title: Evidence of ancillary trigeminal innervation of levator palpebrae in the general population.
abstract: The cranial synkineses are a group of disorders encompassing a variety of involuntary co-contractions of the facial, masticatory, or extraocular muscles that occur during a particular volitional movement. The neuroanatomical pathways for synkineses largely remain undefined. Our studies explored a normal synkinesis long observed in the general population - that of jaw opening during efforts to open the eyelids widely. To document this phenomenon, we observed 186 consecutive participants inserting or removing contact lenses to identify jaw opening. Seeking electrophysiological evidence, in a second study we enrolled individuals undergoing vascular decompression for trigeminal neuralgia or hemifacial spasm, without a history of jaw-winking, ptosis, or strabismus, to record any motor responses in levator palpebrae superioris (LPS) upon stimulation of the trigeminal motor root. Stimulus was applied to the trigeminal motor root while an electrode in levator recorded the response. We found that 37 participants (20%) opened their mouth partially or fully during contact lens manipulation. In the second study, contraction of LPS with trigeminal motor stimulation was documented in two of six patients, both undergoing surgery for trigeminal neuralgia. We speculate these results might provide evidence of an endogenous synkinesis, indicating that trigeminal-derived innervation of levator could exist in a significant minority of the general population. Our observations demonstrate plasticity in the human cranial nerve innervation pattern and may have implications for treating Marcus Gunn jaw-winking.
authors.affiliation: Department of Medical Genetics and Child and Family Research Institute, University of British Columbia, C234 4500 Oak Street, Vancouver, BC, Canada V6H 3N1.
authors.forename: A M
authors.initials: AM
authors.lastname: Lehman
authors.affiliation: Division of Neurosurgery, Department of Surgery, University of British Columbia, Vancouver, BC, Canada.
authors.forename: C C
authors.initials: CC
authors.lastname: Dong
authors.affiliation: Division of Neurosurgery, Department of Surgery, University of British Columbia, Vancouver, BC, Canada.
authors.forename: A M
authors.initials: AM
authors.lastname: Harries
authors.affiliation: Alberta Eye Health Clinic, Edmonton, AB, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Patel
authors.affiliation: Division of Neurosurgery, Department of Surgery, University of British Columbia, Vancouver, BC, Canada.
authors.forename: C R
authors.initials: CR
authors.lastname: Honey
authors.affiliation: Department of Medical Genetics and Child and Family Research Institute, University of British Columbia, C234 4500 Oak Street, Vancouver, BC, Canada V6H 3N1. Electronic address: mpatel@cw.bc.ca.
authors.forename: M S
authors.initials: MS
authors.lastname: Patel
mesh_terms: D000368:Aged; D003261:Contact Lenses; D004558:Electric Stimulation; D004576:Electromyography; D005143:Eyelids / Q000294:innervation* / Q000502:physiology; D005260:Female; D019569:Hemifacial Spasm / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D007568:Jaw / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology; D009119:Muscle Contraction; D009801:Oculomotor Muscles / Q000294:innervation* / Q000502:physiology; D011626:Pterygoid Muscles / Q000294:innervation* / Q000502:physiology; D014276:Trigeminal Nerve / Q000033:anatomy & histology* / Q000502:physiology; D014277:Trigeminal Neuralgia / Q000503:physiopathology / Q000601:surgery
keywords: Maxillopalpebral synkinesis; Oculomotor nerve; Synkinesis; Trigeminal nerve