The Location of the Abducens Nucleus and Facial Nerve Fascicle: Letter to the Editor Regarding the Article “Association Between Multiple Sclerosis and the Symptoms of Vertigo and Facial Nerve Palsy”

Dear editor,

We have perused with a keen interest the case report titled “Association Between Multiple Sclerosis and the Symptoms of Vertigo and Facial Nerve Palsy” authored by Yoshida et al ¹ The case report presents crucial findings that offer valuable insights into other possible etiologies that should be considered, besides Bell’s palsy, when diagnosing peripheral facial palsy. Nevertheless, there are additional factors to be considered regarding the etiology of facial palsy and associated eye movement abnormalities in this patient.

As the fascicles of the facial nerve envelops the abducens nucleus in the dorsal pons, a lesion involving the abducens nucleus due to a stroke or multiple sclerosis frequently causes concurrent damage to the fascicles of ipsilateral facial nerve, leading to development of peripheral type of facial palsy (see Supplemental Figure). ² In this context, the conjugate rightward gaze palsy observed in this patient should have been ascribed to a lesion involving the abducens nucleus rather than the abducens nerve since a lesion involving the abducens nerve would cause abduction palsy only in the ipsilesional eye.

The cause of the patient’s vertigo remains unclear. The 9 gaze photographs provided in the report also raises a suspicion of rightward head tilt, suggesting that the patient may have an ocular tilt reaction probably due to concurrent involvement of right vestibular nucleus or fascicles. If the vestibular nucleus was involved, as suggested by the authors, the presence of gaze-evoked nystagmus and/or unilateral vestibular paresis on video head impulse or caloric tests would have allowed further differentiation of the involvement. ³

Supplemental Material

sj-png-1-ear-10.1177_01455613231184149 – Supplemental material for The Location of the Abducens Nucleus and Facial Nerve Fascicle: Letter to the Editor Regarding the Article “Association Between Multiple Sclerosis and the Symptoms of Vertigo and Facial Nerve Palsy”

Supplemental material, sj-png-1-ear-10.1177_01455613231184149 for The Location of the Abducens Nucleus and Facial Nerve Fascicle: Letter to the Editor Regarding the Article “Association Between Multiple Sclerosis and the Symptoms of Vertigo and Facial Nerve Palsy” by Eek-Sung Lee, Hyo-Jung Kim and Ji-Soo Kim in Ear, Nose & Throat Journal