Disease Entity Findings

Anterior Horn Cell Disease

Early disease manifestations include active denervation, which becomes less prominent as the condition progresses. The evaluation requires sampling a large number of muscles with involvement demonstrated in multiple extremities and spinal levels. Key diagnostic findings encompass neurogenic units, fasciculations, and motor unit dropout. Localized findings within a single extremity may indicate focal spinal cord pathology such as syringomyelia or tumors.

Root Lesion

The EMG assessment focuses on motor root involvement. Evaluation must include both limb muscles and paraspinal muscles at multiple levels, particularly deeper paraspinal structures with less innervation overlap. Systematic sampling above and below the suspected affected root in both axial and extremity muscles is essential.

Plexus Lesions

The brachial plexus examination requires compulsive evaluation of the various levels from which branches arise. Testing progresses from distal to proximal branches, with paraspinal muscle sampling to exclude root involvement. The approach aims to identify normal branches above the lesion site and distinguish between single and multi-segment involvement.

Entrapment Neuropathy

Nerve conduction study results guide muscle selection for sampling. Early disease may show minimal needle findings when only demyelination is present; axonal loss produces more observable abnormalities.

Peripheral Neuropathies

Demyelinating neuropathies demonstrate minimal needle findings with motor unit dropout. Axonal neuropathies display denervation in acute and chronic phases, typically affecting lower extremities more than upper extremities.

Muscle Disease

Inflammatory myopathies exhibit abundant spontaneous activity consisting of fibrillations, positive waves and complex repetitive discharges. Muscular dystrophies show less pronounced changes with reduced spontaneous activity, though Duchenne’s dystrophy may display prominent findings during active stages.