Lesion localization
Michael Y. Wang, Andrea L. Strayer, Odette A. Harris, Cathy M. Rosenberg, Praveen V. Mummaneni in Handbook of Neurosurgery, Neurology, and Spinal Medicine for Nurses and Advanced Practice Health Professionals, 2017
Discussion: The cranial fossae are divided into three large depressions in the skull base. They are the anterior, the middle, and the posterior cranial fossae (Slazinski and Littlejohns, 2004). This is an interesting case because even though the tumor is predominantly in the right middle and posterior cranial fossa, it is very large causing brainstem compression and right-to-left shift. The patient finally presented for care because of symptoms of headache, nausea, and vomiting, which are related to noncommunicating hydrocephalus caused by kinking of the cerebral aqueduct in the dorsal midbrain. Her vision had been affected several years prior, but she did not seek treatment. The optic nerves were damaged by the chronic papilledema due to elevated intracranial pressure from hydrocephalus leading to the loss of vision. The right oculomotor nerve has caused the eyelid to close, impairment of the pupillary light reflex, and impaired eye movement. The trochlear nerve and abducens nerve involvement is evident by her restricted eye movements down and in, as well as laterally (Hobdell et al., 2004).
Complications of Skull Base Surgery
John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed in Paediatrics, The Ear, Skull Base, 2018
The cranial nerves III, IV and VI are at risk during operations of the petrous apex adjacent to the cavernous sinus and the anterior skull base. The trochlear nerve exits the posterior brainstem and has a relatively long intracranial course, but is well protected in the tentorium and is infrequently injured. Abducens nerve palsy has been reported after lumbar drain placement – it is not known whether this is through an ischaemic or traction injury. Abducens nerve palsy management tends to be symptomatic, with recovery tending to be slow and progressive. In paediatric patients occlusive patch therapy for eyes will help avoid amblyopia, until residual palsy improves. Monitoring of extraocular movements is important in recovery.
Eye
Lara Wijayasiri, Kate McCombe, Paul Hatton, David Bogod in The Primary FRCA Structured Oral Examination Study Guide 1, 2017
Remember ‘LR6SO4’. Lateral rectus muscle is supplied by the sixth cranial nerve (abducens nerve).Superior oblique muscle is supplied by the fourth cranial nerve (trochlear nerve).All of the other extraocular muscles (medial rectus, superior rectus, inferior rectus and inferior oblique) are supplied by the third cranial nerve (oculomotor nerve).
Superior oblique palsy: A case report
Published in Cogent Medicine, 2020
Ngozika Esther Ezinne, Kingsley Kenechukwu Ekemiri, Aliyah Khan
The trochlear nerve arises from the trochlear nucleus of the brain, emerging from the posterior aspect of the midbrain (it is the only cranial nerve to exit from the posterior midbrain) (Brazis, 1993). It runs anteriorly and inferiorly within the subarachnoid space before piercing the dura mater adjacent to the posterior clinoid process of the sphenoid bone. The nerve then moves along the lateral wall of the cavernous sinus (along with the oculomotor nerve, the abducens nerve, the ophthalmic and maxillary branches of the trigeminal nerve and the internal carotid artery) before entering the orbit of the eye via the superior orbital fissure. The trochlear nerve innervates the superior oblique, which is a muscle of oculomotion (Kim et al., 2020). The tendon of the superior oblique is tethered by a fibrous structure known as the trochlea, giving the nerve its name. Although the mechanism of action of the superior oblique is complex, in clinical practice it is sufficient to understand that the overall action of the superior oblique is to depress and intort the eyeball (Morillon & Bremner, 2017).
Isolated Sudden-Onset Trochlear Nerve Palsy Associated with Mild Novel Coronavirus Disease (COVID-19) Infection
Published in Journal of Binocular Vision and Ocular Motility, 2023
Mehmet Serhat Mangan, Zeynep Acar
Trochlear nerve palsy is the most common isolated palsy of the extraocular muscles.1 It may not always be possible to differentiate between the congenital and acquired types and an overlap between these two types at presentation can be encountered.1,2 Acquired trochlear nerve palsy is frequently caused by closed head trauma, but uncommonly caused by infarct or tumor compression.1,2 It has rarely been associated with viral infections such as those caused by herpes zoster ophthalmicus,3 herpes simplex-1,4 influenza B,5 human immunodeficiency virus-1,6 human herpesvirus-6,7 and varicella zoster virus.8 We present an otherwise healthy case with isolated trochlear nerve palsy in the setting of a SARS-CoV-2 (COVID-19) infection.
Chameleons, red herrings, and false localizing signs in neurocritical care
Published in British Journal of Neurosurgery, 2022
Boyi Li, Tolga Sursal, Christian Bowers, Chad Cole, Chirag Gandhi, Meic Schmidt, Stephan Mayer, Fawaz Al-Mufti
Trochlear nerve palsy typically presents as binocular diplopia on downward and inward gaze, which can cause a head tilt.21 Population studies have found the most common etiologies to be presumed congenital, hypertension, and trauma, with an incidence of 5.73/100 000/year.22 Given that the trochlear nerve is the thinnest and longest cranial nerve, and the only to emerge from the dorsum of the brain stem, it is the most vulnerable to trauma and other physical stresses.21 Trochlear nerve palsy has also been described as a FLS in IIH, benign intracranial hypertension (BIH), pseudotumor cerebri.3,8,23 Stretching of the nerve fibers due to ICP has been the only proposed mechanism.23 Patients with this FLS may have headache from eye strain, and raised ICP must be suspected if there is no history of head trauma.21 The findings may occur in conjunction with other cranial nerve signs or alone. The palsy may resolve with ICP reduction.3 They are often overlooked, as fourth nerve palsies are more subtle than the other cranial nerve palsies, and it has been suggested that the incidence of false localizing fourth nerve palsies is higher than reported.1,23
Related Knowledge Centers
- Brainstem
- Decussation
- Inferior Colliculus
- Motor Nerve
- Somatic Nervous System
- Superior Oblique Muscle
- Cranial Nerves
- Trochlea of Superior Oblique
- Nerve
- General Somatic Efferent Fibers