Search results for "Fasciculus"
showing 10 items of 23 documents
The Oculo-auricular Phenomenon in Brain-Stem Disease
1993
The oculo-auricular phenomenon (OAP), as described by Wilson in 1908 [26], consists of bilateral coactivation of external ear muscles during lateral gaze. Two ear muscles are innervated by motoneurons of the medial part of the facial nucleus [9, 25]: the transverse auricular muscle (TAM) (Fig. 1), which adducts and curls the helix of the auricle, and the posterior auricular muscle (Fig. 2), which moves the whole auricle backwards [3, 16, 22].
A Pathway in the Brainstem for Roll-Tilt of the Subjective Visual Vertical: Evidence from a Lesion–Behavior Mapping Study
2012
The perceived subjective visual vertical (SVV) is an important sign of a vestibular otolith tone imbalance in the roll plane. Previous studies suggested that unilateral pontomedullary brainstem lesions cause ipsiversive roll-tilt of SVV, whereas pontomesencephalic lesions cause contraversive roll-tilts of SVV. However, previous data were of limited quality and lacked a statistical approach. We therefore tested roll-tilt of the SVV in 79 human patients with acute unilateral brainstem lesions due to stroke by applying modern statistical lesion–behavior mapping analysis. Roll-tilt of the SVV was verified to be a brainstem sign, and for the first time it was confirmed statistically that lesions…
Fluency and rule breaking behaviour in the frontal cortex
2020
Design (DF) and phonemic fluency tests (FAS; D-KEFS, 2001) are commonly used to investigate voluntary generation. Despite this, several important issues remain poorly investigated. In a sizeable sample of patients with focal left or right frontal lesion we established that voluntary generation performance cannot be accounted for by fluid intelligence. For DF we found patients performed significantly worse than healthy controls (HC) only on the switch condition. However, no significant difference between left and right frontal patients was found. In contrast, left frontal patients were significantly impaired when compared with HC and right frontal patients on FAS. These lateralization findin…
In vivo definition of parieto-motor connections involved in planning of grasping movements
2010
We combined bifocal transcranial magnetic stimulation (TMS) and diffusion tensor imaging (DTI) tractography to investigate in humans the contribution of connections originating from different parietal areas in planning of different reaching to grasp movements. TMS experiments revealed that in the left hemisphere functional connectivity between the primary motor cortex (M1) and a portion of the angular gyrus (AG) close to the caudal intraparietal sulcus was activated during early preparation of reaching and grasping movements only when the movement was made with a whole hand grasp (WHG) towards objects in contralateral space. In contrast, a different pathway, linking M1 with a part of the su…
Internuclear ophthalmoplegia of abduction: clinical and electrophysiological data on the existence of an abduction paresis of prenuclear origin.
1992
Three patients showed unilateral and five bilateral abduction paresis. Five had associated adduction nystagmus of the contralateral eye. Electrophysiological testing of masseter and blink reflexes indicated an ipsilateral rostral pontine or mesencephalic lesion, and excluded a lesion of the infranuclear portion of the abducens nerve. Abduction paresis was attributed to impaired inhibition of the tonic resting activity of the antagonistic medial rectus muscle. The prenuclear origin of the disorder is based on morphological and neurophysiological evidence of an ipsilateral inhibitory connection between the paramedian pontine reticular formation and the oculomotor nucleus running close to but …
Mathematical Model Predicts Clinical Ocular Motor Syndromes
2003
: Clinical ocular motor syndromes were compared with ocular motor syndromes simulated by a mathematical model of the vestibuloocular reflex. The mathematical sensorimotor feedforward model of otolith control of three-dimensional binocular eye position is based on relevant anatomical connections of the vestibuloocular reflex from the utricles to extraocular eye muscles. This is the first attempt to simulate static ocular motor syndromes for unilateral utricular or vestibular nerve failure, lesions of the vestibular nucleus, and lesions of the ascending vestibuloocular reflex pathways. Comparison of the predicted syndromes with those found in patients with unilateral disorders of the vestibul…
Diabetic 3rd nerve palsy: evidence for a mesencephalic lesion.
1990
Eleven consecutive adult chronic diabetic patients presented with an isolated 3rd nerve palsy (8 with pupillary sparing) of which 10 had abnormal ipsilateral or bilateral masseter reflexes (MassR). Three patients had an MRI lesion in the ipsilateral oculomotor fasciculus and 3 had subsequent mild brainstem signs. An additional 13 patients with Weber's syndrome had similar ipsilateral or bilateral MassR abnormalities, while 7 patients with 3rd nerve palsies on a known extra-axial basis had none. The findings suggest that an isolated diabetic 3rd nerve palsy, with or without pupillary sparing, is much more likely on the basis of a focal mesencephalic infarct than a peripheral nerve lesion.
Midbrain vs. pontine medial longitudinal fasciculus lesions: The utilization of masseter and blink reflexes
1991
Masseter (MR) and blink reflexes (BL) were investigated in 51 patients with internuclear ophthalmoplegia (INO) due to multiple sclerosis (28) and lacunar infarction (23). The MR was abnormal in 20 of 23 cases with bilateral INO and in 21 of 28 with unilateral INO. The R1 component of the BL (BL-R1) was abnormal in 7 of 23 patients with bilateral INO and 10 of 28 with unilateral INO. Combined MR and BL-R1 changes occurred in 8 of 28 cases with unilateral INO and 7 of 23 with bilateral INO. The findings provide evidence for a rostral/caudal localization of lesions within the medial longitudinal fasciculus causing INO on the basis of MR and BL-R1 abnormalities. An abnormality limited to MR sug…
Treatment of Specific Types of Nystagmus
2007
■ The function of the ocular motor system is to hold images stable on the fovea. The vestibular system and the vestibulo-ocular reflex (VOR) also play an important role in this function. The VOR connects the peripheral vestibular endorgans – the semicircular canals and otoliths – with their appropriate pair of eye muscles via a three-neuronal arc.
The Internuclear Ophthalmoplegias
1993
Internuclear ophthalmoplegia (INO), which is caused by an ipsilateral medial longitudinal fasciculus (MLF) lesion, is characterized by adduction paresis of lateral gaze, usually with spared convergence [1–4]. In the opposite eye, abduction nystagmus and hypermetric abduction saccades are the main clinical and electro-oculographic abnormalities [1, 5, 6]. The origin of both is still debated. Abduction nystagmus has been explained by (a) an additional horizontal gaze paresis [7]; (b) vergence mechanisms aimed at alignment of the visual axes [8]; (c) interruption of descending excitatory projections from oculomotor nucleus internuclear neurons to contralateral abducens nucleus motoneurons [9];…