Key points

Introduction

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS), associated with neural degeneration. The diagnosis is based on the clinical history, physical examination, laboratory findings, imaging of the CNS (magnetic resonance imaging [MRI] and other neuroimaging techniques), spinal fluid analysis, and selected additional laboratory tests to eliminate other diseases. The diagnosis is confirmed when disease has been confirmed in at least 2 different locations of the CNS, occurring at 2 or more points in time, for which there is no alternative disease diagnosed. It can initially manifest itself in several distinct patterns: relapses followed by remissions (relapsing remitting or RR MS), progressive degeneration from onset (primary progressive or PP MS), and a progressive course with superimposed episodes of relapses and remissions (progressive relapsing MS). The fourth clinical type—second progressive MS—evolves from RR MS over time as the disease progresses.

There are 3 types of evoked potentials (EPs) used in MS diagnosis and management: (1) visual evoked potentials (VEPs), which assess neural conduction in the optic pathways. VEPs are most typically triggered by observing an illuminated, alternating checkerboard pattern of black and white squares (pattern reversal VEPs) or a flashing light. Recordings are made over the visual cortex. Prolongation of the latency indicates disease in that neural pathway; (2) somatosensory evoked potentials (SEPs) involve peripheral stimulation of the large 1 A afferent fibers in various mixed nerves in the extremities, with the ascending potentials measured at various points along the peripheral nerves, spinal cord, brainstem, and somatosensory cortex; (3) brainstem auditory evoked responses (BAERs), triggered by auditory clicks and recorded over the cortex. (Motor evoked potentials will not be covered in this review, as they are currently not Food and Drug Administration approved for clinical practice in the United States.)

EPs represent a valuable adjunct to the diagnosis and management of MS because they measure physiology in the CNS. Indeed, it is the abnormal physiology of neural pathways caused by the inflammation and degeneration caused by MS that produces the motor weakness and sensory symptoms. Consequently, EPs are the only laboratory tools that directly measure the abnormal physiology resulting from the disease; all other tests are inferences of diseased pathways.

Introduction

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS), associated with neural degeneration. The diagnosis is based on the clinical history, physical examination, laboratory findings, imaging of the CNS (magnetic resonance imaging [MRI] and other neuroimaging techniques), spinal fluid analysis, and selected additional laboratory tests to eliminate other diseases. The diagnosis is confirmed when disease has been confirmed in at least 2 different locations of the CNS, occurring at 2 or more points in time, for which there is no alternative disease diagnosed. It can initially manifest itself in several distinct patterns: relapses followed by remissions (relapsing remitting or RR MS), progressive degeneration from onset (primary progressive or PP MS), and a progressive course with superimposed episodes of relapses and remissions (progressive relapsing MS). The fourth clinical type—second progressive MS—evolves from RR MS over time as the disease progresses.

There are 3 types of evoked potentials (EPs) used in MS diagnosis and management: (1) visual evoked potentials (VEPs), which assess neural conduction in the optic pathways. VEPs are most typically triggered by observing an illuminated, alternating checkerboard pattern of black and white squares (pattern reversal VEPs) or a flashing light. Recordings are made over the visual cortex. Prolongation of the latency indicates disease in that neural pathway; (2) somatosensory evoked potentials (SEPs) involve peripheral stimulation of the large 1 A afferent fibers in various mixed nerves in the extremities, with the ascending potentials measured at various points along the peripheral nerves, spinal cord, brainstem, and somatosensory cortex; (3) brainstem auditory evoked responses (BAERs), triggered by auditory clicks and recorded over the cortex. (Motor evoked potentials will not be covered in this review, as they are currently not Food and Drug Administration approved for clinical practice in the United States.)

EPs represent a valuable adjunct to the diagnosis and management of MS because they measure physiology in the CNS. Indeed, it is the abnormal physiology of neural pathways caused by the inflammation and degeneration caused by MS that produces the motor weakness and sensory symptoms. Consequently, EPs are the only laboratory tools that directly measure the abnormal physiology resulting from the disease; all other tests are inferences of diseased pathways.