Electrodiagnosis of Lumbar Spine Disorders and Cauda Equina Syndrome

Abstract

Magnetic resonance imaging (MRI) is widely employed in the diagnosis of lumbar spine disorders, such as lumbar spinal stenosis or lumbar disc herniation. However, incomplete specificity is a definite drawback, given that MRI abnormalities are frequently identified in aged control subjects. Relying solely on MRI without considering clinical symptoms/signs or electrodiagnosis may lead to misdiagnosis. In contrast, electrodiagnostic tests are generally considered to have higher specificity than MRI, making them more useful for preventing unnecessary surgeries. Needle EMG can clarify the distribution of the involvement through fibrillation potentials and positive sharp waves, and can complement manual muscle testing. Denervation at the tensor fascia latae muscle can confirm an L5 lesion. Regarding nerve conduction studies (NCS), sensory nerve action potentials are usually normal in lumbar disorders. Somatosensory evoked potentials are useful for localizing the lesion. Amyotrophic lateral sclerosis (ALS) is an important differential diagnosis because spine surgery will promote the disease progression of ALS. Documenting upper extremity and thoracic paraspinal involvements are key to diagnose ALS, in combination with profuse fasciculation potentials in EMG. NCS plays a key role in diagnosing entrapment and demyelinating neuropathies. Electrodiagnostic tests are also useful for confirming functional neurological disorders.