Conway McLean, DPM, Journal columnist

“You’ve got a lot of nerve!” goes the cliche, referring to someone who is acting outrageously. Is it possible for there to be differences in how many nerves people have? Nerves are interesting structures, having a unique function in the body. Their job is to transmit information quickly, with minimal delay, allowing all manner of processes to occur almost immediately, like pulling your hand away from a flame. This response is made possible by the speed at which a single nerve is able to send this important information.

Because of this ability to send signals so rapidly, they serve many important functions, including the reflexive action of pulling away from a painful stimulus. The act of typing this editorial is made possible because of the nerves controlling the appropriate muscles in my hands. These delicate structures work the glands in our skin keeping it healthy. They are able to increase the dilation of the arteries in our legs to supply more blood when someone walks faster. And, of course, nerves allow us to think, to reason, to speak. And what to say, not always wisely perhaps, but miraculous, nonetheless.

Nerves are fragile structures and cannot withstand physical trauma. They are easily damaged, having no rigid support or internal framework. Because of the flow of chemicals allowing this signal transmission along the length of a typical nerve, physical stress to a nerve tract disrupts this ability. A scarring process may occur to the covering of a nerve and nerve death may be seen over time. When traumatized in some fashion, these forces lead to pathologic changes including scar tissue production around the nerve. This is basically the definition of a neuroma, a nerve getting choked by pressure and scar tissue build up.

The most common place on the body for a neuroma to occur is between the metatarsal bones of the foot. Technically this is termed an intermetatarsal neuroma or a Morton’s neuroma, courtesy of Dr. Thomas Morton. When traumatized or diseased in some fashion, nerve problems tend to produce distinctive symptoms. These are often characterized as a burning or a shooting sensation. The neuroma in the ball of the foot often produces a cramping sensation in the toes, which is the nerve’s destination.

Many of those afflicted with a neuroma in the foot describe a feeling of pressure in the ball. The pressure derives from the buildup of scar tissue in the nerve sheath, the structure covering these nerves. As this material accumulates, the size of the mass increases and they feel the pressure of an actual lump in the foot. Many people will believe their sock is balled up, only to find no such thing. With progression of the condition, the two adjacent toes can be physically pushed apart.

Why does a Morton’s neuroma develop? Naturally, there are numerous reasons. Trauma is often the answer, but not that of the stereotypical single injury. More common is the repetitive microtrauma, the day to day pounding of normal life, walking on hard, flat surfaces, 10,000 steps a day. These nerves are close to the weight bearing surface, the ball of the foot, and so receive significant impact.

Certain foot types entail greater trauma to the area, as does certain shoe gear (like higher heeled shoes). Foot mechanics, how the foot moves with each step, varies greatly. For example, a foot that flattens too much will cause the metatarsal bones to roll too much. In doing so, they are rolling onto the nerves in question. This provides added trauma to the nerve and its covering, the nerve sheath.

As is typical of this type of problem, one developing gradually over time, neuroma pain is usually mild at first. But when this problem continues and doesn’t resolve in a timely fashion, it’s likely progressing towards becoming a chronic condition. These intermetatarsal neuromas often worsen slowly, until some successful intervention is utilized.

As might be predicted, treatments, and their success rates, vary. Oral anti-inflammatories like ibuprofen are only band aids, while injected steroids can sometimes resolve these. Arch supports are another approach which vary widely in their benefits. Understandable, since there are a million variations on the theme. Prescription supports tend to help more with neuromas, but that is not a given. Foot orthotics vary greatly in how they are prescribed, and consequently also vary in their success.

Intermetatarsal neuroma symptoms are said to affect around a third of the American population, not an insignificant number. Getting an accurate diagnosis can be challenging since there is little in the way of physical manifestations. Often a condition causing pain in this area will be mistaken for a neuroma, or the opposite may occur, and ineffective therapies attempted. With time, and inadequate care, a neuroma can result in permanent nerve damage.

Surgery for a neuroma has historically consisted of cutting out the enlarged nerve, the only place in the body in which a nerve is surgically removed. Too often, scarring develops where the nerve was cut, resulting in the same pain they had previously. A newer approach is the release of the ligament trapping the nerve between the metatarsal bones, entailing a simple recovery with few complications.

Nerve problems are not ones to minimize, although they don’t lead to infection and aren’t cancerous. But living with pain reduces your quality of life. Just as consequential, chronic foot pain will alter gait and that usually leads to problems from some other structure (since nothing in the human body works independently). But don’t assume any pain in the ball of the foot is a neuroma: it’s a complex part of the body requiring a precise evaluation and specialized care.

EDITORS NOTE: Dr. Conway McLean is a podiatric physician now practicing foot and ankle medicine in the Upper Peninsula, having assumed the practice of Dr. Ken Tabor. McLean has lectured internationally on surgery and wound care, and is board certified in both, with a sub-specialty in foot orthotic therapy. Dr. McLean welcomes questions, comments and suggestions at drcmclean@penmed.com.