Altered Distribution of Motor Neurons in Experimental Facial Nerve Paralysis

Abstract

The alteration of motor neurons in the brainstem after recovery from experimental facial nerve paralysis was examined by the retrograde horseradish peroxidase (HRP) technique in the rabbit. Six months after nerve crush injury at the center of the vertical portion, HRP was injected into the zygomatic muscle on the recovered side. The distribution of labelled neurons in the brainstem was compared with that in the normal rabbit. In control animals, motor neurons in the facial nucleus were somatotopically organized, and there were no labelled neurons in other nuclei in the brainstem. In recovered animals, on the contrary, the somatotopic organization of the facial nucleus was obscure and multipolar neurons of varying size were labelled bilaterally in the reticular formation from the pons to the medulla.

Somatotopic Changes in the Nucleus Ambiguus After Section and Regeneration of the Recurrent Laryngeal Nerve of the Rat

“…Disorganization of the topography following a peripheral nerve injury have been described not only in the Amb but also in other cranial nuclei including; the facial nucleus (Thomander, ; Aldskogius and Thomander, ; Nakao et al, ; Angelov and Neiss, ; Angelov et al, ; Streppel et al, ; Choi and Raisman, ; Guntinas‐Lichius et al, ; Franchi et al, ; Grosheva et al ), extraocular nuclei (Fernández et al, ; Scherer, ; Sibony et al, ), hypoglossal nucleus (Mizuno et al, ), and in the spinal cord after a lesion in the sciatic nerve (Aldskogius et al, ; Wasserschaff, ; Fernández et al, ; Katada et al, ; de Ruiter et al, ; Landegren et al, ). These reports indicate that following a transection and repair of any peripheral nerve in the adult, the reinnervation of the denervated structures is not as selective as that occurring during development and the resulting disorganization of the somatotopic distribution of the denervated motoneurons persists.…”

Central Facial Nervous System Biomolecules Involved in Peripheral Facial Nerve Injury Responses and Potential Therapeutic Strategies

“…MRI of patients with congenital facial palsy, clinically defined as facial palsy of the seventh cranial nerve present at birth or immediately after birth, revealed abnormalities in the facial nucleus, Willis circle, and corpus callosum [29]. After recovery from facial nerve palsy, neurons innervating the zygomatic muscle, identified using retrograde staining with horseradish peroxidase (HRP), were located in the facial nucleus; labeled neurons were also found in the facial nucleus region following injection of HRP into the orbicularis, zygomatic, and orbicularis oris muscles [204,205]. In a monkey model, blocking the facial nerve by inserting a needle into the facial nerve trunk resulted in changes in facial nucleus nerve cells [206].…”

The influence of age in peripheral facial palsy on brainstem reflex excitability

“…[21] In addition to the changes in the neurons, microglial activation and vascular changes associated with reactive astrocytosis in the tissue surrounding the neuron also take place. [22][23][24] Hyper-reactivity of glial cells, and the increase in the pro-inflammatory cytokines following destruction was shown to cause decreased efficiency of repair mechanisms associated with aging of the brain tissue. Increased reactivity of astrocytes has been shown following facial nerve axotomy in aged rats as compared to young rats.…”