Neurology · MU Sofia

25. Electroencephalography, evoked potentials

Covers electroencephalography: how scalp electrodes record cortical activity, the normal alpha, beta, theta and delta waves with their frequencies and states, the main clinical indications, and abnormal findings such as epileptiform discharges and diffuse or focal slowing. It then introduces evoked potentials and describes visual, brainstem auditory and somatosensory types, with their stimuli, pathways tested and clinical uses. A closing section compares where each test is best used.

Inside: 1 section · 2 labelled pictures · 2 tables · 15 flashcards · 2 min

Topic 25 of 88 in the MU Sofia syllabus for Neurology (Medicine, Year 4). The free AceMed note covers it in 1 section, about 204 words (2 min of reading), with 15 flashcards.

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  1. Eectroenecephalography. Evoked potentials

Eectroenecephalography. Evoked potentials

Electroencephalography (EEG)

Definition: EEG records the electrical activity of the cerebral cortex using electrodes placed on the scalp.

Physiological Basis

  • Reflects postsynaptic activity of cortical neurons.
  • Recorded as waves of different frequencies and amplitudes.

Normal EEG Waves

  • Indications: Epilepsy and seizure disorders. Altered consciousness. Encephalopathies. Sleep disorders. Brain death assessment

Abnormal EEG Findings

  • Epileptiform discharges (spikes, sharp waves)
  • Diffuse slowing → metabolic/toxic encephalopathy
  • Focal slowing → localized brain lesion

Evoked Potentials (EP)

Definition: Evoked potentials are electrical responses of the nervous system to a specific sensory stimulus.

  • They assess the functional integrity of sensory pathways.

Types of Evoked Potentials

1. Visual Evoked Potentials (VEP)

  • Stimulus: Flashing light/checkerboard pattern
  • Evaluates: Retina. Optic nerve. Visual pathways
  • Clinical Use: Optic neuritis. Multiple sclerosis. Visual pathway lesions

2. Brainstem Auditory Evoked Potentials (BAEP/BERA)

  • Stimulus: Click sounds
  • Evaluates: Auditory nerve (CN VIII). Brainstem auditory pathways
  • Clinical Use: Acoustic neuroma. Brainstem lesions. Hearing assessment

3. Somatosensory Evoked Potentials (SSEP)

  • Stimulus: Peripheral nerve stimulation
  • Evaluates: Peripheral nerves. Posterior columns. Brainstem. Sensory cortex
  • Clinical Use: Multiple sclerosis. Spinal cord disorders. Sensory pathway lesions

Clinical Significance

  • EEG

Best test for: Epilepsy. Diffuse cerebral dysfunction. Monitoring cerebral activity

  • Evoked Potentials

Best test for: Detecting subclinical lesions. Assessing conduction in sensory pathways. Diagnosing demyelinating diseases

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