Epidemiology of Compressive Neuropathies

Abstract & Commentary

By Michael Rubin, MD, Professor of Clinical Neurology, NewYork-Presbyterian, Hospital, Cornell Campus. Dr. Rubin is on the speaker's bureau for Athena Diagnostics, and does research for Pfizer and Merck.

Synopsis: Compressive neuropathy (carpal tunnel, ulnar neuropathy, and Morton's neuroma) is common in the general population and often requires surgical correction.

Source: Latinovic R, et al. Incidence of Compressive Neuropathies in Primary Care. J Neurol Neurosurg Psychiatry. 2006;77:263-265.

Using the United Kingdom General Practice Research Database, encompassing 1.83 million patient years among 253 general practices, a study was undertaken to examine the epidemiology of common compressive neuropathies. Between January 1, 1992 and December 31, 2000, carpal tunnel syndrome (CTS) and Morton's metatarsalgia had the highest incidence rates, occurring in women (2016/100,000 and 821.9/100,000 population, respectively) more commonly than men (784/100,000 and 446.2/100,000 population, respectively). Ulnar neuropathy had the next highest incidence, with greater frequency among men than women (235/100,000 vs 170.4/100,000 population, respectively). Men and women were equally affected by meralgia paresthetica (108/100,000 population), and radial neuropathy was infrequent in both (29.4/100,000 vs 15/100,000 population, respectively). Overall, the age-related incidences followed a bell-shaped curve, increasing towards middle age with a subsequent decline. Approximately 30% of patients underwent surgical treatment for CTS or ulnar neuropathy, whereas surgery for Morton's metatarsalgia was undertaken in only 3%. Compressive neuropathy is common in the general population and often requires surgical correction.

Commentary

Morton's metatarsalgia, often referred to as Morton's neuroma, is not a true neuroma. It represents perineural fibrosis of an interdigital nerve, as it lies between the heads of adjacent metatarsal bones, most often the 3rd and 4th, and is the result of repetitive irritation. Often causing pain in the forefoot with paresthesiae and numbness in the 2 adjacent toes, examination may be normal and diagnosis uncertain. In such instances, magnetic resonance imaging (MRI) may be helpful in demonstrating a spindle-shaped mass in the appropriate region with enlargement of the nerve. T1-weighted images demonstrate signal intensity that is isointense to muscle, and non-fat-suppressed T2-weighted images demonstrate signal intensity that is hypointense to fat (Zanetti M, Weishaup D. Semin Musculoskelet Radiol. 2005;09: 175-186). Due to variability of signal intensities following contrast infusion, contrast-enhanced MRI is not recommended. Note must also be made of a high prevalence, up to 33%, of Morton's neuroma on MRI in asymptomatic persons. (Bencardino J, et al. AJR Am J Roentgenol. 2000;175:649-653). It appears, however, that neuromas larger than 5 mm are more likely to be causal than coincidental.