Sensory latencies to the ring finger: normal values and relation to carpal tunnel syndrome.

Sensory innervation to the ring finger (digit IV) is generally shared by the digital branches of the median and ulnar nerves. In 74 hand studies on 37 normal adults, all had a recordable response in digit IV upon stimulation of the median and ulnar nerves antidromically 14cm proximally to the recording electrodes. Comparing the median sensory latency to digit IV with the ulnar sensory latency to the same digit, the difference was 0.3msec or less in 93% of the hands. In 18 cases of carpal tunnel syndrome, the difference ranged from 1 to 2.1msec. This procedure may be of value as an easily performed and rapid technique to screen vulnerable nerve syndromes for possible entrapment and to provide baseline data for asymptomatic hands in individuals with carpal tunnel syndrome.

Simultaneous determination of pilocarpine and isopilocarpine in pharmaceutical preparations by liquid chromatography.

A liquid chromatographic assay method is described for the simultaneous determination of pilocarpine and isopilocarpine in pharmaceutical preparations. The method involves separation of the isomers on a high-resolution ion-exchange column, followed by detection of pilocarpine and isopilocarpine by UV absorption in the 217-nm region. The specificity of the method is such that pilocarpine and isopilocarpine can be assayed separately in the presence of one another and in the presence of the excipients commonly found in commercial pilocarpine solutions. Its sensitivity for isopilocarpine is at least 25 ppm (independent of the concentration of pilocarpine). In contrast, USP methods lack both specificity and sensitivity. It is concluded that this method is applicable to the routine analysis of commercial pilocarpine preparations and is an improvement over the official methods.