Ischemic Monomelic Neuropathy Clinical Presentation

Updated: Jun 17, 2021
  • Author: Michael T Andary, MD, MS; Chief Editor: Dean H Hommer, MD  more...
  • Print


The hospital is the most common place for presentation of ischemic monomelic neuropathy (IMN); this presentation can vary depending on the location of the IMN. Patients with upper extremity IMN usually complain of pain in the hand and arm, with weakness in the hand. This pain generally occurs after hours of arterial occlusion of the brachial or subclavian arteries or following surgery to establish an arteriovenous fistula for dialysis graft access.

IMN in the leg usually presents after hours of arterial occlusion, frequently following vascular surgery involving aortic occlusion (eg, abdominal aortic aneurysm repair, use of the IABP, revascularization surgery in the leg). Lower extremity IMN can also occur after prolonged tourniquet time in surgery or as a complication following arterial occlusion. If the patient is alert and not confused, he or she usually complains of pain in the foot and distal leg; the individual may also complain of weakness of toe movement and ankle dorsiflexion.

Immediately after major surgery, it is common for patients to be confused, medicated, and/or not fully cognizant of problems in their legs that occurred during the surgery or as a result of cardiac events. Since the patient is confused, he or she does not complain of symptoms. In the meantime, the treatment team focuses on other pressing medical issues and does not notice the IMN. This results in a delay in diagnosis that frequently lasts days or even weeks after the arterial occlusion has occurred.

Chronic IMN has been reported in patients with chronic critical leg ischemia. The patients studied had angiographic documentation of severe large vessel stenosis or occlusion. They also suffered from limb pain while at rest or had nonhealing foot ulcers for more than 4 weeks. Distal foot and leg symptoms were present, along with some toe weakness. [7, 8]


Physical Examination

Patients who have IMN in the arm usually have decreased sensation in all the fingers of the hand. Occasionally, the median or ulnar nerve territory is primarily affected. Allodynia or hyperesthesia in the distal radial, median, and ulnar nerve distribution is common. Frequently, weakness of the abductor pollicis brevis and the intrinsic muscles of the hand is exhibited. Occasionally, more proximal musculature can be affected (wrist flexors or wrist extensors), but this pattern is exceedingly rare.

Physical examination of the leg frequently shows decreased sensation in the foot and distal calf. Allodynia and hyperesthesia also may be present. Intrinsic wasting in the feet is usually present. Distal leg muscles also can be weak, including the extensor hallucis longus, anterior tibialis, peroneus longus, and gastrocnemius/soleus. In rare cases, the hamstrings, quadriceps, and hip abductors are affected. Gait may be abnormal in that the patient may have steppage gait associated with ankle dorsiflexion weakness (foot drop). Reflexes may be asymmetrical, especially at the ankle, with an absent Achilles reflex in the affected leg.

In cases of chronic disuse, contractures of the distal joints (fingers, toes, wrists, or ankles), with swelling, skin atrophy, and vasomotor changes, can be present. These conditions can coexist with complex regional pain syndrome (CRPS) type 2 (also known as reflex sympathetic dystrophy [RSD]).

Patients with chronic IMN most commonly have hypalgesia in their distal foot and toes and/or nonhealing skin ulcers.