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An electroencephalogram (EEG) is a recording of the electrical activity of the cerebral cortex, which is influenced by subcortical structures. The EEG is consistently abnormal in hydrocephalus, meningoencephalitis, head trauma, and cerebral neoplasia. An EEG may determine whether seizure discharges are focal or diffuse. The EEG is often normal in idiopathic epilepsy, unless seizures are not well controlled and interictal spikes are
present. |
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An electromyogram (EMG) is a recording of the electrical activity of muscles and is used to evaluate the health of the peripheral nerve, neuromuscular junction, and skeletal muscle. The peripheral nerve can be stimulated, and motor and sensory nerve conduction velocities calculated. Repetitive nerve stimulation may lead to a reduction of the evoked potential in myasthenia gravis and distal axonopathies. Abnormalities of late waves may be
associated with disorders of nerve roots. |
| The brain stem auditory evoked response (BAER) is a recording of electrical activity in the auditory pathway from the inner ear receptors through the brain stem to the cerebral cortex. No response is seen in auditory nerve disorders associated with hearing loss. Brain-stem disorders may also alter the BAER. |
| Spinal cord evoked potentials and motor evoked potentials can be used to evaluate spinal cord integrity. |
