2024 Workshop Handout Bundle-W99C Facial Nerve and Blink Reflex Studies Katirji

W99C Facial Nerve and Blink Reflex Studies Katirji

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The document is a detailed summary of anatomical, clinical, and diagnostic aspects of the facial and trigeminal nerves, presented by Dr. Bashar Katirji at the 2024 AANEM Annual Meeting. It covers nerve anatomy, stimulation techniques, reflex pathways, and clinical conditions involving these nerves.<br /><br />### Anatomy<br />- **Facial Nerve**: Begins at the brainstem, traverses through the internal auditory meatus, exits via the stylomastoid foramen, and branches into five segments in the parotid gland.<br />- **Trigeminal Nerve**: Divides into ophthalmic (V1), maxillary (V2), and mandibular (V3) branches within Meckel's cave.<br /><br />### Stimulation and Reflex Studies<br />- **Facial Nerve Stimulation**: Involves motor response measurement in facial muscles like nasalis, orbicularis oculi, and orbicularis oris. Abnormalities indicate issues like axonal loss or Bell’s palsy.<br />- **Blink Reflex**: Assesses both facial and trigeminal nerves by stimulating the supraorbital nerve, recording responses (R1 and R2). R1 latency reflects the conduction along the trigeminal and facial nerves, whereas R2 latency reflects excitability of interneurons.<br /><br />### Clinical Conditions<br />- **Bell’s Palsy**: Characterized by axonal degeneration and Wallerian degeneration indicated by reduced amplitude in the facial nerve's motor response. Blink reflex latencies can show nerve conduction irregularities.<br />- **Synkinesis**: Misdirected axonal regeneration causing unwanted muscle contraction. Measured using selective recording from different facial muscles.<br />- **Hemifacial Spasm**: Involves synkinetic movements and hyperexcitability at the facial nucleus. Blink reflex analysis reveals irregular responses.<br />- **Trigeminal Nerve Lesions**: Reflex delays can indicate tumors or other conditions causing facial pain and affecting reflex pathways.<br /><br />### Polyneuropathy<br />- Conditions like GBS, CIDP present with delayed or absent R1 reflexes. Blink reflex studies help assess nerve involvement in polyneuropathies.<br /><br />### Electromyography (EMG)<br />- Used for assessing various facial muscles. Detects spontaneous activity indicating structural axonal damage. Helps distinguish demyelinating from axonal lesions.<br /><br />The document concludes with references to key studies and literature in the field, underscoring the diagnostic methods and clinical implications of nerve assessments.

Keywords

Facial Nerve

Trigeminal Nerve

Nerve Stimulation

Blink Reflex

Bell’s Palsy

Synkinesis

Hemifacial Spasm

Trigeminal Nerve Lesions

Polyneuropathy

Electromyography