EVOKED POTENTIALS

EVOKED POTENTIALS – Definition, Purpose, Indication, Types of Evoked Potentials, Advantages, Client Preparation, Procedure and After Care

Evoked potentials involve the recording of electrical impulses generated by a sensory stimulus as it travels though the brainstem and into the cerebral cortex. Measuring evoked potentials is a sophisticated way of observing the status of sensory pathways as they enter the central nervous system, travel through the midbrain and reach the cerebral cortex

DEFINITION

Evoke potentials is a recording of electrical activity in central sensory pathways produced by placing electrodes over the scalp or the spine and using a computer to average and amplify the signal which results in characteristic pattern of wave from peaks that have approximate anatomic correlates

PURPOSE

  • To observe the sensory pathway as they enter the central nervous system, travel through the brainstem and reach the cerebral cortex
  • Evoked potentials also used during therapeutically induced comas such as barbiturate coma
  • Evoked potentials used in the determination of the existence of brainstem or spinal cord injury in the traumatically injured patient
  • It is used to assess the function of the cerebral hemispheres and the brainstem
  • It is also used to assess blindness, deafness and brainstem injury

INDICATIONS

  • Used in the diagnosis of multiple sclerosis
  • Hypoxic coma
  • Spinal cord injury
  • Brainstem lesions
  • Acoustic neuroma

TYPES OF EVOKED POTENTIALS

  • Visual evoked responses (VER): it involves monitoring of the visual pathways through the brainstem and cortex in response to the patients viewing a shifting geometric pattern on a screen or placing a mask, which sends a flashing light stimulates over the eye
  • Brainstem auditory evoked responses (BAERs): It involves monitoring of the auditory pathway through the brainstem and cortex in response to a rhythmic clicking sound sent through earphones placed over the patient’s ears
  • Somatosensory evoked response (SSER): it involves monitoring of sensory pathways from the extremities ascending the spinal cord through the brainstem and into the cortex

ADVANTAGES

  • Evoked potential studies can detect abnormalities even if the client is sedated or paralyzed with neuromuscular blocking agents
  • Evoked potential studies are more reliable than clinical assessments in predicting neurological recovery in comatose, head-injured clients

CLIENT PREPARATION

  • Explain the procedure and provide emotional support
  • Head should be washed with soap
  • Inform the client that he should be awake during procedure
  • Do not apply oil over the head after the bath
  • Provide good breakfast one hour before evoked potentials
  • Provide hospital cotton dress to wear

PROCEDURE

  • Place the client comfortably on the examination table
  • Evoked potentials studies are carried out in the same fashion as EEGs
  • Clients brain waves are monitored by giving various stimuli
  • A variety of types of stimuli are used, such as auditory, somatosensory and visual
  • Typical stimuli include flashing lights, buzzing tones and peripheral nerve stimulation

AFTER CARE

  • Monitor the vital signs and neurological status
  • Record the entire procedure in nurse’s record
EVOKED POTENTIALS – Definition, Purpose, Indication, Types of Evoked Potentials, Advantages, Client Preparation, Procedure and After Care
EVOKED POTENTIALS – Definition, Purpose, Indication, Types of Evoked Potentials, Advantages, Client Preparation, Procedure and After Care

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