and Grundström (45) all point in
this direction.
PUS or ”endometriosis-like” syndrome is typically identified by negative
imaging and anatomical findings. The main symptom is severe
dysmenorrhoea; however, pelvic pain from uterine contractions, deep
dyspareunia, and uterus trigger pain at vaginal examination, are among
the diagnostic criteria as defined in the PUS diagnostic score (Table
1).
The Viscero-Visceral sensitization mechanisms, as described by
Giamberardino (46), account for a common association with painful
bladder syndrome through peripheral sensitization phenomena. Similarly,
co-morbidities such as hyperesthesia of the vulvar vestibule, are
connected with the occurrence of the frequent Provoked Vulvar
Vestibulodynia (PVD) (47), which is responsible for introductory
dyspareunia.
But the most frequently associated disorders are pelvic floor muscle
hypertonia and myofascial syndromes (42, 44). This muscle hypertonia is
consistent with pelvic sensitization and, therefore, applies to PUS,
which has been well documented in the various cine MRI studies, as
described above.
In terms of therapeutic consequences, BTX injections have a logical
application here. Besides its widely demonstrated effectiveness in
treating muscle spasms, hypertonia, or hyperactivity by inhibiting the
release of acetylcholine at the neuromuscular junction by competitive
neurotoxin inhibition (48 and 49), BTX may also have direct peripheral
and central analgesic effects. It may also have a direct effect on
inflammation by reducing the release of pro-inflammatory neuropeptides
(50 and 51)
The use of BTX in pelvic floor muscle hypertonia, spasms, and myofascial
pain was first documented by Abbott in 2006 (52). Several publications
have confirmed that botulinum toxin injections are useful for treating
this condition (53, 54, 55, 57, and 58). The effectiveness of BTX
injections on pelvic floor muscle hypertonia and spasms has been proven
in a number of prospective and randomised studies (54 & 57). On the
other hand, for myofascial pain, the randomised studies conducted by
Dessie (59) and Levesque (60) found no significant difference with the
control group for saline and local anaesthetics, respectively.
As far as we know, uterine myometrial BTX injections used in cases of
PUS and/or severe dysmenorrhoea has never been described before. This
indication follows the same pathophysiological approach as that proposed
for OAB or PBS (31, 32 & 33).
The procedure under hysteroscopy is simple and can be easily reproduced.
Our pilot study (34), mentioned above, reported no immediate or remote
post-operative complications.
Although pregnancy was not recommended within 4 months of the myometrial
injection in this study, no maternal or fetal complications were
reported in the literature when a botulinum toxin injection was
administered during pregnancy (61 & 62). One patient in our study
became pregnant, despite being advised against it. This was an
unintended pregnancy and a voluntary termination was performed in the
first trimester. This procedure was carried out without any
complications.