Abstract ID: A29

Abstract Title: INTRATHECAL BACLOFEN FOR TREATING DYSTONIA OF COMPLEX REGIONAL PAIN SYNDROME TYPE 1

Poster Type: Either

ABSTRACT BODY

Introduction
A proportion of patients with complex regional pain syndrome (CRPS) may have dystonia that is often unresponsive to traditional treatment. As the duration of CRPS lengthens, the number of patients who sustain movement disorders increases. In a distinct phenotype of CRPS associated with human leukocyte antigen DR13 patients may even progress to a multifoccal or generalised tonic dystonia. We present a case of CRPS with predominant dystonia that has responded well to intrathecal baclofen.
Case
A 37 year old female with established CRPS of left lower limb was referred to us as a tertiary referral. She has had whiplash injury in a car accident 2 years back. 3 months later her low back pain was treated with epidural infusion of local anaesthetic and opioids. After the termination of epidural she experienced severe radicular pain associated with hyperalgesia in her left leg. She gradually developed symptoms of CRPS (burning pain, hyperalgesia, allodynia, paraesthesiae, dysaesthesia, edema, trophic changes, hyperhydrosis, faster hair and nail growth and change in skin temperature). She was treated with Gabapentin 1800 mg per day, tricyclic antidepressants, simple analgesics and physiotherapy. Intravenous regional guanithidine block resulted in 3 months improvement. There was no response to repeat guanithidine blocks. Subsequently marked dystonia developed in left leg resulting in inversion of left foot. She was unable to weight bear. Below knee plaster cast corrected the foot inversion but the deformity and severe pain associated with it returned after 3 weeks. Examination under anaesthesia revealed no contractures. Her Gabapentin was increased to 2400 mg/day. Trial of intrathecal bolus of baclofen 25 micrograms followed by 25 mcg/day infusion through a microspinal catheter resulted in complete recovery from dystonia. Spontaneous movement was possible and improved analgesia lasted for 4 weeks after stopping infusion. Patient had InDura® Free-Flow Intrathecal Catheter inserted at L3-4 interspace with tip at T10-11 interspace. This was connected to implanted Synchromed®II infusion pump infusing 25 mcg/day Baclofen. Her symptoms and dystonia are completely resolved, and there is good functional improvement.
Discussion
Dystonia is characterised by involuntary abnormal, predominant flexor postures of the fingers, wrist and feet. Impairment of interneuronal circuits that mediate both pre- and post-synaptic inhibition is noted in these patients. Intrathecal administration of baclofen, a Gamma Amino Butyric Acid receptor B agonist, has highlighted the involvement of spinal GABAergic inhibitory interneurons. These interneurons inhibit the amount of excitatory synaptic transmitter released by sensory input on motoneurons in the spinal cord by means of presynaptic inhibition. Through impairment of these interneurons, motoneurons are exposed to an uninhibited sensory and supraspinal input. Baclofen mimics the actions of GABA on presynaptic receptors resulting in inhibition of sensory input to the motor neurons of the spinal cord.
Conclusion
Baclofen is effective in the treatment of dystonia of CRPS. Some patients also report reduction in pain, sensory symptoms and autonomic symptoms during continuous infusion of intrathecal baclofen.

ATTACHED FILES

Reg Anesth Pain Med 2004; 29(2):A29