Analgesia and nerve function following pulsed radiofrequency for postmastectomy pain

About one third of the women undergoing breast surgery for cancer develop
chronic postmastectomy pain (PMPS) in their axilla and chest wall. PMPS is a
neuropathic pain syndrome that is predominantly caused by a lesion of the
intercostobrachial nerve during surgery. As the pain is typically exacerbated
by arm movements and lying on the painful side and is accompanied by
allodynia, PMPS has considerable impact on daily functioning, quality of sleep
and sexual life.
The standard treatment of PMPS with antidepressants, capsaicine-crème and TENS
often gives poor painrelief or has unacceptable side effects. Alternatively,
the isothermal radiofrequency treatment known as pulsed radiofrequency (PRF)
may be used to relieve neuropathic pain. PRF is widely used as a treatment
option for neuropathic pain in the Netherlands. However the effect of PRF on
PMPS has not been shown yet. In addition the effect of PRF on nerve function
has not been evaluated yet.

The aim of this study is the evaluation of efficacy of PRF on the intensity of
pain in patients with PMPS for more than six months after surgery with the
hypothesis that PRF reduces the intensity of pain more than 50%. In addition,
the precise evaluation of afferent nerve function via Quantitative Sensory
Testing (QST) before and after treatment will be performed in order to obtain
information on prognosis possible mode of action of PRF related to subgroups
based on neuropathic pain phenotype.

In a prospective double-blind randomized placebo-controlled trial patients are
assigned to receive PRF of the thoracic dorsal root ganglia Th 6 or Th 1
respectively or a sham-intervention.
See attatchment for flow scheme of the study

The C-arm of the fluoroscopy unit is positioned with the beam vertical to the
axis of the intervertebral foramen. The entry point is located by projecting a
metal ruler over the caudal part of the foramen. The 22 G cannula (SMK Pole
needle 100 mm with 4 mm active tip, Cosman International) is introduced
parallel to the beam and, if necessary, the position is corrected
in the superficial subcutaneous layers. The fluoroscope is then adjusted to the
lateral view and the cannula is inserted further until the tip projected over
the middle or lower dorsal third of the intervertebral foramen. The stylet of
the cannula is then replaced by the RF probe (SMK-TC 10, Radionics, Burlington,
MA). After checking the impedance, indicating a normal, closed electrical
circuit, stimulation is performed at a frequency of 50 Hz to obtain a sensory
stimulation threshold in all patients. If paresthesias are elicited along the
tested thoracic nerve root with less than 0.3 V an adequate proximity of the
DRG (Ford et al., 1984) is achieved. PRF current of 45 V/ 140 mA with pulses of
2 Hz and 20 ms duration is then applied for 6 min generator (Cosman RFG-1B
Lesion Generator)

The intervention studied is frequently performed for the treatment of
neuropathic pain without any complications that can be attributed to pulsed
radiofrequency. The only risks of the treatment is adherent to the placement of
the electrode and the applicated lidocaine, ie pain at the puncture site,
pneumothorax due to accidental puncture of the pleura and allergic reaction to
lidicaine. Pneumothorax is the most serious hypothetic complication. It has
not occured in the personal experience of the study ccordinator (AL) and is not
described in the literature. To keep this risc as low as possible the electrode
is placed onder fluroscopy and patients are controled for dyspnoe 30 min
following PRF treatment.