Paresthesias

PARESTHESIAS (from Greek para- around, against and aisthesis- sensation), sometimes also called dysesthesias, are sensations not caused by external irritation, such as numbness, tingling, formication (myrmeciasis, myrmecismus, formicatio), burning, itching, painful cold (so-called psychroesthesia), movement, etc., sensations in apparently preserved limbs of amputees (pseudomelia paraesthetica). The causes of P. can be various. P. can arise from local circulatory changes, in Raynaud's disease, in erythromelalgia, in acroparesthesia, in endarteritis, as an initial symptom of spontaneous gangrene. Sometimes they occur with damage to the nervous system, in traumatic neuritis (compare typical P. in contusion of n. ulnaris in the area of sulcus olecrani), in toxic and infectious neuritis, in radiculitis, in spinal pachymeningitis (compression of roots), in acute and chronic myelitis, especially in compressions of the spinal cord (spinal cord tumors) and in tabes dorsalis. Their diagnostic value in all these cases is the same as the diagnostic value of pain, anesthesias, and hyperesthesias: appearing in certain territories, along the course of a particular peripheral nerve or in the area of a particular root innervation, they can give valuable indications of the localization of the pathological process. P. are also possible as manifestations of cerebral damage. Thus, in cortical epilepsy, seizures often begin with P., localized in the limb with which the convulsions then begin. They are often observed in cerebral arteriosclerosis or in cerebral syphilis and sometimes are precursors of apoplectic stroke. A special position is occupied by the so-called psychological P., i.e., P. of psychogenic, hypochondriacal origin, which are characterized by the fact that they have not an elementary character, as organic ones, but a complex character-"crawling of worms under the skin of the head", "rising of a ball from the abdomen to the neck" (Oppenheim), etc. Their diagnostic value is of course completely different from that of organic P.