We define “neuromuscular mimic” as any musculoskeletal condition that presents with pain and apparent weakness, and can mimic a neuromuscular etiology such as radiculopathy or entrapment neuropathy. “Limb pain” is a common reason for referral to the clinic and EMG laboratory and the identification of the underlying pain generator is often challenging. For example, in two series of patients referred for electrodiagnostic testing for suspected cervical or lumbosacral radiculopathy, the prevalence of musculoskeletal disorders was 42% and 32%, respectively.1,2 Thus, musculoskeletal disorders are common in patients suspected of having a radiculopathy. They can mimic radiculopathy or coexist with it in many individuals.1,2 Importantly, neuromuscular mimics can often be diagnosed quickly at the bedside and are eminently treatable. Their prompt recognition may avoid unnecessary and expensive diagnostic procedures and result in more efficient clinical practice. It is common for physicians from many specialties to be unfamiliar with recognizing these conditions.3
In this chapter, we will describe the most common mimics of radiculopathy and neuropathy in the upper and lower limbs (Table 36-1). We will not perform an exhaustive review of these pathologies. Rather, this chapter will serve as an entry point for physicians with minimal musculoskeletal training with the goal of providing them with time-efficient and resource-efficient tools to screen for these common conditions in their busy daily practice.
TABLE 36-1.NEUROMUSCULAR MIMICS
A few key “pearls” are worth remembering when performing a musculoskeletal examination. First, it is important to check the bilateral limbs for side-to-side comparison, starting from the noninvolved side first, whenever possible. If the test maneuver elicits pain, one needs to ask the patient whether the elicited pain is the same that he/she has been experiencing. This is important in order to avoid overcalling pathology as musculoskeletal examination maneuvers can trigger some discomfort even in healthy individuals, particularly if palpation and provocative tests are performed too vigorously. Finally, when assessing whether the maneuver reproduces the patient’s chief complaint, it is very helpful to look for the “wince sign,” with the patient blinking and grimacing as the pain is reproduced.
TOP MIMICS IN THE UPPER LIMBS
Supraspinatus tendinopathy is a common cause of shoulder pain and can mimic C5/6/7 radiculopathy.
The rotator cuff consists of four muscles that are responsible for securing the arm into the glenohumeral (shoulder) joint. These muscles are the supraspinatus, infraspinatus, teres minor, and subscapularis. The tendon most commonly injured within the rotator cuff is the supraspinatus.4 Risk factors include older age, ...