Post- stroke victims with central pain can be left with excruciating pain, often one whole side. If their vestibular system is intact (absence of “marked post-stroke disequilibrium.”), then one cold water ear irrigation can drop pain scale levels by more than 2.58/10, lasting 1- 4 weeks or more. Its effects seem primarily for face and arm pains where pain can be replaced by numbness.
J Neurol Neurosurg Psychiatry. 2008 Jun 11. [Epub ahead of print]
Behavioural evidence for vestibular stimulation as a treatment for central post-stroke pain. McGeoch PD, Williams LE, Lee RR, Ramachandran VS.
Procedure:”In all patients the irrigation procedures were carried out with them supine and their head at 30°. All irrigations lasted at least 30-seconds and used at least 30 ml of water. Irrigation in the cold condition continued until nystagmus was observed.
Session 2 was identical to session 1 except that we would switch the ear that underwent the cold CVS “. Seemed that most needed the 2 sides done.
Results – two with poor vestibular function did not respond. One responded but found the procedure “excruciating”. 5/6 remaining had good face and arm relief lasting 2 – 4 weeks+. Annoying part of the study is fact these people are just into these procedures and the long term relief is not known.
To make things more interesting, there is a case report of it being done for SPINAL pain. Given it was a case study I have just included the abstract:
Spinal Cord. 2008 Jun 3. [Epub ahead of print] Vestibular stimulation can relieve central pain of spinal origin.
McGeoch PD, Ramachandran VS. 1Center for Brain and Cognition, University of California, San Diego, CA, USA. Study design:Single-blind, placebo-controlled case report.Setting:Center for Brain and Cognition, University of California, San Diego, CA, USA.
Objective and results:We present the case of a 64-year-old woman with right-sided central pain following transverse myelitis of her cervical spinal cord in 2002. We investigated whether her pain could be improved beyond a placebo response by cold caloric vestibular stimulation. She had very little response to two placebo procedures but felt her pain to be markedly lowered in her neck and upper limb by vestibular stimulation. This reduction lasted around 10 days, during which she reported that her pain in these areas was the lowest they had been for years.
Conclusions:Her pattern of pain relief is very similar to that reported by patients with central pain arising after thalamic stroke who have reported relief from vestibular stimulation. On the basis of thermosensory disinhibition hypothesis of central pain, we suggest that vestibular stimulation has this beneficial effect because of the intimate anatomical connections between the parieto-insular vestibular cortex and the thermosensory cortex in the dorsal posterior insula.
Comment – Did not seem to help the leg. Otherwise it converted pain to numbness in arm and face. It sounds very exciting and one wonders if further benefit could be achieved by repeating the procedure. For those unable to tolerate the procedure, you would think an anesthetist with some fentanyl and modazolam could alleviate that..
I did find evidence of effectiveness from a two case studies done by the same group in 2007:
Neurocase. 2007 Jun;13(3):185-8.
Rapid relief of thalamic pain syndrome induced by vestibular caloric stimulation. Ramachandran VS, McGeoch PD, Williams L, Arcilla G.
These cases had two irrigations. One, one day after; the other, 11 days after. The first irrigation brought pain down from 8.5 – 6 and 7 – bit better. The second one brought it down from 6 – 3 and the other down from bit better that 7 to 4.5. What however was most startling, was the continued improvement in face and arm pains down to 1-3. The leg pains however were not really changed by treatments.
It does appear that the biggest benefit occurs with the second irrigation and this can be repeated as early as 1 day.
If anybody tries it, let me know how well it works.
Recent article:
Acta Neurol Scand. 2008 Oct 7.
Post-stroke tactile allodynia and its modulation by vestibular stimulation: a MEG case study.
McGeoch PD, Williams LE, Song T, Lee RR, Huang M, Ramachandran VS.
http://www.ncbi.nlm.nih.gov/pubmed/18853944?dopt=Abstract
-“58-year-old woman with CPSP [Central Post Stroke Pain], and marked unilateral tactile allodynia”
-Results: “Tactile simulation within the patient’s allodynic area resulted in contralateral activation of the primary motor and anterior cingulate cortices, which had normalized 24 h post-CVS [caloric vestibular stimulation]
-“We suggest that the unexpected primary motor cortex activation in response to light touch in the allodynic area arises from inappropriate activation of a normal mechanism, which may occur when a threat to homeostasis is present, to lower motor thresholds and allow for more rapid performance of corrective actions. We propose this may be mediated by the interoceptive cortex in the dorsal posterior insula”