Tic

Cannabinoids: pathways and role in the management of motor tics

Virginia Thornley, M.D., Neurologist, Epileptologist

July 16, 2018

@VThornleyMD

https://neurologybuzz.com/

Introduction

As medical marijuana emerges from the caves of obscurity in treating illnesses, physicians are at the forefront of rediscovering ailments that can be treated by medical cannabis. While most traditional scientists and trained clinicians do not think highly of anecdotal research, patients in clinical practice are the best parameters in judging whether a medication is working or not. Oftentimes, even with the best research, clinical practice conveys side effects that were never found during the short period of time of the study. Additionally, as hundreds of thousands of patients start using a new product it is only then one can observe the true efficacy and safety profile which accounts for why research does not always correlate with clinical practice.

Sometimes, one comes across a medication where certain other symptoms may be alleviated not listed on the indications. As a growing number of patients areĀ  recommended medical cannabis, they are presenting with a variety of symptoms that are incidentally relieved.

Background of endacannabinoids and relationship to areas in the brain subserving movement

One of the areas where the brain is rich in endocannabinoid receptors CB1 and CB2 receptors are in the basal ganglia which subserves the function of movement modulation. There likely exists a role of endogenous cannabinoids in the regulation of movement given its abundance in this area. The CB1 receptors are found in the striatum and caudate nucleus which are rich in GABA-ergic neurons, and pre-terminals of the internal and external globus pallidus, and substantia nigra. They are found in the glutamatergic pathways within the cortical systems and in the subthalamic nucleus (1).

The endocannabinoid system appears to inhibit glutamatergic pathways and increases GABAergic activity in the basal ganglia. It affects the dopaminergic pathway (2). It is speculated that the endocannabinoids may play a role in modulating the various neurotransmitter systems. While large clinical randomized controlled clinical trials may be lacking there is evidence that cannabinoids may reduce the clinical manifestations of motor tics (2).

Review of case studies and case series

There is a paucity of clinical trials studying the role of cannabis in movement disorders. Most of the data is from pre-clinical studies or case reports. Clinical research undoubtedly has been stunted given the scheduling of the agent under a schedule I category and other related factors.

In a small study of 12 patients, tetrahydrocannabinol was studied to determine effectiveness in treatment of tics(3). The Tourette Syndrome Symptom List (TSSL) was utilized for self-evaluations by patients. The examiners used the Yale Global Tic Severity List, Shapiro Tourette Syndrome Severity Scale for rating the severity of tics. A randomized controlled clinical trial was carried out. Those in the group where delta-9-tetrahydrocannabinol showed improvement compared to the placebo control group. There was great improvement using the TSSL with a p=0.15. Significant improvement found with complex motor tics using examiner ratings. Simple and vocal tics showed improvement (3).

In a case series of 19 patients, there were 60% who had much less motor tics after treatment with cannabinoids. There were 18 patients who felt they significantly improved (4).

In summary

The fact that the endocannabinoid system on which cannabinoids work is widely found within the basal ganglia which modulates fine movement correlates the function it has with modulation of movement.

While the scarcity of clinical trials is evident, cannabinoids continue to be used in clinical practice with some modicum of success for treatment of motor tics.

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References

  1. Koppel, B. Cannabis in the treatment of dystonia, dyskinesias, and tics. Neurotherapeutics. 2015, Oct. 12(4):788-792
  2. Muller-Vahl, K.R., Kolbe, H., Schneider, U., Emrich, H.M. Cannabis in movement disorders. Forsch Komplementarmed. 1999. Oct. 6 Suppl 3:23-27.
  3. Muller-Vahl, K.R., Schneider, U., Koblenz, A., Jobges, M., Kolbe, H., Daldrup, T., Emrich, H.M. Treatment of Touterret’s syndrome with delta 9-tetrahydrocannabinol (THC) a randomized crossover trial. Pharmacopsychiatry. 2002, Mar. 35(2):57-61
  4. Abi-Jaoude, E., Chen, L., Cheung, P., Bhirkram, T., Sandor, P. J. Neuropsychiatry Clin Neurosci. 2017 29(4):391-400
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