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Postnatal developmental changes in facial nerve morphology. Computer-aided 3-D reconstruction and measurement
S Fujita1, S Nakashima, I Sando
1Elizabeth McCullough Knowles Otopathology Laboratory, Department of Otolaryngology, University of Pittsburgh School of Medicine, PA 15213.
Summary
Facial nerve length increases with age, particularly in the mastoid portion. This differential growth causes the chorda tympani nerve
Area of Science:
- Anatomy
- Craniofacial Development
- Neuroscience
Background:
- The facial nerve (CN VII) is crucial for motor and sensory functions.
- Understanding its anatomical variations and age-related changes is vital for surgical procedures and diagnosing pathologies.
- Previous studies have not fully elucidated the age-related dimensional changes of the facial nerve within the temporal bone.
Purpose of the Study:
- To accurately measure the lengths and angles of the human facial nerve throughout its intra-temporal course.
- To investigate age-related changes in the facial nerve and its surrounding bony canal.
- To determine the impact of these changes on the anatomical landmarks, specifically the divergence of the chorda tympani nerve.
Main Methods:
- Acquisition of eight normal human temporal bones from individuals aged 7 days to 76 years.
- Preparation of serial histological sections for detailed analysis.
- Computer-aided three-dimensional (3-D) reconstruction for precise morphometric measurements of the facial nerve and canal.
Main Results:
- Significant age-related lengthening was observed in the mastoid segment of the facial nerve.
- The segment between the second genu and the chorda tympani divergence also increased in length with age.
- The mastoid portion of the facial canal demonstrated greater growth than the facial nerve itself, leading to a relative age-dependent shift in the chorda tympani divergence point concerning the stylomastoid foramen.
Conclusions:
- The facial nerve and its bony canal exhibit differential growth patterns throughout human life.
- The mastoid segment of the facial nerve and the facial canal undergo substantial lengthening with age.
- These age-related dimensional changes influence the anatomical relationship of the chorda tympani nerve, a critical consideration in otologic surgery.