[2 cases with unusual lid-jaw co-movements]

Area of Science:

• Neurology
• Ophthalmology
• Genetics

Background:

• Associated movements between cranial nerves are well-documented, often involving the oculomotor, abducens, facial, and trigeminal nerves.
• Congenital cranial dysinnervation disorders can manifest in various forms, impacting coordinated facial movements.

Observation:

• Two pediatric patients presented with peculiar up and down movements of the left upper eyelid synchronized with mastication.
• These movements were associated with voluntary mouth opening, jaw deviation, and sucking actions.
• Clinical examination revealed normal pupils and no ptosis, while EEG showed bilateral parieto-occipital slow waves.

Findings:

• The observed synkinesis is presumed to be congenital due to the absence of head injury or hereditary defects.
• Abnormal neural connections between the trigeminal and oculomotor nuclei in the midbrain are hypothesized.
• Stretched muscle-spindles in the masseter muscle are considered a key trigger for the synkinetic movements.

Implications:

• This case series highlights an unusual presentation of the Marcus Gunn phenomenon, characterized by synchronized lid-jaw co-movements.
• Understanding these abnormal neural connections provides insights into neurodevelopmental disorders affecting cranial nerve function.
• Further research into congenital synkinesis can aid in diagnosis and management of related neurological conditions.