Autonomic Changes in Patients with ulnar neuropathy as reflected by Photoplethysmography


G. Nierenberg (1), G. Volpin (1), R. Lenger (2), H. Stein (1)

(1) Department of Orthopedic Surgery "A", "Rambam" Medical Center, Haifa, Israel
(2) Department of Rehabilitation, Fleiman Hospital, Haifa, Israel
Correspondence:
Dr. Nierenberg-Gabriel
Division of Orthopedic Surgery
Rambam Medical Center
Bat-Galim, Haifa /Israel
Tel: 00-972-4-8542527
Fax: 00-972-4-8542022
Key words:photopletysmography, ellbow pathology, chronic ulnar neuritis, ellbow injuries

Summary

Forty eight subjects from the diamond polishing industry, exposed to repeated protracted elbow flexion with direct strain to the cubital tunnel were investigated. Thirty had symptoms and clinical signs of chronic ulnar neuritis. Photoplethysmographic evaluation of these subjects, compared to a control group of other 43 healthy people, demonstrate pathological changes in the cutaneous blood flow of the affected hand, with a statistically significant increased magnitude of the hyperemic response following ischemia (p<0.001). Based on this findings and contrary to current knowledge it is suggested that autonomic component of peripheral nerve may have a regulatory roll on the peripheral response to ischemia as well as local humeral factors. Therefore, in some clinical conditions damage to the autonomic component of peripheral nerve can also be evaluated by changes of the hyperemic response, landed to photoplethysmographic evaluation.

Introduction

About 8% of peripheral nerve fibers are of autonomic origin and their course follow large mixed peripheral nerves (1). Peripheral cutaneous circulation is regulated by sympathetic autonomic activity (2). The passive hyperemic response is a physiological condition resulting from a transient local ischemic event, leading to an increased local blood flow to the affected territory (3, 4). It has been previously suggested that the hyperemic reflex is rendered to local factors activity, independent of neural role (5). Presently, the link between peripheral neuropathy and changes in cutaneous blood flow have hithero not been clearly defined (6). Therefore, this study investigate the changes of the hyperemic response in patients with ulnar neuropathy, as compared to normal subject, using the photoplethysmographic technology.

Patients & Methods

This study was conducted on 48 subjects from the diamond industry (34 males, 14 females, mean age 46 years) between December 1990 and July 1992. All of them were investigated by a subjective questionnaire and a detailed clinical and neurological examination. Photoplethysmographic evaluation of the peripheral cutaneous circulation of both hands was performed by application of two surface infrared electrodes placed on the digital pulp of the index and the small finger recording changes in the cutaneous blood flow, through a double channel P.P.G. recorder. Baseline P.P.G. tracings of the cutaneous circulation at rest was registrated, after which an arterial occlusion cuff was applied to the arm for 3 minutes. The hyperemic response ("reflex") was recorded 1, 2 and 3 minutes following deflation of the cuff. Since P.P.G. is a qualitative test, conversion to parametric values was achieved by calculation of the "hyperemic Index". It is the ratio between the baseline trace and the post occlusion recording, measured as the trace surface area, in mm2, by a morphomat apparatus. Control group of other 43 healthy subjects (16 males, 27 females, mean age 44 years) were examined in the same manner. Statistical analysis was performed using the student t test for numerical variables. The temporal flow pattern of the hyperemic reflex in the different groups was studied by the correlation coefficient test.

Results

Of the 48 diamonds polishers consisting the study group, 30 subjects had complaints compatible with ulnar neuropathy ("symptomatic group"), of them 19 had positive objective findings such as hypothenar muscle wasting and sensory changes in the ulnar territory of enervation ("objective group"). The right arm was involved in 21 patients, 15 had left arm involvement, and 6 had bilateral ulnar neuropathy. The remaining 18 subjects were nonsymptomatic and had no signs suggestive of ulnar nerve damage ("nonsymptomatic group"). The hyperemic index in the study group of patients with complaints and/or objective signs of ulnar neuropathies was statistically significant higher then that of the control group (p<0.001). However, no significant difference in the hyperenic index of the nonsymptomatic members of the study group and the control group were observed (Fig. 1). The correlation coefficient test showed similar temporal flow pattern of the hyperermic response in all groups, peaking to the highest point in the first minute following cuff deflation (Fig. 2).

Discussion

Post occlusion passive hyperemic response considered to result solely from local activity of humeral factors, namely PGE, ATP, Bradikinin, Histamine etc. (7). Experimental data in denervated or sympathectomized limbs renders the hyperemic reflex independent of neural activity (8). Our observation suggest that in patients with chronic ulnar neuropathy there are pathological changes in the cutaneous blood flow of the hands, expressed by a significant increase in the hyperemic response as compared to normal subjects. These findings in patients with chronic ulnar neuropathy suggest that the hyperemic reflex is influenced by more than just local vasoactive substances and are accounted to changes in the sympathetic activity. In our opinion, as damage to the autonomic fibers insues, vasomotor activity controlled by sympathetic component is relatively decreased resulting in a lower peripheral vascular resistance. These intern, result in the increase of blood flow to the affected territory expressed as a significant rise in the hyperemic response magnitude following ischemia. Therefore, following chronic neural damage increase in the hyperemic index values of the affected group is most probably a superimposed sympathetic effect on the local humeral factors activity. Our findings also support previous observation that photoplethysmography is a sensitive, non-invasive, qualitative method foe evaluation changes in the cutaneous blood flow (9). It may be applied in the early diagnosis of peripheral neuropathy, by addressing the autonomic component of the peripheral nerve.

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