Post-traumatic Unilateral Avulsion of the Abducens Nerve with Damage to Cranial Nerves VII and VIII: Case Report

Abstract

Traumatic injuries of the abducens nerve as a consequence of facial and/or head trauma occur with or without associated cervical or skull base fracture. This is the first report on unilateral avulsion of the abducens nerve in a 29-year-old man with severe right facial trauma. In addition, he exhibited mild left facial palsy, and moderate left hearing disturbance. Magnetic resonance imaging (MRI) using fast imaging employing steady-state acquisition (FIESTA) revealed avulsion of left sixth cranial nerve. We recommend thin-slice MR examination in patients with abducens palsy after severe facial and/or head trauma.

A Case of Unilateral Sixth Cranial Nerve (CN VI) Avulsion in the Prepontine Cistern After Severe Head Trauma

“…The abducens nerve innervates the ipsilateral lateral rectus muscle, which is a muscle that abducts the eye or moves it laterally [5]. Several imaging case reports have previously described CN VI avulsion, both unilateral and bilateral, following trauma [3,4,6]. Post-trauma CN VI palsy, in general, has been relatively more greatly reported [7].…”

“…Given the long, complex path of the abducens nerve, the mechanism of injury leading to avulsion is suspected to be related to contusion or stretching of the nerve at some point along its course [3,9]. While CN VI palsies can be characterized by both etiology and section of nerve implicated, such as various brainstem syndromes, the cavernous sinus syndrome, or diseases that increase intracranial pressure (ICP) leading to stretching of CN VI in the subarachnoid space, a specific section of CN VI vulnerable to severe head trauma has not yet been identified.…”

“…While CN VI palsies can be characterized by both etiology and section of nerve implicated, such as various brainstem syndromes, the cavernous sinus syndrome, or diseases that increase intracranial pressure (ICP) leading to stretching of CN VI in the subarachnoid space, a specific section of CN VI vulnerable to severe head trauma has not yet been identified. Interestingly, of the few reported MRI cases of abducens avulsion due to head trauma, both bilateral and unilateral [3,4,6], the section of nerve implicated in each case was the cisternal segment between the nerve's exit from the brainstem and its entrance into Dorello's canal. This section could be particularly vulnerable to mechanical stress, such as stretching due to upward or downward displacement, as it is tethered at both ends [3,6].…”

“…The complex and extended intracranial course of the abducens nerve makes it susceptible to traumatic injury, including avulsion. A few case reports have documented imaging findings suggestive of unilateral or bilateral CN VI avulsion following severe head trauma [3,4]. We report a patient with right lateral gaze palsy following head trauma from a motor vehicle accident.…”

Transient Bilateral Sixth Nerve Palsy: A Rare Sequela of Head Trauma

“…Unilateral abducens nerve palsy occurs in 1%-2.7% of all head traumas. However, bilateral palsy is extremely rare and is mostly associated with additional intracranial or spinal injury [ 2 - 3 ]. If the damage involved the nerve bilaterally, this usually would present with persistent diplopia, large-angle esotropia, and severe restrictions of abduction [ 4 ].…”