Neurosurgery notes/Procedures/Cranial procedures/Neurophysiology/Cranial nerve monitoring

Cranial nerve monitoring

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Neurophysiology
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BAER
Facial nerve monitoring
Other CN monitoring
  • If a nerve is severed, stimulation distal to the injury will still give a response.
    • In addition, spread of excessive stimulation— ‘current jump’— can be misleading, or conversely stimulus applied to pooled saline may result in current shunting and a failure of stimulation.
  • Cannot test CN 1
      • Using Visual evoked potential (VEP) googles
      • Flash stimuli giving visual evoked responses that can be recorded from the occipital cortex
      • Responses can be recorded from optic tracts in anaesthetised patients. In the awake patient stimulation of the optic tract causes phosphenes, while visual pathway stimulation within association cortex can elicit formed visual memories
      A close-up of a goggles AI-generated content may be incorrect.
      CN3 and 4
      • Superior rectus muscle and superior oblique muscle
      • Intramuscular needle is bent just past 90° and slips underneath the mid-aspect of the superior orbital rim.
      rectu s. Super i cy s u perior oblique Xian Marie 2022 Xian Marie gees 2022
      CN6 Lateral rectus muscle
      • Intramuscular needle is bent just past 90 degrees and slides within inside of the lateral orbital rim to rest in the lateral rectus muscle.
      Ground Ground Lateral rectos Lateral rectus
      CN5
      • V1: Ophthalmic: Supraorbital nerve, Intramuscular needles placed around supraorbital foramen. The blink reflex can test sensory pathways— single stimuli awake, in theatre monitored by trains of stimuli.
      • V2: Maxillary: Infraorbital nerve, Intramuscular needles placed around infraorbital foramen
      • V3: Mandibular: Mental nerve and masseter muscle, Intramuscular needles placed around mental foramen (sensory branch) and in masseter muscle (motor branch)
      A drawing of a person's head AI-generated content may be incorrect.
      CN7
      • Intramuscular needles can be placed in:
        • Frontalis muscle
        • Orbicularis Oculi muscle
            • (Upper and lower lids may be monitored separately)
        • Buccal muscle
        • Nasalis muscle
        • Orbicularis Oris muscle
            • (Upper lip and lower lip may be monitored separately)
        • Mentalis muscle
        • Platysma
      • In hemifacial spasm the irritation that produces the spasm alters the ‘lateral spread’ of a response like an F- wave (e.g. stimulation of the facial zygomatic branch giving responses in the mandibular branch supplied muscle mentalis until the irritating vessel is removed). When this is lifted from the seventh nerve, the ‘lateral spread response’ is modified and usually vanishes. The response resolving suggests a good outcome likely.
      A diagram of a person's head AI-generated content may be incorrect.
      CN 10
      • Vocal cords
        • NIM (Neural Integrity Monitor) tube
      • Cricothyroid muscle
        • Additional coverage of CN X may be provided by insertion of insulated or regular needles into the cricothyroid muscle.
        • The Laryngeal Adductor Reflex (LAR) may be measured with paired electrodes on the vocal cord (such as with the NIM tube) and monitors the afferent and efferent pathway involved in the vagus nerve function.
      NIM tube Vocal cord Vocal cords NIM tube O Xian Marie Boles 2022
      notion image
      CN11
      • Trapezius muscle
      • Intramuscular needles
      Trapezius
      Hypoglossal (XII) nerve
      • Bilateral pairs of intramuscular needles in Tongue
      @ Xian Marie Boles 2022