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An Approach to Oculomotor Anomalies in a Child
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
The presentation of an isolated abducens nerve palsy can vary depending on the severity of the paralysis. Patients may present with a small esotropia and face turn, or a large esotropia that precludes fusion in any direction of gaze. Due to the anatomical course of the sixth nerve, several associated symptoms must be sought in order to localize the lesion. In the sixth nerve nucleus, neurons that are destined to climb within the medial longitudinal fasciculus to innervate the contralateral medial rectus muscle for ipsilateral gaze reside. For this reason, a nuclear abducens palsy is typically associated with a gaze palsy in the ipsilateral direction. In addition, nuclear abducens palsies are also almost always associated with facial nerve palsies due to the proximity of the facial nerve nucleus and genu. As the sixth nerve traverses the petrous apex, it can be affected by intracranial pressure changes as well as by skull base tumors. In the cavernous sinus, the oculosympathetic fibers are adjacent to the abducens nerve, and therefore, a co-existent Horner syndrome must be sought.
Head and Neck Muscles
Published in Eve K. Boyle, Vondel S. E. Mahon, Rui Diogo, Handbook of Muscle Variations and Anomalies in Humans, 2022
Eve K. Boyle, Vondel S. E. Mahon, Rui Diogo, Warrenkevin Henderson, Hannah Jacobson, Noelle Purcell, Kylar Wiltz
The absence of medial rectus may be associated with divergent strabismus (Macalister 1875; Le Double 1897; Lee et al. 2013). A bifid insertion of medial rectus may contribute to intermittent distance exotropia (Sundaram et al. 2005). An accessory medial rectus muscle may be present in cases of strabismus fixus convergens (Lee and Kim 2009). An inferiorly shifted insertion of medial rectus may be associated with microcornea and iris coloboma (Matsuo et al. 2009).
Neuromuscular Junction Disorders
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
Diana Mnatsakanova, Qin Li Jiang
Diplopia results from extraocular muscle weakness which can be subtle. The medial rectus muscle is preferentially affected. Fatiguing maneuvers, such as sustained upgaze or lateral gaze for 30–60 seconds, can aid in demonstrating weakness and fatigability. The cover–uncover test can help bring out subtle extraocular muscle weakness by causing shifting fixation in the direction of the weak muscle.
A Case of Compressive Optic Neuropathy Secondary to Lymphoma of the Extraocular Muscles
Published in Neuro-Ophthalmology, 2020
Yoshiyuki Kitaguchi, Atsushi Watanabe, Kohji Nishida
Incisional biopsy of the medial rectus muscle was performed via a transcaruncular approach. A soft, pinkish-grey mass was encountered at the site of the medial rectus muscle. Methylprednisolone pulse therapy (500mg per day for one course of three days) was initiated immediately after surgical biopsy, followed by 30 mg oral prednisolone per day. The patient’s visual acuity improved to 20/25 in the right eye with obvious proptosis reduction (Figure 3A), and the right visual field showed recovery with the exception of the superior nasal step (Figure 3B) at 14 days postoperatively. Because his intraocular pressure was 30 mmHg in the right eye and 24 mmHg in the left eye, topical 0.5% timolol maleate therapy was started bilaterally. At this point, an exotropia due to post-operative swelling of the surgical site and/or paralysis of the medial rectus muscle was noted (Figure 3A).
Compartmental Strabismus
Published in Journal of Binocular Vision and Ocular Motility, 2020
Stacy L. Pineles, Melinda Y. Chang, Federico G. Velez
The vertical rectus muscles are even less compartmentalized. There is no compartmentalization for the superior rectus muscle as it has been shown to receive mixed innervation throughout the entire muscle width.2 The inferior rectus muscle innervation is also more intermingled than that of the horizontal muscles. One study showed selective innervation of the temporal third of the muscle1 but most of the inferior rectus is innervated by a lateral trunk that extends over the entire inferior rectus muscle with a smaller selective innervation to the medial portion of the muscle.2 Interestingly there is evidence of some innervational anastomosis between the medial compartment of the inferior rectus muscle and the medial rectus muscle.2 Also there is some innervational overlap between the inferior rectus muscle and the inferior oblique muscle.2
Unilateral Recession-Resection Surgery for Infantile Esotropia: Survival of Motor Outcomes and Postoperative Drifts
Published in Seminars in Ophthalmology, 2018
Klio I. Chatzistefanou, Dimitrios Brouzas, Konstantinos D. Droutsas, Chryssanthi Koutsandrea, Eleutheria Chimonidou
The surgical approach consisted of a recession of the medial rectus muscle and a resection of the lateral rectus muscle in the same eye, performed in one session. The habitually nonfixating eye or the previously amblyopic or more ametropic eye was chosen for surgery. Our standard approach was to perform 1 mm of recession and 1 mm of resection for the correction of each 6Δ of esotropia (approximately), with the dose being reduced for larger angles of esotropia. Conversely, the amount of surgery was modified up in the face of smaller esodeviations because smaller presenting angles may still need a minimum amount of surgery to be addressed.