New AAN Review of Medical Marijuana in Neurologic Disease

Susan Jeffrey

April 28, 2014

PHILADELPHIA — Results of a review of the evidence supporting the use of medical marijuana in neurologic diseases by the American Academy of Neurology's (AAN's) Guideline Development Subcommittee concludes that certain forms medical marijuana can be helpful to treat some symptoms of multiple sclerosis (MS).

However, it does not appear to help in managing levodopa-induced dyskinesias in Parkinson's disease (PD), and the evidence was insufficient to draw conclusions for now about its effectiveness in Huntington's disease (HD), Tourette's syndrome, cervical dystonia, and epilepsy.

The review is intended to help neurologists and their patients understand the current evidence on medical marijuana, first author Barbara S. Koppel, MD, from New York Medical College, said in an AAN statement. "The AAN review also highlights the need for more high-quality studies of the long-term efficacy and safety of medical marijuana in the treatment of neurologic diseases."

"In conclusion, there's a place for it, and more work is going to need to be done to figure out exactly where its indications will be," Dr. Koppel said during the press conference.

Dr. Barbara S. Koppel

Coauthor Gary Gronseth, MD, University of Kansas School of Medicine, Kansas City, added that the systematic review is meant only to summarize what is known and what is not known about the efficacy of medical marijuana.

In the document, the reviewers assert that marijuana should be studied and, if found to be effective, prescribed.

"Cannabinoids should be studied as other drugs are, to determine their efficacy, and when evidence is available, should be prescribed as other drugs are," they conclude. "Twenty states and the District of Columbia have legalized the medical use of marijuana, and 2 have decriminalized all use. This should encourage researchers to continue seeking answers to the benefits of marijuana use in patients who have neurologic illness."

Dr. Gary Gronseth

The review is published online April 28 in Neurology and appears in the April 29 print issue of the journal. It was also presented at a press conference here during the AAN 66th Annual Meeting. The document is endorsed by the American Autonomic Society, the American Epilepsy Society, and the International Rett Syndrome Foundation.

Systematic Review

For this systematic review, the researchers looked at studies of marijuana in the treatment of symptoms of MS, epilepsy, and movement disorders reported between 1948 and November 2013. After grading the studies using the AAN classification scheme, they found 34 studies that met their inclusion criteria. Of these, 8 were rated as class I.

Their main findings include the following:

  • For spasticity in MS, they concluded that oral cannabis extract is effective, and nabiximols (oromucosal spray Sativex, GW Pharmaceuticals) and tetrahydrocannabinol (THC) are probably effective for reducing patient-centered measures.

    • "It is possible both OCE [oral cannabis extracts] and THC are effective for reducing both patient-centered and objective measures at 1 year," they write.

    • Also in MS, central pain or painful spasms — including spasticity-related pain but excluding neuropathic pain — OCE is effective, and nabiximols and THC are probably effective, they conclude.

    • For urinary dysfunction in MS, nabiximols is "probably effective" for reduction the number of bladder voids per day, they write, while THC and OCE are "probably ineffective" for bladder symptoms.

    • For MS-related tremor, however, they conclude that THC and OCE are "probably ineffective," based on the evidence, and nabiximols is "possibly ineffective."

  • In other neurologic disorders, the review suggests that OCE is "probably ineffective" for levodopa-induced dyskinesias in patients with PD.

  • Finally, oral cannabinoids are of "unknown efficacy" in the non–chorea-related symptoms of HD, tics related to Tourette syndrome, cervical dystonia, or seizure frequency in epilepsy, they further conclude.

Adverse Events

In their review, the authors say that "the risks and benefits of medical marijuana should be weighed carefully."

"There are safety concerns with marijuana use," Dr. Koppel told the press conference here. Adverse effects that were reported in at least 2 studies include nausea, fatigue, increased weakness, behavior or mood changes, suicidal thoughts or hallucinations, dizziness or vasovagal symptoms, fainting, and feelings of intoxication. There were reports of 2 seizures; in 1 case, the seizure was followed by fatal aspiration pneumonia deemed "possibly related" to treatment.

"Mood changes and suicidal thoughts are of special concern when a medication is used in patients for a neurologic illness such as MS or Parkinson's because they are at increased risk of depression and suicide," Dr. Koppel noted.

Studies showed the risk for serious psychological effects overall to be about 1%, or 1 in 100 people, she added.

"In general, medical marijuana is prescribed as a treatment for use only when standard treatment was not helpful in controlling all the patients' symptoms, and standard treatments were allowed to be continued during all of these studies," Dr. Koppel.

She added that doctors should bear in mind that the marijuana products studied in trials to date are generally rigorously monitored to ensure a certain content of various components. "The type of marijuana you can buy so far is not so rigorously defined, so I think they should caution that it may be helpful, but what we're really hoping will come from this is a lot more studies done so that these other forms will become available for use."

Later this week, on May 1, Dr. Koppel will take part in the Controversies in Neurology plenary session looking at the question "Should Neurologists Prescribe Marijuana?" where she will take the "pro" position, and John C.M. Brust, MD, professor of clinical neurology at the Neurological Institute of New York, Columbia University Medical Center, will argue the "con" position.

This systematic review was developed with financial support from the AAN. None of the authors received reimbursement, honoraria, or stipends for their participation in the development of this systematic review. Dr. Koppel has disclosed no relevant financial relationships.

Neurology. 2014;82:1556-1563. Abstract


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