When Neurosensory Testing Can Help Pinpoint The Cause Of Heel Pain

By David Soomekh, DPM and Babak Baravarian, DPM

While there are many different causes of primary heel pain, it is often misdiagnosed as simple plantar fasciitis without the proper diagnostic tools. This is especially true for patients who have recurring symptoms and/or have failed multiple conservative and or surgical treatments. It takes a conscientious clinician to know when to begin thinking of a different diagnosis and a new course of treatment. This is especially true when it comes to heel pain. Many of the patients who walk into our offices complaining of heel pain have either been told by another doctor they have plantar fasciitis or have diagnosed themselves. Armed with that knowledge, it would be easy to assume this is the correct diagnosis and to perform only the minimum of diagnostic examinations. However, this approach would be ineffective in treating the patient and his or her symptoms fairly. A more effective approach would be one that we have employed in our offices. Key Pointers On Making An Accurate Diagnosis After obtaining a thorough history of the symptoms and complaints, one should perform a physical examination. Begin by palpating the medial tuberosity of the calcaneus and the surrounding areas to determine the point of maximum tenderness. If the patient relates a specific area of pinpoint tenderness at this site, one cannot assume a diagnosis of plantar fasciitis even if there is a correlation of subjective signs. A further examination of the heel should include side to side compression of the calcaneus to rule out any fractures. Proceed to gently tap on the posterior tibial nerve with a finger or reflex hammer as it passes posterior to the medial malleolus to determine any nerve involvement. Use the same approach at the level of the medial calcaneal branch as well. If the patient relates any positive reaction from the nerve palpation, one may suspect nerve pathology. To complete the physical exam, clinicians should determine the presence of ankle equinus. Proceed to perform an ultrasound examination of the plantar fascia of the symptomatic and non-symptomatic foot. If the plantar fascia is less than 4 mm, one cannot make a diagnosis of plantar fasciitis. If there is hypertrophy of the fascia, you will be able to see an increase in its thickness from 5 mm and higher. You can also determine if there is any attenuation or complete tear in the fascia. Using ultrasound also allows one to visualize the plantar calcaneal bursae. Keep in mind that pathology of the bursae can mimic symptoms of plantar fasciitis without any pathology to the fascia itself. At this point, if you are satisfied that a diagnosis of plantar fasciitis is accurate, proceed with conservative treatment. If there is any suspicion of nerve involvement at this time or any time during the treatment course, then a neurosensory examination is indicated. How PSSD Neurosensory Testing Can Enhance Your Diagnosis In our offices, we use the PSSD sensory unit from Sensory Services Management. This is a very sensitive test that can identify early changes in sensation, document the extent of sensory loss and monitor conservative or surgical management of the patient. This test can be very useful when attempting to determine if a patient truly has a plantar fasciitis versus a tarsal tunnel or other nerve pathology around the heel. The PSSD neurosensory examination will determine if there is any sensory loss and which nerve is affected. In order to use this test effectively, one should have a strong understanding of nerve injury, specifically nerve compression. (See “What You Should Know About Nerve Compression” below.) The PSSD also tests the patient’s ability to determine between one point and two points of pressure. Distinguishing two points of pressure is important in evaluating the extent of axonal damage. As the patient’s ability to distinguish two points of pressure decreases — as the two points are brought closer together — there is more severity of axonal damage and death to the nerve. Accordingly, more aggressive treatment would be indicated. With one point sensory testing, one is testing for the level of sensory function. Pressure thresholds above normal indicate abnormal functioning of touch receptors and the nerve fibers innervating those receptors. The loss of two point sensation is to the sensory nerve what weakness is to muscle. The PSSD measurements are pressure measurements in gm/mm2.

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