Ischaemic and post-ischaemic paraesthesiae; normal responses in the upper limb with special reference to the effect of age.

Paraesthesiae consequent on peripheral nerve compression or general limb ischaemia have long attracted interest, and many features suggest their possible value in the study of peripheral nerve disorders. However, it is not certain if they are an essential feature of normal nervous function or if any significance can be attached to their absence. To clarify this and to determine features suitable as criteria of normality in the clinical application of paraesthesiae tests, the responses produced by a standard test have been studied in normal subjects of different ages. This showed that age appeared to modify the response, and the results are reported here. The usual method of eliciting paraesthesiae is by occlusion of the circulation with a sphygmomanometer cuff applied above the elbow. During such a procedure ischaemic paraesthesiae (I.P.) appear within a minute or so as faint tingling, buzzing, or vibrating sensations in the hand spreading a variable distance up the limb before dying away some minutes later (Kugelberg, 1944; Weddell and Sinclair, 1947). On releasing the cuff post-ischaemic paraesthesiae (P.I.P.) follow (Lewis, Pickering, and Rothschild, 1931; Zotterman, 1933; Kugelberg, 1944; Weddell and Sinclair, 1947). Four elenfients have been distinguished (Merrington and Nathan, 1949)-thermal, pseudo-cramp, tingling, and pricking-but the present study concerns only the last two to which the term P.I.P. is here restricted. These form the prominent pins-and-needles sensation which appears distally in the hand approximately one minute after circulatory release and persists for some minutes. The presence, intensity, and duration of P.I.P. are determined by the length of provocative occlusion at any site; upper arm occlusions of seven minutes (or even less) have been found usually adequate to produce P.I.P. in previous studies. Post-ischaemic paraesthesiae, unlike I.P., require a standard period of ischaemia for any comparative assessments, and it seemed of importance in the present study to employ an occlusion normally adequate but sufficiently short to be generally tolerable (even in pathological states) and with the minimum of risk of ischaemic damage. An important associated feature of post-ischaemic responses also considered in this study is postischaemic muscle twitching (Reid, 1931). This occurs predominantly in the small muscles of the hand where it provides objective evidence of responses analogous to P.I.P. though less readily induced (Kugelberg, 1944, 1946, 1948; Magladery, McDougal, and Stoll, 1950; Kugelberg and Cobb, 1951).