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Neuro-Ophthalmological Findings in Patients with Posterior Circulation Stroke
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
The structures in the most rostral portion of the midbrain tegmentum are damaged in patients with occlusions of the thalamic-subthalamic arteries, or the rostral tip of the basilar artery (“top of the basilar syndrome”) or thalamic hemorrhages with postero-medial involvement or extension. Vertical plane eye motions are generated by simultaneous activation of the bilateral frontal and parieto-occipital conjugate gaze centers. Projections from these centers converge on the periaqueductal region in the brainstem tectum just beneath the collicular plate near the INC and the posterior commissure. The riMLF is also located in this region. This area is often referred to as the vertical gaze center.
The natural history of brainstem ocular motility disorders due to vascular pathology
Published in Jan-Tjeerd de Faber, 28th European Strabismological Association Meeting, 2020
Gaze palsies result from involvement of the brainstem nuclei and their projections responsible for generating vertical and horizontal eye movements (Rowe 2003). Vertical gaze palsies commonly result from lesions in the brainstem as bilateral input is required to generate vertical gaze. The nuclei responsible for generating vertical gaze movements are connected via the MLF and posterior commissure and vertical gaze palsies result from lesions to the riMLF and rostral midbrain (Bender 1980, Green 1993, Lagreze 1996). Innervation is unilateral to depressor extraocular muscles but bilateral to elevator muscles. Therefore gaze palsies on elevation are more common. Upward gaze palsies were noted in four of the patients in this study. Horizontal gaze palsies result from lesions involving the sixth nerve nucleus often of a vascular pathology. Seventh nerve involvement can occur with horizontal gaze palsies or sixth nerve palsies because of its close proximity with the sixth nerve (Miller 2002). One patient had a fascicular bilateral sixth nerve palsy with unilateral seventh nerve involvement in association with the ocular motility deficit of abduction.
Gastrointestinal bleeding
Published in Michael JG Farthing, Anne B Ballinger, Drug Therapy for Gastrointestinal and Liver Diseases, 2019
Matthew R Banks, Peter D Fairclough
The majority of fissures have no underlying cause; however, they may be associated with Crohn’s disease, ulcerative colitis or sexually transmitted diseases. There is often spasm of the anal sphincter associated with anal fissures and the maximum resting anal pressure (which relates to internal anal sphincter smooth muscle activity) is often raised.13 It has been suggested that this spasm perpetuates the ulceration and reduces healing through localized ischaemia and trauma to the lining of the canal.14 Angiographic studies have demonstrated that the posterior commissure is poorly perfused, and this where most idiopathic fissures occur. Treatments therefore have generally focused on reducing the sphincter pressure through surgical and pharmacological approaches.
Altered dynamic parahippocampus functional connectivity in patients with post-traumatic stress disorder
Published in The World Journal of Biological Psychiatry, 2021
Hui Juan Chen, Rongfeng Qi, Jun Ke, Jie Qiu, Qiang Xu, Zhiqiang Zhang, Yuan Zhong, Guang Ming Lu, Feng Chen
Magnetic resonance imaging scans were conducted at Hainan General Hospital using a 3 Tesla MR scanner (Skyra, Siemens Medical Solutions, Erlangen, Germany) equipped with a 32 channel standard head coil. Subjects’ heads were immobilised using a foam pad and a Plexiglas head cradle. Whole brain resting-state functional images were obtained using an echo-planar imaging sequence with the following parameters: TR/TE = 2000/30 ms, flip angle = 90°, FOV = 230 × 230 mm2, matrix = 64 × 64, 35 slices, slice thickness = 3.6 mm, no intersection gap, and total volume number = 250. The sections were placed approximately parallel to the anterior commissure-posterior commissure line. High resolution T1-weighted 3 D anatomical images were also acquired with a sagittal magnetization-prepared rapid gradient echo sequence for later co-registration and normalisation (TR/TE = 2300/1.97 ms, flip angle = 9°, FOV = 256 × 256 mm2, matrix = 256 × 256, 176 slices, slice thickness = 1 mm). Each fMRI scan lasted for 500 seconds. During the functional scanning, subjects were instructed to lie quietly, keep their eyes closed, and let their mind wander without falling asleep.
Systematic review of visual rehabilitation interventions for oculomotor deficits in patients with brain injury
Published in Brain Injury, 2019
Takayuki Watabe, Hisayoshi Suzuki, Marina Abe, Shuichi Sasaki, Jun Nagashima, Nobuyuki Kawate
Our systematic review, which includes case series’, highlights the small number of studies that have focused on oculomotor rehabilitation for patients with brain injury. This is remarkable, given the frequency with which oculomotor deficits (in addition to physical and cognitive impairments) are encountered by physical and occupational therapists rehabilitating patients with brain injury. Horizontal eye movements are coordinated by the paramedian pontine reticular formation (PPRF) and medial longitudinal fasciculus (MLF) (26), while vertical movements are controlled by the rostral interstitial nuclei of the MLF (Ri-MLF; located in the mesencephalic reticular formation), and the posterior commissure (27). The frontal eye field has intracerebral connections through the above systems (28), and through other oculomotor domains. Damage to any of these systems secondary to stroke can result in oculomotor deficits. Such deficits are even more likely to occur following a traumatic brain injury (TBI) in which diffuse damage harms these systems and the constituent oculomotor nuclei (19,20). Several studies that we reviewed did not use brain imaging to describe lesion sites. Consequently, for these studies it is not possible to distinguish between the contributions of interventions, and natural recovery, to improvements in eye movement. This highlights the importance of brain imaging in future studies.
Don’t Miss This! Red Flags in the Pediatric Eye Exam: Pupils
Published in Journal of Binocular Vision and Ocular Motility, 2019
Jennifer E. Lambert, Stephen P. Christiansen, Crandall E. Peeler
The posterior commissure and its nucleus, located in the dorsal part of the midbrain, contain connections from the interstitial nucleus of Cajal as well as the rostral interstitial nucleus of the medial longitudinal fasciculus. These pathways are important for vertical gaze and vertical saccades, projecting to the third and fourth nerve nuclei. Lesions in these pathways cause the signs and symptoms associated with dorsal midbrain or pretectal syndrome, including vertical gaze palsy (worse in upgaze), convergence-retraction nystagmus, skew deviation, and lid retraction. In the pediatric population, the more common causes of dorsal midbrain syndrome are hydrocephalus secondary to congenital aqueductal stenosis in infants and pineal gland tumors in older children.6