Focal entrapment neuropathies in diabetes

Peripheral neuropathies in diabetes are a diverse group of syndromes, not all of which are the common distal symmetric polyneuropathy. The focal and multifocal neuropathies are confined to the distribution of single or multiple peripheral nerves and their involvement is referred to as mononeuropathy or mononeuritis multiplex. Mononeuropathies are due to vasculitis and subsequent ischemia or infarction of nerves (1). Common mononeuropathies involve cranial nerves III, IV, VI, and VII and thoracic and peripheral nerves, including peroneal, sural, sciatic, femoral, ulnar, and median. Their onset is acute, associated with pain, and their course is self-limiting, resolving over a period of 6 weeks. They must be distinguished from entrapment syndromes that start slowly, progress, and persist without intervention (Fig. 1). Common entrapments involve the median, ulnar, and peroneal nerves, the lateral cutaneous of the thigh, and the tibial nerve in the tarsal canal. The entrapment neuropathies are highly prevalent in the diabetic population, one in every three patients has one, and it should be actively sought in every patient with the signs and symptoms of neuropathy because the treatment may be surgical (2) (Table 1). Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy encountered in diabetic patients and occurs as a result of median nerve compression under the transverse carpal ligament. It occurs thrice as frequently in a diabetic population compared with a normal healthy population (3,4). The increased prevalence in diabetes may be related to repeated undetected trauma, metabolic changes, accumulation of fluid or edema within the confined space of the carpal tunnel, and diabetic cheiroarthropathy (5), rheumatoid arthritis, and hypothyroidism (1,3). CTS is found in up to one-third of patients with diabetes, when demonstrated electrophysiologically, but may only be symptomatic in ∼5.8% (6). It is more common in females and in obese …