Prognostic factors in microvascular decompression for trigeminal neuralgia.

The results of microvascular decompression (MVD) in 68 patients with trigeminal neuralgia followed for 1 to 5 years were compared with the clinical and operative findings and with the surgical modalities. Among 20 factors analyzed, the mode of pain manifestation proved to be the only factor significantly related to prognosis (p less than 0.001). In patients with paroxysmal pain only, a cure was obtained in 95%, whereas in those with paroxysmal and permanent pain, 58% were cured. None of the remaining factors showed any unfavorable influence on the results of MVD in cases of paroxysmal pain only. Some factors seemed to be related to prognosis in patients with a permanent pain component, and the following conclusions concern this group of patients only. Two factors proved to be statistically significant. First, patients with pain extending to two or three branches responded to MVD less favorably than those with pain in one branch only. The interposition of a piece of periosteum to separate a conflicting artery from the root led to worse results than the use of a square of Dacron. Other conclusions were based on small numbers and should be verified. A sensory deficit extending to two or three branches was related to worse results that a sensory deficit in one branch or its absence; a prior surgical procedure plays an additional unfavorable role. The patients with the least advanced degree of vasculonervous conflict (VNC) responded to MVD less favorably than those with severe cross compression; a posterosuperior site of VNC seems to play an additional unfavorable role. The distribution of some factors among types of pain manifestation showed marked differences, which seem to relate to results. The clinical and operative findings indicate that the sensory deficit corresponds to the extent of compression by the conflicting vessel. The necessity of distinguishing various clinical forms of trigeminal neuralgia for practical and cognitive reasons is emphasized.