Cutaneous Pinprick Sensibility as a Screening Device

JULY/AUGUST 2006 I DIABETIC MICROVASCULAR COMPLICATIONS TODAY I 33 C utaneous pinprick sensibility testing is routinely used in neurology and diabetes. It is asserted here that the test is valuable for the prognoses of conditions with pathophysiologies dominated by small nerve fiber destruction. Contemporary literature neglects neurological pinprick among the cutaneous modalities. Rarely is it clinically or technically reviewed for its diagnostic virtues, however, closer scrutiny of the relevant neuropathophysiology suggests that adequately executed pinprick is a logical choice. The pinprick deficit produced by small fiber population loss is commonly reported to precede that of light touch. It may reflect the development of clinically critical thresholds of neuropathy not revealed by testing with other modalities. The following represents part of a larger peer-reviewed effort to address issues of clinical efficacy and infection control. Nerve constituents typically damaged by metabolic disorders (eg, diabetes) are small fiber populations, implying that protective sensation (ie, focusing on larger-diameter fiber populations), as opposed to protective pain may lack sufficient discrimination for refined diagnosis and prognostication.1-6 Pinprick data from the 10,000-patient cohort North-West Diabetes Foot Care Study corroborates this notion.7 Where early detection of neuropathic change is considered useful, there emerges a case to redefine the stages or thresholds at which loss of protective sensation is clinically apparent. Early diagnosis of diabetic peripheral neuropathy (DPN) is a critical part of clinical management. Combined with proper management, it may avoid debilitating diabetes complications. Yet, recent Diabetes UK research showed that people may have diabetes for 9 to12 years before they are diagnosed.8 By this stage, many patients may develop neuropathy, and their responses to standard examination procedures are likely to demonstrate altered nerve function. Techniques to identify DPN risk factors are usually applied at annual check-ups, although it is contended that current techniques are crude and may be insufficiently sensitive to detect the early deficit. If so, we may fail to predict subtle loss of protective thresholds in time to avoid critical management of complications.