| Level I | Good quality evidence |
Systematic review of RCTs with consistent findings High quality individual RCT |
| Level II | Limited quality patient orientated evidence |
Systematic review of lower quality studies or studies with inconsistent findings Low quality clinical trial Cohort studies Case-control studies |
| Level III | Other | Consensus guidelines, extrapolations from bench research, usual practice, opinion, disease-oriented evidence (intermediate or physiologic outcomes only), or case series |
[68] Propranolol: Zesiewicz TA, Elble RJ, Louis ED, Gronseth GS, Ondo WG, Dewey RB Jr, Okun MS, Sullivan KL, Weiner WJ. Evidence-based guideline update: treatment of essential tremor: report of the Quality Standards subcommittee of the American Academy of Neurology. Neurology. 2011 Nov 8;77(19):1752-5. https://www.ncbi.nlm.nih.gov/pubmed/26678329
Zesiewicz TA, Kuo SH. Essential tremor. BMJ Clin Evid. 2015 Dec 15;2015. pii: 1206. https://www.ncbi.nlm.nih.gov/pubmed/26678329
Propanolol: Jefferson D, Jenner P, Marsden CD. Relationship between plasma propranolol concentration and relief of essential tremor.J NeurolNeurosurg Psychiatry. 1979 Sep;42(9):831-7. http://www.ncbi.nlm.nih.gov/pubmed/501384