Related Experiment Video
Updated: Sep 27, 2026

Facial Nerve Axotomy in Mice: A Model to Study Motoneuron Response to Injury
Published on: February 23, 2015
Functionally essential neuronal population of the facial motor nucleus
S Kobayashi1, J Koyama, K Yokouchi
1Department of Anatomy, Shinshu University School of Medicine, 3-1-1 Asahi, Nagano 390-8621, Matsumoto, Japan.
Abstract:
Cranial nerve impairment is one of the more serious complications in neurosurgery. Nevertheless, the important question of how many neurons are required for cranial nerve functions remains unanswered. The VIIth cranial nerve (facial nerve) in mice was subjected to graded crush injuries. After assessment of the facial function, the number of uninjured, healthy facial motor neurons was quantified with a retrograde neuronal tracer. We report that normal facial function is preserved if intact neurons account for more than 56% of the control value, while complete facial paralysis occurs if intact neurons are reduced to less than 32% of the control value.
Related Concept Videos
Cranial Nerves: Types Part I
Olfactory Nerve (Cranial Nerve I)
The olfactory nerve, or cranial nerve I, is unique as it is purely sensory and dedicated to the sense of smell. This nerve originates in the olfactory epithelium of the...
Muscles for Facial Expressions
Brainstem
The Midbrain
The midbrain is located beneath the diencephalon and connects the cerebrum with the lower parts of the brain. The cerebral peduncles are prominent midbrain structures that house the...
Cranial Nerves: Types Part II
Facial Nerve (Cranial Nerve VII)
Cranial nerve VII, or the facial nerve,...
Cranial Nerves: Overview and Anatomy
Brainstem: Control Centers of Medulla
Olivary Nucleus
The olivary nucleus, or inferior olivary nucleus, is located within the ventrolateral part of the medulla oblongata. It is primarily involved in motor coordination and motor learning. The olivary nucleus receives input from the spinal cord, cerebellum, and motor...

