[Quantitative determination of corneal sensitivity in idiopathic trigeminal neuralgia and after neurosurgical interventions on the trigeminal nerve].

The purpose of our study was to determine, by use of the electronic Draeger esthesiometer in quantitative, reproductive measurements, the corneal sensitivity in 55 patients with medically treated idiopathic trigeminal neuralgia before and after surgical treatment of the trigeminal nerve and root. 37 patients were included in a prospective study with measurements before and after glycerol rhizotomy, radiofrequency rhizotomy and microvascular decompression (MVD) of the trigeminal root. Moreover, 18 patients were examined retrospectively 7 to 17 years after retrogasserian rhizotomy according to Spiller/Frazier. Corneal sensitivity was determined by the mean value of 3 measurements in each of 5 positions on both eyes. Evaluation of data leads to the following conclusions: In case of neuralgia in the V1 and V2 divisions, corneal sensitivity may decrease without any clinical manifestation. The hypothesis that V2 contributes to corneal innervation got further evidence. Microvascular decompression may lead to a severe decrease of corneal sensitivity. In terms of complications concerning sensory loss of cornea, radiofrequency rhizotomy was the less risky treatment, followed by glycerol rhizotomy, MVD and the retrogasserian rhizotomy according to Spiller/Frazier. Sensitivity affected by prior medical or surgical treatment does not necessarily decrease by further surgical therapy. Postoperatively up to six weeks, corneal sensitivity remained almost the same as shortly after surgical procedure. Keratitis was observed in only one case retrospectively.