Loss of Ipsidirectional Quick Phases of Torsional Nystagmus with a Unilateral Midbrain Lesion1

1993 ◽  
Vol 3 (2) ◽  
pp. 115-121
Author(s):  
R. John Leigh ◽  
Scott H. Seidman ◽  
Michael P. Grant ◽  
Joseph P. Hanna
Keyword(s):  
Eye Movements ◽  
Medial Longitudinal Fasciculus ◽  
Unilateral Lesion ◽  
Interstitial Nucleus Of Cajal ◽  
Torsional Nystagmus

We report a patient with a long-standing, unilateral lesion of the midbrain who showed ipsidirectional loss of torsional quick phases, impairment of all vertical eye movements and normal horizontal eye movements. The findings are consistent with recent reports of the effects of experimental lesions, in monkeys, of the,rostral interstitial nucleus of the medial longitudinal fasciculus and the interstitial nucleus of Cajal.

Structure of the primate oculomotor burst generator. I. Medium-lead burst neurons with upward on-directions

1991 ◽  
Vol 65 (2) ◽  
pp. 203-217 ◽  
Author(s):  
A. K. Moschovakis ◽  
C. A. Scudder ◽  
S. M. Highstein
Keyword(s):  
Eye Movements ◽  
Mesencephalic Reticular Formation ◽  
Medial Longitudinal Fasciculus ◽  
Posterior Commissure ◽  
Inferior Rectus ◽  
Interstitial Nucleus Of Cajal ◽  
Burst Neurons ◽  
Physiological Characterization ◽  
Highly Correlated ◽  
Oculomotor Complex

1. To investigate the structure of the primate burst generator for vertical saccades, we obtained intra-axonal records from vertical medium-lead burst neurons with upward on-directions (UMLBs) in alert, behaving squirrel monkeys, while monitoring their spontaneous eye movements. After physiological characterization, these UMLBs were injected with horseradish peroxidase. 2. UMLBs (n = 14) had no spontaneous activity and emitted bursts of action potentials that preceded rapid eye movements by approximately 6 ms. Parameters of the burst (duration and number of spikes) were highly correlated with parameters of the rapid eye movement (duration and amplitude of the upward displacement of the eyes). 3. The axons of six UMLBs projected to the oculomotor complex. Their somata (4 were recovered) were all in the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF). Their axons traveled caudally in the medial longitudinal fasciculus (MLF) and ramified in the interstitial nucleus of Cajal (NIC) before entering the oculomotor nucleus. Five axons terminated bilaterally in the subdivisions innervating the superior rectus and inferior oblique muscles and therefore were presumed to be excitatory. One axon terminated in the ipsilateral inferior rectus and superior oblique subdivisions of the oculomotor complex and was presumed to be inhibitory. 4. Additionally, our data demonstrate that the nucleus of the posterior commissure (nPC) may also contain UMLBs. The axon of one such neuron crossed the midline within the posterior commissure and provided terminal fields to the contralateral nPC, riMLF, NIC, and the mesencephalic reticular formation but not to the oculomotor complex. 5. In conclusion, our data demonstrate that the rostral mesencephalon of the monkey contains neurons that have both the activity and the connections that are necessary either to provide motoneurons innervating extraocular muscles of both eyes with the pulse of activity they display during upward saccades or to inhibit their antagonists. Furthermore, our data demonstrate that some UMLBs are better suited for closing the feedback path of the local feedback loop rather than for providing direct input to extraocular motoneurons.

Lidocaine-induced unilateral internuclear ophthalmoplegia: effects on convergence and conjugate eye movements

1989 ◽  
Vol 62 (1) ◽  
pp. 82-95 ◽  
Author(s):  
P. D. Gamlin ◽  
J. W. Gnadt ◽  
L. E. Mays
Keyword(s):  
Eye Movements ◽  
Smooth Pursuit ◽  
Open Loop ◽  
Medial Longitudinal Fasciculus ◽  
Slow Phase ◽  
Internuclear Ophthalmoplegia ◽  
Unaffected Side ◽  
Affected Side ◽  
Position Signal ◽  
Slow Drift

1. To characterize the vergence signal carried by the medial longitudinal fasciculus (MLF), it was subjected to reversible blockade by small injections of 10% lidocaine hydrochloride. The effects of these blockades on both conjugate and vergence eye movements were studied. 2. With this procedure, experimentally induced internuclear ophthalmoplegia (INO) and its effects on conjugate eye movements could be studied acutely, without possible contamination from long-term oculomotor adaptation. In the eye contralateral to the MLF blockade, saccadic and horizontal smooth-pursuit eye movements were normal. Horizontal abducting nystagmus, often seen in patients with INO, was not observed in this eye. 3. As previously reported for INO, profound oculomotor deficits were seen in the eye ipsilateral to the MLF blockade. During maximal blockade, adducting saccades and horizontal smooth-pursuit movements in this eye did not cross the midline. Adducting saccades were reduced in amplitude and peak velocity and showed significantly increased durations. Abducting saccades, which were slightly hypometric, displayed a marked postsaccadic centripetal drift. 4. The eye ipsilateral to the blockade displayed a pronounced, upward, slow drift, whereas the eye contralateral to the blockade showed virtually no drift. Furthermore, although vertical saccades to visual targets remained essentially conjugate, the size of the resetting quick phases in each eye was related to the amplitude of the slow phase movement in that eye. Thus the eye on the affected side displayed large quick phases, whereas the eye on the unaffected side showed only slight movements. On occasion, unilateral downbeating nystagmus was seen. This strongly suggests that the vertical saccade generators for the two eyes can act independently. 5. The effect of MLF blockade on the vergence gain of the eye on the affected side was investigated. As a measure of open-loop vergence gain, the relationship of accommodative convergence to accommodation (AC/A) was measured before, during, and after reversible lidocaine block of the MLF. After taking conjugate deficits into account, the net vergence signal to the eye ipsilateral to the injection was found to increase significantly during the reversible blockade. 6. The most parsimonious explanation for this increased vergence signal is suggested by the accompanying single-unit study. This study showed that abducens internuclear neurons, whose axons course in the MLF, provide medial rectus motoneurons with an appropriate horizontal conjugate eye position signal but an inappropriate vergence signal. Ordinarily, this incorrect vergence signal is overcome by another, more potent, v

Activity of Mesencephalic Vertical Burst Neurons During Saccades and Smooth Pursuit

2000 ◽  
Vol 83 (4) ◽  
pp. 2080-2092 ◽  
Author(s):  
M. Missal ◽  
S. de Brouwer ◽  
P. Lefèvre ◽  
E. Olivier
Keyword(s):  
Vertical Velocity ◽  
Smooth Pursuit ◽  
Medial Longitudinal Fasciculus ◽  
Eye Position ◽  
Interstitial Nucleus Of Cajal ◽  
Burst Neurons ◽  
Preferred Direction ◽  
Saccade Onset ◽  
Vertical Saccades ◽  
Eye Velocity

The activity of vertical burst neurons (BNs) was recorded in the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF-BNs) and in the interstitial nucleus of Cajal (NIC-BNs) in head-restrained cats while performing saccades or smooth pursuit. BNs emitted a high-frequency burst of action potentials before and during vertical saccades. On average, these bursts led saccade onset by 14 ± 4 ms (mean ± SD, n = 23), and this value was in the range of latencies (∼5–15 ms) of medium-lead burst neurons (MLBNs). All NIC-BNs ( n = 15) had a downward preferred direction, whereas riMLF-BNs showed either a downward ( n = 3) or an upward ( n = 5) preferred direction. We found significant correlations between saccade and burst parameters in all BNs: vertical amplitude was correlated with the number of spikes, maximum vertical velocity with maximum of the spike density, and saccade duration with burst duration. A correlation was also found between instantaneous vertical velocity and neuronal activity during saccades. During fixation, all riMLF-BNs and ∼50% of NIC-BNs (7/15) were silent. Among NIC-BNs active during fixation (8/15), only two cells had an activity correlated with the eye position in the orbit. During smooth pursuit, most riMLF-BNs were silent (7/8), but all NIC-BNs showed an activity that was significantly correlated with the eye velocity. This activity was unaltered during temporary disappearance of the visual target, demonstrating that it was not visual in origin. For a given neuron, its on-direction during smooth pursuit and saccades remained identical. The activity of NIC-BNs during both saccades and smooth pursuit can be described by a nonlinear exponential function using the velocity of the eye as independent variable. We suggest that riMLF-BNs, which were not active during smooth pursuit, are vertical MLBNs responsible for the generation of vertical saccades. Because NIC-BNs discharged during both saccades and pursuit, they cannot be regarded as MLBNs as usually defined. NIC-BNs could, however, be the site of convergence of both the saccadic and smooth pursuit signals at the premotoneuronal level. Alternatively, NIC-BNs could participate in the integration of eye velocity to eye position signals and represent input neurons to a common integrator.

Abducens internuclear neurons carry an inappropriate signal for ocular convergence

1989 ◽  
Vol 62 (1) ◽  
pp. 70-81 ◽  
Author(s):  
P. D. Gamlin ◽  
J. W. Gnadt ◽  
L. E. Mays
Keyword(s):  
Eye Movements ◽  
Action Potentials ◽  
Vestibular Nuclei ◽  
Lateral Rectus ◽  
Medial Rectus ◽  
Medial Longitudinal Fasciculus ◽  
Unit Recording ◽  
Antidromic Activation ◽  
Prepositus Hypoglossi ◽  
Ocular Convergence

1. Single-unit recording studies in alert Rhesus monkeys characterized the vergence signal carried by abducens internuclear neurons. These cells were identified by antidromic activation and the collision of spontaneous with antidromic action potentials. The behavior of abducens internuclear neurons during vergence was compared with that of horizontal burst-tonic fibers in the medial longitudinal fasciculus (MLF) and to that of a large sample of unidentified abducens cells (presumably both motoneurons and internuclear neurons). 2. The results indicate that abducens internuclear neurons and lateral rectus motoneurons behave similarly during vergence eye movements: the majority of both groups of cells decrease their firing rate for convergence eye movements: a minority show no change for vergence. This finding is strongly supported by recordings of horizontal burst-tonic fibers in the MLF, the majority of which decrease their activity significantly for convergence eye movements. 3. These findings indicate that a net inappropriate vergence signal is sent to medial rectus motoneurons via the abducens internuclear pathway. Because medial rectus motoneurons increase their activity appropriately during symmetrical convergence, this inappropriate MLF signal must be overcome by a more potent direct vergence input. 4. Overall, both abducens internuclear neurons and lateral rectus motoneurons decrease their activity for convergence less than would be expected based on their conjugate gain. This implies that some degree of co-contraction of the lateral and medial rectus muscles occurs during convergence eye movements. 5. Some horizontal burst-tonic MLF fibers decrease their activity more for convergence than any recorded abducens neuron. These fibers may arise from cells in the nucleus prepositus hypoglossi or vestibular nuclei.

scholarly journals Isolated medial longitudinal fasciculus syndrome: Review of imaging, anatomy, pathophysiology and differential diagnosis

2017 ◽  
Vol 31 (1) ◽  
pp. 95-99 ◽  
Author(s):  
Puneet S Kochar ◽  
Yogesh Kumar ◽  
Pranav Sharma ◽  
Vikash Kumar ◽  
Nishant Gupta ◽  
...  
Keyword(s):  
Differential Diagnosis ◽  
Eye Movements ◽  
Brain Stem ◽  
Medial Longitudinal Fasciculus ◽  
Rare Occurrence ◽  
Comprehensive Review ◽  
Fiber Tracts ◽  
Imaging Characteristics ◽  
The Brain

Isolated medial longitudinal fasciculus (MLF) syndrome due to infarction limited only to the midbrain is a rare occurrence. The MLF are a group of fiber tracts located in the paramedian area of the midbrain and pons. They control horizontal eye movements by interconnecting oculomotor and abducens nuclei in the brain stem. Such small infarcts can easily be overlooked by young neuroradiologists and trainees. In this review, we discuss the clinical and imaging characteristics, comprehensive review of the anatomy, pathophysiology, and differential diagnosis.

Vertical eye movement-related secondary vestibular neurons ascending in medial longitudinal fasciculus in cat. II. Direct connections with extraocular motoneurons

1990 ◽  
Vol 63 (4) ◽  
pp. 918-935 ◽  
Author(s):  
Y. Iwamoto ◽  
T. Kitama ◽  
K. Yoshida
Keyword(s):  
Rectus Muscle ◽  
Medial Longitudinal Fasciculus ◽  
Field Potentials ◽  
Oculomotor Nucleus ◽  
Inferior Rectus ◽  
Interstitial Nucleus Of Cajal ◽  
Excitatory Connection ◽  
Superior Rectus ◽  
Spike Triggered Averaging ◽  
Trochlear Nucleus

1. The preceding study in the alert cat has shown that many secondary vestibular axons that ascend in the medial longitudinal fasciculus (MLF) increase their firing rate in proportion to downward eye position. In the present study, projection and termination of these downward-position-vestibular (DPV) neurons within extraocular motoneuron pools were studied electrophysiologically by spike-triggered averaging techniques and morphologically be reconstructing their axonal trajectory after intra-axonal injection of horseradish peroxidase (HRP). 2. Extracellular field potentials recorded within the trochlear nucleus and/or the inferior rectus subdivision of the oculomotor nucleus were averaged by the use of spike potentials of single DPV neurons as triggers. All the crossed-DPV axons tested induced negative unitary field potentials in the trochlear nucleus (n = 9) and in the inferior rectus subdivision of the oculomotor nucleus (n = 5), suggesting that they made monosynaptic excitatory connection with motoneurons in these nuclei. The four crossed-DPV axons tested in the two motoneuron pools induced unitary field potentials in both. The majority of crossed-DPV axons terminated in these nuclei were directly activated from the caudal MLF, indicating that they had descending collaterals projecting to the spinal cord as well. The uncrossed-DPV axons did not induce such unitary field potentials either in the trochlear nucleus (n = 4) or in the inferior rectus subdivision (n = 3). 3. All the uncrossed-DPV axons examined (n = 14) induced positive unitary field potentials in the superior rectus subdivision of the oculomotor nucleus, suggesting that they made monosynaptic inhibitory connections with motoneurons innervating the superior rectus muscle. These uncrossed-DPV axons displayed regular firing patterns and were not activated from the caudal MLF. None of the crossed-DPV axons tested (n = 4) induced unitary field potentials in the superior rectus subdivision. 4. Five crossed-DPV axons were injected with HRP. All these axons ascended in the MLF contralateral to their soma, gave off many collaterals to the trochlear nucleus, and projected more rostrally. For three well-stained axons, numerous terminal branches were also found in the rostroventral part of the contralateral oculomotor nucleus, the area corresponding to the inferior rectus subdivision. Some collaterals in the oculomotor nucleus recrossed the midline to terminate in the medial part of the ipsilateral oculomotor nucleus. Other terminations were observed in the interstitial nucleus of Cajal and in the periaqueductal gray adjacent to the oculomotor nucleus. The crossed axons injected included both regular and irregular types, and three of the four examined were activated from the caudal MLF.(ABSTRACT TRUNCATED AT 400 WORDS)

Disconjugate Eye Movements during Electronystagmographic Testing in Patients with Known Central Nervous System Lesions

1975 ◽  
Vol 84 (3) ◽  
pp. 368-373
Author(s):  
Joseph Kimm ◽  
James B. MacLean
Keyword(s):  
Central Nervous System ◽  
Eye Movements ◽  
Eye Movement ◽  
Motor System ◽  
Treatment Plan ◽  
Medial Longitudinal Fasciculus ◽  
Ocular Motor ◽  
Measuring Techniques ◽  
Ocular Motor System ◽  
Cns Lesions

A tacit assumption underlying current ENG testing is that the eyes move conjugately. However, considering the intricate neuroanatomical pathways within the ocular motor system in addition to the elaborate vestibulo-ocular connections, we think it reasonable that disconjugate eye movements may result with certain CNS lesions. Recently we have employed independent eye movement measuring techniques in order to assess the movement of each eye separately during our ENG valuations. The preliminary work has revealed that disconjugate eye movements occurred even with extra-axial lesions which spared the medial longitudinal fasciculus. These data may be valuable for the neurotologist with regard to differential diagnosis and prescription of a treatment plan for the patient. The eye movement patterns of patients with confirmed CNS lesions and other interesting findings are presented.

Vertical eye movement-related secondary vestibular neurons ascending in medial longitudinal fasciculus in cat I. Firing properties and projection pathways

1990 ◽  
Vol 63 (4) ◽  
pp. 902-917 ◽  
Author(s):  
Y. Iwamoto ◽  
T. Kitama ◽  
K. Yoshida
Keyword(s):  
Eye Movements ◽  
Firing Rate ◽  
Vestibular Nucleus ◽  
Vestibular Nerve ◽  
Medial Longitudinal Fasciculus ◽  
Eye Position ◽  
Phase Lag ◽  
Antidromic Activation ◽  
Head Velocity ◽  
Stimulation Of

1. The firing characteristics and projection patterns of secondary vestibular nucleus neurons involved in the vertical vestibuloocular pathways were investigated in alert cats. Single-unit recordings were made in the medial longitudinal fasciculus (MLF) near the trochlear nucleus from axons that were monosynaptically activated after electrical stimulation of the vestibular nerve. In a total of 253 identified secondary neurons, 225 discharged in relation to vertical eye movements; 189 of these increased their firing rate for downward eye movements and 36 for upward movements. The activity of the remaining 28 axons was not related to eye movements when the head was still. 2. Virtually all of the secondary neurons with downward on-direction displayed tonic activity that was primarily related to steady eye position during fixation (DPV neurons). The slope of the relationship between firing rate and vertical eye position ranged from 1.2 to 9.1 (spikes/s)/deg with a mean of 3.2 (spikes/s)/deg. The regularity of firing was quantified by calculating the coefficient of variation (CV) of interspike intervals. A comparison of the CV in the population units indicated that DPV neurons could be classified as either regular or irregular neurons. There was a tendency for regular neurons to have higher firing rates and higher correlation coefficients for the rate-position relationships than irregular neurons. 3. During pitch rotation in the light, all the DPV neurons tested increased their firing rate with upward head rotation. Both the phase and the amplitude of the response indicated that DPV neurons discharged not only in relation to eye position but also in relation to head velocity, suggesting that they received monosynaptic input from the posterior semicircular canal. The gain and phase lag of the response relative to head velocity were measured at 0.5 Hz. The range of the gain was 1.1-5.1 (spikes/s)/(deg/s), and that of the phase lag was 18.3-62.4 degrees. There was a tendency for irregular DPV neurons to have a larger gain and smaller phase lag than regular DPV neurons. 4. Ascending and descending projection pathways were determined for 147 DPV axons. Of these, 69 ascended in the contralateral MLF with respect to their soma (crossed-DPV axons), and 78 in the ipsilateral MLF (uncrossed-DPV axons), as revealed by their monosynaptic activation from the contralateral or ipsilateral vestibular nerve. Stimulation of the caudal MLF at the level of the obex evoked direct responses caused by antidromic activation of descending collaterals in approximately 70% (49/69) of the crossed-DPV axons.(ABSTRACT TRUNCATED AT 400 WORDS)

Brainstem and Cranial Nerves: Longitudinal Pathways of the Brainstem

2021 ◽  
pp. 99-104
Author(s):  
Kelly D. Flemming
Keyword(s):  
Spinal Cord ◽  
Eye Movements ◽  
Blood Vessels ◽  
Reticular Formation ◽  
Cranial Nerves ◽  
Ventrolateral Medulla ◽  
Unilateral Lesion ◽  
Horner Syndrome ◽  
Single Level ◽  
Autonomic Pathways

This chapter reviews pathways that are not at a single level of the brainstem but rather involve multiple areas with supratentorial input. The chapter highlights autonomic pathways, the reticular formation and chemically defined groups, and coordination of eye movements. Sympathetic fibers travel from the hypothalamus to the intermediolateral column in the spinal cord through the lateral brainstem. Patients with a unilateral lesion of the lateral brainstem may have ipsilateral Horner syndrome. The ventrolateral medulla, also a sympathetic region of the brainstem, projects to the spinal cord and is involved in the innervation of blood vessels in the limbs.

Sign in / Sign up

Export Citation Format

Share Document