American Board of Psychiatry and Neurology (ABPN) Practice Exam 2025 - Free ABPN Practice Questions and Study Guide

In needle electromyography (EMG), the presence of positive sharp waves and fibrillations is a classic finding indicative of radiculopathy. Radiculopathy occurs when a nerve root is compressed, inflamed, or otherwise damaged, often leading to denervation of the muscle fibers innervated by that nerve root.

Positive sharp waves and fibrillations are signs of ongoing muscle denervation. These potentials appear due to the disruption of the connection between the nerve and muscle, causing spontaneous activity in the muscle fibers that are no longer receiving proper neural input. This finding is particularly relevant in radiculopathy because it reflects the underlying nerve root pathology that can lead to muscle weakness and atrophy in specific muscle groups.

In contrast, high-frequency, short-duration potentials indicate reinnervation or muscle overactivity, which is not characteristic of radiculopathy. Fasciculations are associated with lower motor neuron lesions, which may or may not involve nerve root damage but do not specifically indicate radiculopathy. Myotonia, on the other hand, is a distinct condition associated with increased muscle tone and delayed relaxation, not a hallmark of radiculopathy.

Thus, the identification of positive sharp waves and fibrillations during EMG effectively points towards radial nerve root