Definitions of the classification of screening evidence (Classes I–IV), classification of therapeutic evidence (Classes I–IV), and strength of recommendations (A, B, C, U) are provided at the end of the "Major Recommendations" field.
For patients with trigeminal neuralgia (TN), routine imaging may be considered to identify symptomatic TN (STN) (Level C).
The presence of trigeminal sensory deficits or bilateral involvement of the trigeminal nerves should be considered useful to identify patients with STN. However, because of poor specificity, the absence of these features is not useful for excluding STN (Level B).
Measuring trigeminal reflexes in a qualified electrophysiologic laboratory should be considered useful for distinguishing STN from classic TN (CTN) (Level B).
Younger age at onset, involvement of the first division of the trigeminal nerve, unresponsiveness to treatment, and abnormal trigeminal evoked potentials should be disregarded as useful for accurately identifying patients with STN (Level B).
To control pain in patients with TN: carbamazepine should be offered (Level A), oxcarbazepine should be considered (Level B), baclofen, lamotrigine, and pimozide may be considered (Level C), and topical ophthalmic anesthesia should not be considered (Level B).
For patients with TN refractory to medical therapy: early surgical therapy may be considered (Level C), and percutaneous procedures on the Gasserian ganglion, gamma knife, and microvascular decompression may be considered (Level C).
Definitions:
Classification of Evidence for Rating of a Screening Article
Class I: A statistical, population-based sample of patients studied at a uniform point in time (usually early) during the course of the condition. All patients undergo the intervention of interest. The outcome, if not objective, is determined in an evaluation that is masked to the patients' clinical presentations.
Class II: A statistical, non-referral-clinic-based sample of patients studied at a uniform point in time (usually early) during the course of the condition. Most patients undergo the intervention of interest. The outcome, if not objective, is determined in an evaluation that is masked to the patients' clinical presentations.
Class III: A sample of patients studied during the course of the condition. Some patients undergo the intervention of interest. The outcome, if not objective, is determined in an evaluation by someone other than the treating physician.
Class IV: Expert opinion, case reports or any study not meeting criteria for Class I to III.
Classification of Evidence for Rating of a Diagnostic Article
Class I: Evidence provided by a prospective study in a broad spectrum of persons with the suspected condition, using a reference (gold) standard for case definition, where test is applied in a blinded evaluation, and enabling the assessment of appropriate tests of diagnostic accuracy. All patients undergoing the diagnostic test have the presence or absence of the disease determined.
Class II: Evidence provided by a prospective study of a narrow spectrum of persons with the suspected condition, or a well designed retrospective study of a broad spectrum of persons with an established condition (by "gold standard") compared to a broad spectrum of controls, where test is applied in a blinded evaluation, and enabling the assessment of appropriate tests of diagnostic accuracy.
Class III: Evidence provided by a retrospective study where either persons with the established condition or controls are of a narrow spectrum, and where the reference standard, if not objective, is applied by someone other than the person that performed the test.
Class IV: Any design where test is not applied in an independent evaluation OR evidence provided by expert opinion alone or in descriptive case series (without controls).
Classification of Evidence for Rating of a Therapeutic Article
Class I: Prospective, randomized, controlled clinical trial with masked outcome assessment, in a representative population. The following are required:
- Concealed allocation
- Primary outcome(s) clearly defined
- Exclusion/inclusion criteria clearly defined
- Adequate accounting for drop-outs and cross-overs with numbers sufficiently low to have minimal potential for bias
- Relevant baseline characteristics are presented and substantially equivalent among treatment groups or there is appropriate statistical adjustment for differences.
Class II: Prospective matched group cohort study in a representative population with masked outcome assessment that meets a-e above OR a randomized controlled trial in a representative population that lacks one criteria a-d.
Class III: All other controlled trials (including well-defined natural history controls or patients serving as own controls) in a representative population, where outcome is independently assessed, or independently derived by objective outcome measurement.*
Class IV: Evidence from uncontrolled studies, case series, case reports, or expert opinion.
*Objective outcome measurement: an outcome measure that is unlikely to be affected by an observer's (patient, treating physician, investigator) expectation or bias (e.g., blood tests, administrative outcome data).
Classification of Recommendations
Level A = Established as effective, ineffective, or harmful (or established as useful/predictive or not useful/predictive) for the given condition in the specified population. (Level A rating requires at least two consistent Class I studies.)**
Level B = Probably effective, ineffective, or harmful (or probably useful/predictive or not useful/predictive) for the given condition in the specified population. (Level B rating requires at least one Class I study or at least two consistent Class II studies.)
Level C = Possibly effective, ineffective, or harmful (or possibly useful/predictive or not useful/predictive) for the given condition in the specified population. (Level C rating requires at least one Class II study or two consistent Class III studies.)
Level U = Data inadequate or conflicting; given current knowledge, treatment (test, predictor) is unproven. (Studies not meeting criteria for Class I–Class III.)
**In exceptional cases, one convincing Class I study may suffice for an "A" recommendation if 1) all criteria are met, 2) the magnitude of effect is large (relative rate improved outcome >5 and the lower limit of the confidence interval is <2).
