Ischaemic monomelic neuropathy in a non-diabetic patient following creation of an upper limb arteriovenous fistula Open Access

Introduction

The incidence of end-stage renal disease (ESRD) in Australia is estimated at 0.05% of the population. The majority of these patients will choose haemodialysis as the preferred form of renal replacement therapy, requiring creation of an arteriovenous fistula (AVF). The subsequent haemodynamic disturbance can lead to neurological or ischaemic problems. The reported frequency of such complications varies between 1 and 10% and is most common following proximal procedures involving the upper limb.

Ischaemic neuropathy describes damage to a peripheral nerve caused by compromise of blood supply. The first description of such an injury following formation of an arteriovenous shunt was made by Bolton et al. [1], although the term ischaemic monomelic neuropathy (IMN) was coined by Wilbourn et al. [2]. He described a type of ischaemic neuropathy associated with interference of a major limb artery resulting in multiple, distal, axonal-loss mononeuropathies.

The clinical features of IMN are typically sensorimotor with dysaesthetic sensory symptoms in the hand and forearm and associated weakness or paralysis of muscles in the same area [3]. The syndrome develops quickly (typically within hours) of AVF formation. There is no description of IMN precipitated by distal forearm procedure. It is distinct from steal syndrome, the most commonly recognized complication of vascular access surgery [4]. In the latter, the onset is more insidious, there are typically signs of skin and muscle infarction and other trophic changes, and the degree of ischaemia is generally more profound.

IMN has been reported exclusively in patients with diabetes mellitus (DM), who often have pre-existing neuropathy and concomitant accelerated atherosclerosis. Brachiocephalic fistulae are most commonly associated with ischaemic complications; anatomically the brachial artery provides the only arterial inflow to the distal arm and in the absence of collateral blood vessels the risk of ischaemia is increased. In addition, the antecubital area is the watershed area of vasae nervorum for the three nerves supplying the upper limb [5].

We report on the first documented case in a non-diabetic individual.

Case report

A 38-year-old indigenous Australian man was referred for assessment of chronic kidney disease. His past medical history included morbid obesity (body mass index: 42), previous alcohol abuse and hypertension. He did not smoke. He was not known to be diabetic: a fasting BSL was 4.2 mmol/l, although a formal oral glucose tolerance test had not been performed. The creatinine clearance was 20 ml/min (calculated by MDRD 4-variable equation) at presentation and he was referred for fistula creation in anticipation of ESRD requiring haemodialysis. Due to his body habitus, he was not suitable for peritoneal dialysis. He was admitted for formation of a right brachiocephalic AVF, after an ipsilateral radiocepahlic fistula had failed 1 month previously.

The procedure was uncomplicated; however, eight hours post-operatively, the patient complained of pain in the right hand. On examination the fistula was patent but there were absent radial and ulnar pulses even with compressive occlusion of the fistula. The right hand was cool, there was absent finger movement and weak thumb movement, and sensory loss involving all modalities in a glove distribution affecting the right hand only. The fistula was ligated within four hours resulting in a return of radial and ulnar pulses. There was mild motor recovery involving finger abduction but significant weakness of all intrinsic muscles remained.

Nerve conduction studies were performed 1 year later and the results are shown in Tables 1 and 2.

Discussion

Most reports of IMN are confined to surgical or neurological literature. The condition is under-recognized clinically, and often misdiagnosed, hence the exact incidence is not known [6]. In most cases, the syndrome develops rapidly post-operatively. In the absence of diagnostic delay and rapid fistula ligation, patients appear to have some recovery of motor function in the affected hand and residual sensory symptoms.

The long-term outcome following development of IMN has not been widely studied. Previous case reports have documented long-standing pain phenomena, similar to causalgia resulting from IMN, which is not always amenable to analgesic medication [7]. Clinical features include loss of function of the intrinsic hand musculature, with less severe weakness of the wrist. Nerve conduction studies typically reveal decreased amplitudes and low-normal or mildly slowed conduction velocities, but latencies are typically within normal limits. The EMG demonstrates denervation in the acute phase, including fibrillation potentials and motor unit loss, not confirmatory of primary muscle pathology. In addition there is usually no evidence of a discrete infarction level and the changes seen characteristically gradually revert to normal as one moves proximally in the affected limb [1].

The surgical literature advocates immediate closure of the access once the diagnosis of IMN is made, in order to maximize the chance of neurological recovery [3]. Some experts have recommended ‘banding’ of the native fistula or graft in an attempt to increase resistance, reduce flow and improve distal perfusion [8]. This procedure runs the risk of insufficient placation, or of inducing thrombosis due to excessive narrowing.

Diabetes mellitus is the predominant risk factor for IMN, possibly because the pre-existing (and often subclinical) neuropathy lowers the threshold for further ischaemic injury. Indeed, the profound sensorimotor dysfunction seen is surprising, given the relatively moderate degree of ischaemia. To our knowledge, there have been no previous case reports of this syndrome affecting individuals who are not diabetic. This patient did not have any other risk factors for, or manifestations of, peripheral vascular disease. We must conclude that all patients undergoing upper fistula creations are potentially at risk for developing IMN. Certainly there is no definitive test to identify those vulnerable, although the syndrome is rare. There is some literature recommending peri-operative finger pressure evaluation and digital-brachial index assessment [9], or ultrasonography [10] to predict and diagnose steal syndrome, respectively, but no such tools are available for IMN. Post-operative vigilance and assessment of distal perfusion, motor and sensory function should be assessed prior to patient discharge, with the knowledge that presentation may be delayed. Following development of symptoms urgent nerve conduction studies and EMG can be performed to aid diagnosis but the most appropriate treatment is immediate surgical intervention.

Conflict of interest statement. None declared.

References