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Ocular Motor Cranial Neuropathies
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
Zane Foster, Ashwini Kini, Bayan Al-Othman, Andrew G. Lee
The sixth cranial nerve arises from the pons anteriorly at the junction of pons and medulla from the medial aspect and travels through the subarachnoid space, climbs superiorly over the clivus in the Dorellos canal and makes a sharp bend over the petrous temporal bone to pierce the dura. The sharp angled turn by the nerve and its relatively tethered position within the canal makes the sixth nerve susceptible to compression in either elevated intracranial pressure as well as very low intracranial pressures giving rise to a “nonlocalizing sign of sixth nerve palsy.” It then enters the cavernous sinus, where it joins with sympathetic fibers. Then it courses through the superior orbital fissure and innervates the ipsilateral lateral rectus muscle. The sixth cranial nerve only innervates the lateral rectus, so damage to this nerve will result in an abduction deficit and/or esotropia of the affected eye.
Abnormal Skull
Published in Swati Goyal, Neuroradiology, 2020
It is a purely motor nerve and provides innervation to the lateral rectus muscle (abduction). It has five segments: The intra-axial segment is located in the pons.The cisternal segment lies in the prepontine cistern.The inter-dural segment lies in the Dorello canal.The cavernous segment exits the CS through the superior orbital fissure.The intraorbital segment.
Evaluation of the Skull Base Patient
Published in John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed, Paediatrics, The Ear, Skull Base, 2018
Jeyanthi Kulasegarah, Richard M. Irving
Diplopia on lateral gaze due to VIth nerve involvement is a characteristic feature of petrous apex pathology. At the tip of the petrous apex, the VIth nerve is within Dorello’s canal, which makes it susceptible to various pathologic processes. Blurred vision can result from involvement of the optic tracts, raised intracranial pressure or lesions of the anterior skull base.
A Case Report of Bilateral Abducens Palsy in the Setting of Clival Fracture – Recovery Related to Pathophysiological Basis of Injury
Published in Neuro-Ophthalmology, 2021
Stefan Dimou, Lobna Alukaidey, Girish Nair
The course of the abducens nerve from the brainstem to the lateral rectus is long and tortuous, leaving it vulnerable to injury. Emerging from the lower border of the pons, above the medullary pyramid, it travels ventrally through the pontine cistern before turning superiorly to pierce the dura mater along the clivus and courses upwards between the layers of the dura. It then passes through the osteofibrous conduit known as Dorello’s canal at the petrous apex to pass into the cavernous sinus, where it runs adjacent to the cavernous segment of the internal carotid artery before entering the superior orbital fissure (Figure 4). Here it runs through the cone of muscles to enter the ocular surface of the lateral rectus muscle, approximately one-third of the way along.2
Trigeminal schwannoma: a single-center experience with 43 cases and review of literature
Published in British Journal of Neurosurgery, 2021
Mingchu Li, Xu Wang, Ge Chen, Jiantao Liang, Hongchuan Guo, Gang Song, Yuhai Bao
Patients with TS often suffered from numbness and hypoesthesia in the distribution of trigeminal branches due to trigeminal nerve dysfunction. Some patients also presented with facial pain secondary to tumor compression of the trigeminal root.7,14 In addition, patients might develop dysmasesia when the motor root was involved. In the present study, 29 patients (67.4%) developed facial numbness, in which merely four (9.3%) patients suffered from facial pain. Furthermore, nine patients presented with abducent paralysis, which was considered to be induced by tumor compression of the abducens at the entrance of Dorello’s canal or inside the CS. When TS enlarged and compressed the brainstem or other cranial nerves, the corresponding symptoms, such as weakness, hearing decrease and diplopia, occurred.
Scrub Typhus Presenting as Unilateral Abducens Nerve Palsy
Published in Neuro-Ophthalmology, 2022
Ritwik Ghosh, Subhrajyoti Biswas, Arnab Mandal, Kaustav De, Srijit Bandyopadhyay, Sona Singh Sardar, Arpan Mandal, Julian Benito-León
Infection as the cause of abducens nerve palsy is well known.1 However, only four cases of scrub typhus associated with abducens nerve palsy have been reported (Table 1).3–6 Our case differs from the previous ones in some aspects. First, our patient neither reported nor was found to have a febrile episode associated with the illness. Although rare, afebrile cases of scrub typhus disease have been reported.9,10 Second, our patient did not have the pathognomonic “eschar” on her body, similar to the recently reported case by Ozair et al.6 Atypical manifestations of scrub typhus are on the rise in the tropics, which in turn increases the level of difficulty in diagnosing this multi-systemic infection.11 Last but not least, there was an apparent mismatch between the clinical findings (i.e., the right abducens nerve palsy) and the neuroimaging findings (contrast enhancement surrounding the cavernous sinus was more evident on the left side). The abducens nerve can be affected along its subarachnoid course, specifically as it ascends the clivus and turns 90 degrees anteriorly to enter Dorello’s canal.1 Indeed, lesions located elsewhere intracranially can secondarily affect the abducens nerve (an example of the poor localising value of a sixth nerve palsy).1 We think that the enhancement encircling the cavernous sinus was not the major contributing factor for the development of the nerve palsy in this case, rather that the nerve might have been subjected to infective (exudative) damage while traversing the subarachnoid space (headache, an extra-axial manifestation further supports this assumption).