Neuropathy following abuse of nitrous oxide. 
A disabling peripheral neuropathy, mainly sensory, developed in three health workers who habitually abused nitrous oxide.  The distinctive clinical picture included patterns of numbness that were radicular rather than purely distal, and a "reverse" Lhermitte sign, in the absence of signs of spinal cord involvement.  Nerve conduction studies suggested an axonal rather than demyelinative neuropathy.  The neurologic disorder improved slowly when the patients abstained from further nitrous oxide abuse.